502

What Yoursquoll Learn You will differentiate among

the major groups of protists You will recognize the ecolo-

gical niches of protists You will identify some human

diseases and the protists re-sponsible for them

Why Itrsquos ImportantBecause protists are responsiblefor much of the oxygen in theatmosphere and are the basefor most food chains in aquaticenvironments most other or-ganisms depend on protists fortheir own existences

ProtistsProtists

Matt Meadows

Visit tobull study the entire chapter

onlinebull access Web Links for more

information and activities onprotists

bull review content with theInteractive Tutor and self-check quizzes

This pretzel slime mold is a multicellular protist that growson logs and branches Its appear-ance and growth are similar tothose of a fungus

Understandingthe Photo

ncbdolglencoecom

0502-0502 C19CO BDOL-829900 8404 1153 PM Page 502

191SECTION PREVIEWObjectivesIdentify the characteris-tics of Kingdom ProtistaCompare and contrast thefour groups of protozoans

Review Vocabularyeukaryote unicellular or

multicellular organismwhose cells containmembrane-boundorganelles (p 173)

New Vocabularyprotozoanalgapseudopodiaasexual reproductionflagellateciliatesporozoanspore

protozoa from theGreek words protos meaningldquofirstrdquo and zoameaning ldquoani-malsrdquo Protozoaare animal-likeprotists

191 THE WORLD OF PROTISTS 503

How do you classifythese thingsUsing Prior Knowledge Youhave learned that the six king-dom classification systemincludes many obviously distinctkingdoms such as animalsplants and fungi Although mostof the organisms in these king-doms are very different fromeach other Kingdom Protistacontains organisms that are oftenalmost impossible to tell apartfrom animals plants or fungiThis kingdom includes an amaz-ingly diverse group many of which move like an animal photosynthesize like a plant or produce spores like a fungusExplain Read Section 191 and decide how you would define a protist

The World of Protists

James W EvartsPhoto Researchers

A protist in a water environment

Color-enhanced LM Magnification 120

What is a protistKingdom Protista contains the most diverse organisms of all the king-

doms Protists may be unicellular or multicellular microscopic or very largeand heterotrophic or autotrophic In fact there is no such organism as a typ-ical protist When you look at different protists you may wonder how theycould be grouped together The characteristic that all protists share is thatunlike bacteria they are all eukaryotes which means that most of theirmetabolic processes occur inside their membrane-bound organelles

Although there are no typical protists some resemble animals in the way they get food The animal-like protists are called protozoa(proh tuh ZOH uh) (singular protozoan) Unlike animals though all proto-zoans are unicellular Other protists are plantlike autotrophs using photo-synthesis to make their food Plantlike protists are called algae (AL jee)(singular alga) Unlike plants algae do not have organs such as roots stemsand leaves Still other protists are more like fungi because they decomposedead organisms However unlike fungi funguslike protists are able to moveat some point in their life and do not have chitin in their cell walls

It might surprise you to learn how much protists affect other organ-isms Some protists cause diseases such as malaria and sleeping sicknessthat result in millions of human deaths throughout the world every year

Objective 402 Analyze the processes by which organisms rep-resentative of the following groups accomplish essential life functions including Unicellularprotists annelid worms insects amphibians mammals non vascular plants gymnosperms andangiosperms

North Carolina Objectives

503-509 C19S1 BDOL-829900 8404 855 AM Page 503

BDOL-191

null

36604785

Unicellular algae produce much ofthe oxygen in Earthrsquos atmosphere andare the basis of aquatic food chainsSlime molds and water molds decom-pose a significant amount of organicmaterial making the nutrients avail-able to living organisms Protozoansalgae and funguslike protists playimportant roles on Earth Look atFigure 191 to see some protists

Describe the charac-teristics of animal-like plantlikeand funguslike protists

What is a protozoanIf you sat by a pond you might

notice clumps of dead leaves at thewaterrsquos edge Under a microscope apiece of those wet decaying leavesreveals a small world probablyinhabited by animal-like protistsAlthough a diverse group all proto-zoans are unicellular heterotrophsthat feed on other organisms or deadorganic matter They usually repro-duce asexually but some also repro-duce sexually

Diversity of ProtozoansMany protozoans are grouped

according to the way they moveSome protozoans use cilia or flagellato move Others move and feed bysending out cytoplasm-containingextensions of their plasma mem-branes These extensions are calledpseudopodia (sew duh POH dee uh)Other protozoans are groupedtogether because they are parasitesThere are four main groups of proto-zoans the amoebas (uh MEE buz) theflagellates the ciliates and the sporo-zoans (spor uh ZOH unz)

Amoebas Shapeless protistsThe phylum Rhizopoda includes

hundreds of species of amoebas andamoebalike organisms Amoebas haveno cell wall and form pseudopodia to move and feed As a pseudopodforms the shape of the cell changesand the amoeba moves Amoebasform pseudopodia around their foodas you can see in Figure 192

Although most amoebas live in saltwater there are freshwater ones that

504

pseudopodia fromthe Greek wordspseudo meaningldquofalserdquo and podosmeaning ldquofootrdquoAn amoeba usespseudopodia toobtain food

(l)E

ric G

rave

Pho

to R

esea

rche

rs

(c)F

lip N

ickl

inM

inde

n P

ictu

res

(r)

Bill

Bea

ttyV

isua

ls U

nlim

ited

Figure 191Members of Kingdom Protista areanimal-like plantlike and funguslike

During part of their life cyclefunguslike protists resemblesome types of fungi

C

Plantlike protists arephotosynthetic autotrophsand may be unicellular ormulticellular like this one

B

Animal-like protists areunicellular heterotrophs thatmove in a variety of ways

A

Color-enhanced LMMagnification 125

503-509 C19S1 BDOL-829900 8404 856 AM Page 504

(t)M AbbeyVisuals Unlimited (bl)Polaroid-OldfieldVisuals Unlimited (br)Juergen Berger Max-Planck InstituteScience Photo LibraryPhoto Researchers

Nucleus Cytoplasm

Contractilevacuole

Food vacuole

PseudopodiaFigure 192An amoeba feeds onsmall organisms suchas bacteria

As an amoeba approachesfood pseudopodia formand eventually surroundthe food

A The food becomesenclosed in a foodvacuole

B Digestive enzymes break down the food and the nutrients diffuse into the cytoplasm

C

LM Magnification 160

AA

191 THE WORLD OF PROTISTS 505

Figure 193Foraminiferans (A) andradiolarians (B) areamoebas that extendpseudopodia throughtiny holes in their shellsPseudopodia act likesticky nets that trapfood Explain Whatare pseudopodiacomposed of

Color-enhanced LM Magnification 100 SEM Magnification unavailable

BB

live in the ooze of ponds in wetpatches of moss and even in moist soilBecause amoebas live in moist placesnutrients dissolved in the water aroundthem can diffuse directly through theircell membranes However becausefreshwater amoebas live in hypotonicenvironments they constantly take inwater Their contractile vacuoles col-lect and pump out excess water

Two groupings of mostly marineamoebas the foraminiferan (foh ramih NIH fer in) and radiolarian shown inFigure 193 have shells Foram-iniferans which are abundant on thesea floor have hard shells made of cal-cium carbonate Fossil forms of theseprotists help geologists determine the

ages of some rocks and sedimentsUnlike foraminiferans radiolarianshave shells made of silica Under amicroscope you can see the complex-ity of these shells In addition radio-larians are an important part ofmarine planktonmdashan assortment ofmicroscopic organisms that float inthe oceanrsquos photic zone and form thebase of marine food chains

Most amoebas commonly repro-duce by asexual reproduction inwhich a single parent produces one ormore identical offspring by dividinginto two cells When environmentalconditions become unfavorable sometypes of amoebas form cysts that cansurvive extreme conditions

503-509 C19S1 BDOL-829900 8404 857 AM Page 505

Flagellates Protozoans with flagella

The phylum Zoomastigina consistsof protists called flagellates whichhave one or more flagella Flagellatedprotists move by whipping their fla-gella from side to side

Some flagellates are parasites thatcause diseases in animals such asAfrican sleeping sickness in humansOther flagellates are helpful Forexample termites like those you seein Figure 194B survive on a diet ofwood Without the help of a certainspecies of flagellate that lives in theguts of termites some termites couldnot survive on such a diet In a mutu-alistic relationship flagellates convertcellulose from wood into a carbo-hydrate that both they and their ter-mite hosts can use

Ciliates Protozoans with ciliaThe roughly 8000 members of the

protist phylum Ciliophora known asciliates use the cilia that cover theirbodies to move Use the MiniLab onthis page to observe a typical ciliatersquosmotion Ciliates live in every kind ofaquatic habitatmdashfrom ponds andstreams to oceans and sulfur springsWhat does a typical ciliate look likeTo find out look at Figure 195 onthe next page

(t)Matt Meadows (bl)M AbbeyVisuals Unlimited (br)Ken LucasVisuals Unlimited

Figure 194The flagellated protozoans (A)that live in the guts of termites(B) produce enzymes that digest wood making nutrients available to their hosts

LM Magnification 120

506 PROTISTS

AABB

Observe and InferObserving Ciliate Motion The cilia on the surface of a paramecium move so that the cell normally swims through the water with one end directed forward But when this end bumps into an obstacle the paramecium responds by changing direction

Procedure Observe a paramecium culture that has had boiled

crushed wheat seeds in it for several days Carefully place a drop of water containing wheat seed

particles on a microscope slide Gently add a coverslip Using low power locate a paramecium near some wheat

seed particles CAUTION Use caution when working witha microscope glass slides and coverslips

$ Watch the paramecium as it swims around among the particles Record your observations of the organismrsquosresponses each time it contacts a particle

Analysis1 Describe What does a paramecium do when it encoun-

ters an obstacle 2 Observe How long does the parameciumrsquos response last 3 Describe How does the shape of the paramecium change

as it moves among the particles

Observing a paramecium

503-509 C19S1 BDOL-829900 8404 857 AM Page 506

M AbbeyVisuals Unlimited

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny hairlike cilia emerge Theparamecium can move bybeating its cilia

AA

Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that line theoral groove

BB

Contractile vacuoleBecause a paramecium lives in a freshwater hypotonicenvironment water constantlyenters its cell by osmosis Apair of contractile vacuolespump out the excess water

FF

Anal pore Wastematerials leave the cellthrough the anal pore

EE

Micronucleus and macronucleus Thesmall micronucleus plays a major role in sexualreproduction The largemacronucleus controls theeveryday functions of the cell

DD

Gullet Food moves intothe gullet becomingenclosed at the end in afood vacuole Enzymes break down the food andthe nutrients diffuse into the cytoplasm

CC

191 THE WORLD OF PROTISTS 507

LM Magnification 110

Paramecium caudatum

A ParameciumFigure 195Paramecia are unicellular organisms but their cellsare quite complex Within a paramecium are manyorganelles and structures that are each adapted tocarry out a distinct function Critical Thinking Howmight the contractile vacuoles of a parameciumrespond if the organism were placed in a dilutesalt solution

503-509 C19S1 BDOL-829900 8404 858 AM Page 507

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

Unicellular algae produce much ofthe oxygen in Earthrsquos atmosphere andare the basis of aquatic food chainsSlime molds and water molds decom-pose a significant amount of organicmaterial making the nutrients avail-able to living organisms Protozoansalgae and funguslike protists playimportant roles on Earth Look atFigure 191 to see some protists

Describe the charac-teristics of animal-like plantlikeand funguslike protists

What is a protozoanIf you sat by a pond you might

notice clumps of dead leaves at thewaterrsquos edge Under a microscope apiece of those wet decaying leavesreveals a small world probablyinhabited by animal-like protistsAlthough a diverse group all proto-zoans are unicellular heterotrophsthat feed on other organisms or deadorganic matter They usually repro-duce asexually but some also repro-duce sexually

Diversity of ProtozoansMany protozoans are grouped

according to the way they moveSome protozoans use cilia or flagellato move Others move and feed bysending out cytoplasm-containingextensions of their plasma mem-branes These extensions are calledpseudopodia (sew duh POH dee uh)Other protozoans are groupedtogether because they are parasitesThere are four main groups of proto-zoans the amoebas (uh MEE buz) theflagellates the ciliates and the sporo-zoans (spor uh ZOH unz)

Amoebas Shapeless protistsThe phylum Rhizopoda includes

hundreds of species of amoebas andamoebalike organisms Amoebas haveno cell wall and form pseudopodia to move and feed As a pseudopodforms the shape of the cell changesand the amoeba moves Amoebasform pseudopodia around their foodas you can see in Figure 192

Although most amoebas live in saltwater there are freshwater ones that

504

pseudopodia fromthe Greek wordspseudo meaningldquofalserdquo and podosmeaning ldquofootrdquoAn amoeba usespseudopodia toobtain food

(l)E

ric G

rave

Pho

to R

esea

rche

rs

(c)F

lip N

ickl

inM

inde

n P

ictu

res

(r)

Bill

Bea

ttyV

isua

ls U

nlim

ited

Figure 191Members of Kingdom Protista areanimal-like plantlike and funguslike

During part of their life cyclefunguslike protists resemblesome types of fungi

C

Plantlike protists arephotosynthetic autotrophsand may be unicellular ormulticellular like this one

B

Animal-like protists areunicellular heterotrophs thatmove in a variety of ways

A

Color-enhanced LMMagnification 125

503-509 C19S1 BDOL-829900 8404 856 AM Page 504

(t)M AbbeyVisuals Unlimited (bl)Polaroid-OldfieldVisuals Unlimited (br)Juergen Berger Max-Planck InstituteScience Photo LibraryPhoto Researchers

