ch 28 lecture_presentation

InvertebratesChapter 28

Phylum Porifera• Classified as Parazoa

– Animals lacking tissues (and therefore organs) and a definite symmetry

• 7000 marine species; 150 freshwater species• Among the most abundant animals in the deep

ocean

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Eumetazoa

Protostomes

Spiralia

LophotrochozoaPlatyzoa

Para

zoa

Aco

elo-

mor

pha

Porif

era

Cni

daria

Cte

noph

ora

Aco

ela

Mic

rogn

atho

zoa

Rot

ifera

Cyc

lioph

ora

Plat

yhel

min

thes

Bra

chio

poda

Bry

ozoa

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

• Most members lack symmetry

• Larval sponges are free-swimming

• Adults remain attached – “sessile”

• Intracellular digestion only

• Sexual and asexual reproduction

• Embryo never undergoes gastrulation, so no true tissues

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© Andrew J. Martinez/Photo Researchers, Inc.a.

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OsculumWater

Epidermal cell

Amoebocyte

Pore

Choanocyte

Sponginfiber

Spicule

Nucleusb.

Collar

Flagellum

Choanocyte

Ostium

Eumetazoa (i.e. everything except Parazoa)

• Animals with true tissues that form after gastrulation• Embryos have distinct layers

– Inner endoderm forms the “gastrodermis”– Outer ectoderm forms the “epidermis” and “nervous

system” – Middle mesoderm (only in bilateral animals) forms the

muscles• True body symmetry

– Radial symmetry– Bilateral symmetry

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Phylum Cnidaria• Most marine, few fresh water species• Diploblastic• Bodies have distinct tissues but no organs

– No reproductive, circulatory, or excretory systems• No concentrated nervous system

– “Latticework” or “net” of nerve cells– Respond to touch, gravity, light

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• Cnidarians use stinging cells to capture prey– Some carry venom

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Tentacles

Mouth

Gastrodermis EpidermisNematocyte Trigger

Undischargednematocyst

TubuleDischargednematocyst

Nematocytewith nematocyst

Sensorycell

Mesoglea

Hydra3.3 mm(inset): © Roland Birke/Phototake


• 2 basic body formsPolyps – cylindrical and sessileMedusa – umbrella-shaped and free-living

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Gastrovascular cavity

MedusaMouth

Mesoglea

Mouth

Polyp

Gastrodermis

Epidermis

Tentacles

EpidermisMesogleaGastrovascular cavityGastrodermis


• Body plan has single opening (mouth) leading to gastrovascular cavity lined by gastrodermis– GVC is the site of extracellular digestion (key innovation), which

is followed by phagocytosis – Most gas exchange occurs here– Waste discharge– Formation of gametes in many

• 2 layers to body1.Epidermis2.Gastrodermis

– Mesoglea between layers

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• Gastrovascular space also serves as hydrostatic skeleton– Provides a rigid structure against which

muscles can operate– Gives the animal shape

• Many polyp species build an exoskeleton of chitin or calcium carbonate around themselves– Some build an internal skeleton

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– Sea anemone– Coral animals– Box jellies– Star jellies– Jellies– Hydra, Portuguese man-of-

war

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Clades of Protostomes

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Bra

chio

poda

Plat

yhel

min

thes

Cyc

lioph

ora

Rot

ifera

Mic

rogn

atho

zoa

Bry

ozoa

Ann

elid

a

Mol

lusc

a

Nem

erte

a

Loric

ifera

Kin

orhy

ncha

Nem

atod

a

Tard

igra

da

Art

hrop

oda

Ony

chop

hora

Cha

etog

nath

a

Echi

node

rmat

a

Cho

rdat

a


Protostomes

Spiralia

EcdysozoaLophotrochozoaPlatyzoa

• Flatworms are ciliated, soft-bodied animals• Bodies are solid aside from an incomplete

digestive cavity• Many species are parasitic;

others are free-living (marine, freshwater, moist terrestrial)

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Phylum Platyhelminthes - Flatworms

