campbell - napa valley

CAMPBELL

BIOLOGYReece • Urry • Cain • Wasserman • Minorsky • Jackson

© 2014 Pearson Education, Inc.

TENTH

EDITION

28Protists

Lecture Presentation by

Nicole Tunbridge and

Kathleen Fitzpatrick


Living Small

Even a low-power microscope can reveal a great

variety of organisms in a drop of pond water

Protist is the informal name of the group of mostly

unicellular eukaryotes

Advances in eukaryotic systematics have caused

the classification of protists to change significantly

Protists constitute a polyphyletic group, and

Protista is no longer valid as a kingdom


Figure 28.1

1 μm


Figure 28.1a

Trumpet-shaped protists (Stentor coeruleus)


Concept 28.1: Most eukaryotes are single-celled organisms

Protists are eukaryotes

Eukaryotic cells have organelles and are more

complex than prokaryotic cells

It is important to bear in mind that

The organisms in most eukaryotic lineages are

protists, and

Most protists are unicellular


Structural and Functional Diversity in Protists

Protists exhibit more structural and functional

diversity than any other group of eukaryotes

Though most protists are unicellular, there are

some colonial and multicellular species

Single-celled protists can be very complex, as all

biological functions are carried out by organelles in

each individual cell


Protists, the most nutritionally diverse of all

eukaryotes, include

Photoautotrophs, which contain chloroplasts

Heterotrophs, which absorb organic molecules or

ingest larger food particles

Mixotrophs, which combine photosynthesis and

heterotrophic nutrition


Some protists reproduce asexually, while others

reproduce sexually, or by the sexual processes of

meiosis and fertilization


Four Supergroups of Eukaryotes

It is no longer thought that amitochondriates

(lacking mitochondria) are the oldest lineage of

eukaryotes

Many have been shown to have mitochondria and

have been reclassified

Our understanding of the relationships among

protist groups continues to change rapidly

One hypothesis divides all eukaryotes (including

protists) into four supergroups


Figure 28.2

Diplomonads

100 μm

100 μm

50 μm

50 μm20 μm

5 μm■ Excavata ■ Archaeplastida

■ “SAR” Clade ■ Unikonta

Parabasalids

Euglenozoans

Excavata

Diatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“S

AR

” c

lad

e

Stra

men

op

iles

Alv

eo

late

sR

hiz

aria

ns

Gre

en

alg

ae

Red algae

Chlorophytes

Charophytes

Land plants

Arc

ha

ep

lastid

a

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Un

iko

nta

Choanoflagellates

Animals

Am

oe

bo

zo

an

sO

pis

tho

ko

nts


Figure 28.2aDiplomonads

Parabasalids

Euglenozoans

Excav

ata

Diatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“S

AR

” c

lad

e

Stra

men

op

iles

Alv

eo

late

sR

hiz

aria

ns

Gre

en

alg

ae

Red algae

Chlorophytes

Charophytes

Land plants

Arc

haep

lastid

a

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Un

iko

nta

Choanoflagellates

Animals

Am

oeb

ozo

an

sO

pis

tho

ko

nts


Figure 28.2aa

Diplomonads

Parabasalids

Euglenozoans

Exca

vata

Diatoms

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

“S

AR

” c

lad

e

Stra

men

op

iles

Alv

eo

late

sR

hiz

aria

ns


Figure 28.2ab

Gre

en

alg

ae

Red algae

Chlorophytes

Charophytes

Land plants

Arc

haep

lastid

a

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Un

iko

nta

Choanoflagellates

Animals

Am

oe

bo

zo

an

sO

pis

tho

ko

nts


Figure 28.2b

100 μm

100 μm

50 μm

50 μm

20 μm

5 μm■ Excavata ■ Archaeplastida■ “SAR” Clade

■ Unikonta


Figure 28.2ba

Giardia intestinalis, a diplomonad parasite

5 μm■Excavata


Figure 28.2bb

Diatom diversity

50 μm■ “SAR” Clade


Figure 28.2bc

Globigerina, a rhizarian in the SAR clade

100 μm

■ “SAR” Clade


Figure 28.2bca

Globigerina, a rhizarian in the SAR clade

100 μm

■ “SAR” Clade


Figure 28.2bcb

■ “SAR” Clade


Figure 28.2bd

Volvox, a colonial freshwater green alga

50 μm20 μm

■Archaeplastida


Figure 28.2bda

Volvox, a colonial freshwater green alga

50 μm■Archaeplastida


Figure 28.2bdb

■Archaeplastida

20 μm


Figure 28.2be

A unikont amoeba

100 μm

■Unikonta


Endosymbiosis in Eukaryotic Evolution

There is now considerable evidence that much

protist diversity has its origins in endosymbiosis

Endosymbiosis is a relationship between two

species in which one organism lives inside the cell

or cells of the other organism (the host)


