Transcript 1. List characteristics that distinguish animals from

1. List characteristics that distinguish
animals from organisms in the other four
kingdoms.
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Multicellular eukaryotes
Heterotrophy by ingestion
Carbohydrate reserves as glycogen
No cell walls
Highly differentiated body cells  tissues
 organs  organ systems
• Nervous and muscle tissue is unique 
2. Distinguish between radial and bilateral
symmetry.
• Radial  have a top and bottom but no
“sides” – can be divided along any plane for
roughly equal halves
• Bilateral  have dorsal, ventral, anterior
and posterior body surfaces
 exhibit “cephalization” – an evolutionary
trend towards concentration of sensory
structures towards the anterior end 
3. Page 591  Outline the major phylogenetic branches of the
animal kingdom, which are based upon grade of organization;
symmetry and embryonic germ layers; absence or presence of a
body cavity; and protostome-deuterostome dichotomy.
• Symmetry  none, radial, bilateral
• Germ layers  ectoderm, mesoderm, endoderm
• Body cavity  acoelomate, pseudocoelomate,
coelomate
• Coelomates divided into two lines:
1. The protostomes: mollusks, annelids, arthropods
2. The deuterostomes: echinoderms & chordates
 This division is based on cell cleavage, coelom
formation, and the blastopore fate (comparisons
on a later slide) 
4. Distinguish among acoelomate,
psuedocoelomate and coelomate.
• Acoelomate  an animal body plan
characterized by no body cavity between
the digestive tract and outer body wall
• Pseudocoelomate  a fluid filled body
cavity that separates the digestive tract
and outer body wall
• Coelomate  fluid-filled body cavity
completely lined with tissue derived from
mesoderm and separates the digestive
from the outer body wall 
5. Distinguish between spiral and radial
cleavage; determinant and indeterminate
cleavage; schizocoelous and enterocoelous.
• Spiral cleavage  cleavage in which the
planes of cell division are diagonal to the
vertical axis of the embryo
• Radial cleavage  cleavage during which
the cleavage planes are either parallel or
perpendicular to the vertical axis of the
embryo
continued…
#5 continued…
• Determinate  the developmental fate of
each embryonic cell is established very
early
 if a cell is isolated from the 4-cell stage
the embryo will not fully develop
• Indeterminate  early embryonic cells
retain capacity to develop into a complete
embryo if isolated from other cells: this
type of cleavage in the human zygote
results in identical twins 
#5 continued…
• Schizocoelous  descriptive term for
coelom development during which, as the
archenteron forms, the coelom begins as
splits within the solid mesodermal mass;
this is found in protostomes
• Enterocoelous  coelom development
during which the mesoderm arises as
lateral outpocketings of the archenteron
with hollows that become coelomic cavities;
formation found in deuterostomes 
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6. Compare developmental differences
between protostomes and deuterostomes
including: plane of cleavage, determination,
coelom formation, fate of the blastopore
Protostomes
Deuterostomes
Spiral cleavage
• Radial cleavage
Determinate
• Indeterminate
cleavage
cleavage
Schizocoelous
• Enterocoelous
coelom formation
coelom formation
Blastopore forms
• Blastopore forms
the mouth
the anus 
7. Describe the hypothesis about animal
origins from unicellular ancestors.
• The animal kingdom probably originated
from colonial protists related to
choanoflagellates
• Colonial protist  an aggregate of identical
cells
- can be the beginning of specialization and
division of labor among a group of cells 
8. Explain why it is difficult to resolve what
the first animals looked like.
• Animals diversified so rapidly that it is
difficult from the fossil record to sort out
the sequence of branching in animal
phylogeny 
9. Describe two views about discontinuities
between Ediacaran and Cambrian fauna.
• Ediacaran fossils  appear to represent
cnidarians, but soft-bodied mollusks and
worms were also present
• Cambrian  the ancient animals of the
Ediacaran appeared to die out early
- debate still exists on the phylogenetic
conditions between the animals on the
Cambrian boundary 
Ediacaran
Cambrian