Invertebrate and
Vertebrate Evolution
and Diversity
AP Biology
2007-2008
Animal Evolution
Cnidaria
Porifera
sponges
jellyfish
Nematoda
Platyhelminthes
Annelida
Mollusca
Echinoderm
Arthropoda
flatworms roundworms mollusks segmented
worms
insects
spiders
Chordata
starfish
vertebrates
backbone
segmentation
endoskeleton
coelom
body cavity
bilateral symmetry
tissues
multicellularity
AP Biology
Ancestral Protist
Phylum Porifera
 Sponges

no distinct tissues or organs
 do have specialized cells
no symmetry
 sessile (as adults)

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food taken into each
cell by endocytosis
Phylum Cnidaria
 Jellyfish, hydra, sea anemone, coral
tissues, but no organs
 two cell layers
 radial symmetry
 predators

 tentacles surround
gut opening
 extracellular
digestion
 release enzymes
into gut cavity
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Stinging cells of Cnidarians
mouth
tentacles
sensory
cell
stinging
cell
hydra
trigger
stinging cell
with nematocyst
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discharged
nematocyst
undischarged
nematocyst
Phylum Platyhelminthes
 Flatworms
tapeworm, planaria
 mostly parasitic
 bilaterally symmetrical

 allows high level of specialization
within parts of the body
 now have a mouth at one end
& an anus at the other!
ectoderm
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mesoderm
endoderm
Phylum Nematoda
 Roundworms
bilaterally symmetrical
 have both mouth & anus

 well-developed digestive system

many are parasitic
 hookworm
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C. elegans
Phylum Mollusca
 Mollusks
clams, snails, squid
 bilaterally symmetrical (with exceptions)
 soft bodies, mostly protected by hard shells
 true coelem

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Phylum Annelida
 Segmented worms
earthworms, leeches
 segments are not specialized
 bilaterally symmetrical
 true coelem
fan worm

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leech
Phylum Arthropoda
 Spiders, insects, crustaceans
most successful animal phylum
 bilaterally symmetrical
 segmented

 allows jointed appendages

exoskeleton
 chitin + protein
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Arthropod groups
arachnids
8 legs, 2 body parts
spiders, ticks, scorpions
crustaceans
gills, 2 pairs antennae
crab, lobster, barnacles,
shrmp
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insects
6 legs, 3 body parts
Phylum Echinodermata
 Starfish, sea urchins, sea cucumber

Water vascular system (hydraulic canals)
 Locomotion, feeding, gas exchange


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radially symmetrical
spiny exoskeleton
Phylum Chordata
 Two subphyla of invertebrate animals…
 And the subphylum Vertebrata
fish, amphibians, reptiles, birds, mammals
hollow dorsal
nerve cord
 internal bony skeleton

 backbone encasing
becomes brain
& spinal cord
spinal column
 skull-encased brain
becomes gills or
Eustachian tube
Oh, look…
your first
baby picture!
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pharyngeal
pouches
postanal
becomes tail tail
or tailbone
becomes
vertebrae
notochord
450 mya
salmon, trout, sharks
Vertebrates: Fish
 Characteristics

gills
body structure
 bony & cartilaginous skeleton
 jaws & paired appendages (fins)
 scales

body function
 gills for gas exchange
 two-chambered heart;
single loop blood circulation
 ectotherms

reproduction
 external fertilization
 external development in
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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
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Early amphibian
Ulna
Shoulder
Radius
350 mya
frogs
salamanders
toads
Class Amphibia
 Characteristics

lung
body structure
 legs (tetrapods)
 moist skin

buccal
cavity
glottis
closed
body function
 lungs (positive pressure) &
diffusion through skin for gas exchange
 three-chambered heart;
veins from lungs back to heart
 ectotherms

reproduction
 external fertilization
 external development in aquatic egg
 metamorphosis (tadpole to adult)
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250 mya
Class Reptilia
 Characteristics

dinosaurs, turtles
lizards, snakes
alligators, crocodile
body structure
 dry skin, scales, armor

body function





lungs for gas exchange
thoracic breathing; negative pressure
three-chambered heart
ectotherms
leathery
reproduction
shell
embryo
amnion
 internal fertilization
 external development in
amniotic egg
chorion
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allantois
yolk sac
150 mya
finches, hawk
ostrich, turkey
Class Aves (Birds)
 Characteristics

body structure
 feathers & wings
 thin, hollow bone;
flight skeleton

body function
 very efficient lungs & air sacs
 four-chambered heart
 endotherms

reproduction
 internal fertilization
 external development in
amniotic egg
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trachea
lung
anterior
air sacs
posterior
air sacs
220 mya / 65 mya
mice, ferret
elephants, bats
whales, humans
Class Mammalia
 Characteristics

body structure
 hair
 specialized teeth

body function
muscles
contract
 lungs, diaphragm; negative pressure
 four-chambered heart
diaphragm
 endotherms
contracts

reproduction
 internal fertilization
 internal development in uterus
 nourishment through placenta
 birth live young
 mammary glands make milk
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Class Mammalia
 Sub-groups

monotremes
 egg-laying mammals
 duckbilled platypus, echidna

marsupials
 pouched mammals
 short-lived placenta
 koala, kangaroo, opossum

placental
 true placenta
 shrews, bats, whales, humans
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Vertebrate quick check…





Which vertebrates lay eggs with shells?
Which vertebrates are covered with scales?
What adaptations do birds have for flying?
What kind of symmetry do all vertebrates have?
Which vertebrates are ectothermic and which
are endothermic
 Why must amphibians live near water?
 What reproductive adaptations made mammals
very successful?
 What characteristics distinguish the 3 subgroups of mammals?
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