Nucleus Cytoplasm

Contractilevacuole

Food vacuole

PseudopodiaFigure 192An amoeba feeds onsmall organisms suchas bacteria

As an amoeba approachesfood pseudopodia formand eventually surroundthe food

A The food becomesenclosed in a foodvacuole

B Digestive enzymes break down the food and the nutrients diffuse into the cytoplasm

C

LM Magnification 160

AA

191 THE WORLD OF PROTISTS 505

Figure 193Foraminiferans (A) andradiolarians (B) areamoebas that extendpseudopodia throughtiny holes in their shellsPseudopodia act likesticky nets that trapfood Explain Whatare pseudopodiacomposed of

Color-enhanced LM Magnification 100 SEM Magnification unavailable

BB

live in the ooze of ponds in wetpatches of moss and even in moist soilBecause amoebas live in moist placesnutrients dissolved in the water aroundthem can diffuse directly through theircell membranes However becausefreshwater amoebas live in hypotonicenvironments they constantly take inwater Their contractile vacuoles col-lect and pump out excess water

Two groupings of mostly marineamoebas the foraminiferan (foh ramih NIH fer in) and radiolarian shown inFigure 193 have shells Foram-iniferans which are abundant on thesea floor have hard shells made of cal-cium carbonate Fossil forms of theseprotists help geologists determine the

ages of some rocks and sedimentsUnlike foraminiferans radiolarianshave shells made of silica Under amicroscope you can see the complex-ity of these shells In addition radio-larians are an important part ofmarine planktonmdashan assortment ofmicroscopic organisms that float inthe oceanrsquos photic zone and form thebase of marine food chains

Most amoebas commonly repro-duce by asexual reproduction inwhich a single parent produces one ormore identical offspring by dividinginto two cells When environmentalconditions become unfavorable sometypes of amoebas form cysts that cansurvive extreme conditions

503-509 C19S1 BDOL-829900 8404 857 AM Page 505

Flagellates Protozoans with flagella

The phylum Zoomastigina consistsof protists called flagellates whichhave one or more flagella Flagellatedprotists move by whipping their fla-gella from side to side

Some flagellates are parasites thatcause diseases in animals such asAfrican sleeping sickness in humansOther flagellates are helpful Forexample termites like those you seein Figure 194B survive on a diet ofwood Without the help of a certainspecies of flagellate that lives in theguts of termites some termites couldnot survive on such a diet In a mutu-alistic relationship flagellates convertcellulose from wood into a carbo-hydrate that both they and their ter-mite hosts can use

Ciliates Protozoans with ciliaThe roughly 8000 members of the

protist phylum Ciliophora known asciliates use the cilia that cover theirbodies to move Use the MiniLab onthis page to observe a typical ciliatersquosmotion Ciliates live in every kind ofaquatic habitatmdashfrom ponds andstreams to oceans and sulfur springsWhat does a typical ciliate look likeTo find out look at Figure 195 onthe next page

(t)Matt Meadows (bl)M AbbeyVisuals Unlimited (br)Ken LucasVisuals Unlimited

Figure 194The flagellated protozoans (A)that live in the guts of termites(B) produce enzymes that digest wood making nutrients available to their hosts

LM Magnification 120

506 PROTISTS

AABB

Observe and InferObserving Ciliate Motion The cilia on the surface of a paramecium move so that the cell normally swims through the water with one end directed forward But when this end bumps into an obstacle the paramecium responds by changing direction

Procedure Observe a paramecium culture that has had boiled

crushed wheat seeds in it for several days Carefully place a drop of water containing wheat seed

particles on a microscope slide Gently add a coverslip Using low power locate a paramecium near some wheat

seed particles CAUTION Use caution when working witha microscope glass slides and coverslips

$ Watch the paramecium as it swims around among the particles Record your observations of the organismrsquosresponses each time it contacts a particle

Analysis1 Describe What does a paramecium do when it encoun-

ters an obstacle 2 Observe How long does the parameciumrsquos response last 3 Describe How does the shape of the paramecium change

as it moves among the particles

Observing a paramecium

503-509 C19S1 BDOL-829900 8404 857 AM Page 506

M AbbeyVisuals Unlimited

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny hairlike cilia emerge Theparamecium can move bybeating its cilia

AA

Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that line theoral groove

BB

Contractile vacuoleBecause a paramecium lives in a freshwater hypotonicenvironment water constantlyenters its cell by osmosis Apair of contractile vacuolespump out the excess water

FF

Anal pore Wastematerials leave the cellthrough the anal pore

EE

Micronucleus and macronucleus Thesmall micronucleus plays a major role in sexualreproduction The largemacronucleus controls theeveryday functions of the cell

DD

Gullet Food moves intothe gullet becomingenclosed at the end in afood vacuole Enzymes break down the food andthe nutrients diffuse into the cytoplasm

CC

191 THE WORLD OF PROTISTS 507

LM Magnification 110

Paramecium caudatum

A ParameciumFigure 195Paramecia are unicellular organisms but their cellsare quite complex Within a paramecium are manyorganelles and structures that are each adapted tocarry out a distinct function Critical Thinking Howmight the contractile vacuoles of a parameciumrespond if the organism were placed in a dilutesalt solution

503-509 C19S1 BDOL-829900 8404 858 AM Page 507

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

(t)M AbbeyVisuals Unlimited (bl)Polaroid-OldfieldVisuals Unlimited (br)Juergen Berger Max-Planck InstituteScience Photo LibraryPhoto Researchers

Nucleus Cytoplasm

Contractilevacuole

Food vacuole

PseudopodiaFigure 192An amoeba feeds onsmall organisms suchas bacteria

As an amoeba approachesfood pseudopodia formand eventually surroundthe food

A The food becomesenclosed in a foodvacuole

B Digestive enzymes break down the food and the nutrients diffuse into the cytoplasm

C

LM Magnification 160

AA

191 THE WORLD OF PROTISTS 505

Figure 193Foraminiferans (A) andradiolarians (B) areamoebas that extendpseudopodia throughtiny holes in their shellsPseudopodia act likesticky nets that trapfood Explain Whatare pseudopodiacomposed of

Color-enhanced LM Magnification 100 SEM Magnification unavailable

BB

live in the ooze of ponds in wetpatches of moss and even in moist soilBecause amoebas live in moist placesnutrients dissolved in the water aroundthem can diffuse directly through theircell membranes However becausefreshwater amoebas live in hypotonicenvironments they constantly take inwater Their contractile vacuoles col-lect and pump out excess water

Two groupings of mostly marineamoebas the foraminiferan (foh ramih NIH fer in) and radiolarian shown inFigure 193 have shells Foram-iniferans which are abundant on thesea floor have hard shells made of cal-cium carbonate Fossil forms of theseprotists help geologists determine the

ages of some rocks and sedimentsUnlike foraminiferans radiolarianshave shells made of silica Under amicroscope you can see the complex-ity of these shells In addition radio-larians are an important part ofmarine planktonmdashan assortment ofmicroscopic organisms that float inthe oceanrsquos photic zone and form thebase of marine food chains

Most amoebas commonly repro-duce by asexual reproduction inwhich a single parent produces one ormore identical offspring by dividinginto two cells When environmentalconditions become unfavorable sometypes of amoebas form cysts that cansurvive extreme conditions

503-509 C19S1 BDOL-829900 8404 857 AM Page 505

Flagellates Protozoans with flagella

The phylum Zoomastigina consistsof protists called flagellates whichhave one or more flagella Flagellatedprotists move by whipping their fla-gella from side to side

Some flagellates are parasites thatcause diseases in animals such asAfrican sleeping sickness in humansOther flagellates are helpful Forexample termites like those you seein Figure 194B survive on a diet ofwood Without the help of a certainspecies of flagellate that lives in theguts of termites some termites couldnot survive on such a diet In a mutu-alistic relationship flagellates convertcellulose from wood into a carbo-hydrate that both they and their ter-mite hosts can use

Ciliates Protozoans with ciliaThe roughly 8000 members of the

protist phylum Ciliophora known asciliates use the cilia that cover theirbodies to move Use the MiniLab onthis page to observe a typical ciliatersquosmotion Ciliates live in every kind ofaquatic habitatmdashfrom ponds andstreams to oceans and sulfur springsWhat does a typical ciliate look likeTo find out look at Figure 195 onthe next page

(t)Matt Meadows (bl)M AbbeyVisuals Unlimited (br)Ken LucasVisuals Unlimited

Figure 194The flagellated protozoans (A)that live in the guts of termites(B) produce enzymes that digest wood making nutrients available to their hosts

LM Magnification 120

506 PROTISTS

AABB

Observe and InferObserving Ciliate Motion The cilia on the surface of a paramecium move so that the cell normally swims through the water with one end directed forward But when this end bumps into an obstacle the paramecium responds by changing direction

Procedure Observe a paramecium culture that has had boiled

crushed wheat seeds in it for several days Carefully place a drop of water containing wheat seed

particles on a microscope slide Gently add a coverslip Using low power locate a paramecium near some wheat

seed particles CAUTION Use caution when working witha microscope glass slides and coverslips

$ Watch the paramecium as it swims around among the particles Record your observations of the organismrsquosresponses each time it contacts a particle

Analysis1 Describe What does a paramecium do when it encoun-

ters an obstacle 2 Observe How long does the parameciumrsquos response last 3 Describe How does the shape of the paramecium change

as it moves among the particles

Observing a paramecium

503-509 C19S1 BDOL-829900 8404 857 AM Page 506

M AbbeyVisuals Unlimited

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny hairlike cilia emerge Theparamecium can move bybeating its cilia

AA

Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that line theoral groove

BB

Contractile vacuoleBecause a paramecium lives in a freshwater hypotonicenvironment water constantlyenters its cell by osmosis Apair of contractile vacuolespump out the excess water

FF

Anal pore Wastematerials leave the cellthrough the anal pore

EE

Micronucleus and macronucleus Thesmall micronucleus plays a major role in sexualreproduction The largemacronucleus controls theeveryday functions of the cell

DD

Gullet Food moves intothe gullet becomingenclosed at the end in afood vacuole Enzymes break down the food andthe nutrients diffuse into the cytoplasm

CC

191 THE WORLD OF PROTISTS 507

LM Magnification 110

Paramecium caudatum

A ParameciumFigure 195Paramecia are unicellular organisms but their cellsare quite complex Within a paramecium are manyorganelles and structures that are each adapted tocarry out a distinct function Critical Thinking Howmight the contractile vacuoles of a parameciumrespond if the organism were placed in a dilutesalt solution

503-509 C19S1 BDOL-829900 8404 858 AM Page 507

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

Flagellates Protozoans with flagella

The phylum Zoomastigina consistsof protists called flagellates whichhave one or more flagella Flagellatedprotists move by whipping their fla-gella from side to side

Some flagellates are parasites thatcause diseases in animals such asAfrican sleeping sickness in humansOther flagellates are helpful Forexample termites like those you seein Figure 194B survive on a diet ofwood Without the help of a certainspecies of flagellate that lives in theguts of termites some termites couldnot survive on such a diet In a mutu-alistic relationship flagellates convertcellulose from wood into a carbo-hydrate that both they and their ter-mite hosts can use

Ciliates Protozoans with ciliaThe roughly 8000 members of the

protist phylum Ciliophora known asciliates use the cilia that cover theirbodies to move Use the MiniLab onthis page to observe a typical ciliatersquosmotion Ciliates live in every kind ofaquatic habitatmdashfrom ponds andstreams to oceans and sulfur springsWhat does a typical ciliate look likeTo find out look at Figure 195 onthe next page

(t)Matt Meadows (bl)M AbbeyVisuals Unlimited (br)Ken LucasVisuals Unlimited

Figure 194The flagellated protozoans (A)that live in the guts of termites(B) produce enzymes that digest wood making nutrients available to their hosts

LM Magnification 120

506 PROTISTS

AABB

Observe and InferObserving Ciliate Motion The cilia on the surface of a paramecium move so that the cell normally swims through the water with one end directed forward But when this end bumps into an obstacle the paramecium responds by changing direction

Procedure Observe a paramecium culture that has had boiled

crushed wheat seeds in it for several days Carefully place a drop of water containing wheat seed

particles on a microscope slide Gently add a coverslip Using low power locate a paramecium near some wheat

seed particles CAUTION Use caution when working witha microscope glass slides and coverslips

$ Watch the paramecium as it swims around among the particles Record your observations of the organismrsquosresponses each time it contacts a particle

Analysis1 Describe What does a paramecium do when it encoun-

ters an obstacle 2 Observe How long does the parameciumrsquos response last 3 Describe How does the shape of the paramecium change

as it moves among the particles

Observing a paramecium

503-509 C19S1 BDOL-829900 8404 857 AM Page 506

M AbbeyVisuals Unlimited

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny hairlike cilia emerge Theparamecium can move bybeating its cilia

AA

Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that line theoral groove

BB

Contractile vacuoleBecause a paramecium lives in a freshwater hypotonicenvironment water constantlyenters its cell by osmosis Apair of contractile vacuolespump out the excess water

FF

Anal pore Wastematerials leave the cellthrough the anal pore

EE

Micronucleus and macronucleus Thesmall micronucleus plays a major role in sexualreproduction The largemacronucleus controls theeveryday functions of the cell

DD

Gullet Food moves intothe gullet becomingenclosed at the end in afood vacuole Enzymes break down the food andthe nutrients diffuse into the cytoplasm

