Download animal diversity 25

Overview of Animal Diversity
LEARNING OUTCOMES
• Understand how the animals are organized and
how this organization is different from that of
plants, fungi, protists, and prokaryotes.
• Compare and contrast Parazoa and Eumetazoa in
terms of evolution, complexity, symmetry, and
organization of embryonic cell layers.
• Compare and contrast asymmetry, radial
symmetry, and bilateral symmetry.
• Differentiate among acoelomate,
pseudocoelomate, and coelomate organisms;
indicate how they are evolutionarily related and
give examples of each.
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• Differentiate between protostomes and
deuterostomes.
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General Features of Animals
Animals are the consumers of the Earth
They are a very diverse group
-However, they share major
characteristics
-Are heterotrophs
-Are multicellular
-Have cells without cell walls
-Most are able to move
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General Features of Animals
-Are very diverse in form and habitat
-Most reproduce sexually
-Have a characteristic pattern of
embryonic development
-Cells of all animals (except sponges)
are organized into tissues
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Evolution of the Animal Body
Plan
1. Tissues
2. Symmetry
3. Body cavity
4. Development
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Evolution of the Animal Body
Plan
1. Evolution of tissues
Metazoans are divided into two main
branches:
-Parazoa (Sponges - the simplest animals)
lack defined tissues and organs
-Have the ability to disaggregate and
aggregate their cells
-Eumetazoa (all other animals) have distinct
and well-defined tissues
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-Have irreversible differentiation for most
Evolution of the Animal Body
Plan
2. Evolution of symmetry
-Sponges also lack any definite symmetry
-Eumetazoa have a symmetry defined along
an imaginary axis drawn through the animal’s
body
-There are two main types of symmetry
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Evolution of the Animal Body
Plan
-Radial symmetry
-Body parts arranged around central axis
-Can be bisected into two equal halves in
any 2-D plane
-Bilateral symmetry
-Body has right and left halves that are
mirror images
-Only the sagittal plane bisects the
animal into two equal halves
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Top
Back
Front
Bottom
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Evolution of the Animal Body
Plan
Bilaterally symmetrical animals have two
main advantages over radially
symmetrical ones
1. Cephalization
-Evolution of a definite brain area
2. Greater mobility
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Evolution of the Animal Body
Plan
3. Evolution of a body cavity
-Eumetazoa produce three germ layers
-Outer ectoderm (body coverings and nervous
system)
-Middle mesoderm (skeleton and muscles)
-Inner endoderm (digestive organs and
intestines)
Body cavity = Space surrounded by mesoderm
tissue that is formed during development
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Diploblastic vs. Triploblastic – Cell
Layers
Diploblastic – two cell layers
– Ectoderm – outer layer
– Endoderm – inner layer
– The Radiata
Triploblastic – three cell layers
– Ectoderm, endoderm
– Mesoderm – layer between ectoderm
and endoderm
– The Bilateria
Ectoderm – outer covering of the body; nervous system
Endoderm – digestive organs and intestines
Mesoderm – skeleton and muscles
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Evolution of the Animal Body
Plan
3. Evolution of a body cavity
-Three basic kinds of body plans
-Acoelomates = No body cavity
-Pseudocoelomates = Body cavity
between mesoderm and endoderm
-Called the pseudocoel
-Coelomates = Body cavity entirely within
the mesoderm
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-Called the coelom
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Evolution of the Animal Body
Plan
-The body cavity made possible the
development of advanced organs systems
• Pseudocoelomates use pseudocoel for circ.
• Coelomates developed a circulatory system
to flow nutrients and remove wastes
-Open circulatory system: blood
passes from vessels into sinuses, mixes
with body fluids and reenters the vessels
-Closed circulatory system: blood
moves continuously through vessels that
are separated from body fluids
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• Why do you think closed is more advanced?
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Evolution of the Animal Body
Plan
4. Evolution of different patterns of
development
-The basic Bilaterian pattern of development:
-Mitotic cell divisions of the egg form a
hollow ball of cells, called the blastula
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Evolution of the Animal Body
Plan
Bilaterians can be divided into two groups:
-Protostomes develop the mouth first from or
near the blastopore
-Anus (if present) develops either from
another region of embryo
-Deuterostomes develop the anus first from the
blastopore
-Mouth develops later from another region
of the embryo
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Embryonic development in protostomes and
deuterostomes
Protostomes
Mesoderm
Archenteron
Coelom
Mesoderm splits
Blastula
Blastopore
Archenteron
Blastula
Blastopore
Coelom
Archenteron outpockets
to form coelom
Anus
Coelom
Mouth forms Mouth
from blastopore
Mouth
Coelom
Anus
Anus forms
from blastopore
Deuterostomes
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