Chapter 18

Defining AnimalsMulticellular, heterotrophic eukaryotes that

obtain nutrients by ingestion or eating foodNo cell walls for structureJoined by extracellular proteins and

intercellular junctionsMost have muscle cells for movement and

nerve cells for signal conductionAbout 35 phyla in kingdom animalia; we

examine 9All but 1 are invertebrates or lack a backbone

Animal Life CyclesHaploid gametes fuse into

zygote Mitosis forms a hollow ball of

cells = blastulaInvagination produces a

gastrulaBecomes GI system lined with

endoderm Ectoderm for outer covering,

some nervous systemsMesoderm for muscles and

internal organsLarva stage metamorphosis

to adult (some animals)

Constructing Phylogenetic TreesMorphological

similarities and differences in body plans

SymmetryTissue organizationEmbryonic developmentBody cavity is an

additional body plan feature

Kingdom Animalia

SymmetryRadial often

sedentaryBilateral (most)

often mobileAnterior and

posteriorVentral and dorsal

Location of brain, sense organs, and mouth

Tissue OrganizationTrue tissues are

specialized cells, separated by layersAbsent in Porifera

(level of organization?)

Formed during gastrulation

2 layers is ecto- and endoderm

3 layers is ecto-, meso-, and endoderm

Body CavityA coelom or fluid filled

space between GI tract and outer body wallAllows organ movement,

protection, and development

Presence or absence divides 3 tissue layer organisms

True coelom is completely lined with mesoderm

Pseudocoelom not completely linedPlatyhelminthes (flat

worms) lacks (acoelomate)

Embryonic DevelopmentBased on gastrula

opening formedProtostomes: opening

becomes mouthE.g Arthropoda

Deuterostomes: opening becomes anusMouth forms

elsewhereE.g Chordates

Phylum Porifera (Sponges)Most are stationary (sessile), marine, and

asymmetricalDraws water in through pores and out an osculumSuspension feeders

Choanocytes pull in food and water

Amoebocytes provide support Spicules is mineralized material Spongin is flexible protein

No muscles or nervesToxins and antibiotics release

for protection

Phylum Cnidaria (Cnidarians)Radial symmetry and 2

tissue layersJelly like substance

betweenContractile and nervous

tissue (simple)Exist as polyps or

medusasCarnivorous, use

cnidocytesIncomplete GI tracthttp://www.youtube.com/

watch?v=fBkmzzAh8Eo&feature=related

Phylum Platyhelminthes (flatworms)

3 tissue layers, acoelomate, incomplete GI tractClass Turbellaria (free living)

Simple brain, branched GI, shared mouth/anus http://www.youtube.com/watch?

v=axBaCD4wYXE&feature=PlayList&p=E9E1093124E2F9C9&playnext=1&index=10

Class Trematoda (flukes)Animal parasites

Suckers to attach and interior all repro. organs Larval intermediate stage

Class Cestoda (tapeworms)Vertebrate GI tract parasites

Scolex, no mouth (absorption), hermaphrodite, eggs released from end in feces

Multiple hosts http://www.youtube.com/watch?v=GMSc2RZ19Us

Tapeworm

Phylum Mulluska (Mollusks)Coelomates, separate sexes, larval stage (trochophore),

circulatory and advanced sensory systemsMuscular foot, visceral mass, mantle, radula (chitinous

tongue)Class Gastropoda (snails and slugs)

Live on land and in all watersClass Cephalopoda (squids and octopuses)

http://www.youtube.com/watch?v=9-azBDt0kik&feature=related http://www.youtube.com/watch?v=5mBhKe4DxQ4

Mouth at end of foot, shell small or absentMost advanced invertebrate brain and sense organs (eyes)

Class Bivalva (scallops, oysters, and clams)2 shells hinged togetherSuspension feeders, mantle has gills for food and gas

exchange

Phylum Nematoda (Roundworms)Pseudocoelomate, GI tract with 2 openings,

separate sexes, and lateral musclesFree-living (C. elegans)Parasitic

Dog heartworm50 species in humans

Trichinella spiralis Hook worms Pinworms

Phylum Annelida (Segmented Worms)Segmentation, longitudinal and circular muscles,

closed circulatory systemClass Polychaeta

Marine organisms, live in tubes, can be colonialClass Oligochaeta (earthworms)

Segmented excretory, circulatory, repro, and nervous systems; unsegmented GI tract

Hermaphroditic, thickened region gathers gametes and is left in soil

Class Hirudinea (leeches)Blood-sucking, releases an anesthetic and

anticoagulant Consume 10X’s weight, can go months w/o another meal Medicinal uses

Phylum Arthropoda (Arthropods)Most successful phylumExoskeleton

Protects and allows joint attachmentProtein and chitin that Is molted with growth

SegmentationHead, thorax (fused is cephalothorax), and abdomen Sensory, protection and walking, and swimming

respectivelyOpen circulatory system, blood not contained in

vesselsAquatic species with gills, terrestrial with air sacs

SubphylumsChelicerates (arachnids)

Hollow mouth appendagesFirst terrestrial carnivores, deliver venom or

toxinsE.g scorpions (night), spiders (day), and ticks/mites

MandibulataSolid mouth organsExamples

Millipedes are herbivores with 2 leg sets per segment Centipedes are carnivores with 1 leg set per segment Lobsters, and insects

ClassesCrustacea (Crustaceans)

Aquatic (mostly) and have gills (rolly-polly)Include lobsters, crayfish, shrimp, barnacles,

and crabsInsecta (Insects)

Most diverse groupWings, advanced sensory organs,

communication, and social structureWaterproof cuticle, short lives, complex life

cycles, and large offspring broods

Class InsectaLife cycles

Only adults can reproduce or have functional wingsMultiple molts allow for metamorphosis, complete

or incompleteFood sources differ so enhances adaptability

Body plan3 parts: head, thorax, and abdomenEmbryonic segments develop independently

Connects with mutation and evolution 3 pairs of legs, not at cost to legs

ColorationCamouflage, mimicry, and coloration from

independent development

Phylum EchinodermataE.g sea stars, sand dollars, sea urchin and sea

cucumberRadial symmetry internally and externally as an adultBilateral symmetry in larval stageCalcium containing plates form endoskeletonTube feet that are extensions of a water vascular

systemFor locomotion, feeding, and gas exchange

Mouth and stomach adaptationsdeuterostomes

Capable of regeneration

Phylum Chordata4 characteristics

Dorsal, hollow nerve cordsNotocord between GI tract and nerve cordPharyngeal slits Post-anal tail

Tunicates (Sea squirts)Adult has pharyngeal slits only,

larva has all fourLancet

Suspension feedersMucus net to trap food

Phylogeny Review