CC

191 THE WORLD OF PROTISTS 507

LM Magnification 110

Paramecium caudatum

A ParameciumFigure 195Paramecia are unicellular organisms but their cellsare quite complex Within a paramecium are manyorganelles and structures that are each adapted tocarry out a distinct function Critical Thinking Howmight the contractile vacuoles of a parameciumrespond if the organism were placed in a dilutesalt solution

503-509 C19S1 BDOL-829900 8404 858 AM Page 507

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

M AbbeyVisuals Unlimited

Fullvacuole

Empty vacuoleCanals

Canals takeup water fromcytoplasm

Pore opens andvacuole contracts

Pore

Cilia The cell is encased by anouter covering called a pelliclethrough which thousands oftiny hairlike cilia emerge Theparamecium can move bybeating its cilia

AA

Oral groove Parameciafeed primarily on bacteriathat are swept into thegullet by cilia that line theoral groove

BB

Contractile vacuoleBecause a paramecium lives in a freshwater hypotonicenvironment water constantlyenters its cell by osmosis Apair of contractile vacuolespump out the excess water

FF

Anal pore Wastematerials leave the cellthrough the anal pore

EE

Micronucleus and macronucleus Thesmall micronucleus plays a major role in sexualreproduction The largemacronucleus controls theeveryday functions of the cell

DD

Gullet Food moves intothe gullet becomingenclosed at the end in afood vacuole Enzymes break down the food andthe nutrients diffuse into the cytoplasm

CC

191 THE WORLD OF PROTISTS 507

LM Magnification 110

Paramecium caudatum

A ParameciumFigure 195Paramecia are unicellular organisms but their cellsare quite complex Within a paramecium are manyorganelles and structures that are each adapted tocarry out a distinct function Critical Thinking Howmight the contractile vacuoles of a parameciumrespond if the organism were placed in a dilutesalt solution

503-509 C19S1 BDOL-829900 8404 858 AM Page 507

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

Many structures found in ciliatesrsquocells may work together to performjust one important life function Forexample a paramecium uses its ciliaoral groove gullet and food vacuolesin the process of digestion Use theProblem-Solving Lab on this page toexplore how a paramecium digests thefood in a vacuole

A paramecium usually reproducesasexually by dividing crosswise andseparating into two daughter cells asyou can see in Figure 196 When-ever their food supplies dwindle ortheir environmental conditionschange paramecia usually undergo aform of conjugation In this complexprocess two paramecia join andexchange genetic material Thenthey separate and each divides asex-ually passing on its new geneticcomposition

Sporozoans Parasitic protozoansProtists in the phylum Sporozoa are

often called sporozoans because mostproduce spores A spore is a repro-ductive cell that forms without fertil-ization and produces a new organism

All sporozoans are parasites Theylive as internal parasites in one ormore hosts and have complex lifecycles Sporozoans are usually foundin a part of a host that has a readyfood supply such as an animalrsquos bloodor intestines Plasmodium members ofthe sporozoan genus are organismsthat cause the disease malaria inhumans and other mammals and inbirds

Sporozoans and malariaThroughout the world today more

than 300 million people have malariaa serious disease that usually occurs inplaces that have tropical climates ThePlasmodium that mosquitoes transmitto people cause human malaria Asyou can see in Figure 197 the

508 PROTISTS

Draw a ConclusionHow do digestive enzymes function in paramecia Paramecia ingest food particles and enclose them in food vacuoles Each food vacuole circulates in the cell as the food is digestedby enzymes that enter the vacuole Digested nutrients areabsorbed into the cytoplasm

Solve the Problem1 Some digestive enzymes function best at high pH levels

while others function best at low (more acidic) pH levels2 Congo red is a pH indicator dye it is red when the pH is

above 5 and blue when the pH is below 3 (very acidic)3 Yeast cells that contain Congo red can be produced by

adding dye to the solution in which the cells are growing4 When paramecia feed on dyed yeast cells the yeast is visi-

ble inside food vacuoles5 Examine the drawing above The appearance of a yeast-

filled food vacuole over time is indicated by the coloredcircles inside the paramecium Each arrow indicates move-ment and the passing of time

Thinking CriticallyObserve and Infer What happens to the pH in the food vac-uole over time Explain what sequence of digestive enzymesmight function in a paramecium

M AbbeyPhoto Researchers

Figure 196A parameciumreproduces by dividing into twoidentical daughtercells

Color-enhanced LM Magnification 84

503-509 C19S1 BDOL-829900 8404 859 AM Page 508

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

Understanding Main Ideas1 Describe the characteristics of the protist king-

dom Then compare the characteristics of the fourmajor groups of protozoans How is each group ofprotozoans animal-like

2 How do amoebas obtain food3 Explain any differences that exist between ciliates

and flagellates4 What makes a sporozoan different from other

protozoan groups

Thinking Critically5 What role do contractile vacuoles play in helping

freshwater protozoans maintain homeostasis

6 Sequence Trace the life cycle of a Plasmodiumthat causes human malaria Identify all forms ofthe sporozoan and the role each plays in the disease For more help refer to Sequence in the Skill Handbook

SKILL REVIEWSKILL REVIEW

191 THE WORLD OF PROTISTS 509

Gametes

Zygote

Gut wallof mosquito

Mosquito feedson infected person

Mosquito bites a new uninfected person

Human host

Sporozoites

Figure 197The life cycle ofPlasmodium involvestwo hostsmdashmosquitoesand humans

Sporozoites enter themosquitorsquos salivary glandand are injected into themosquitorsquos human host

BB

The blood cellsrupture releasingboth toxins and newspores that infectmore red blood cellsand multiply

DD

malaria-causing Plasmodium live inboth humans and mosquitoes

Until World War II the drug qui-nine was used to treat malaria Todaya combination of the drugs chloro-quine and primaquine are most often

used to treat this disease because theycause few serious side effects inhumans But some species ofPlasmodium have begun to resist thesedrugs Therefore new drugs areunder development to treat malaria

Some spores developinto gametes that flowin the bloodstream andmay be taken up byother mosquitos

EEPlasmodium gametes enter the mosquitofrom infected human blood In the mosquitorsquosgut a zygote develops from the gametes andeventually releases cells called sporozoites

AA

The sporozoites reproduce asexually inthe humanrsquos liver forming sporelikecells that enter the humanrsquos red bloodcells and multiply rapidly

CC

ncbdolglencoecomself_check_quiz

503-509 C19S1 BDOL-829900 8604 1058 AM Page 509

Algae Plantlike Protists192

Fold a vertical sheet of paper from side to side Make the back edge about 15 cm longer than the front edge

Turn lengthwise and fold into six sections

Protists Make the following Foldable to help identify and study the characteristics of each type of algae

STEP 1 STEP 2

510 PROTISTS

SECTION PREVIEWObjectivesCompare and contrastthe variety of plantlikeprotistsExplain the process ofalternation of generationsin algae

Review Vocabularyphotosynthesis process by

which autotrophs trapenergy from sunlightwith chlorophyll andconvert carbon dioxideand water into simplesugars (p 225)

New Vocabularythalluscolonyfragmentationalternation of generationsgametophytesporophyte

Read and Write As you read Section 192 list the characteristics of each type of algae under the appropriate tab Use your foldable to take notes and as a study guide

Unfold and cut only the top layer along all five folds to make six tabs

Label each tab as follows Euglenoids Diatoms Dinoflagellates Red Algae Brown Algae Green Algae Label the edge as Unicellular and Multicellular Algae

STEP 3 STEP 4

What are algaePhotosynthesizing protists are called algae All algae contain up to four

kinds of chlorophyll as well as other photosynthetic pigments These pig-ments produce a variety of colors in algae including purple rusty-redolive-brown yellow and golden-brown and are a way of classifying algaeinto groups

Algae include both unicellular and multicellular organisms Thephotosynthesizing unicellular protists known as phytoplankton (fi tohPLANK tun) are so numerous that they are one of the major producers ofnutrients and oxygen in aquatic ecosystems in the world Through photo-synthesis algae produce much of the oxygen used on Earth Althoughmulticellular algae may look like plants because they are large and some-times green they have no roots stems or leaves Use the MiniLab on thenext page to observe algae

Objective 402 Analyze the processes by which organisms rep-resentative of the following groups accomplish essential life functions including Unicellularprotists annelid worms insects amphibians mammals non vascular plants gymnosperms

and angiosperms

North Carolina Objectives

510-516 C19S2 BDOL-829900 8404 905 AM Page 510

BDOL-192

null

3942106

Diversity of AlgaeAlgae are classified into six phyla

Three of these phylamdashthe eugle-noids diatoms and dinoflagellatesmdashinclude only unicellular speciesHowever in the other three phylawhich are the green red and brownalgae most species are multicellular

Euglenoids Autotrophs and heterotrophs

Hundreds of species of euglenoids(yoo GLEE noydz) make up the phy-lum Euglenophyta Euglenoids areunicellular aquatic protists that haveboth plant and animal characteristicsUnlike plant cells they lack a cell wallmade of cellulose However they dohave a flexible pellicle made of pro-tein that surrounds the cell mem-brane Euglenoids are plantlike inthat most have chlorophyll and pho-tosynthesize However they are alsoanimal-like because when light is notavailable they can ingest food in waysthat might remind you of some proto-zoans In other words euglenoids canbe heterotrophs In Figure 198 youcan see a typical euglenoid

Euglenoids might also remindyou of protozoans because they have one or more flagella to move

TE AdamsVisuals Unlimited

Nucleus

Chloroplast

Mitochondrion

Eyespot

FlagellumPellicle

Contractile vacuole

Figure 198Notice the eyespot in this Euglena gracilis It shadesa light-sensitive receptor that helps E gracilis orientitself toward light

Stained LMMagnification 180

Data Table

Diagram MotileNonmotile UnicellularMulticellular

511

ObserveGoing on an Algae Hunt Pond water may be teeming withorganisms Some are macroscopic organisms but the majorityare microscopic Some may be heterotrophs and othersautotrophs How can you tell them apart

Procedure Copy the data table

Place a drop of pond water onto a glass slide and add acoverslip CAUTION Use caution when working with amicroscope glass slides and coverslips

Observe the pond water under low magnification of yourmicroscope and look for algae that may be present Algaefrom a pond will usually be green or yellow-green in color

$ Diagram several different species of algae in your datatable and indicate if each is motile or nonmotile Indicateif the algae are unicellular or multicellular

Analysis1 Analyze What characteristic distinguished algae from any

protozoans that may have been present2 Describe Explain how the characteristic in question 1 cat-

egorizes algae as autotrophs3 Observe Did you observe any relationship between

movement and size Explain your answer

510-516 C19S2 BDOL-829900 8404 906 AM Page 511

They use their flagella to movetoward light or food In the BioLabat the end of this chapter you canlearn more about how a euglenoidresponds to light

Diatoms The golden algaeDiatoms (DI uh tahmz) members

of the phylum Bacillariophyta are unicellular photosynthetic organismswith shells composed of silica Theymake up a large component of the

phytoplankton population in bothmarine and freshwater ecosystems

The delicate shells of diatoms likethose you see in Figure 199 mightremind you of boxes with lids Eachspecies has its own unique shape dec-orated with grooves and pores

Diatoms contain chlorophyll aswell as other pigments calledcarotenoids (ke RUH tuhn oydz) thatusually give them a golden-yellowcolor The food that diatoms make isstored as oils rather than starch Theseoils give fishes that feed on diatoms anoily taste They also give diatomsbuoyancy so that they float near thesurface where light is available

When diatoms reproduce asexuallythe two halves of the box separateeach half then produces a new half tofit inside itself This means that half ofeach generationrsquos offspring are smallerthan the parent cells When diatoms

Biophoto AssociatesScience SourcePhoto Researchers

Asexual reproduction

Sexual reproduction

Zygote

Mitosis

Meiosis

Wall formationaround cell

Gametes

Fusion of gametes

Spermreleased

Figure 199Diatom shells have many shapes

Color-enhanced LM Magnification 450

512 PROTISTS

Figure 1910Diatoms reproduce asexually for several generations beforereproducing sexually Infer How is the size of the diatomrelated to its mode of reproduction

510-516 C19S2 BDOL-829900 8404 907 AM Page 512

are about one-quarter of their originalsize they reproduce sexually by pro-ducing gametes that fuse to formzygotes The zygote develops into afull-sized diatom which will divideasexually for a while You can see boththe asexual and sexual reproductiveprocesses of diatoms in Figure 1910

When diatoms die their shells sinkto the ocean floor The deposits ofdiatom shellsmdashsome of which are mil-lions of years oldmdashare dredged ormined processed and used as abrasivesin tooth and metal polishes or added topaint to give the sparkle that makespavement lines more visible at night

Dinoflagellates The spinning algae

Dinoflagellates (di nuh FLA juh layts)members of the phylum Dinoflagellatahave cell walls that are composed ofthick cellulose plates They come in agreat variety of shapes and stylesmdashsome even resemble helmets and oth-ers look like suits of armor

Dinoflagellates contain chloro-phyll carotenoids and red pigmentsThey have two flagella located ingrooves at right angles to each otherThe cell spins slowly as the flagellabeat A few species of dinoflagellateslive in freshwater but most aremarine and like diatoms are a major

component of phytoplankton Manyspecies live symbiotically with jelly-fishes mollusks and corals Somefree-living species are biolumines-cent which means that they emitlight

Several species of dinoflagellatesproduce toxins One toxin-producingdinoflagellate Pfiesteria piscicida thatsome North Carolina researchers dis-covered in 1988 has caused a numberof fish kills in the coastal waters fromDelaware to North Carolina

