Animals: The InvertebratesAnimals: The Invertebrates

Chapter 25Chapter 25

Characteristics of AnimalsCharacteristics of Animals

• Multicelled heterotrophic eukaryotesMulticelled heterotrophic eukaryotes

• Require oxygen for aerobic respirationRequire oxygen for aerobic respiration

• Reproduce sexually, and perhaps Reproduce sexually, and perhaps asexuallyasexually

• Motile at some stageMotile at some stage

• Develop from embryosDevelop from embryos

Major Major Animal Animal Phyla Phyla

Chordates

Echinoderms

Arthropods

Annelids

Mollusks

Rotifers

Roundworms

Flatworms

Cnidarians

SpongesMulticelled Ancestry

Radial Ancestry

Bilateral Ancestry

Coelomate Ancestry

Single-celled, protistanlike ancestorsFigure 25.2Page 415

SymmetrySymmetry

Radial Bilateral Figure 25.3Figure 25.3Page 416Page 416

dorsal

posterior

ventral

anterior

The GutThe Gut

• Region where food is digested and Region where food is digested and then absorbedthen absorbed

• Saclike gutSaclike gut– One opening for taking in food and One opening for taking in food and

expelling wasteexpelling waste

• Complete digestive systemComplete digestive system– Opening at both ends; mouth and anusOpening at both ends; mouth and anus

Body Cavities - AcoelomateBody Cavities - Acoelomate

epidermisgut cavity

no body cavity; region between gut and body wall packed with organs

Figure 25.4aPage 417

Body Cavities - PseudocoelBody Cavities - Pseudocoel

epidermis gut cavity

unlined body cavity (pseudocoel) around gut

Figure 25.4bPage 417

Body Cavities - CoelomBody Cavities - Coelom

gut cavity

peritoneumlined body cavity (coelom) Figure 25.4c

Page 417

SegmentationSegmentation

• Repeating series of body unitsRepeating series of body units

• Units may or may not be similar to Units may or may not be similar to one anotherone another

• Earthworms - segments appear Earthworms - segments appear similarsimilar

• Insects - segments may be fused Insects - segments may be fused and/or have specialized functionsand/or have specialized functions

Animal Origins Animal Origins

• Originated during the Precambrian Originated during the Precambrian

(1.2 billion - 670 million years ago)(1.2 billion - 670 million years ago)

• From what? Two hypotheses:From what? Two hypotheses:– Multinucleated ciliate became Multinucleated ciliate became

compartmentalizedcompartmentalized

– Cells in a colonial flagellate became Cells in a colonial flagellate became

specializedspecialized

Phylum PlacozoaPhylum Placozoa

• One living species, One living species,

Tricoplax adherensTricoplax adherens

• Simplest known Simplest known

animalanimal

• Two-layer body, Two-layer body,

3 mm across3 mm across

Figure 25.5Page 418

Sponges - Phylum Porifera Sponges - Phylum Porifera

• No symmetryNo symmetry

• No tissuesNo tissues

• No organsNo organs

• Reproduce sexuallyReproduce sexually

• Microscopic swimming larval stageMicroscopic swimming larval stage

Sponge StructureSponge Structure

central cavity

water out

water in

flagellum microvilli nucleus

glasslike structural elements

amoeboid cell

pore

semifluid matrix

flattened surface cells

Figure 25.7aPage 419

Phylum Cnidaria Phylum Cnidaria

• Only Only animals that animals that produce produce nematocystnematocystss

• Nerve netNerve net

• Hydrostatic Hydrostatic skeletonskeleton

• Saclike gutSaclike gutFigure 25.8Page 420

barbed thread inside capsule

capsule’s lid at free surface of epidermal cell

trigger

nematocyst

Cnidarian DiversityCnidarian Diversity

• ScyphozoansScyphozoans– JellyfishJellyfish

• AnthozoansAnthozoans– Sea anemonesSea anemones

– CoralsCorals

• HydrozoansHydrozoans

Two Main Body PlansTwo Main Body Plans

Figure 25.9 Page 420

outer epithelium (epidermis)

mesoglea(matrix)

inner epithelium (gastrodermis)