10 mm


© Tom Adams/Visuals Unlimited

• Only one opening to digestive cavity– Muscular contractions in the pharynx allows

food to be ingested and torn into small bits• Lack circulatory system

– Diffusion for gas transport– Gut functions in digestion and food distribution– Some particles digested extracellularly– Cells engulf particles by phagocytosis– Tapeworms (parasitic flatworms) lack digestive

systems – absorb food directly through body walls

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EyespotProtruding pharynx

Mouth

Testis

Oviduct

Spermduct

Circular muscles

Longitudinalmuscles

Parenchymalmuscle

EpidermisNerve cord Intestine

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ReproductiveSystem

ExcretorySystem

NervousSystem

Intestine

Nervecord

Testis

Ovary

Anteriorcerebralganglion


• Have an excretory and osmoregulatory system – Network of fine tubules runs through body– Metabolic wastes are excreted into the gut and eliminated

through the mouth

• Simple nervous system– Anterior cerebral ganglion and ventral nerve cords– Eyespot can distinguish light from dark

• Reproduction– Most are hermaphroditic– Undergo sexual reproduction– Also have capacity for asexual regeneration

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Metacercarialcysts in fishmuscle

Metacercariae areconsumed by humans

or other mammals

Adult fluke

Miracidium hatches afterbeing eaten by snail

Liver

Bileduct

Egg containing miracidium in feces

(into water)

Cercaria

Sporocyst

Redia

57 µm© Dwight R. Kuhn

• Tapeworms– Adult hangs onto inner wall of host intestine

using scolex

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500 µm


© Dennis Kunkel/Phototake

• Most of tapeworm body is proglottids– Complete hermaphroditic unit, containing both male and female reproductive

organs– Formed continuously

• Beef tapeworm, Taenia saginata– Frequent human parasite– From eating uninspected rare beef

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Scolex

Hooks

Sucker

Proglottids

Scolex attachedto intestinal wall

Uterus

Proglottid

Genitalpore


Phylum Mollusca

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• Second in diversity only to arthropods

• Include snails, slugs, clams, octopuses and others

• Some have a shell, some do not

Mollusk Body Plan• Mantle

– Epidermal sheet– Secretes the shell (if there is one)

• Foot– Primary means of locomotion for many– Divided into arms or tentacles in cephalopods

• Internal organs– Coelom is highly reduced– Digestive, excretory, and reproductive organs are

concentrated in a visceral mass

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Radula

Gut

Lung

Foot

Gastropods

Shell

Antenna

Radula

Mantle

Gut

Shell

Gill Foot

Chitons

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Gut

Gill

Gut

Gill

Foot Mantle

Shell

Cephalopods

Bivalves

Siphons

Siphon

Eye ArmMantlecavity

Adductormuscle

Tentacle

• Shell– Protects against predators and adverse

environments– Secreted by outer surface of mantle– Clearly not essential (some mollusks have a

small or absent)– Typical shell has 2 layers of calcium carbonate

• Internal layer may be mother-of-pearl or “nacre”• Pearls are formed by coating foreign object with

nacre to reduce irritation

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• Radula– Characteristic of most mollusks– Rasping, tonguelike structure used in feeding– Used to scrape up algae– In predatory gastropods, modified to drill

through clam shells– In Conus snails, modifies into harpoon with

venom gland– Bivalves do not have a radula

• Gills used in filter feeding26

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Esophagus

Radula toothMuscles

Mouth RadulaMouth

25 µmBottom: © Eye of Science/Photo Researchers, Inc.

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Classes of Mollusks

• Main Classes:1. Polyplacophora – chitons2. Gastropoda – limpets, snails, slugs3. Bivalvia – clams, oysters, scallops4. Cephalopoda – squids, octopuses,

cuttlefishes, and chambered nautilus

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Class Polyplacophora (Chitons)• Marine mollusks that have oval bodies• 8 overlapping dorsal calcareous plates• Body is not segmented under the plates• Most chitons are grazing herbivores

Class Gastropoda

• Limpets, snails, slugs• Marine, freshwater, and terrestrial animals• Most have a single shell – some lost it• Heads typically have pairs of tentacles

with eyes• Exhibit “torsion”

– Mantle cavity and anus are moved from the posterior to the front

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• Torsion should not be confused with coiling• Coiling – spiral winding of the shell

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• Nudibranchs are active predators– Exposed gills– Many secrete distasteful chemicals– Some extract nematocysts from cnidarian

prey and transfer them to their body surface32

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Class Bivalvia (Bivalves)