Another toxic species Gonyaulaxcatanella produces an extremelystrong nerve toxin that can be lethalIn the summer these organisms maybecome so numerous that the oceantakes on a reddish color as you can seein Figure 1911 This populationexplosion is called a red tide In somered tides there can be as many as 40 to 60 million dinoflagellates perliter of seawater

The toxins produced during a redtide may make humans ill During redtides the harvesting of shellfish isusually banned because shellfish feedon the toxic algae and the toxins con-centrate in their tissues People whoeat such shellfish risk being poisonedYou can learn more about the causesand effects of red tides in the Problem-Solving Lab on the next page

192 ALGAE PLANTLIKE PROTISTS 513(l)Peter JS FranksScripps Institution of Oceanography (r)David M PhillipsVisuals Unlimited

Figure 1911Red tides such as theone shown here (A)are often caused bydinoflagellates suchas this one calledGonyaulax (B)

AA

BBColor-enhanced SEM Magnification 12 000

510-516 C19S2 BDOL-829900 8404 907 AM Page 513

Red algaeRed algae members of the phylum

Rhodophyta are mostly multicellu-lar marine seaweeds The body of aseaweed as well as that of someplants and other organisms is calleda thallus and lacks roots stems orleaves Red algae use structurescalled holdfasts to attach to rocksThey grow in tropical waters oralong rocky coasts in cold water Youcan see a red alga in Figure 1912

In addition to chlorophyll redalgae also contain photosynthetic pig-ments called phycobilins These pig-ments absorb green violet and bluelightmdashthe only part of the light spec-trum that penetrates water belowdepths of 100 m Therefore the redalgae can live in deep water wheremost other seaweeds cannot thrive

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta Almost all of thesespecies live in salt water along rockycoasts in cool areas of the worldBrown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin which gives themtheir brown color Many species ofbrown algae have air bladders thatkeep their bodies floating near thesurface where light is available

The largest and most complex ofbrown algae are kelp In kelp thethallus is divided into the holdfast

514 PROTISTS(t)Joyce PhotoPhoto Researchers (b)R DeGourseyVisuals Unlimited

Figure 1912This Coralline alga is only one of about 4000species of red algae Some species are popularfoods in Japan and other countries

Recognize Cause and EffectWhy is the number of red tides increasingScientists have been awareof red tide poisoning ofbirds fishes and mammalssuch as whales and humans for years Could the rise in red tide poisoning be related to human activities

Solve the ProblemThe following events are associated with the appearance ofred tides

The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish such as clams and oysters

Within five weeks 14 humpback whales died on beaches inMassachusetts The whalesrsquo stomachs contained mackerelwith high levels of dinoflagellate toxin

Between 1976 and 1986 the human population of HongKong increased sixfold and its harbor had an eightfoldincrease in red tides Human waste water was commonlyemptied into the harbor

$ Studies show that red tides are increasing worldwide

An algal bloom occurs when algae using sunlight andabundant nutrients increase rapidly in number to hun-dreds of thousands of cells per milliliter of water

Thinking Critically1 Think Critically Which statement above provides evi-

dence that supports each of the following ideas Explaineach answera Dinoflagellate poisons flow through the food chainb Dinoflagellates are autotrophsc There is a correlation between human activities and

algae growth

2 Think Critically Based on the evidence presented abovecan you conclude that human activity is responsible for theincrease in red tides Why or why not

A sperm whalersquos carcass

510-516 C19S2 BDOL-829900 8404 908 AM Page 514

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

(l)D

ale

Sar

ver

Ani

mal

s A

nim

als

(c)

Nur

idsa

ny e

t P

eren

nou

Pho

to R

esea

rche

rs

(r)M

IW

alke

rP

hoto

Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

Diversity of AlgaeAlgae are classified into six phyla

Three of these phylamdashthe eugle-noids diatoms and dinoflagellatesmdashinclude only unicellular speciesHowever in the other three phylawhich are the green red and brownalgae most species are multicellular

Euglenoids Autotrophs and heterotrophs

Hundreds of species of euglenoids(yoo GLEE noydz) make up the phy-lum Euglenophyta Euglenoids areunicellular aquatic protists that haveboth plant and animal characteristicsUnlike plant cells they lack a cell wallmade of cellulose However they dohave a flexible pellicle made of pro-tein that surrounds the cell mem-brane Euglenoids are plantlike inthat most have chlorophyll and pho-tosynthesize However they are alsoanimal-like because when light is notavailable they can ingest food in waysthat might remind you of some proto-zoans In other words euglenoids canbe heterotrophs In Figure 198 youcan see a typical euglenoid

Euglenoids might also remindyou of protozoans because they have one or more flagella to move

TE AdamsVisuals Unlimited

Nucleus

Chloroplast

Mitochondrion

Eyespot

FlagellumPellicle

Contractile vacuole

Figure 198Notice the eyespot in this Euglena gracilis It shadesa light-sensitive receptor that helps E gracilis orientitself toward light

Stained LMMagnification 180

Data Table

Diagram MotileNonmotile UnicellularMulticellular

511

ObserveGoing on an Algae Hunt Pond water may be teeming withorganisms Some are macroscopic organisms but the majorityare microscopic Some may be heterotrophs and othersautotrophs How can you tell them apart

Procedure Copy the data table

Place a drop of pond water onto a glass slide and add acoverslip CAUTION Use caution when working with amicroscope glass slides and coverslips

Observe the pond water under low magnification of yourmicroscope and look for algae that may be present Algaefrom a pond will usually be green or yellow-green in color

$ Diagram several different species of algae in your datatable and indicate if each is motile or nonmotile Indicateif the algae are unicellular or multicellular

Analysis1 Analyze What characteristic distinguished algae from any

protozoans that may have been present2 Describe Explain how the characteristic in question 1 cat-

egorizes algae as autotrophs3 Observe Did you observe any relationship between

movement and size Explain your answer

510-516 C19S2 BDOL-829900 8404 906 AM Page 511

They use their flagella to movetoward light or food In the BioLabat the end of this chapter you canlearn more about how a euglenoidresponds to light

Diatoms The golden algaeDiatoms (DI uh tahmz) members

of the phylum Bacillariophyta are unicellular photosynthetic organismswith shells composed of silica Theymake up a large component of the

phytoplankton population in bothmarine and freshwater ecosystems

The delicate shells of diatoms likethose you see in Figure 199 mightremind you of boxes with lids Eachspecies has its own unique shape dec-orated with grooves and pores

Diatoms contain chlorophyll aswell as other pigments calledcarotenoids (ke RUH tuhn oydz) thatusually give them a golden-yellowcolor The food that diatoms make isstored as oils rather than starch Theseoils give fishes that feed on diatoms anoily taste They also give diatomsbuoyancy so that they float near thesurface where light is available

When diatoms reproduce asexuallythe two halves of the box separateeach half then produces a new half tofit inside itself This means that half ofeach generationrsquos offspring are smallerthan the parent cells When diatoms

Biophoto AssociatesScience SourcePhoto Researchers

Asexual reproduction

Sexual reproduction

Zygote

Mitosis

Meiosis

Wall formationaround cell

Gametes

Fusion of gametes

Spermreleased

Figure 199Diatom shells have many shapes

Color-enhanced LM Magnification 450

512 PROTISTS

Figure 1910Diatoms reproduce asexually for several generations beforereproducing sexually Infer How is the size of the diatomrelated to its mode of reproduction

510-516 C19S2 BDOL-829900 8404 907 AM Page 512

are about one-quarter of their originalsize they reproduce sexually by pro-ducing gametes that fuse to formzygotes The zygote develops into afull-sized diatom which will divideasexually for a while You can see boththe asexual and sexual reproductiveprocesses of diatoms in Figure 1910

When diatoms die their shells sinkto the ocean floor The deposits ofdiatom shellsmdashsome of which are mil-lions of years oldmdashare dredged ormined processed and used as abrasivesin tooth and metal polishes or added topaint to give the sparkle that makespavement lines more visible at night

Dinoflagellates The spinning algae

Dinoflagellates (di nuh FLA juh layts)members of the phylum Dinoflagellatahave cell walls that are composed ofthick cellulose plates They come in agreat variety of shapes and stylesmdashsome even resemble helmets and oth-ers look like suits of armor

Dinoflagellates contain chloro-phyll carotenoids and red pigmentsThey have two flagella located ingrooves at right angles to each otherThe cell spins slowly as the flagellabeat A few species of dinoflagellateslive in freshwater but most aremarine and like diatoms are a major

component of phytoplankton Manyspecies live symbiotically with jelly-fishes mollusks and corals Somefree-living species are biolumines-cent which means that they emitlight

Several species of dinoflagellatesproduce toxins One toxin-producingdinoflagellate Pfiesteria piscicida thatsome North Carolina researchers dis-covered in 1988 has caused a numberof fish kills in the coastal waters fromDelaware to North Carolina

Another toxic species Gonyaulaxcatanella produces an extremelystrong nerve toxin that can be lethalIn the summer these organisms maybecome so numerous that the oceantakes on a reddish color as you can seein Figure 1911 This populationexplosion is called a red tide In somered tides there can be as many as 40 to 60 million dinoflagellates perliter of seawater

The toxins produced during a redtide may make humans ill During redtides the harvesting of shellfish isusually banned because shellfish feedon the toxic algae and the toxins con-centrate in their tissues People whoeat such shellfish risk being poisonedYou can learn more about the causesand effects of red tides in the Problem-Solving Lab on the next page

192 ALGAE PLANTLIKE PROTISTS 513(l)Peter JS FranksScripps Institution of Oceanography (r)David M PhillipsVisuals Unlimited

Figure 1911Red tides such as theone shown here (A)are often caused bydinoflagellates suchas this one calledGonyaulax (B)

AA

BBColor-enhanced SEM Magnification 12 000

510-516 C19S2 BDOL-829900 8404 907 AM Page 513

Red algaeRed algae members of the phylum

Rhodophyta are mostly multicellu-lar marine seaweeds The body of aseaweed as well as that of someplants and other organisms is calleda thallus and lacks roots stems orleaves Red algae use structurescalled holdfasts to attach to rocksThey grow in tropical waters oralong rocky coasts in cold water Youcan see a red alga in Figure 1912

In addition to chlorophyll redalgae also contain photosynthetic pig-ments called phycobilins These pig-ments absorb green violet and bluelightmdashthe only part of the light spec-trum that penetrates water belowdepths of 100 m Therefore the redalgae can live in deep water wheremost other seaweeds cannot thrive

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta Almost all of thesespecies live in salt water along rockycoasts in cool areas of the worldBrown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin which gives themtheir brown color Many species ofbrown algae have air bladders thatkeep their bodies floating near thesurface where light is available

The largest and most complex ofbrown algae are kelp In kelp thethallus is divided into the holdfast

514 PROTISTS(t)Joyce PhotoPhoto Researchers (b)R DeGourseyVisuals Unlimited

Figure 1912This Coralline alga is only one of about 4000species of red algae Some species are popularfoods in Japan and other countries

Recognize Cause and EffectWhy is the number of red tides increasingScientists have been awareof red tide poisoning ofbirds fishes and mammalssuch as whales and humans for years Could the rise in red tide poisoning be related to human activities

Solve the ProblemThe following events are associated with the appearance ofred tides

The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish such as clams and oysters

Within five weeks 14 humpback whales died on beaches inMassachusetts The whalesrsquo stomachs contained mackerelwith high levels of dinoflagellate toxin

Between 1976 and 1986 the human population of HongKong increased sixfold and its harbor had an eightfoldincrease in red tides Human waste water was commonlyemptied into the harbor

$ Studies show that red tides are increasing worldwide

An algal bloom occurs when algae using sunlight andabundant nutrients increase rapidly in number to hun-dreds of thousands of cells per milliliter of water

Thinking Critically1 Think Critically Which statement above provides evi-

dence that supports each of the following ideas Explaineach answera Dinoflagellate poisons flow through the food chainb Dinoflagellates are autotrophsc There is a correlation between human activities and

algae growth

2 Think Critically Based on the evidence presented abovecan you conclude that human activity is responsible for theincrease in red tides Why or why not

A sperm whalersquos carcass

510-516 C19S2 BDOL-829900 8404 908 AM Page 514

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

(l)D

ale

Sar

ver

Ani

mal

s A

nim

als

(c)

Nur

idsa

ny e

t P

eren

nou

Pho

to R

esea

rche

rs

(r)M

IW

alke

rP

hoto

Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

They use their flagella to movetoward light or food In the BioLabat the end of this chapter you canlearn more about how a euglenoidresponds to light

Diatoms The golden algaeDiatoms (DI uh tahmz) members

of the phylum Bacillariophyta are unicellular photosynthetic organismswith shells composed of silica Theymake up a large component of the

phytoplankton population in bothmarine and freshwater ecosystems

The delicate shells of diatoms likethose you see in Figure 199 mightremind you of boxes with lids Eachspecies has its own unique shape dec-orated with grooves and pores

Diatoms contain chlorophyll aswell as other pigments calledcarotenoids (ke RUH tuhn oydz) thatusually give them a golden-yellowcolor The food that diatoms make isstored as oils rather than starch Theseoils give fishes that feed on diatoms anoily taste They also give diatomsbuoyancy so that they float near thesurface where light is available

When diatoms reproduce asexuallythe two halves of the box separateeach half then produces a new half tofit inside itself This means that half ofeach generationrsquos offspring are smallerthan the parent cells When diatoms

