1. What is an Animal?

2. Characteristics of Animals
Animals are eukaryotic, multicellular organisms with ways of moving that help them reproduce, obtain food, and protect themselves.
Section 25.1 Summary – pages

3. Animals are composed of cells that do not have cell walls.
Most animals have specialized cells that form tissues and organs—such as nerves and muscles.
Animals are composed of cells that do not have cell walls.
Animals obtain food
Some animals do not move throughout their lives – they are sessile.
Usually, if the adult is sessile, the larva is motile and vice versa.
Section 25.1 Summary – pages

4. Animal Development Most develop from a fertilized egg = ZYGOTE.
Blastula to Gastrula
Three cell layers: ectoderm, endoderm, mesoderm

5. Body Plans: SYMMETRY – the arrangement of body structures.
1. Asymmetry or no symmetry
irregularly shaped body
often sessile

6. 2. Radial Symmetry
can be divided on any plane, through a central axis, into roughly equal halves.
an adaptation that allows an animal to detect and capture prey coming from any direction.
generally two layers and one body opening.

7. 3. Bilateral Symmetry
Can be divided in half along one plane = right and left
3 cell layers = muscles
Sense organs in anterior end – adaptation for finding food and mates and avoiding predators

8. Categories of Animals Invertebrates: no backbone
Vertebrate: Endoskeleton
and a backbone.

9. Animal Protection and Support
Exoskeleton: hard covering on the OUTSIDE of the body
Framework for support
Prevents water loss
Protection from predators.
Made of chitin
Disadvantage: must MOLT (shed) to grow.

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11. Endoskeleton: INTERNAL skeleton
Made of calcium carbonate (starfish) or bone (vertebrates).
Provides support for body
Protects internal organs.
Advantage: grows with body.

12. Origin of Animals
Probably developed from aquatic, colonial protists.