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Animals
AP Biology
Mrs. Ramon
Intro. To Animal Evolution
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What is an animal?
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Multicellular, heterotrophic eukaryotes
Lack cell walls
Two unique types of tissues: nervous tissue for
impulse conduction and muscle tissue for
movement.
Most animals reproduce sexually, with the diploid
stage usually dominating the life cycle
Animal Evolution
Cnidaria
Porifera
sponges
jellyfish
Nematoda
Platyhelminthes
Annelida
Mollusca
Echinodermata
Arthropoda
flatworms roundworms mollusks segmented
worms
redundancy,
segmentation
specialization,  mobility
insects
spiders
starfish
Chordata
vertebrates
 body & brain
backbone
size,  mobility
 body size endoskeleton
coelom  digestive sys
radial
body cavity  body complexity
 digestive & repro sys
bilateral symmetry
tissues
multicellularity
Ancestral Protist
distinct body plan; cephalization
specialized structure & function,
muscle & nerve tissue
specialization &  body complexity
bilateral
Early Embryonic Development
From Protozoans to Animals
Body Cavity
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Space for organ system
development
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increase digestive &
reproductive systems
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increase food capacity
& digestion
increase gamete
production
Coelem
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mesoderm & endoderm
interact during
development
allows complex
structures to develop in
digestive system
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ex. stomach
acoelomate
ectoderm
mesoderm
endoderm
pseudocoelomate
ectoderm
mesoderm
endoderm
pseudocoel
coelomate
ectoderm
mesoderm
coelom cavity
endoderm
protostome vs. deuterostome
Body Cavities (cont.)
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Acoelomates (the phylum Platyhelminthes) have a
solid body and lack a body cavity.
Body Cavities (cont.)
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In some organisms, there is a body cavity, but it is
not completely lined by mesoderm.
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This is termed a pseudocoelom.
These pseudocoelomates include the rotifers (phylum
Rotifera) and the roundworms (phylum Nematoda).
Body Cavities (cont.)
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Coelomates are organisms with a true coelom, a
fluid-filled body cavity completely lined by
mesoderm.
Invertebrates: Porifera
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Sponges
 Adults sessile
 No distinct tissues or
organs
 No symmetry
Invertebrates: Cnidaria
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Hydras, jellies, sea
anemones and corals
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Tissues, but no organs
Two cell layers
Gastrovascular cavity
Sessile (anemone) or
floating (jelly)
Cnidocytes (tentacles)
Invertebrates: Platyhelminthes
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Flatworms
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Tapeworm, planaria
Mostly parasitic
Bilateral symmetry
Cephalization
Acoelomates with
gastrovascular
cavities
Asexual or sexual
reproduction
Invertebrates: Nematoda
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Roundworms
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Bilateral symmetry
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Nonsegmented
pseudocoelomates
covered with tough
cuticles
Digestive system
Many are parasitic:
 Hook worm
 Trichinella spiralis
causes trichinosis
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Undercooked meat
Invertebrates: Mollusca
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Snails, slugs, clams
squid
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Bilateral symmetry
(some exceptions)
True coelem
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Polyplacophora (chitons)
Gastropoda (snails and
slugs),
Bivalvia (clams, oysters,
and other bivalves)
Cephalopoda (squids,
octopuses and
nautiluses).
Invertebrates: Annelida
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Segmented worms
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Earthworms, leeches
Segments
 Increase mobility
 Redundancy in body
sections
Bilateral symmetry
True coelem
Invertebrates: Arthropoda
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Spiders, insects,
crustaceans
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A billion billion (1018)
individuals (2/3
organisms)
Bilateral symmetry
Body segmentation
Hard exoskeleton
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Chitin and protein
Jointed appendages
Arthropod Classes: Insecta
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26 different orders within
the Class Insecta
Defining features:
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6 legs
3 body parts
Arthropod Classes: Crustacea
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Lobsters, crab, crayfish,
shrimp and barnacles
Defining features:
 Gills
 2 pairs of antennae
Invertebrates: Echinodermata
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Sea stars, brittle stars, sea
urchins, sand dollars and sea
cucumbers
 Sessile or slow moving
 Water vascular system
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Locomotion, feeding
and gas exchange
Spiny endoskeleton
Radial symmetry
Vertebrates: Chordata
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Fish, amphibians,
reptiles, birds and
mammals
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Features:
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Notochord
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Disks
Nerve chord
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Brain and spinal
chord
Pharyngeal slits
Muscular postanal tail
Vertebrates: Fish
450 mya
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Characteristics
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bony & cartilaginous skeleton
jaws & paired appendages (fins)
scales
body function
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gills
body structure
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salmon, trout
gills for gas exchange
two-chambered heart;
single loop blood circulation
ectotherms
reproduction
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external fertilization
external development in
aquatic egg
body
Transition to Land
Evolution of tetrapods
Humerus
Femur
Pelvis
Tibia
Ulna
Shoulder
Radius
Lobe-finned fish
Fibula
Pelvis
Femur
Humerus
Tibia
Fibula
Early amphibian
Ulna
Shoulder
Radius
Vertebrates: Amphibian
350 mya
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Characteristics
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legs (tetrapods)
moist skin
buccal
cavity
glottis
closed
body function
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lung
body structure
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frogs
salamanders
toads
lungs (positive pressure) &
diffusion through skin for gas exchange
three-chambered heart;
veins from lungs back to heart
ectotherms
reproduction
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external fertilization
external development in aquatic egg
metamorphosis (tadpole to adult)
Vertebrates: Reptiles
250 mya
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Characteristics
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body structure
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dry skin, scales, armor
body function
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dinosaurs, turtles
lizards, snakes
alligators, crocodile
lungs for gas exchange
thoracic breathing; negative pressure
three-chambered heart
ectotherms
leathery
reproduction
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shell
embryo
amnion
internal fertilization
external development in
amniotic egg
chorion
allantois
yolk sac
Vertebrates: Birds (Aves)
150 mya
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finches, hawk
ostrich, turkey
Characteristics
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body structure
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body function
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feathers & wings
thin, hollow bone;
flight skeleton
very efficient lungs & air sacs
four-chambered heart
endotherms
reproduction
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internal fertilization
external development in
amniotic egg
trachea
lung
anterior
air sacs
posterior
air sacs
Vertebrates: Mammals
220 mya / 65 mya
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Characteristics
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body structure
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hair
specialized teeth
body function
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mice, ferret
elephants, bats
whales, humans
muscles
contract
lungs, diaphragm; negative pressure
four-chambered heart
endotherms
reproduction
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internal fertilization
internal development in uterus
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nourishment through placenta
birth live young
mammary glands make milk
diaphragm
contracts
Vertebrates: Mammals
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Sub-groups
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monotremes
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egg-laying mammals
lack placenta & true nipples
duckbilled platypus, echidna
marsupials
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pouched mammals
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offspring feed from nipples in pouch
short-lived placenta
koala, kangaroo, opossum
placental
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true placenta
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nutrient & waste filter
shrews, bats, whales, humans