Biophoto AssociatesScience SourcePhoto Researchers

Asexual reproduction

Sexual reproduction

Zygote

Mitosis

Meiosis

Wall formationaround cell

Gametes

Fusion of gametes

Spermreleased

Figure 199Diatom shells have many shapes

Color-enhanced LM Magnification 450

512 PROTISTS

Figure 1910Diatoms reproduce asexually for several generations beforereproducing sexually Infer How is the size of the diatomrelated to its mode of reproduction

510-516 C19S2 BDOL-829900 8404 907 AM Page 512

are about one-quarter of their originalsize they reproduce sexually by pro-ducing gametes that fuse to formzygotes The zygote develops into afull-sized diatom which will divideasexually for a while You can see boththe asexual and sexual reproductiveprocesses of diatoms in Figure 1910

When diatoms die their shells sinkto the ocean floor The deposits ofdiatom shellsmdashsome of which are mil-lions of years oldmdashare dredged ormined processed and used as abrasivesin tooth and metal polishes or added topaint to give the sparkle that makespavement lines more visible at night

Dinoflagellates The spinning algae

Dinoflagellates (di nuh FLA juh layts)members of the phylum Dinoflagellatahave cell walls that are composed ofthick cellulose plates They come in agreat variety of shapes and stylesmdashsome even resemble helmets and oth-ers look like suits of armor

Dinoflagellates contain chloro-phyll carotenoids and red pigmentsThey have two flagella located ingrooves at right angles to each otherThe cell spins slowly as the flagellabeat A few species of dinoflagellateslive in freshwater but most aremarine and like diatoms are a major

component of phytoplankton Manyspecies live symbiotically with jelly-fishes mollusks and corals Somefree-living species are biolumines-cent which means that they emitlight

Several species of dinoflagellatesproduce toxins One toxin-producingdinoflagellate Pfiesteria piscicida thatsome North Carolina researchers dis-covered in 1988 has caused a numberof fish kills in the coastal waters fromDelaware to North Carolina

Another toxic species Gonyaulaxcatanella produces an extremelystrong nerve toxin that can be lethalIn the summer these organisms maybecome so numerous that the oceantakes on a reddish color as you can seein Figure 1911 This populationexplosion is called a red tide In somered tides there can be as many as 40 to 60 million dinoflagellates perliter of seawater

The toxins produced during a redtide may make humans ill During redtides the harvesting of shellfish isusually banned because shellfish feedon the toxic algae and the toxins con-centrate in their tissues People whoeat such shellfish risk being poisonedYou can learn more about the causesand effects of red tides in the Problem-Solving Lab on the next page

192 ALGAE PLANTLIKE PROTISTS 513(l)Peter JS FranksScripps Institution of Oceanography (r)David M PhillipsVisuals Unlimited

Figure 1911Red tides such as theone shown here (A)are often caused bydinoflagellates suchas this one calledGonyaulax (B)

AA

BBColor-enhanced SEM Magnification 12 000

510-516 C19S2 BDOL-829900 8404 907 AM Page 513

Red algaeRed algae members of the phylum

Rhodophyta are mostly multicellu-lar marine seaweeds The body of aseaweed as well as that of someplants and other organisms is calleda thallus and lacks roots stems orleaves Red algae use structurescalled holdfasts to attach to rocksThey grow in tropical waters oralong rocky coasts in cold water Youcan see a red alga in Figure 1912

In addition to chlorophyll redalgae also contain photosynthetic pig-ments called phycobilins These pig-ments absorb green violet and bluelightmdashthe only part of the light spec-trum that penetrates water belowdepths of 100 m Therefore the redalgae can live in deep water wheremost other seaweeds cannot thrive

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta Almost all of thesespecies live in salt water along rockycoasts in cool areas of the worldBrown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin which gives themtheir brown color Many species ofbrown algae have air bladders thatkeep their bodies floating near thesurface where light is available

The largest and most complex ofbrown algae are kelp In kelp thethallus is divided into the holdfast

514 PROTISTS(t)Joyce PhotoPhoto Researchers (b)R DeGourseyVisuals Unlimited

Figure 1912This Coralline alga is only one of about 4000species of red algae Some species are popularfoods in Japan and other countries

Recognize Cause and EffectWhy is the number of red tides increasingScientists have been awareof red tide poisoning ofbirds fishes and mammalssuch as whales and humans for years Could the rise in red tide poisoning be related to human activities

Solve the ProblemThe following events are associated with the appearance ofred tides

The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish such as clams and oysters

Within five weeks 14 humpback whales died on beaches inMassachusetts The whalesrsquo stomachs contained mackerelwith high levels of dinoflagellate toxin

Between 1976 and 1986 the human population of HongKong increased sixfold and its harbor had an eightfoldincrease in red tides Human waste water was commonlyemptied into the harbor

$ Studies show that red tides are increasing worldwide

An algal bloom occurs when algae using sunlight andabundant nutrients increase rapidly in number to hun-dreds of thousands of cells per milliliter of water

Thinking Critically1 Think Critically Which statement above provides evi-

dence that supports each of the following ideas Explaineach answera Dinoflagellate poisons flow through the food chainb Dinoflagellates are autotrophsc There is a correlation between human activities and

algae growth

2 Think Critically Based on the evidence presented abovecan you conclude that human activity is responsible for theincrease in red tides Why or why not

A sperm whalersquos carcass

510-516 C19S2 BDOL-829900 8404 908 AM Page 514

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

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to R

esea

rche

rs

(r)M

IW

alke

rP

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Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

are about one-quarter of their originalsize they reproduce sexually by pro-ducing gametes that fuse to formzygotes The zygote develops into afull-sized diatom which will divideasexually for a while You can see boththe asexual and sexual reproductiveprocesses of diatoms in Figure 1910

When diatoms die their shells sinkto the ocean floor The deposits ofdiatom shellsmdashsome of which are mil-lions of years oldmdashare dredged ormined processed and used as abrasivesin tooth and metal polishes or added topaint to give the sparkle that makespavement lines more visible at night

Dinoflagellates The spinning algae

Dinoflagellates (di nuh FLA juh layts)members of the phylum Dinoflagellatahave cell walls that are composed ofthick cellulose plates They come in agreat variety of shapes and stylesmdashsome even resemble helmets and oth-ers look like suits of armor

Dinoflagellates contain chloro-phyll carotenoids and red pigmentsThey have two flagella located ingrooves at right angles to each otherThe cell spins slowly as the flagellabeat A few species of dinoflagellateslive in freshwater but most aremarine and like diatoms are a major

component of phytoplankton Manyspecies live symbiotically with jelly-fishes mollusks and corals Somefree-living species are biolumines-cent which means that they emitlight

Several species of dinoflagellatesproduce toxins One toxin-producingdinoflagellate Pfiesteria piscicida thatsome North Carolina researchers dis-covered in 1988 has caused a numberof fish kills in the coastal waters fromDelaware to North Carolina

Another toxic species Gonyaulaxcatanella produces an extremelystrong nerve toxin that can be lethalIn the summer these organisms maybecome so numerous that the oceantakes on a reddish color as you can seein Figure 1911 This populationexplosion is called a red tide In somered tides there can be as many as 40 to 60 million dinoflagellates perliter of seawater

The toxins produced during a redtide may make humans ill During redtides the harvesting of shellfish isusually banned because shellfish feedon the toxic algae and the toxins con-centrate in their tissues People whoeat such shellfish risk being poisonedYou can learn more about the causesand effects of red tides in the Problem-Solving Lab on the next page

192 ALGAE PLANTLIKE PROTISTS 513(l)Peter JS FranksScripps Institution of Oceanography (r)David M PhillipsVisuals Unlimited

Figure 1911Red tides such as theone shown here (A)are often caused bydinoflagellates suchas this one calledGonyaulax (B)

AA

BBColor-enhanced SEM Magnification 12 000

510-516 C19S2 BDOL-829900 8404 907 AM Page 513

Red algaeRed algae members of the phylum

Rhodophyta are mostly multicellu-lar marine seaweeds The body of aseaweed as well as that of someplants and other organisms is calleda thallus and lacks roots stems orleaves Red algae use structurescalled holdfasts to attach to rocksThey grow in tropical waters oralong rocky coasts in cold water Youcan see a red alga in Figure 1912

In addition to chlorophyll redalgae also contain photosynthetic pig-ments called phycobilins These pig-ments absorb green violet and bluelightmdashthe only part of the light spec-trum that penetrates water belowdepths of 100 m Therefore the redalgae can live in deep water wheremost other seaweeds cannot thrive

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta Almost all of thesespecies live in salt water along rockycoasts in cool areas of the worldBrown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin which gives themtheir brown color Many species ofbrown algae have air bladders thatkeep their bodies floating near thesurface where light is available

The largest and most complex ofbrown algae are kelp In kelp thethallus is divided into the holdfast

514 PROTISTS(t)Joyce PhotoPhoto Researchers (b)R DeGourseyVisuals Unlimited

Figure 1912This Coralline alga is only one of about 4000species of red algae Some species are popularfoods in Japan and other countries

Recognize Cause and EffectWhy is the number of red tides increasingScientists have been awareof red tide poisoning ofbirds fishes and mammalssuch as whales and humans for years Could the rise in red tide poisoning be related to human activities

Solve the ProblemThe following events are associated with the appearance ofred tides

The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish such as clams and oysters

Within five weeks 14 humpback whales died on beaches inMassachusetts The whalesrsquo stomachs contained mackerelwith high levels of dinoflagellate toxin

Between 1976 and 1986 the human population of HongKong increased sixfold and its harbor had an eightfoldincrease in red tides Human waste water was commonlyemptied into the harbor

$ Studies show that red tides are increasing worldwide

An algal bloom occurs when algae using sunlight andabundant nutrients increase rapidly in number to hun-dreds of thousands of cells per milliliter of water

Thinking Critically1 Think Critically Which statement above provides evi-

dence that supports each of the following ideas Explaineach answera Dinoflagellate poisons flow through the food chainb Dinoflagellates are autotrophsc There is a correlation between human activities and

algae growth

2 Think Critically Based on the evidence presented abovecan you conclude that human activity is responsible for theincrease in red tides Why or why not

A sperm whalersquos carcass

510-516 C19S2 BDOL-829900 8404 908 AM Page 514

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

(l)D

ale

Sar

ver

Ani

mal

s A

nim

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(c)

Nur

idsa

ny e

t P

eren

nou

Pho

to R

esea

rche

rs

(r)M

IW

alke

rP

hoto

Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

Red algaeRed algae members of the phylum

Rhodophyta are mostly multicellu-lar marine seaweeds The body of aseaweed as well as that of someplants and other organisms is calleda thallus and lacks roots stems orleaves Red algae use structurescalled holdfasts to attach to rocksThey grow in tropical waters oralong rocky coasts in cold water Youcan see a red alga in Figure 1912

In addition to chlorophyll redalgae also contain photosynthetic pig-ments called phycobilins These pig-ments absorb green violet and bluelightmdashthe only part of the light spec-trum that penetrates water belowdepths of 100 m Therefore the redalgae can live in deep water wheremost other seaweeds cannot thrive

Brown algaeAbout 1500 species of multicellular

brown algae make up the phylumPhaeophyta Almost all of thesespecies live in salt water along rockycoasts in cool areas of the worldBrown algae contain chlorophyll aswell as a yellowish-brown carotenoidcalled fucoxanthin which gives themtheir brown color Many species ofbrown algae have air bladders thatkeep their bodies floating near thesurface where light is available

The largest and most complex ofbrown algae are kelp In kelp thethallus is divided into the holdfast

514 PROTISTS(t)Joyce PhotoPhoto Researchers (b)R DeGourseyVisuals Unlimited

Figure 1912This Coralline alga is only one of about 4000species of red algae Some species are popularfoods in Japan and other countries

Recognize Cause and EffectWhy is the number of red tides increasingScientists have been awareof red tide poisoning ofbirds fishes and mammalssuch as whales and humans for years Could the rise in red tide poisoning be related to human activities

Solve the ProblemThe following events are associated with the appearance ofred tides

The dinoflagellate toxin that causes illness and sometimesdeath in humans accumulates in the body tissues of shell-fish such as clams and oysters

Within five weeks 14 humpback whales died on beaches inMassachusetts The whalesrsquo stomachs contained mackerelwith high levels of dinoflagellate toxin

Between 1976 and 1986 the human population of HongKong increased sixfold and its harbor had an eightfoldincrease in red tides Human waste water was commonlyemptied into the harbor

$ Studies show that red tides are increasing worldwide

An algal bloom occurs when algae using sunlight andabundant nutrients increase rapidly in number to hun-dreds of thousands of cells per milliliter of water

Thinking Critically1 Think Critically Which statement above provides evi-

dence that supports each of the following ideas Explaineach answera Dinoflagellate poisons flow through the food chainb Dinoflagellates are autotrophsc There is a correlation between human activities and

algae growth

2 Think Critically Based on the evidence presented abovecan you conclude that human activity is responsible for theincrease in red tides Why or why not

A sperm whalersquos carcass

510-516 C19S2 BDOL-829900 8404 908 AM Page 514

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

(l)D

ale

Sar

ver

Ani

mal

s A

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(c)

Nur

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ny e

t P

eren

nou

Pho

to R

esea

rche

rs

(r)M

IW

alke

rP

hoto

Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

stipe and blade The holdfasts anchorkelp to rocks or the sea bottom Somegiant kelp may grow up to 60 meterslong In some parts of the world such as off the California coast giant kelps form dense underwater forestsThese kelp forests are rich ecosystemsand provide a wide variety of marineorganisms with their habitats