Mitochondria and plastids are derived from

prokaryotes that were engulfed by the ancestors of

early eukaryotic cells

Mitochondria evolved once by endosymbiosis of

an alpha proteobacterium

Plastids evolved later by endosymbiosis of a

photosynthetic cyanobacterium

The ancestral host cell may have been an

archaean or a “protoeukaryote,” from a lineage

related to, but diverged from archaeal ancestors


Plastid Evolution: A Closer Look

Mitochondria arose first through descent from a

bacterium that was engulfed by a cell from an

archaeal lineage

The plastid lineage evolved later from a

photosynthetic cyanobacterium that was engulfed

by a heterotrophic eukaryote

The plastid-bearing lineage of protists evolved into

photosynthetic protists, red and green algae


Figure 28.3

Cyanobacterium

Nucleus

Membranes

are represented

as dark lines

in the cell.

1 2 3

Heterotrophic

eukaryoteOne of thesemembraneswas lost inred andgreen algaldescendants.

Red alga

Green alga

Primary

endosymbiosis

Secondary

endosymbiosis

Dinoflagellates

Plastid

Stramenopiles

Plastid

Euglenids

Chlorarachniophytes

Secondary

endosymbiosis

Secondary

endosymbiosis


Figure 28.3a

Cyanobacterium

Nucleus

Membranes

are represented

as dark lines

in the cell.

1 2 3

Heterotrophic

eukaryoteOne of thesemembraneswas lost inred andgreen algaldescendants.

Primary endosymbiosis

Red alga

Green alga


Figure 28.3b

Red alga

Secondary endosymbiosis

Dinoflagellates

Plastid

Stramenopiles


Figure 28.3c

Green

alga

Plastid

Euglenids

Chlorarachniophytes

Secondary endosymbiosis


Video: Volvox Colony


Video: Volvox Daughter


Video: Volvox Flagella


Video: Volvox Inversion 1


Video: Volvox Inversion 2


Video: Volvox Sperm and Female


Video: Amoeba


Video: Amoeba Pseudopodia


Like cyanobacteria, plastids of red algae and

green algae have two membranes

Transport proteins in the membranes of red and

green algae are homologous to those found in

cyanobacteria


On several occasions during eukaryotic evolution,

red and green algae underwent secondary

endosymbiosis, in which they were ingested by a

heterotrophic eukaryote

For example, chlorarachniophytes likely evolved

when a heterotrophic eukaryote engulfed a green

alga

The engulfed cell contains a vestigial nucleus called

a nucleomorph


Figure 28.4

Inner plastid

membrane

Nucleomorph

Outer plastid

membrane

Nuclear pore-like gap


Figure 28.4a

Inner plastid

membrane

Nucleomorph

Outer plastid

membrane

Nuclear pore-like gap


Concept 28.2: Excavates include protists with modified mitochondria and protists with unique flagella

The clade Excavata is characterized by its

cytoskeleton

Some members have an “excavated” feeding

groove

This group includes the diplomonads,

parabasalids, and euglenozoans


Figure 28.UN02

Diplomonads

Parabasalids

Euglenozoans

SAR clade

Archaeplastida

Unikonta

Exc

av

ata


Diplomonads and Parabasalids

These two groups lack plastids, have modified

mitochondria, and most live in anaerobic

environments

Diplomonads

Have reduced mitochondria called mitosomes

Derive energy from anaerobic biochemical

pathways

Have two equal-sized nuclei and multiple flagella

Are often parasites, for example, Giardia intestinalis


Parabasalids

Have reduced mitochondria called

hydrogenosomes that generate some energy

anaerobically

Include Trichomonas vaginalis, the pathogen that

causes yeast infections in human females


Figure 28.5

Flagella

Undulating

membrane 5 μm


Euglenozoans

Euglenozoa is a diverse clade that includes

predatory heterotrophs, photosynthetic autotrophs,

mixotrophs, and parasites

The main feature distinguishing them as a clade is

a spiral or crystalline rod inside their flagella

This clade includes the kinetoplastids and

euglenids


Figure 28.6

Flagella

8 μm

0.2 μm

Crystalline rod

(cross section)