Medusa

Polyp

ObeliaObelia Life Cycle Life Cycle (Hydrozoan)(Hydrozoan)

reproductivepolyp

female medusa male medusa

sperm

zygote

ovum

planula

polyp forming

feeding polyp

Figure 25.10Page 421

Flatworms: Flatworms: Phylum Platyhelminthes Phylum Platyhelminthes

• Acoelomate, bilateral, Acoelomate, bilateral, cephalized animals cephalized animals

• All have simple or complex All have simple or complex organ systemsorgan systems

• Most are hermaphroditesMost are hermaphrodites

Three Classes Three Classes

• Turbellarians (Turbellaria)Turbellarians (Turbellaria)

• Flukes (Trematoda)Flukes (Trematoda)

• Tapeworms (Cestoda)Tapeworms (Cestoda)

Planarian Organ SystemsPlanarian Organ Systems

pharynx

protonephridia

flame cellnucleus

cilia

fluid filters through membrane foldsflame cell

opening of tubule at body surface

Fig. Fig. 25.11a,b25.11a,bPage 422Page 422

Planarian Organ SystemsPlanarian Organ Systems

brain nerve cord

genital poreoviducttestisovary

penis

Fig. 25.11cdFig. 25.11cdPage 422Page 422

Roundworms (Nematoda)Roundworms (Nematoda)

• False coelomFalse coelom• Complete digestive systemComplete digestive system

gonadpharynx intestine

false coelom

eggs in uterus anus

muscularized body wall

Figure Figure 25.1325.13Page 423Page 423

Flukes: Class TrematodaFlukes: Class Trematoda

• Parasitic wormsParasitic worms

• Complicated life Complicated life

cyclecycle

– Larval stage Larval stage

infects a mollusk infects a mollusk

– Adult infects a Adult infects a

vertebrate vertebrate

Ciliated larva

Worms mate in human host

Fertilized egg

Asexual reproduction in intermediate host

Larvae form, leave snail

Larvae bore into human skin

Southeast Asian blood fluke Figure 25.14Page 424

Tapeworms: Class CestodaTapeworms: Class Cestoda

Larvae encysted in muscle tissue

Intermediate host Mature proglottid with fertilized eggs

Scolex attaches to host intestinal wall

Definitive host

Figure 25.15Page 424

RotifersRotifers

• BilateralBilateral

• CephalizedCephalized

• False coelomFalse coelom

• Crown of cilia at Crown of cilia at

head endhead end

• Complete gutComplete gut

Figure 25.17Page 425

Two Coelomate LineagesTwo Coelomate Lineages

ProtostomesProtostomes

• MollusksMollusks

• AnnelidsAnnelids

• ArthropodsArthropods

DeuterostomesDeuterostomes

• EchinodermsEchinoderms

• Chordates Chordates

Cleavage PatternsCleavage Patterns

Protostome embryo(spiral cleavage)

Deuterostome embryo(radial cleavage)

In-text In-text figurefigurePage 426Page 426

• Bilateral, soft-bodied, coelomateBilateral, soft-bodied, coelomate

• Most have a shell or reduced version Most have a shell or reduced version of oneof one

• Mantle drapes over body and secretes Mantle drapes over body and secretes shellshell

• Most have a fleshy footMost have a fleshy foot

• Many have a radula for shredding foodMany have a radula for shredding food

Mollusks: Phylum MolluscaMollusks: Phylum Mollusca

• Gastropods Gastropods

• ChitinsChitins

• BivalvesBivalves

• CephalopodsCephalopods

Molluscan DiversityMolluscan Diversity

• Twisting of body Twisting of body parts during parts during larval larval development development

• Occurs only in Occurs only in gastropodsgastropods

TorsionTorsion

mouth

anusgill

Figure 25.18Page 426

Body Plan of a SnailBody Plan of a Snail

gillanus

radula

foot

mantle cavity

digestive gland

mantle

heart

Figure Figure 25.1825.18Page 426Page 426

Body Plan of a ClamBody Plan of a Clam

mouthretractor muscle

left mantle

retractor muscle

foot

palpsleft gill shell

Figure Figure 25.2125.21Page 429Page 429

CephalopodsCephalopods

• Only the nautilus retains external shellOnly the nautilus retains external shell