Green algaeGreen algae make up the phylum

Chlorophyta The green algae arethe most diverse algae with morethan 7000 species The major pig-ment in green algae is chlorophyllbut some species also have yellowpigments that give them a yellow-green color Most species of greenalgae live in freshwater but some livein the oceans in moist soil on treetrunks in snow and even in the fur ofslothsmdashlarge slow-moving mammalsthat live in the tropical rain forestcanopy

Green algae can be unicellularcolonial or multicellular in organiza-tion As you can see in Figure 1913

Chlamydomonas is a unicellular andflagellated green alga Spirogyra is amulticellular species that forms slen-der filaments Volvox is a green algathat can form a colony a group of cellsthat lives together in close association

A Volvox colony is composed ofhundreds or thousands of flagel-lated cells arranged in a single layerforming a hollow ball-shaped struc-ture The cells are connected bystrands of cytoplasm and the fla-gella of individual cells face out-ward The flagella can beat in acoordinated fashion spinning thecolony through the water Smallballs of daughter colonies forminside the large sphere The wall ofthe large colony will eventuallybreak open and release the daughtercolonies

Green algae can reproduce bothasexually and sexually For exampleSpirogyra can reproduce asexuallythrough fragmentation During fragmentation an individual breaksup into pieces and each piece growsinto a new individual

515

(l)D

ale

Sar

ver

Ani

mal

s A

nim

als

(c)

Nur

idsa

ny e

t P

eren

nou

Pho

to R

esea

rche

rs

(r)M

IW

alke

rP

hoto

Res

earc

hers

Figure 1913Chlamydomonas is a unicellular species of green algae (A) whileSpirogyra is a multicellular form (B)The wall of a Volvox colony containshundreds of cells (C) The smaller ballsinside the sphere are daughtercolonies

Color-enhanced LMMagnification 15

Color-enhanced LM Magnification unavailable

Magnification unavailable

AA

BB

CC

PhysicalScience

Connection

Interaction oflight and waterWhen light wavesinteract withmatter some wavesare reflected someare absorbed andsome might passthrough Waterabsorbs red lightmore than 150times more stronglythan blue light Asa result belowabout 10 m depthin the oceanalmost allwavelengths in thered part of thevisible spectrumhave beenabsorbed

510-516 C19S2 BDOL-829900 8404 725 PM Page 515

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

Green algae and some other typesof algae have a complex life cycleThis life cycle consists of individualsthat alternate between producingspores and producing gametes

Alternation ofGenerations

The life cycles of some of the algaeand all plants have a pattern calledalternation of generations An organism that has this pattern alter-nates between existing as a haploidand a diploid organism creating twodifferent generations

The haploid form of the organismis called the gametophyte because itproduces gametes The gametes fuseto form a zygote from which thediploid form of the organism whichis called the sporophyte developsCertain cells in the sporophyteundergo meiosis Eventually thesecells become haploid spores that candevelop into a new gametophyteLook at Figure 1914 to see the life cycle of Ulva a multicellulargreen alga

List and describethe different types of algae

Understanding Main Ideas1 In what ways are algae important to all living

things on Earth2 Give examples that show why the green algae are

considered to be the most diverse of the six phylaof algae

3 In what ways do the sporophyte and gametophytegenerations of an alga such as Ulva differ fromeach other

4 Why are phycobilins an important pigment in red algae

Thinking Critically5 Use a table to list the reasons why euglenoids

should be classified as protozoans and also asalgae

6 Make and Use Tables Construct a table listing the different phyla of algae Indicate whether they have one or more cells their color and give an example of each For more help refer to Makeand Use Tables in the Skill Handbook

SKILL REVIEWSKILL REVIEW

516 PROTISTSAndrew J MartinezPhoto Researchers

Malegametophyte

Gametophyte (n)

Gametophyte (n) Femalegametophyte

Gamete Gamete

Spore

Spore

Fertilization

MeiosisZygote

2n 2n 2n n

n

Sporophyte (2n)Figure 1914In the life cycle of the sealettuce (Ulva) the genera-tions alternate betweenhaploid (gametophyte)and diploid (sporophyte) Both fungi and plants alsoalternate generations

ncbdolglencoecomself_check_quiz

510-516 C19S2 BDOL-829900 8604 1059 AM Page 516

193SECTION PREVIEWObjectivesContrast the cellular dif-ferences and life cycles ofthe two types of slimemoldsDiscuss the economicimportance of the downymildews and water molds

Review Vocabularyheterotroph organisms

that cannot make theirown food and must feedon other organisms forenergy and nutrients (p 47)

New Vocabularyplasmodium

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 517

Slime Molds Water Moldsand Downy Mildews

David M DennisTom Stack amp Associates

Why arenrsquot theyfungiFinding the Main Idea Untilrecently many of the fungus-like protists were classified asfungi Slime molds watermolds and downy mildews canoften look and act like fungiand many cause diseases inplants the way fungi doDescribe As you read the sectionwrite a description or draw yourperception of how the funguslikeprotists appear physically and howthey live Compare and contrastthese descriptions with how you would describe fungi

A plasmodial slime

What are funguslike protistsCertain groups of protists the slime molds the water molds and the

downy mildews consist of organisms with some funguslike featuresRecall that fungi are heterotrophic organisms that decompose organicmaterials to obtain energy Like fungi the funguslike protists decomposeorganic materials

There are three phyla of funguslike protists Two of these phyla con-sist of slime molds Slime molds have characteristics of both protozoansand fungi and are classified by the way they reproduce Water molds anddowny mildews make up the third phylum of funguslike protistsAlthough funguslike protists are not an everyday part of human livessome disease-causing species damage vital crops

Slime MoldsMany slime molds are beautifully colored ranging from brilliant yel-

low or orange to rich blue violet and jet black They live in cool moistshady places where they grow on damp organic matter such as rottingleaves or decaying tree stumps and logs

Objective 402 Analyze the processes by which organisms repre-sentative of the following groups accomplish essential life functions including Unicellular protistshellip

North Carolina Objectives

517-527 C19S3 BDOL-829900 8404 908 AM Page 517

BDOL-193

null

17805235

There are two major types of slimemoldsmdashplasmodial slime molds andcellular slime molds The plasmodialslime molds belong to the phylumMyxomycota and the cellular slimemolds make up another grouping thephylum Acrasiomycota

Slime molds are animal-like duringmuch of their life cycle moving aboutand engulfing food in a way similar tothat of amoebas However like fungislime molds make spores to repro-duce Use the Problem-Solving Lab onthis page to learn more about the lifecycle of a slime mold

Plasmodial slime moldsPlasmodial slime molds get their

name from the fact that they form aplasmodium (plaz MOH dee um) amass of cytoplasm that contains manydiploid nuclei but no cell walls ormembranes This slimy multinucle-ate mass like the one you see inFigure 1915 is the feeding stage ofthe organism The plasmodiumcreeps like an amoeba over the sur-faces of decaying logs or leaves Somequicker plasmodiums move at the rateof about 25 centimeters per hourengulfing microscopic organisms anddigesting them in food vacuoles Atthat rate a plasmodium would crossyour textbook page in eight hours

A plasmodium may reach morethan a meter in diameter and con-tain thousands of nuclei Howeverwhen moisture and food become

518 PROTISTS

PredictWhat changes occur during a slime moldrsquos life cyclePlasmodial slime molds undergo a number of different stagesduring their life cycle The most visible stage is the plasmodialstage where the organism looks like a slimy mass of materialThe plasmodium changes into a reproductive stage that ismicroscopic and therefore less visible

Solve the ProblemExamine the life cycle of a plasmodial slime mold The struc-tures below the dashed line are diploid in chromosome num-ber Based on the diagram and your understanding of mitosisand meiosis answer the questions below

Thinking Critically1 Explain What cell process mitosis or meiosis takes place

between F and G Explain why Between A and B Explain why

2 Explain What letter best shows fertilization occurringMotile spores An embryo Explain why in each case

3 Observe During which stage does the slime mold feedExplain

Patrick W GracePhoto Researchers

Figure 1915The moving feeding form of a plas-modial slime mold is a multinucleate blobof cytoplasm Infer How does a plas-modial slime mold acquire food

AB

C

D

EF

G

AB

C

D

EF

G

Spores

Reproductivestages

Growth stages

517-527 C19S3 BDOL-829900 8404 908 AM Page 518

Cellsgather

The mass compactsand forms asluglike structure

The sluglikestructuremigrates

Spore-filledcapsule on astalk forms

SporesAmoeba-likecells released

Cells feedgrow and divide

Multicellularamoeboidlikemass forms

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 519

plasmodium fromthe Greek wordplassein meaningldquomoldrdquo and theLatin word odiosusmeaning ldquohate-fulrdquo One form of a slime mold is aplasmodium

CabiscoVisuals Unlimited

Figure 1916The reproductive cycle of acellular slime mold is com-plex (A) Single cells clumpand form a structure thatresembles a small gardenslug (B) Eventually theclump forms a stalkedreproductive structure thatproduces spores (C)

scarce in its surroundings a plas-modium transforms itself into manyseparate stalked spore-producingstructures Meiosis takes placewithin these structures and produceshaploid spores which the wind disperses A spore germinates intoeither a flagellated or an amoeboidcell or a gamete that can fuse withanother cell to form a zygote Thediploid zygote grows into a newplasmodium

Cellular slime moldsUnlike plasmodial slime molds

cellular slime molds spend part oftheir life cycle as an independentamoeboid cell that feeds grows anddivides by cell division as shown inFigure 1916 When food becomes

scarce these independent cells joinwith hundreds or thousands of othersto reproduce Such an aggregation ofamoeboid cells resembles a plasmod-ium However this mass of cells ismulticellularmdashmade up of many indi-vidual amoeboid cells each with a dis-tinct cell membrane Cellular slimemolds are haploid during their entirelife cycle

Compare and contrast the two types of slimemolds

Color-enhanced LM Magnification 50

AA

BB

CC

Color-enhanced LM Magnification 50

517-527 C19S3 BDOL-829900 8404 909 AM Page 519

Water Molds and Downy Mildews

Water molds and downy mildewsare both members of the phylumOomycota Most members of thislarge and diverse group of funguslikeprotists live in water or moist placesAs shown in Figure 1917 some feedon dead organisms and others areplant parasites

Most water molds appear as fuzzywhite growths on decaying matterThey resemble some fungi becausethey grow as a mass of threads over afood source digest it and then absorbthe nutrients But at some point intheir life cycle water molds produceflagellated reproductive cellsmdashsome-thing that fungi never do This is whywater molds are classified as protistsrather than fungi

One economically important mem-ber of the phylum Oomycota is adowny mildew that causes disease inmany plants A downy mildew called

Phytophthora infestans affected the livesof the people of Ireland by destroyingtheir major food crop of potatoes Thefamine that followed caused a massimmigration to America

Origin of ProtistsHow are the many different kinds

of protists related to each other and tofungi plants and animals You cansee the relationships of protists toeach other in Figure 1918

Although taxonomists are nowcomparing the RNA and DNA ofthese groups there is little conclusiveevidence to indicate whether ancientprotists were the evolutionary ances-tors of fungi plants and animals orwhether protists emerged as evolu-tionary lines that were separateBecause of evidence from compara-tive RNA sequences in modern greenalgae and plants many biologistsagree that ancient green algae wereprobably ancestral to modern plants

520 PROTISTS(l)Holt Studios InternationalNigel CattlinPhoto Researchers (r)James W RichardsonVisuals Unlimited

Figure 1917Water molds and downy mildews live inmoist places and cause both plant and animaldiseases

The downy mildewPhytophthora infestans is killingthis potato plant

A

The water mold growing onthis insect is decomposing theinsectrsquos tissues and absorbingthe nutrients

B

517-527 C19S3 BDOL-829900 8404 909 AM Page 520

Understanding Main Ideas1 Describe the protozoan and funguslike character-

istics of slime molds2 Why might some biologists refer to plasmodial

slime molds as acellular slime molds (Hint Look in the Skill Handbook for the origins of scientific terms)

3 How could a water mold eventually kill a fish4 How does a plasmodial slime mold differ from a

cellular slime mold

Thinking Critically5 In what kinds of environments would you expect

to find slime molds Explain your answer

6 Observe and Infer If you know that a plasmod-ium consists of many nuclei within a single cellwhat can you infer about the process that formedthe plasmodium For more help refer to Observeand Infer in the Skill Handbook

SKILL REVIEWSKILL REVIEW

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 521

Species numbers are approximate and subject to change pending discoveries or extinctions

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 1918This fanlike diagram shows therelationships of the differentprotist phyla

PROTISTS

ncbdolglencoecomself_check_quiz

517-527 C19S3 BDOL-829900 8404 730 PM Page 521

There are two major types of slimemoldsmdashplasmodial slime molds andcellular slime molds The plasmodialslime molds belong to the phylumMyxomycota and the cellular slimemolds make up another grouping thephylum Acrasiomycota

Slime molds are animal-like duringmuch of their life cycle moving aboutand engulfing food in a way similar tothat of amoebas However like fungislime molds make spores to repro-duce Use the Problem-Solving Lab onthis page to learn more about the lifecycle of a slime mold

Plasmodial slime moldsPlasmodial slime molds get their

name from the fact that they form aplasmodium (plaz MOH dee um) amass of cytoplasm that contains manydiploid nuclei but no cell walls ormembranes This slimy multinucle-ate mass like the one you see inFigure 1915 is the feeding stage ofthe organism The plasmodiumcreeps like an amoeba over the sur-faces of decaying logs or leaves Somequicker plasmodiums move at the rateof about 25 centimeters per hourengulfing microscopic organisms anddigesting them in food vacuoles Atthat rate a plasmodium would crossyour textbook page in eight hours

