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