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Section 26-2
Section 26-3
Animal Characteristics
 Heterotrophs
 must ingest others for nutrients
 Multicellular
 complex bodies
 No cell walls
 allows active movement
 Sexual reproduction
 no alternation of generations
 no haploid gametophyte
Animal Evolution
Cnidaria
Porifera
sponges
jellyfish
Nematoda
Platyhelminthes
Annelida
Mollusca
flatworms roundworms mollusks segmented
worms
Echinodermata
Arthropoda
insects
spiders
Jointed appendages
redundancy,
segmentation  mobility
specialization,  mobility
starfish
Chordata
vertebrates
 body & brain
notochord
size,  mobility
 body size
endoskeleton
coelom  digestive sys
radial
body cavity
bilateral symmetry
tissues
distinct body plan; cephalization
specialized structure & function,
muscle & nerve tissue
multicellularity specialization &  body complexity
Ancestral Protist
 body complexity
 digestive & repro sys
bilateral
Body Cavity
 Space for organ system
development
acoelomate
ectoderm
mesoderm
endoderm
 increase digestive &
reproductive systems


increase food capacity &
digestion
increase gamete
production
 Coelem
 mesoderm & endoderm
interact during
development
 allows complex
structures to develop in
digestive system

ex. stomach
pseudocoelomate
ectoderm
mesoderm
endoderm
pseudocoel
coelomate
ectoderm
mesoderm
coelom cavity
endoderm
protostome vs. deuterostome
Early Embryonic Development
Protostomes
Gastrula
Embryo
Opening that forms first
key
Deuterostomes
Protostomes
Gastrula (
Embryo (
weeks)
weeks)
First opening
Key to tissue layers
Deuterostomes