Ring of microtubules

(cross section)


Figure 28.6a

0.2 μm

Crystalline rod

(cross section)

Ring of microtubules

(cross section)


Kinetoplastids

Kinetoplastids have a single mitochondrion with

an organized mass of DNA called a kinetoplast

Free-living species are consumers of prokaryotes

in freshwater, marine, and moist terrestrial

ecosystems


Some species are parasitic

Kinetoplastids in the genus Trypanosoma cause

sleeping sickness in humans

Another pathogenic trypanosome causes Chagas’

disease


Figure 28.7

9 μm


Trypanosomes evade immune responses by

switching surface proteins

A cell produces millions of copies of a single

protein

The new generation produces millions of copies of

a different protein

These frequent changes prevent the host from

developing immunity


Euglenids

Euglenids have one or two flagella that emerge

from a pocket at one end of the cell

Some species can be both autotrophic and

heterotrophic


Figure 28.8

Long flagellum

5 μm

Eyespot

Short flagellum

Contractile vacuole

Nucleus

Chloroplast

Plasma

membrane

Light

detector

PellicleEuglena (LM)


Figure 28.8a

Long

flagellum

5 μm

Eyespot

Contractile

vacuole

Nucleus

Chloroplast

Plasma

membraneEuglena (LM)


Video: Euglena


Video: Euglena Motion


Concept 28.3: The “SAR” clade is a highly diverse group of protists defined by DNA similarities

The “SAR” clade is a diverse monophyletic

supergroup named for the first letters of its three

major clades stramenopiles, alveolates, and

rhizarians

This group is one of the most controversial of the

four supergroups


Figure 28.UN03

Diatoms

SA

R c

lad

e

Archaeplastida

Unikonta

Excavata

Golden algae

Brown algae

Dinoflagellates

Apicomplexans

Ciliates

Forams

Cercozoans

Radiolarians

Stramenopiles

Alveolates

Rhizarians


Stramenopiles

The stramenopiles clade includes some of the

most important photosynthetic organisms on Earth

Most have a “hairy” flagellum paired with a

“smooth” flagellum

Stramenopiles include diatoms, golden algae, and

brown algae


Figure 28.9

Smooth

flagellum

5 μm

Hairy

flagellum


Diatoms

Diatoms are unicellular algae with a unique two-

part, glass-like wall of silicon dioxide


Figure 28.10

40 μ

m


Video: Diatoms Moving


Video: Various Diatoms


Diatoms are a major component of phytoplankton

and are highly diverse

Fossilized diatom walls compose much of the

sediments known as diatomaceous earth

After a diatom population has bloomed, many

dead individuals fall to the ocean floor

undecomposed


This removes carbon dioxide from the atmosphere

and “pumps” it to the ocean floor

Some scientists advocate fertilizing the ocean to

promote diatom blooms and the movement of

carbon dioxide from the atmosphere to the ocean

floor


Golden Algae

Golden algae are named for their color, which

results from their yellow and brown carotenoids

The cells of golden algae are typically

biflagellated, with both flagella near one end

All golden algae are photosynthetic, and some are

mixotrophs

Most are unicellular, but some are colonial


Figure 28.11

Flagellum

25 μm

Outer container

Living cell


Brown Algae

Brown algae are the largest and most complex

algae

All are multicellular, and most are marine

Brown algae include many species commonly

called “seaweeds”