• Includes clams, scallops, mussels, oysters, and others

• Most marine, some freshwater• No radula or distinct head• Have 2 shells (valves) hinged together

– Adductor muscles counter hinge ligament• Water enters through inhalant siphon and

exits through exhalant siphon

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Inhalantsiphon

GillsMantle

Intestine

Foot

Stomach

Mouth

Adductormuscle

KidneyHeart

HingeShell

Exhalantsiphon

Gonad

Anus

Class Cephalopoda

• More than 600 strictly marine species• Active marine predators • The only mollusks with closed circulatory system• Foot has evolved into a series of arms equipped

with suction cups • Largest relative brain sizes among invertebrates• Highly developed nervous system

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Problem-solving by an octopus

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• Living cephalopods lack external shell– Except chambered nautilus– Squid and cuttlefish have internal shells

• Jet propulsion using siphon• Ink can be ejected from siphon• Chromatophores allow for changing skin color for

camouflage or communication37

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Phylum Annelida – segmented worms

• Body plan– Head has well-developed cerebral ganglion– Segments divided internally by septa– Closed circulatory system– Ventral nerve cord– Complete digestive tract

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Brain

Dorsal bloodvessel

Septa

IntestineNephridium

MouthPharynx

Esophagus

Clitellum

Setae

Ventral bloodvessel

Nerve cord

Female gonads

Male gonads

Segments

Hearts

• Leeches– Occur mostly in freshwater– Usually flattened dorsoventrally

40Medicinal leech, Hirudo medicinalis

• Vinegar eels, Ascaris, heartworm, trichonella, and other roundworms

• Members of this phylum are found everywhere – abundant and diverse

• Marine, freshwater, parasites, free-living

41181.1µm


© Educational Images Ltd., Elmira, NY, USA. Used by Permission

Phylum Nematoda - Roundworms

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Mouth

Dorsal nerve cord

Intestine

TestisPharynxExcretory pore

Muscle

Pseudocoelom

Excretory ductIntestine

TestisEpidermis

Ventral nerve cordCuticle

Genital pore

AnusSpicules

• About 50 species cause human diseases– Hookworms

– Common in southern U.S.– Produce anemia

– Trichinella causes trichinosis– Forms cysts in muscles – Infection from eating undercooked meat (pork)

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50 µm© Gary D. Gaugler/Photo Researchers, Inc.

• By far the most successful animals– Well over 1,000,000 species (2/3 of all named

species) • Arthropods affect all aspects of human life• Divided into four extant classes

• Chelicerata• Crustacea• Hexapoda• Myriapoda

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3.4% Crustaceans

36.2%Beetles

12.1%Flies

12.1%Butterflies,

moths

10.3%Bees, wasps,

ants8.6% Other insects 12.1%

Otherarthropods

5.2% Arachnids

Arthropods are a successful group

About two-thirds of all named species are arthropods. About 80% of all arthropods are insects, and about half of the named species of insects are beetles

Arthropod MorphologyPart of arthropod success explained by:•Segmentation

– Head, thorax, abdomen•Exoskeleton

– Made of chitin and protein– Protects against water loss– Must undergo “ecdysis” – molting

•Jointed appendages– Evolution has modified some into antennae, mouthparts,

or wings– Can be extended and retracted

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• Open circulatory system

• Nervous system– Double chain of

segmented ganglia– Ventral ganglia control

most activities• Can eat, move, or

copulate with brain removed

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Head Thorax Abdomen

Spiracles

Tympanum

Compoundeye

Ocellus

Antennae

BrainAorta Stomach Ovary

Heart Rectum

MouthCrop Gastric

cecaMalpighian

tubulesNerve

ganglia

a.

b.

