1. Overview of Animal Diversity

2. 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.

3. Differentiate between protostomes and deuterostomes.

4. 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

5. 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

6. Evolution of the Animal Body Plan
1. Tissues
2. Symmetry
3. Body cavity
4. Development

7. Evolution of the Animal Body Plan
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
-Have irreversible differentiation for most cell types

8. 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

9. 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

10. Top
Back
Front
Bottom

11. 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

12. 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

13. 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

14. 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
-Called the coelom

16. 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
Why do you think closed is more advanced?

18. 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

19. 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

20. Embryonic development in protostomes and deuterostomes
Coelom
Archenteron
Mesoderm splits
Mouth forms
from blastopore
Mouth
Coelom
Anus
Mesoderm
Blastopore
Blastula
Coelom
Archenteron
Archenteron outpockets
to form coelom
Mouth
Coelom
Anus
Anus forms
from blastopore
Blastopore
Blastula
Deuterostomes