Giant seaweeds called kelps live in deep parts of

the ocean

Brown algal seaweeds have plantlike structures:

the rootlike holdfast, which anchors the alga, and

a stemlike stipe, which supports the leaflike

blades

Similarities between algae and plants are

examples of analogous structures


Figure 28.12

Blade

Stipe

Holdfast


Alternation of Generations

A variety of life cycles have evolved among the

multicellular algae

The most complex life cycles include an

alternation of generations, the alternation of

multicellular haploid and diploid forms

Heteromorphic generations are structurally

different, while isomorphic generations look

similar


The diploid sporophyte produces haploid

flagellated spores called zoospores

The zoospores develop into haploid male and

female gametophytes, which produce gametes

Fertilization of gamates results in a diploid zygote,

which grows into a new sporophyte


Figure 28.13

Haploid (n)

Diploid (2n)

Sporangia

MEIOSIS

Sporophyte

(2n) Zoospore

Gameto-

phytes

(n)

Female

Male

Sperm

Egg

Zygote

(2n)Mature female

gametophyte

(n)

Developing

sporophyte

FERTILIZATION

10 cm


Figure 28.13a-1

Haploid (n)

Diploid (2n)

Sporangia

MEIOSIS

Sporophyte

(2n) Zoospore

Gameto-

phytes

(n)

Female

Male

Sperm

Egg


Figure 28.13a-2

Haploid (n)

Diploid (2n)

Sporangia

MEIOSIS

Sporophyte

(2n) Zoospore

Gameto-

phytes

(n)

Female

Male

Sperm

Egg

Zygote

(2n)Mature female

gametophyte

(n)

Developing

sporophyte

FERTILIZATION


Figure 28.13b

10 cm


Alveolates

Members of the clade Alveolata have membrane-

enclosed sacs (alveoli) just under the plasma

membrane

The alveolates include

Dinoflagellates

Apicomplexans

Ciliates


Figure 28.14

Flagellum Alveoli

Alveolate

0.2

μm


Figure 28.14a

Flagellum Alveoli

0.2

μm


Dinoflagellates

Dinoflagellates have two flagella and each cell is

reinforced by cellulose plates

They are abundant components of both marine

and freshwater phytoplankton

They are a diverse group of aquatic phototrophs,

mixotrophs, and heterotrophs

Toxic “red tides” are caused by dinoflagellate

blooms


Figure 28.15

Flagella

3 μm

(a) Dinoflagellate

flagella

(b) Red tide in the Gulf

of Carpentaria in

northern Australia


Figure 28.15a

Flagella

3 μm(a) Dinoflagellate flagella


Figure 28.15b

(b) Red tide in the Gulf of

Carpentaria in northern

Australia


Video: Dinoflagellate


Apicomplexans

Apicomplexans are parasites of animals, and

some cause serious human diseases

They spread through their host as infectious cells

called sporozoites

One end, the apex, contains a complex of

organelles specialized for penetrating host cells

and tissues

Most have sexual and asexual stages that require

two or more different host species for completion


The apicomplexan Plasmodium is the parasite that

causes malaria

Plasmodium requires both mosquitoes and

humans to complete its life cycle

Approximately 900,000 people die each year from

malaria

Efforts are ongoing to develop vaccines that target

this pathogen


Figure 28.16

Merozoite

0.5 μm

Apex

Red blood

cell

Haploid (n)

Diploid (2n)

Sporozoites

(n)

Inside mosquito Inside human

Liver

Liver

cell

Red

blood

cells

Merozoite

(n)

Game-

tocytes

(n)

Gametes

Zygote

(2n)

Oocyst

MEIOSIS

FERTILIZATION


Figure 28.16a-1

Haploid (n)

Diploid (2n)


Liver

Liver

cell

Red

blood

cells

Merozoite

(n)

Game-

tocytes

(n)

Gametes

Zygote

(2n)

FERTILIZATION


Figure 28.16a-2

Haploid (n)

Diploid (2n)

Sporozoites

(n)


Liver

Liver

cell

Red

blood

cells

Merozoite

(n)

Game-

tocytes

(n)

Gametes

Zygote

(2n)

Oocyst

MEIOSIS

FERTILIZATION


Figure 28.16b

Merozoite

0.5 μm

Apex

Red blood

cell


Ciliates

Ciliates, a large varied group of protists, are

named for their use of cilia to move and feed

They have large macronuclei and small

micronuclei

Genetic variation results from conjugation, in

which two individuals exchange haploid

micronuclei

Conjugation is a sexual process, and is separate

from reproduction, which generally occurs by

binary fission


Figure 28.17

Contractile

vacuole

50 μm Cilia

Micronucleus

Macronucleus

Oral grooveCell mouth

Food vacuoles

(a) Feeding, waste removal, and water balance.