• Compound eyes are found in many arthropods – Composed of independent visual units called

ommatidia• Other arthropods have simple eyes, or

ocelli– May be in addition to compound eyes– Have single lenses– Distinguish light from darkness

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OmmatidiumCorneal lens

Crystallinecone

Rhabdom

Retinularcells

Pigmentcell

NervefiberOmmatidiumOptic nerve

Compound Eye

• Respiratory system– Many marine arthropods have gills– Some tiny arthropods have no structure for

gas exchange – Terrestrial arthropods use tracheae– Many spiders use book lungs

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Class Chelicerata• Spiders, ticks, mites, scorpions, daddy

long-legs, horseshoe crabs, sea spiders• Most anterior appendages called

chelicerae

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Class Crustacea

• Largely marine, some freshwater• Crabs, shrimps, lobsters, barnacles, crayfish, copepods,

pill bugs, sand fleas• Gas exchange through gills or across cuticle

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• Decapod crustaceans– Shrimps, lobsters, crabs, and crayfish– Have 10 feet (5 pairs of thoracic appendages)– Exoskeleton usually reinforced with CaCO3

– Cephalothorax covered by carapace

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Class Hexapoda

• Insects are by far the largest group of animals– Number of species and number of individuals

• More than half of all named animal species

• Approximately one billion billions (1018) insects are alive at any one time

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Order: Lepidoptera

a.© Cleveland P. Hickman


Order: Homoptera

b.© Valorie Hodgson/Visuals Unlimited


c.

Order: Coleoptera

© Gyorgy Csoka, Hungary Forest Research Institute, Bugwood.org


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Order: Diptera

d.© Kjell Sandved/Butterfl y Alphabet


e.

Order: Orthoptera

© Greg Johnston/Lonely Planet Images/Getty Images

Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

f.

Order: Isoptera

© Nature’s Images/Photo Researchers, Inc.

External features

•Three body regions1. Head 2. Thorax has three segments, each with a pair

of legs (=6 legs)3. Abdomen

•Most insects have compound eyes

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The aquatic larvae of mosquitoes are quite active. They breathe through tubes at the surface of the water, as shown here. Covering the water with a thin film of oil suffocates them.

• Insect life histories– Many insects undergo metamorphosis

– Simple metamorphosis (grasshoppers)• Immature stages similar to adults

– Complete metamorphosis (butterflies)• Immature larva are wormlike• A resting stage, pupa or chrysalis, precedes the

final molt into adult form

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Class Myriapoda• Centipedes

– One pair of appendages per segment– Carnivorous – poison fangs

• Millipedes– Two pairs of appendages per segment

• Each segment is a tagma of 2 segments– Herbivores

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Phylum Echinodermata• Exclusively marine• Deuterostomes with an

endoskeleton• Pentaradial symmetry, but

bilateral as larvae• Sea stars, brittle stars, sea

urchins, sand dollars, sea cucumbers

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• Water-vascular system– Radially organized– Radial canal extends from ring canal into

each body branch– Water enters through madreporite– Flows through stone canal to ring canal– Tube feet – may or may not have suckers

• Ampulla – muscular sac at base• Used in movement, feeding, gas exchange

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a.

b. Tube feetSkeletal plates

Digestive glands

Radial canalAmpulla

Tube feet

Gonad

Stomach Anus

MadreporiteWater-vascularsystem

b: © Frederic Pacorel/Getty Images

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Phylum Chordata• Chordates are deuterostome coelomates• Nearest relatives are echinoderms (the only other

deuterostomes)• Fishes, amphibians, reptiles, birds, and mammals


Protostomes

SpiraliaEcdysozoa

Platyzoa Lophotrochozoa

Mic

rogn

atho

zoa

Rot

ifera

Cyc

lioph

ora

Plat

yhel

min

thes

Bra

chio

poda

Bry

ozoa

Ann

elid

a

Mol

lusc

a

Nem

erte

a

Loric

ifera

Kin

orhy

ncha

Nem

atod

a

Tard

igra

da

Art

hrop

oda

Ony

chop

hora

Cha

etog

nath

a

Echi

node

rmat

a

Cho

rdat

a

Deuter-ostomes

4 Features

1. Dorsal nerve cord (not ventral like other animal phyla)

2. Notochord3. Pharyngeal slits4. Postanal tail

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Hollow dorsal nerve cord

Pharyngeal pouches

Notochord

Postanal tail

• All chordates have all four of these characteristics at some time in their lives

• Other characteristics also distinguish chordates– Chordate muscles are

arranged in segmented blocks called somites

– Most chordates have an internal skeleton against which the muscles work

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500 µm© Eric N. Olson, Ph.D./The University of Texas MD Anderson Cancer Center