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Chapter 18
Defining Animals
 Multicellular, heterotrophic eukaryotes that obtain
nutrients by ingestion or eating food
 No cell walls for structure
 Joined by extracellular proteins and intercellular
junctions
 Most have muscle cells for movement and nerve cells
for signal conduction
 About 35 phyla in kingdom animalia; we examine 9
 All but 1 are invertebrates or lack a backbone
Animal Life Cycles
 Haploid gametes fuse into zygote
 Mitosis forms a hollow ball of cells
= blastula
 Invagination produces a gastrula
 Becomes GI system lined with
endoderm
 Ectoderm for outer covering,
some nervous systems
 Mesoderm for muscles and
internal organs
 Larva stage metamorphosis to
adult (some animals)
Constructing Phylogenetic Trees
 Morphological similarities
and differences in body
plans
 Symmetry
 Tissue organization
 Embryonic development
 Body cavity is an additional
body plan feature
Kingdom Animalia
Symmetry
 Radial often sedentary
 Bilateral (most) often
mobile
 Anterior and posterior
 Ventral and dorsal
 Location of brain, sense
organs, and mouth
Tissue Organization
 True tissues are
specialized cells,
separated by layers
 Absent in Porifera (level
of organization?)
 Formed during
gastrulation
 2 layers is ecto- and
endoderm
 3 layers is ecto-, meso-,
and endoderm
Body Cavity
 A coelom or fluid filled space
between GI tract and outer
body wall
 Allows organ movement,
protection, and development
 Presence or absence divides 3
tissue layer organisms
 True coelom is completely
lined with mesoderm
 Pseudocoelom not
completely lined
 Platyhelminthes (flat worms)
lacks (acoelomate)
Embryonic Development
 Based on gastrula
opening formed
 Protostomes: opening
becomes mouth
 E.g Arthropoda
 Deuterostomes: opening
becomes anus
 Mouth forms elsewhere
 E.g Chordates
Phylum Porifera (Sponges)
 Most are stationary (sessile), marine, and asymmetrical
 Draws water in through pores and out an osculum
 Suspension feeders
 Choanocytes pull in food and
water
 Amoebocytes provide support


Spicules is mineralized material
Spongin is flexible protein
 No muscles or nerves
 Toxins and antibiotics release
for protection
Phylum Cnidaria (Cnidarians)
 Radial symmetry and 2
tissue layers
 Jelly like substance between
 Contractile and nervous




tissue (simple)
Exist as polyps or medusas
Carnivorous, use
cnidocytes
Incomplete GI tract
http://www.youtube.com/w
atch?v=fBkmzzAh8Eo&feat
ure=related
Phylum Platyhelminthes (flatworms)
 3 tissue layers, acoelomate, incomplete GI tract
 Class 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 systems
 Muscular foot, visceral mass, mantle, radula (chitinous
tongue)
 Class Gastropoda (snails and slugs)
 Live on land and in all waters
 Class 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 absent
 Most advanced invertebrate brain and sense organs (eyes)
 Class Bivalva (scallops, oysters, and clams)
 2 shells hinged together
 Suspension feeders, mantle has gills for food and gas exchange
Phylum Nematoda (Roundworms)
 Pseudocoelomate, GI tract with 2 openings, separate
sexes, and lateral muscles
 Free-living (C. elegans)
 Parasitic
 Dog heartworm
 50 species in humans



Trichinella spiralis
Hook worms
Pinworms
Phylum Annelida (Segmented Worms)
 Segmentation, longitudinal and circular muscles, closed
circulatory system
 Class Polychaeta
 Marine organisms, live in tubes, can be colonial
 Class 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 phylum
 Exoskeleton
 Protects and allows joint attachment
 Protein and chitin that Is molted with growth
 Segmentation
 Head, thorax (fused is cephalothorax), and abdomen
 Sensory, protection and walking, and swimming
respectively
 Open circulatory system, blood not contained in vessels
 Aquatic species with gills, terrestrial with air sacs
Subphylums
 Chelicerates (arachnids)
 Hollow mouth appendages
 First terrestrial carnivores, deliver venom or toxins
 E.g scorpions (night), spiders (day), and ticks/mites
 Mandibulata
 Solid mouth organs
 Examples



Millipedes are herbivores with 2 leg sets per segment
Centipedes are carnivores with 1 leg set per segment
Lobsters, and insects
Classes
 Crustacea (Crustaceans)
 Aquatic (mostly) and have gills (rolly-polly)
 Include lobsters, crayfish, shrimp, barnacles, and crabs
 Insecta (Insects)
 Most diverse group
 Wings, advanced sensory organs, communication, and
social structure
 Waterproof cuticle, short lives, complex life cycles, and
large offspring broods
Class Insecta
 Life cycles
 Only adults can reproduce or have functional wings
 Multiple molts allow for metamorphosis, complete or
incomplete
 Food sources differ so enhances adaptability
 Body plan
 3 parts: head, thorax, and abdomen
 Embryonic segments develop independently


Connects with mutation and evolution
3 pairs of legs, not at cost to legs
 Coloration
 Camouflage, mimicry, and coloration from independent
development
Phylum Echinodermata
 E.g sea stars, sand dollars, sea urchin and sea
cucumber
 Radial symmetry internally and externally as an adult
 Bilateral symmetry in larval stage
 Calcium containing plates form endoskeleton
 Tube feet that are extensions of a water vascular
system
 For locomotion, feeding, and gas exchange
 Mouth and stomach adaptations
 deuterostomes
 Capable of regeneration
Phylum Chordata
 4 characteristics
 Dorsal, hollow nerve cords
 Notocord between GI tract and nerve cord
 Pharyngeal slits
 Post-anal tail
 Tunicates (Sea squirts)
 Adult has pharyngeal slits only,
larva has all four
 Lancet
 Suspension feeders
 Mucus net to trap food
Phylogeny Review