Compatible

mates

(b) Conjugation and reproduction.

MEIOSIS

The originalmacronucleusdisintegrates.

Diploid

micronucleus

Haploid

micronucleus

MICRO-

NUCLEAR

FUSION

Conjugation

Asexual

reproduction

Diploid

micronucleus


Figure 28.17a

Contractile

vacuole

50 μmCilia

Micronucleus

Macronucleus

Oral groove

Cell mouth

Food

vacuoles

(a) Feeding, waste removal, and water balance.


Figure 28.17b-1

Compatible

mates


MEIOSIS

Haploid

micronucleus

Conjugation

Asexual

reproduction

Diploid

micronucleus


Figure 28.17b-2

Compatible

mates


MEIOSIS

The original macro-nucleus disintegrates.

Haploid

micronucleus

MICRO-

NUCLEAR

FUSION

Conjugation

Asexual

reproduction

Diploid

micronucleus

Diploid

micronucleus


Figure 28.17c

50 μm


Video: Paramecium Vacuole


Video: Paramecium Cilia


Video: Vorticella Cilia


Video: Vorticella Detail


Video: Vorticella Habitat


Rhizarians

Many species in the rhizarian clade are amoebas

Amoebas are protists that move and feed by

pseudopodia, extensions of the cell surface

Rhizarian amoebas differ from amoebas in other

clades by having threadlike pseudopodia

Rhizarians include radiolarians, forams, and

cercozoans


Radiolarians

Marine protists called radiolarians have delicate,

symmetrical internal skeletons that are usually

made of silica

Radiolarians use their pseudopodia to engulf

microorganisms through phagocytosis

The pseudopodia of radiolarians radiate from the

central body


Figure 28.18

Pseudopodia

200 μm


Forams

Foraminiferans, or forams, are named for

porous, generally multichambered shells, called

tests

Pseudopodia extend through the pores in the test

Many forams have endosymbiotic algae


Foram tests in marine sediments form an

extensive fossil record

Researchers can use measures of the magnesium

content in fossilized forams to estimate changes in

ocean temperature over time


Figure 28.19


Cercozoans

Cercozoans include most amoeboid and

flagellated protists with threadlike pseudopodia

They are common in marine, freshwater, and soil

ecosystems

Most are heterotrophs, including parasites and

predators


Paulinella chromatophora is an autotroph with a

unique photosynthetic structure called a

chromoatophore

This structure evolved from a different

cyanobacterium than the plastids of other

photosynthetic eukaryotes


Figure 28.20

Chromatophore

5 μm


Concept 28.4: Red algae and green algae are the closest relatives of land plants

Plastids arose when a heterotrophic protist

acquired a cyanobacterial endosymbiont

The photosynthetic descendants of this ancient

protist evolved into red algae and green algae

Land plants are descended from the green algae

Archaeplastida is the supergroup that includes

red algae, green algae, and land plants


Figure 28.UN04

Chlorophytes

SAR cladeA

rch

ae

pla

stid

a

Unikonta

Excavata

Charophytes

Red algae

Green algae

Land plants


Red Algae

Red algae are reddish in color due to an

accessory pigment called phycoerythrin, which

masks the green of chlorophyll

The color varies from greenish-red in shallow

water to dark red or almost black in deep water

Red algae are usually multicellular; the largest are

seaweeds

Red algae are the most abundant large algae in

coastal waters of the tropics


Figure 28.21

▼ Nori

8 mm

20 cm

◀ Dulse (Palmaria palmata)

► Bonnemaisonia

hamifera


Figure 28.21a

8 mmBonnemaisonia

hamifera


Figure 28.21b

20 cm

Dulse (Palmaria palmata)


