1. Unit 8 Chapter 25 What is an animal?

2. Characteristics of Animals
1) They are multicellular
2) They are heterotrophs (consumers)
Motility = most animals use locomotion to find their food sources
Sessile = organisms that are permanently attached (don’t spend much energy to obtain food)
Sponges are sessile animals

3. Characteristics of Animals
3) They injest their food
4) They have specialized cells, tissues, organs, & systems
Ex: the complex digestive tract of the earthworm

4. Characteristics of Animals
5) They have similar stages of development:
Blastula
Fluid-filled ball formed from many cell divisions
Gastrula
Blastula folds inward to form two layers

5. Gastrulation
Formation of a cavity of two or more layers with an opening at one end
1) Ectoderm = outermost layer
2) Endoderm = innermost layer
Higher animals have a third, middle layer:
3) Mesoderm = develops into muscles, etc 1 2 3

6. Symmetry the arrangement of body structures 1) Radial symmetry
Can be divided along any plane, through a central axis, into roughly equal halves

7. 2) Bilateral symmetry
Can be divided down its length into similar right & left halves
Has a definite front (anterior,) rear (posterior), top (dorsal,) and belly side (ventral)

8. Body plans Acoelomates
Develop from 3 cell layers, but have NO body cavity
Ex: flatworms

9. Body plans Pseudocoelomates
A fluid=filled body cavity only partially lined with mesoderm
Ex: Roundworms

10. Body plans
Coelomates
Has a fluid-filled body cavity completely surrounded by mesoderm
Ex: segmented worms & all higher animals

11. Animal Diversity Invertebrates Animals without backbones
Often having exoskeletons outside their body for framework & support

12. Animal Diversity Vertebrates
An animal with an endoskeleton & a backbone
Endoskeletons are internal frameworks that provide protection, support, & muscle attachment
Ex: fishes, amphibians, reptiles, birds & mammals