• Other cephalopods are streamlined, Other cephalopods are streamlined, active swimmersactive swimmers

• All move by jet propulsionAll move by jet propulsion– Water is forced out of mantle cavity Water is forced out of mantle cavity

through a funnel-shaped siphonthrough a funnel-shaped siphon

• Have large brains relative to body sizeHave large brains relative to body size

Cuttlefish Body PlanCuttlefish Body Plan

Closed circulatory system with heart Closed circulatory system with heart and accessory heartand accessory heart

stomachkidneyesophagus

digestive gland

brain

arm

jaw

tentacle radula

siphon

anusink sac

gillheart accessory

heart

reproductive organ

mantleinternal

shell

Figure 25.22Page 429

Segmented, coelomate wormsSegmented, coelomate worms

• Class Polychaeta Class Polychaeta

• Class Oligochaeta Class Oligochaeta

• Class Hirudinea Class Hirudinea

Annelids: Phylum AnnelidaAnnelids: Phylum Annelida

PolychaetesPolychaetes

• Most are marineMost are marine• Bristles extend Bristles extend

from paired, from paired, fleshy parapods fleshy parapods on each on each segment segment

• Head end is Head end is specialized specialized

Fig. 25.24cFig. 25.24cPage 430Page 430

“jaws”

toothlike structurespharynx (everted)antenna

palp (food handling)

tentacle

eyes

chemical-sensing pit

parapod

• Predators and parasitesPredators and parasites

• Less obvious body Less obvious body

segmentationsegmentation

• Most have sharp jaws Most have sharp jaws

Leeches - Class HirudineaLeeches - Class Hirudinea

No parapodia, few bristles per segmentNo parapodia, few bristles per segment

Earthworm - An OligochaeteEarthworm - An Oligochaete

Nerve cord

Nerve cord

Dorsal blood vessel

Nephridium

Coelom

Circular muscle

Longitudinal muscle

Seta (retracted)Figure Figure 25.25a25.25aPage 431Page 431

Earthworm NephridiumEarthworm Nephridiumbladderlike storage region of nephridium

nephridium’s thin loop reabsorbs some solutes, relinquishes them to blood

blood vessels

body wall

external pore (fluid containing wastes discharged here)

funnel (coelomic fluid with waste enters here)

Figure Figure 25.25b25.25bPage 431Page 431

Earthworm Circulatory Earthworm Circulatory SystemSystem

Hearts

Figure Figure 25.25c25.25cPage 431Page 431

Earthworm Digestive Earthworm Digestive SystemSystem

PharynxEsophagus

Crop Gizzard

Coelomic chambers

Mouth

Figure 25.25dFigure 25.25dPage 431Page 431

Earthworm Nervous SystemEarthworm Nervous System

Brain

Nerve cord Figure Figure 25.25e25.25ePage Page 431431

• The phylum with the greatest number The phylum with the greatest number of speciesof species

• Four lineages:Four lineages:– Trilobites (all extinct)Trilobites (all extinct)

– Chelicerates (spiders, mites, scorpions)Chelicerates (spiders, mites, scorpions)

– Crustaceans (crabs, shrimps, barnacles)Crustaceans (crabs, shrimps, barnacles)

– Uniramians (insects, centipedes, millipedes)Uniramians (insects, centipedes, millipedes)

Arthropods: Arthropods: Phylum ArthropodaPhylum Arthropoda

Adaptations for SuccessAdaptations for Success

• Hardened exoskeletonHardened exoskeleton

• Jointed appendagesJointed appendages

• Fused and modified segmentsFused and modified segments

• Respiratory structuresRespiratory structures

• Specialized sensory structuresSpecialized sensory structures

• Division of laborDivision of labor

Do not post on Internet

Figure 25.26Page 432

• Originated in seasOriginated in seas

• A few are still marine: horseshoe A few are still marine: horseshoe crabs, sea spiders crabs, sea spiders

• The arachnids are all terrestrialThe arachnids are all terrestrialSpiders Mites Spiders Mites