Figure 28.21c

Nori


Figure 28.21d

Nori


Green Algae

Green algae are named for their grass-green

chloroplasts

Plants are descended from the green algae

Green algae are a paraphyletic group

The two main groups are the charophytes and the

chlorophytes

Charophytes are most closely related to land

plants


Most chlorophytes live in fresh water, although

many are marine

Other chlorophytes live in damp soil, as symbionts

in lichens, or in environments exposed to intense

visible and ultraviolet radiation


Larger size and greater complexity evolved in

chlorophytes by

1. The formation of colonies from individual cells

2. The formation of true multicellular bodies by cell

division and differentiation (e.g., Ulva)

3. The repeated division of nuclei with no

cytoplasmic division (e.g., Caulerpa)


Figure 28.22

(a) Ulva, or sea lettuce

(b) Caulerpa, an

intertidal

chlorophyte

2 cm


Figure 28.22a

(a) Ulva, or sea lettuce

2 cm


Figure 28.22b

(b) Caulerpa, an intertidal chlorophyte


Most chlorophytes have complex life cycles with

both sexual and asexual reproductive stages


Figure 28.23

Haploid (n)

1 μm

Diploid (2n)

Flagella

Cell wall

Nucleus

Cross

section

of cup-

shaped

chloroplast(TEM)

Zoospore

ASEXUAL

REPRODUCTION

Gamete

(n)

Mature cell

(n)

Zygote

(2n)

FERTILIZATION

MEIOSIS

+

+

+

+

−

−

−

−

SEXUAL

REPRODUCTION


Figure 28.23a-1

Haploid (n)

Diploid (2n)

Zoospore

ASEXUAL

REPRODUCTION

Mature cell

(n)


Figure 28.23a-2

Haploid (n)

Diploid (2n)

Zoospore

ASEXUAL

REPRODUCTION

Gamete

(n)

Mature cell

(n)

Zygote

(2n)

FERTILIZATION

MEIOSIS

+

+

+

+

−

−

−

−

SEXUAL

REPRODUCTION


Figure 28.23b

1 μmFlagella

Cell wall

Nucleus

Cross

section

of cup-

shaped

chloroplast(TEM)


Video: Chlamydomonas


Concept 28.5: Unikonts include protists that are closely related to fungi and animals

The supergroup Unikonta includes animals, fungi,

and some protists

This group includes two clades: the amoebozoans

and the opisthokonts (animals, fungi, and related

protists)

The root of the eukaryotic tree remains

controversial

It is unclear whether unikonts separated from

other eukaryotes relatively early or late


Figure 28.UN05

SAR clade

Archaeplastida

Un

iko

nta

Excavata

Slime molds

Tubulinids

Entamoebas

Nucleariids

Fungi

Choanoflagellates

Animals


Figure 28.24Results

Choanoflagellates

Animals

Fungi

Amoebozoans

Unikonta

Common

ancestor

of all

eukaryotesDiplomonads

EuglenozoansExcavata

Stramenopiles

Alveolates

Rhizarians

SAR clade

Red algae

Green algae

Plants

Archaeplastida

DHFR-TS

gene

fusion


Amoebozoans

Amoebozoans are amoeba that have lobe- or

tube-shaped, rather than threadlike, pseudopodia

They include slime molds, tubulinids, and

entamoebas


Slime Molds

Slime molds, or mycetozoans, were once thought

to be fungi

DNA sequence analyses indicate that the

resemblance between slime molds and fungi is a

result of convergent evolution

Slime molds include two lineages, plasmodial

slime molds and cellular slime molds


Plasmodial Slime Molds

Many species of plasmodial slime molds are

brightly pigmented, usually yellow or orange


Figure 28.25

Haploid (n)

4 cm

Diploid (2n)

Zygote

(2n)

Feeding

plasmodiumFERTILIZATION

Mature

plasmodium

(preparing to fruit)

Young

sporangium

Mature

sporangium

Stalk

MEIOSIS

Spores (n)

Germinating

spore

Amoeboid

cells (n)Flagellated

cells

(n)


Figure 28.25a-1

Haploid (n)

Diploid (2n)

Feeding

plasmodium

Mature

plasmodium


Young

sporangium

Mature

sporangium

Stalk


Figure 28.25a-2

Haploid (n)

Diploid (2n)

Feeding

plasmodium

Mature

plasmodium


Young

sporangium

Mature

sporangium

Stalk

MEIOSIS

Spores (n)

Germinating

spore

Amoeboid


cells

(n)


Figure 28.25a-3

Haploid (n)

