Animal Form and Function
Chapter 32
What you need to know!
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The characteristics of animals.
The stages of animal development
How to sort the animal phyla based on
symmetry, development of a body
cavity, and the fate of the blastopore
The traits used to divide animals into
groups
All animals
Multicellular
Heterotrophic
1.
2.

Obtain nutrients by ingestion (eating)
Extracellular matrices hold the cells together
(tight junctions)
3.
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No cell walls
Mobility (at some point in their life)
Diploid dominant
Nervous and muscular tissue (most)
Sexual Reproduction
4.
5.
6.
7.
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Gametes fuse to form zygotes
Embryonic Stages
a)
b)
c)
Morula: mitosis
forms cell ball
through
cleavage of
zygote
Blastula: hollow
cell ball
Gastrula:
infolding of
cellular layers
Embryonic Germ Layers
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Endoderm
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Ectoderm
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Internal sac that
becomes the
digestive system
Outermost layer that
becomes the skin
and nerves
Mesoderm
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Cells between the
endo- and ectoderm
that become muscles
and other organs
Embryonic Development
Coelom
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Fluid filled body cavity
for cushioning organs or
to form a hydrostatic
skeleton
Animals with 3 germ
layers may develop this
Coelomates: organisms
with coelom
Acoelomates: organisms
w/out coelom
Coelom
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True coelom: body cavity
is completely lined by
mesoderm cells
(segmented worms and
vertebrates)
Pseudocoelom:
mesoderm and other
tissue cells form body
cavity (roundworms)
Animal Evolutionary Trends
Tissue Complexity
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Cells grouped into tissues according to similar
function
Tissues develop from germ layers during
embryogenesis
Organisms are said to be diploblastic when they
have 2 layers, triploblastic when they have 3
layers
Body symmetry
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Either radial (circular) symmetry with top and
bottom or
Bilateral symmetry with front (anterior), behind
(posterior), backside (dorsal), and stomach
(ventral)
Animal Evolutionary Trends

Cephalization
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Gastrovascular cavity
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fluid filled cavity cushioning internal organs
Segmentation
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Digestion of foods can have one opening: saclike gut, or 2
openings: digestive tract
Coelom
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In animals with bilateral symmetry progressive accumulation of
nerve tissue anterior as animals gain complexity: accessory
organs for seeing, feeling, tasting evolve
Body is divided into segments sometimes repeating (worms,
insects) or are modified into body parts
Protostomes and Deuterostomes
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Forms different cleavage patterns of early morula – spiral
cleavage or radial cleavage
Protostome vs. Deuterostome
Characteristic Proto
Deutero
Early cleavages
spiral(angle)
Radial(straight)
Infolding of
archenteron
Forms mouth
Forms anus
Coelom develops
from
split of archenteron Outpouching of
sides
archenteron