Scorpions ChiggersScorpions Chiggers

““Daddy longlegs” TicksDaddy longlegs” Ticks

CheliceratesChelicerates

Body Plan of a SpiderBody Plan of a Spider

eye

poison gland

chelicera

mouth

book lung

sperm receptacle

ovary silk gland

spinners

anus

Malpighian tubuledigestive glandheartbrain

pedipalp

Figure 25.28Page 433

• Most are marine, Most are marine, some freshwater, a some freshwater, a few terrestrialfew terrestrial

• Head has two pairs of Head has two pairs of

antenna, three pairs of antenna, three pairs of

food-handling food-handling

appendagesappendages

CrustaceansCrustaceans

Copepods

Crayfish

Barnacles

Lobsters

Shrimps

Crabs

Isopods (pillbugs)

Lobster Body PlanLobster Body Plan

antennae (two pairs)

one of two eyes

fused segments of cephalothorax

segments of abdomen

tail fin

swimmerets

five walking legs (five pairs total)

first leg

food-handling appendages (three pairs)

Figure 25.29aPage 434

Crab Life Crab Life CycleCycle

Larval and juvenile stages molt repeatedly and grow in size

egg

Figure 25.30Page 435

Millipedes and CentipedesMillipedes and Centipedes

• Segmented bodies with many legsSegmented bodies with many legs• MillipedesMillipedes

– Two pairs of legs per “segment”Two pairs of legs per “segment”– ScavengersScavengers

• CentipedesCentipedes– Flattened, with one pair of legs per Flattened, with one pair of legs per

segmentsegment– PredatorsPredators

Insect Body PlanInsect Body Plan

• Thorax usually has three pairs of Thorax usually has three pairs of legs and one or two pairs of wingslegs and one or two pairs of wings

• Abdomen contains most internal Abdomen contains most internal organs and specialized structure for organs and specialized structure for reproduction reproduction

• Three-part gutThree-part gut

• Malpighian tubules attach to midgut Malpighian tubules attach to midgut

and serve in elimination of wastesand serve in elimination of wastes

Insect HeadpartsInsect Headparts

antenna labrum

palps

maxilla

labium

mandible

GrasshopperButterfly

Fly

Mosquito

Figure Figure 25.3225.32Page 436Page 436

Insect DiversityInsect Diversity

• The only winged invertebratesThe only winged invertebrates

• More than 800,000 known speciesMore than 800,000 known species

• Most successful species are small Most successful species are small in size and have a great in size and have a great reproductive capacityreproductive capacity

adult

adult

adult

youngegg

nymphsegg

egg

Growth and molting

Incomplete metamorphosis

Complete metamorphosis

Types ofTypes ofInsect Insect DevelopmenDevelopmentt

larvae pupa

Different stages exploit different resources at different times

Unwelcome ArthropodsUnwelcome Arthropods

• Poisonous Poisonous spidersspiders

• Disease-carrying Disease-carrying ticksticks

• Venomous Venomous scorpionsscorpions

• Agricultural pests Agricultural pests Corn rootworm (Diabrotica virgifera)

Do not post on Internet

Figure 25.38Page 439

EchinodermsEchinoderms

• Deuterostomes Deuterostomes

• Body wall has spines Body wall has spines

or plates or plates

• No brainNo brain

• Adults are radial with Adults are radial with

bilateral featuresbilateral features

Do not post

photos on

Internet

Figure 25.39Page 440

Sea urchin

Sea cucumber

Brittle star

Echinoderm DiversityEchinoderm Diversity

• Crinoids (sea lilies and feather stars)Crinoids (sea lilies and feather stars)

• Sea starsSea stars

• Brittle starsBrittle stars

• Sea urchins, heart urchins, sand Sea urchins, heart urchins, sand

dollarsdollars

• Sea cucumbers Sea cucumbers

Body Plan of a Sea StarBody Plan of a Sea Star

eyespot

digestive gland

gonad

anus

lower stomach

upper stomach

coelomsieve plate

Figure 25.40aPage 441

Water Vascular SystemWater Vascular System

sieve plate

ampulla

Figure Figure 25.40b25.40bPage 441Page 441