Diploid (2n)

Zygote

(2n)

Feeding

plasmodiumFERTILIZATION

Mature

plasmodium


Young

sporangium

Mature

sporangium

Stalk

MEIOSIS

Spores (n)

Germinating

spore

Amoeboid


cells

(n)


Figure 28.25b

4 cm


At one point in the life cycle, plasmodial slime

molds form a mass called a plasmodium (not to be

confused with malarial Plasmodium)

The plasmodium is not multicellular

It is undivided by plasma membranes and contains

many diploid nuclei

It extends pseudopodia through decomposing

material, engulfing food by phagocytosis


Cellular Slime Molds

Cellular slime molds form multicellular aggregates

in which cells are separated by their membranes

Cells feed individually but can aggregate to

migrate and form a fruiting body

Dictyostelium discoideum is an experimental

model for studying the evolution of multicellularity


Figure 28.26-1

Haploid (n)

200 μm

600 μm

Diploid (2n)

Spores

(n)

Emerging

amoeba (n)

Solitary amoebas

(feeding stage)

(n)

Fruiting

bodies

(n)

ASEXUAL

REPRODUCTION

Aggregated

amoebas

Migrating

aggregate


Figure 28.26-2

Haploid (n)

200 μm

600 μm

Diploid (2n)

Spores

(n)

Emerging

amoeba (n)

Solitary amoebas

(feeding stage)

(n)

Fruiting

bodies

(n)

ASEXUAL

REPRODUCTION

Aggregated

amoebas

Migrating

aggregate

SEXUAL

REPRO-

DUCTION

Zygote

(2n)

Amoebas

(n)

FERTILIZATION

MEIOSIS


Figure 28.26a

200 μm


Figure 28.26b

600 μm


Tubulinids

Tubulinids are a diverse group of amoebozoans

with lobe- or tube-shaped pseudopodia

They are common unicellular protists in soil as

well as freshwater and marine environments

Most tubulinids are heterotrophic and actively seek

and consume bacteria and other protists


Entamoebas

Entamoebas are parasites of vertebrates and

some invertebrates

Entamoeba histolytica causes amebic dysentery,

the third-leading cause of human death due to

eukaryotic parasites


Opisthokonts

Opisthokonts include animals, fungi, and several

groups of protists


Concept 28.6: Protists play key roles in ecological communities

Protists are found in diverse aquatic and moist

terrestrial environments

Protists play two key roles in their habitats: that of

symbiont and that of producer


Symbiotic Protists

Some protist symbionts benefit their hosts

Dinoflagellates nourish coral polyps that build reefs

Wood-digesting protists inhabit the gut of termites


Figure 28.27

10 μ

m


Some protists are parasitic

Plasmodium causes malaria

Pfiesteria shumwayae is a dinoflagellate that

causes fish kills

Phytophthora ramorum causes sudden oak death

P. infestans causes potato late blight, which

contributed to the Irish famine of the 19th century


Figure 28.28


Photosynthetic Protists

Many protists are important producers that obtain

energy from the sun

In aquatic environments, photosynthetic protists

and prokaryotes are the main producers

In aquatic environments, photosynthetic protists

are limited by nutrients

These populations can explode when limiting

nutrients are added


Figure 28.29

Other

consumers

Herbivorous

plankton Carnivorous

plankton

Prokaryotic

producers

Protistan

producers


Biomass of photosynthetic protists has declined as

sea surface temperature has increased

Growth of phytoplankton communities relies on

nutrients delivered from the ocean bottom through

the process of upwelling

Warm surface water acts as a barrier to upwelling


If sea surface temperature continues to warm due

to global warming, this could have large effects on

Marine ecosystems

Fishery yields

The global carbon cycle


Figure 28.30

NP

NI

SIS SP

SA

EA

NAAEP

−2.50 −1.25 0.00 1.25 2.50

Sea-surface temperature (SST) change (°C)

(a) (b)

−0.02 −0.01 0.00 0.01 0.02

Chlorophyll change (mg/[m2 ⋅ yr])O

ce

an

re

gio

n

Arctic (A)

North Atlantic (NA)

Equatorial Atlantic (EA)

South Atlantic (SA)

North Indian (NI)

South Indian (SI)