A plasmodium may reach morethan a meter in diameter and con-tain thousands of nuclei Howeverwhen moisture and food become

518 PROTISTS

PredictWhat changes occur during a slime moldrsquos life cyclePlasmodial slime molds undergo a number of different stagesduring their life cycle The most visible stage is the plasmodialstage where the organism looks like a slimy mass of materialThe plasmodium changes into a reproductive stage that ismicroscopic and therefore less visible

Solve the ProblemExamine the life cycle of a plasmodial slime mold The struc-tures below the dashed line are diploid in chromosome num-ber Based on the diagram and your understanding of mitosisand meiosis answer the questions below

Thinking Critically1 Explain What cell process mitosis or meiosis takes place

between F and G Explain why Between A and B Explain why

2 Explain What letter best shows fertilization occurringMotile spores An embryo Explain why in each case

3 Observe During which stage does the slime mold feedExplain

Patrick W GracePhoto Researchers

Figure 1915The moving feeding form of a plas-modial slime mold is a multinucleate blobof cytoplasm Infer How does a plas-modial slime mold acquire food

AB

C

D

EF

G

AB

C

D

EF

G

Spores

Reproductivestages

Growth stages

517-527 C19S3 BDOL-829900 8404 908 AM Page 518

Cellsgather

The mass compactsand forms asluglike structure

The sluglikestructuremigrates

Spore-filledcapsule on astalk forms

SporesAmoeba-likecells released

Cells feedgrow and divide

Multicellularamoeboidlikemass forms

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 519

plasmodium fromthe Greek wordplassein meaningldquomoldrdquo and theLatin word odiosusmeaning ldquohate-fulrdquo One form of a slime mold is aplasmodium

CabiscoVisuals Unlimited

Figure 1916The reproductive cycle of acellular slime mold is com-plex (A) Single cells clumpand form a structure thatresembles a small gardenslug (B) Eventually theclump forms a stalkedreproductive structure thatproduces spores (C)

scarce in its surroundings a plas-modium transforms itself into manyseparate stalked spore-producingstructures Meiosis takes placewithin these structures and produceshaploid spores which the wind disperses A spore germinates intoeither a flagellated or an amoeboidcell or a gamete that can fuse withanother cell to form a zygote Thediploid zygote grows into a newplasmodium

Cellular slime moldsUnlike plasmodial slime molds

cellular slime molds spend part oftheir life cycle as an independentamoeboid cell that feeds grows anddivides by cell division as shown inFigure 1916 When food becomes

scarce these independent cells joinwith hundreds or thousands of othersto reproduce Such an aggregation ofamoeboid cells resembles a plasmod-ium However this mass of cells ismulticellularmdashmade up of many indi-vidual amoeboid cells each with a dis-tinct cell membrane Cellular slimemolds are haploid during their entirelife cycle

Compare and contrast the two types of slimemolds

Color-enhanced LM Magnification 50

AA

BB

CC

Color-enhanced LM Magnification 50

517-527 C19S3 BDOL-829900 8404 909 AM Page 519

Water Molds and Downy Mildews

Water molds and downy mildewsare both members of the phylumOomycota Most members of thislarge and diverse group of funguslikeprotists live in water or moist placesAs shown in Figure 1917 some feedon dead organisms and others areplant parasites

Most water molds appear as fuzzywhite growths on decaying matterThey resemble some fungi becausethey grow as a mass of threads over afood source digest it and then absorbthe nutrients But at some point intheir life cycle water molds produceflagellated reproductive cellsmdashsome-thing that fungi never do This is whywater molds are classified as protistsrather than fungi

One economically important mem-ber of the phylum Oomycota is adowny mildew that causes disease inmany plants A downy mildew called

Phytophthora infestans affected the livesof the people of Ireland by destroyingtheir major food crop of potatoes Thefamine that followed caused a massimmigration to America

Origin of ProtistsHow are the many different kinds

of protists related to each other and tofungi plants and animals You cansee the relationships of protists toeach other in Figure 1918

Although taxonomists are nowcomparing the RNA and DNA ofthese groups there is little conclusiveevidence to indicate whether ancientprotists were the evolutionary ances-tors of fungi plants and animals orwhether protists emerged as evolu-tionary lines that were separateBecause of evidence from compara-tive RNA sequences in modern greenalgae and plants many biologistsagree that ancient green algae wereprobably ancestral to modern plants

520 PROTISTS(l)Holt Studios InternationalNigel CattlinPhoto Researchers (r)James W RichardsonVisuals Unlimited

Figure 1917Water molds and downy mildews live inmoist places and cause both plant and animaldiseases

The downy mildewPhytophthora infestans is killingthis potato plant

A

The water mold growing onthis insect is decomposing theinsectrsquos tissues and absorbingthe nutrients

B

517-527 C19S3 BDOL-829900 8404 909 AM Page 520

Understanding Main Ideas1 Describe the protozoan and funguslike character-

istics of slime molds2 Why might some biologists refer to plasmodial

slime molds as acellular slime molds (Hint Look in the Skill Handbook for the origins of scientific terms)

3 How could a water mold eventually kill a fish4 How does a plasmodial slime mold differ from a

cellular slime mold

Thinking Critically5 In what kinds of environments would you expect

to find slime molds Explain your answer

6 Observe and Infer If you know that a plasmod-ium consists of many nuclei within a single cellwhat can you infer about the process that formedthe plasmodium For more help refer to Observeand Infer in the Skill Handbook

SKILL REVIEWSKILL REVIEW

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 521

Species numbers are approximate and subject to change pending discoveries or extinctions

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 1918This fanlike diagram shows therelationships of the differentprotist phyla

PROTISTS

ncbdolglencoecomself_check_quiz

517-527 C19S3 BDOL-829900 8404 730 PM Page 521

Cellsgather

The mass compactsand forms asluglike structure

The sluglikestructuremigrates

Spore-filledcapsule on astalk forms

SporesAmoeba-likecells released

Cells feedgrow and divide

Multicellularamoeboidlikemass forms

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 519

plasmodium fromthe Greek wordplassein meaningldquomoldrdquo and theLatin word odiosusmeaning ldquohate-fulrdquo One form of a slime mold is aplasmodium

CabiscoVisuals Unlimited

Figure 1916The reproductive cycle of acellular slime mold is com-plex (A) Single cells clumpand form a structure thatresembles a small gardenslug (B) Eventually theclump forms a stalkedreproductive structure thatproduces spores (C)

scarce in its surroundings a plas-modium transforms itself into manyseparate stalked spore-producingstructures Meiosis takes placewithin these structures and produceshaploid spores which the wind disperses A spore germinates intoeither a flagellated or an amoeboidcell or a gamete that can fuse withanother cell to form a zygote Thediploid zygote grows into a newplasmodium

Cellular slime moldsUnlike plasmodial slime molds

cellular slime molds spend part oftheir life cycle as an independentamoeboid cell that feeds grows anddivides by cell division as shown inFigure 1916 When food becomes

scarce these independent cells joinwith hundreds or thousands of othersto reproduce Such an aggregation ofamoeboid cells resembles a plasmod-ium However this mass of cells ismulticellularmdashmade up of many indi-vidual amoeboid cells each with a dis-tinct cell membrane Cellular slimemolds are haploid during their entirelife cycle

Compare and contrast the two types of slimemolds

Color-enhanced LM Magnification 50

AA

BB

CC

Color-enhanced LM Magnification 50

517-527 C19S3 BDOL-829900 8404 909 AM Page 519

Water Molds and Downy Mildews

Water molds and downy mildewsare both members of the phylumOomycota Most members of thislarge and diverse group of funguslikeprotists live in water or moist placesAs shown in Figure 1917 some feedon dead organisms and others areplant parasites

Most water molds appear as fuzzywhite growths on decaying matterThey resemble some fungi becausethey grow as a mass of threads over afood source digest it and then absorbthe nutrients But at some point intheir life cycle water molds produceflagellated reproductive cellsmdashsome-thing that fungi never do This is whywater molds are classified as protistsrather than fungi

One economically important mem-ber of the phylum Oomycota is adowny mildew that causes disease inmany plants A downy mildew called

Phytophthora infestans affected the livesof the people of Ireland by destroyingtheir major food crop of potatoes Thefamine that followed caused a massimmigration to America

Origin of ProtistsHow are the many different kinds

of protists related to each other and tofungi plants and animals You cansee the relationships of protists toeach other in Figure 1918

Although taxonomists are nowcomparing the RNA and DNA ofthese groups there is little conclusiveevidence to indicate whether ancientprotists were the evolutionary ances-tors of fungi plants and animals orwhether protists emerged as evolu-tionary lines that were separateBecause of evidence from compara-tive RNA sequences in modern greenalgae and plants many biologistsagree that ancient green algae wereprobably ancestral to modern plants

520 PROTISTS(l)Holt Studios InternationalNigel CattlinPhoto Researchers (r)James W RichardsonVisuals Unlimited

Figure 1917Water molds and downy mildews live inmoist places and cause both plant and animaldiseases

The downy mildewPhytophthora infestans is killingthis potato plant

A

The water mold growing onthis insect is decomposing theinsectrsquos tissues and absorbingthe nutrients

B

517-527 C19S3 BDOL-829900 8404 909 AM Page 520

Understanding Main Ideas1 Describe the protozoan and funguslike character-

istics of slime molds2 Why might some biologists refer to plasmodial

slime molds as acellular slime molds (Hint Look in the Skill Handbook for the origins of scientific terms)

3 How could a water mold eventually kill a fish4 How does a plasmodial slime mold differ from a

cellular slime mold

Thinking Critically5 In what kinds of environments would you expect

to find slime molds Explain your answer

6 Observe and Infer If you know that a plasmod-ium consists of many nuclei within a single cellwhat can you infer about the process that formedthe plasmodium For more help refer to Observeand Infer in the Skill Handbook

SKILL REVIEWSKILL REVIEW

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 521

Species numbers are approximate and subject to change pending discoveries or extinctions

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 1918This fanlike diagram shows therelationships of the differentprotist phyla

PROTISTS

ncbdolglencoecomself_check_quiz

517-527 C19S3 BDOL-829900 8404 730 PM Page 521

Water Molds and Downy Mildews

Water molds and downy mildewsare both members of the phylumOomycota Most members of thislarge and diverse group of funguslikeprotists live in water or moist placesAs shown in Figure 1917 some feedon dead organisms and others areplant parasites

Most water molds appear as fuzzywhite growths on decaying matterThey resemble some fungi becausethey grow as a mass of threads over afood source digest it and then absorbthe nutrients But at some point intheir life cycle water molds produceflagellated reproductive cellsmdashsome-thing that fungi never do This is whywater molds are classified as protistsrather than fungi

One economically important mem-ber of the phylum Oomycota is adowny mildew that causes disease inmany plants A downy mildew called

Phytophthora infestans affected the livesof the people of Ireland by destroyingtheir major food crop of potatoes Thefamine that followed caused a massimmigration to America

Origin of ProtistsHow are the many different kinds

of protists related to each other and tofungi plants and animals You cansee the relationships of protists toeach other in Figure 1918

Although taxonomists are nowcomparing the RNA and DNA ofthese groups there is little conclusiveevidence to indicate whether ancientprotists were the evolutionary ances-tors of fungi plants and animals orwhether protists emerged as evolu-tionary lines that were separateBecause of evidence from compara-tive RNA sequences in modern greenalgae and plants many biologistsagree that ancient green algae wereprobably ancestral to modern plants

520 PROTISTS(l)Holt Studios InternationalNigel CattlinPhoto Researchers (r)James W RichardsonVisuals Unlimited

Figure 1917Water molds and downy mildews live inmoist places and cause both plant and animaldiseases

The downy mildewPhytophthora infestans is killingthis potato plant

A

The water mold growing onthis insect is decomposing theinsectrsquos tissues and absorbingthe nutrients

B

517-527 C19S3 BDOL-829900 8404 909 AM Page 520

Understanding Main Ideas1 Describe the protozoan and funguslike character-

istics of slime molds2 Why might some biologists refer to plasmodial

slime molds as acellular slime molds (Hint Look in the Skill Handbook for the origins of scientific terms)

3 How could a water mold eventually kill a fish4 How does a plasmodial slime mold differ from a

cellular slime mold

Thinking Critically5 In what kinds of environments would you expect

to find slime molds Explain your answer

6 Observe and Infer If you know that a plasmod-ium consists of many nuclei within a single cellwhat can you infer about the process that formedthe plasmodium For more help refer to Observeand Infer in the Skill Handbook

SKILL REVIEWSKILL REVIEW

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 521

Species numbers are approximate and subject to change pending discoveries or extinctions

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 1918This fanlike diagram shows therelationships of the differentprotist phyla

PROTISTS

ncbdolglencoecomself_check_quiz

517-527 C19S3 BDOL-829900 8404 730 PM Page 521

Understanding Main Ideas1 Describe the protozoan and funguslike character-

istics of slime molds2 Why might some biologists refer to plasmodial

slime molds as acellular slime molds (Hint Look in the Skill Handbook for the origins of scientific terms)

3 How could a water mold eventually kill a fish4 How does a plasmodial slime mold differ from a

cellular slime mold

Thinking Critically5 In what kinds of environments would you expect

to find slime molds Explain your answer

6 Observe and Infer If you know that a plasmod-ium consists of many nuclei within a single cellwhat can you infer about the process that formedthe plasmodium For more help refer to Observeand Infer in the Skill Handbook

SKILL REVIEWSKILL REVIEW

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 521

Species numbers are approximate and subject to change pending discoveries or extinctions