North Pacific (NP)

Equatorial Pacific (EP)

South Pacific (SP)

Southern (S)


Figure 28.30a

NP

NI

SIS SP

SA

EA

NAAEP

−2.50 −1.25 0.00 1.25 2.50

Sea-surface temperature (SST) change (°C)

(a)


Figure 28.30b

(b)

−0.02 −0.01 0.00 0.01 0.02

Chlorophyll change (mg/[m2 ⋅ yr])

Oc

ea

n r

eg

ion

Arctic (A)

North Atlantic (NA)

Equatorial Atlantic (EA)

South Atlantic (SA)

North Indian (NI)

South Indian (SI)

North Pacific (NP)

Equatorial Pacific (EP)

South Pacific (SP)

Southern (S)


Figure 28.UN01a

Wheat mitochondrion

Wheat mitochondrion

A. tumefaciens

A. tumefaciens

C. testosteroni

C. testosteroni

E. coli

M. capricolum

E. coli M. capricolum

A. nidulans

A. nidulans

–

–

–

–

–

–

48 38

55

35

57

61

34

52

48

34

53

52

50

52

52


Figure 28.UN01b

Wheat, used as the source of

mitochondrial RNA


Figure 28.UN06Eukaryote

Supergroup Major Groups

Key Morphological

Characteristics Specific Examples

Excavata

“SAR” Clade

Archaeplastida

Unikonta

Giardia,

Trichomonas

Phytophthora,

Laminaria

Pfiesteria,

Plasmodium,

Paramecium

Globigerina

Porphyra

Chlamydomonas,

Ulva

Mosses, ferns,

conifers,

flowering

plants

Amoeba, Dictyostelium

Choanoflagellates,

nucleariids,

animals, fungi

Diplomonads and

parabasalids

Euglenozoans

Kinetoplastids

Euglenids

Modified mitochondria

Stramenopiles

Diatoms

Golden algae

Brown algae

Alveolates

Dinoflagellates

Apicomplexans

Ciliates

Rhizarians

Radiolarians

Forams

Cercozoans

Red algae

Amoebozoans

Slime molds

Tubulinids

Entamoebas

Opisthokonts

Green algae

Land plants

Spiral or crystalline rod in-

side flagella

Hairy and smooth flagella

Membrane-enclosed sacs

(alveoli) beneath plasma

membrane

Amoebas with threadlike

pseudopodia

Phycoerythrin (photosyn-

thetic pigment)

Plant-type chloroplasts

(See Chapters 29 and 30.)

Amoebas with lobe-

shaped or tube-shaped

pseudopodia

(Highly variable; see

Chapters 31–34.)

Trypanosoma,

Euglena


Figure 28.UN06a

Eukaryote

Supergroup Major GroupsKey Morphological


Excavata

“SAR” Clade

Giardia,

Trichomonas

Phytophthora,

Laminaria

Pfiesteria,

Plasmodium,

Paramecium

Globigerina

Diplomonads and

parabasalids

Euglenozoans

Kinetoplastids

Euglenids

Modified mitochondria

Stramenopiles

Diatoms

Golden algae

Brown algae

Alveolates

Dinoflagellates

Apicomplexans

Ciliates

Rhizarians

Radiolarians

Forams

Cercozoans

Spiral or crystalline rod in-

side flagella

Hairy and smooth flagella

Membrane-enclosed sacs

(alveoli) beneath plasma

membrane

Amoebas with threadlike

pseudopodia

Trypanosoma,

Euglena


Figure 28.UN06b

Eukaryote

Supergroup Major GroupsKey Morphological


Archaeplastida

Unikonta

Porphyra

Chlamydomonas,

Ulva

Mosses, ferns,

conifers,

flowering

plants

Amoeba, Dictyostelium

Choanoflagellates,

nucleariids,

animals, fungi

Red algae

Amoebozoans

Slime molds

Tubulinids

Entamoebas

Opisthokonts

Green algae

Land plants

Phycoerythrin (photosyn-

thetic pigment)

Plant-type chloroplasts

(See Chapters 29 and 30.)

Amoebas with lobe-

shaped or tube-shaped

pseudopodia

(Highly variable; see

Chapters 31–34.)


Figure 28.UN07

campbell - napa valley

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