Oomycotes175 species

Myxomycotes450 species

Phaeophytes1500 species

Bacillariophytes10 000 species

Chlorophytes7000 species

Rhizopods11 500 species

Flagellates2500 species

Ciliates8000 species

Sporozoans3900 species

Animals

Plants

Fungi

Euglenophytes800 species

Dinoflagellates1000 species

Rhodophytes4000 species

Acrasiomycotes65 species

Figure 1918This fanlike diagram shows therelationships of the differentprotist phyla

PROTISTS

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Before YouBegin

Members of the genusParamecium are ciliatedprotozoansmdashunicellularheterotrophic protists thatmove around in search ofsmall food particlesEuglena are unicellularalgaemdashautotrophic pro-tists that usually containnumerous chloroplasts Inthis BioLab yoursquoll investi-gate how these two pro-tists respond to light intheir environment

How do Paramecium andEuglena respond to light

ProblemDo both Paramecium and Euglena respond to light and dothey respond in different ways Decide on one type of protistactivity that would constitute a response to light

HypothesesDecide on one hypothesis that you will test Your hypothesismight be that Paramecium will not respond to light andEuglena will respond or that Paramecium will move awayfrom light and Euglena will move toward light

ObjectivesIn this BioLab you will Prepare slides of Paramecium and Euglena cultures and

observe swimming patterns in the two organisms Compare how these two different protists respond to light

Possible MaterialsEuglena culture coverslipsParamecium culture metric rulermicroscope index cardsmicroscope slides scissorsdropper toothpicksmethyl cellulose

Safety PrecautionsCAUTION Always wear goggles in the lab Use caution whenworking with a microscope glass slides and coverslipsWash your hands with soap and water immediately afterworking with protists and chemicals

Skill HandbookIf you need help with this lab refer to the Skill Handbook

1 Decide on an experimental procedure that you can useto test your hypothesis

2 Record your procedure step-by-step and list the mate-rials you will be using

3 Design a data table in which to record your observationsand results

PLAN THE EXPERIMENTPLAN THE EXPERIMENT

PREPARATIONPREPARATION

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1 Compare and Contrast Compare and con-trast all the responses of the Paramecium andEuglena to both light and darkness Whatexplanations can you suggest for theirbehavior

2 Make Inferences Can you use your resultsto suggest what sort of responses to light and darkness you might observe using other heterotrophic or autotrophic protists

3 Did your data support yourhypothesis Why or why notERROR ANALYSIS

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 523

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Project You may want to extend this experi-ment by varying the shapes or relative sizesof light and dark areas or by varying thebrightness or color of the light In each casemake hypotheses before you begin Keepyour data in a notebook and draw up atable of your results at the end of your investigations

Web Links To find out more about protists visit ncbdolglencoecomprotists

Check the PlanDiscuss all the following points with other group membersto determine your final procedure1 What variables will you have to measure What will be

your control2 What will be the shape of the light-controlled area(s)

on your microscope slide3 Decide who will prepare materials make observations

and record data4 Make sure your teacher has approved your experimen-

tal plan before you proceed further5 To mount drops of Paramecium culture and Euglena

culture on microscope slides use a toothpick to place a small ring of methyl cellulose on a clean microscopeslide Place a drop of Paramecium or Euglena culturewithin this ring Place a coverslip over the ring and cul-ture The thick consistency of methyl cellulose shouldslow down the organisms for easy observation

6 Make preliminary observations of swimming Parameciumand Euglena Then think again about the observationtimes that you have planned Maybe you will decide toallow more or less time between your observations

7 Carry out your experiment8 Work with your teacher to make

wise choices concerning disposal of materials CLEANUP AND DISPOSAL

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1 Compare and Contrast Compare and con-trast all the responses of the Paramecium andEuglena to both light and darkness Whatexplanations can you suggest for theirbehavior

2 Make Inferences Can you use your resultsto suggest what sort of responses to light and darkness you might observe using other heterotrophic or autotrophic protists

3 Did your data support yourhypothesis Why or why notERROR ANALYSIS

193 SLIME MOLDS WATER MOLDS AND DOWNY MILDEWS 523

ANALYZE AND CONCLUDEANALYZE AND CONCLUDE

Project You may want to extend this experi-ment by varying the shapes or relative sizesof light and dark areas or by varying thebrightness or color of the light In each casemake hypotheses before you begin Keepyour data in a notebook and draw up atable of your results at the end of your investigations

Web Links To find out more about protists visit ncbdolglencoecomprotists

Check the PlanDiscuss all the following points with other group membersto determine your final procedure1 What variables will you have to measure What will be

your control2 What will be the shape of the light-controlled area(s)

on your microscope slide3 Decide who will prepare materials make observations

and record data4 Make sure your teacher has approved your experimen-

tal plan before you proceed further5 To mount drops of Paramecium culture and Euglena

culture on microscope slides use a toothpick to place a small ring of methyl cellulose on a clean microscopeslide Place a drop of Paramecium or Euglena culturewithin this ring Place a coverslip over the ring and cul-ture The thick consistency of methyl cellulose shouldslow down the organisms for easy observation

6 Make preliminary observations of swimming Parameciumand Euglena Then think again about the observationtimes that you have planned Maybe you will decide toallow more or less time between your observations

7 Carry out your experiment8 Work with your teacher to make

wise choices concerning disposal of materials CLEANUP AND DISPOSAL

517-527 C19S3 BDOL-829900 8404 732 PM Page 523

The Diversity ofDiatoms

W hat do most swimming pool filters fineporcelain metal polishes and some

insecticides have in common All contain theremains of millions of single-celled algae knownas diatoms In addition to their many industrialuses diatoms can be used to solve crimes andmay someday aid in fighting cancer

Diatoms are unicellular algae enclosed inhard perforated shells made of silica Each halfof a diatomrsquos shell resembles the top or bottomof a miniature circular box When diatoms dietheir shells fall to the bottom of the water bodyin which they lived Over time the shellsundergo physical changes to becomediatomitemdasha very porous highly absorbentpowdery rock with many uses

Some industrial uses for diatoms As a resultof the structure and composition of diatomsrsquoshells diatomite is extremely absorbent and essen-tially chemically inert Thus diatomite is a com-mon component in many industrial absorbentsused to clean up chemical spills Diatomite is alsoa critical ingredient in some types of pet litter andpotting soils and can also be added to fertilizersand pesticides to prevent caking

Another important use of diatomite is as aninsecticide When added to stored grains therazor-sharp diatom shells in diatomite can piercethe cuticles of insects that may be in the silocausing them to dehydrate and die Diatomite isnontoxic to most other animals and thus doesnot have to be removed before the grain is used

Diatomite can also be cut into blocks andbricks and used for thermal and acoustic insula-tion It can be ground up to produce filters thatare used in swimming pools and in the process-ing of some beverages Ground diatomite is alsoused as filler in many kinds of paints plasticscements pesticides and pharmaceuticals and isa major component of most fine porcelain andmany mild abrasives

Diatoms and forensics In addition to theirmany industrial uses diatoms may be used inforensics Forensic biology is a science that usesbiological evidence in court to support or dis-prove guilt Diatoms can be collected from theshoes or clothing of persons involved or sus-pected in a crime in order to identify the crimi-nal(s) andor the scene of the crime Diatomscan also pinpoint the time of year during whicha crime occurred

DiatomsmdashPossible cancer drugs In naturecertain species of diatoms produce substancesthat kill the developing embryos of copepods andsea urchins In the lab these same substanceshave been shown to prevent some human cancercells from dividing Such studies suggest that adrug made from certain types of diatoms mightbe able to slow down or even prevent the abnor-mal reproduction of some kinds of cancer cells

Draw Conclusions Suppose that police find adead body at the edge of a pond in early MayExamination of the body showed drowning as thecause of death The time of death was estimated tohave been about two weeks prior to the discoveryof the body Very few diatoms were found in thewater that filled the personrsquos lungs Did this persondrown in the pond Explain

To find out more about diatoms visit

Color-enhanced SEM Magnification 160

524 PROTISTS

Diatoms

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Section 193

Section 191

Section 192

Vocabularyalga (p 503)asexual reproduction

(p 505)ciliate (p 506)flagellate (p 506)protozoan (p 503)pseudopodia (p 504)spore (p 508)sporozoan (p 508)

The World of Protists

Vocabularyalternation of

generations (p 516)colony (p 515)fragmentation (p 515)gametophyte (p 516)sporophyte (p 516)thallus (p 514)

Vocabularyplasmodium (p 518)

Algae PlantlikeProtists

Slime MoldsWater Moldsand DownyMildews

STUDY GUIDESTUDY GUIDE

CHAPTER 19 ASSESSMENT 525

(t)B

ill B

eatty

Vis

uals

Unl

imite

d (

c)B

ioph

oto

Ass

ocia

tes

Sci

ence

Sou

rce

Pho

to R

esea

rche

rs

(b)C

abis

coV

isua

ls U

nlim

ited

To help you review protists use the Organizational StudyFold on page 510

Key Concepts Kingdom Protista is a diverse group of

living things that contains animal-likeplantlike and funguslike organisms

Some protists are heterotrophs some areautotrophs and some get their nutrients by decomposing organic matter

Amoebas move by extending pseudopodiaThe flagellates use one or more flagella tomove The beating of cilia produces cilliatemovement Sporozoans live as parasitesand produce spores

Key Concepts Algae are unicellular and multicellular

photosynthetic autotrophs Unicellularspecies include the euglenoids diatomsdinoflagellates and some green algaeMulticellular species include red brownand green algae

Green red and brown algae often calledseaweeds have complex life cycles thatalternate between haploid and diploid generations

Key Concepts Slime molds water molds and downy

mildews are funguslike protists thatdecompose organic material to obtainnutrients

Plasmodial and cellular slime molds change in appearance and behavior before produc-ing reproductive structures

Color-enhanced LM Magnification 50

Color-enhanced LM Magnification 450

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Review the Chapter 19 vocabulary words listed inthe Study Guide on page 525 Match the wordswith the definitions below

1 cytoplasm-containing extensions of proto-zoan plasma membranes

2 haploid form of an alga that producesgametes

3 mass of cytoplasm that contains manydiploid nuclei but no separating cell walls or membranes

4 diploid form of an alga that contains cellsthat undergo meiosis

5 a group of cells that lives together in closeassociation

6 Which organisms may cause red tidesA dinoflagellates C green algaeB euglenoids D red algae

7 Which organelle in protists is able to elimi-nate excess waterA anal pore C contractile vacuoleB mouth D gullet

8 Producers in aquatic food chains include________A algae C slime moldsB protozoans D amoebas

9 Protists are classified on the basis of their________A nutritionB method of locomotionC reproductive abilitiesD size

10 Euglenoids are unique algae because of their________A flagellaB ciliaC silica wallsD heterotrophic nature

11 Which of the following is not a protist

A C

B D

12 The algae that can survive in the deepestwater are the ________A brown algae C diatomsB red algae D green algae

13 The largest and most complex of brownalgae are the ________A kelp C sea lettuceB Chlamydomonas D Spirogyra

14 Which of the following are protected by armored platesA kelp C dinoflagellatesB fire algae D diatoms

15 Unlike bacteria all protists are ________A prokaryotes C nonlivingB eukaryotes D both prokaryotic

and eukaryotic16 What type of structure

does the protist shown to the right use to moveA ciliumB gulletC pellicleD flagellum

17 Infer In which ecosystem would a plas-modial slime mold transform itself intospore-producing structures more frequentlya rainy forest in the Pacific Northwest or adry oak forest in the Midwest Explain

18 Infer Give three examples of organelles thathelp protists maintain homeostasis

19 Explain To fight malaria wetlands were oftendrained How did this cut down on malariacases

526 CHAPTER 19 ASSESSMENT ncbdolglencoecomchapter_test

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Constructed ResponseGrid InRecord your answer on your answer document

26 Open Ended Describe how protozoa eliminate excess water from their internal environments

20 Concept Map Complete the concept mapwith the terms amoebas sporozoans flagel-lates protozoans ciliates

21 More than twomillion people worldwide die from malariainfections transmitted by just four species ofthe sporozoan Plasmodium Recent attemptsto decrease deaths caused by malaria areyielding promising new methods of preven-tion Visit to discoverthe potential of this research What are thehosts of the malaria parasite Discuss withyour classmates how the number of peoplewho die from malaria could be reduced

REAL WORLD BIOCHALLENGE

Animal-like protists are called

1

2 3 4

that usecilia tomove

that usepseudopods

to move

that useflagella to

move

that producespores and

are parasites

5

whichinclude

whichinclude

whichinclude

whichinclude

CHAPTER 19 ASSESSMENT 527

ncbdolglencoecom

Multiple ChoiceUse the graph to answer questions 22 and 23

A group of high school students studied unicellu-lar algae in the middle of a pond For two daysthey measured the number of cells in the water at various depths They produced the followinggraph based on their data

22 At what time were the highest concentra-tions of diatoms at the surfaceA midnight C 3 AMB noon D 6 PM

23 At what time were the highest concentrationsof diatoms about a meter below the surfaceA midnight C 3 AMB noon D 6 PM

Study the diagram and answer questions 24 and 25

24 Which of the following represents fertilizationA A C CB B D D

25 Cells in stage C have ________ chromosomesA n C a diploid number ofB 2n D no

Spores

Reproductivestages

AB

C

D

Loca

tio

n o

f h

igh

est

con

cen

trat

ion

of

dia

tom

s

Times in hours

100 cm

50 cm

Surface

12 AM 12 PM 12 AM 12 PM 12 AM

Locations of Diatoms

102

402

102

The assessed North Carolina objective appears next to the question

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