1. Key Features of Animals
ingest food
multicellular
no cell walls
classified largely based on:
body symmetry
digestive tract type
skeletal type
muscle type

2. FIGURE 23-1 An evolutionary tree of some major animal phyla

3. FIGURE 23-2a Body symmetry and cephalization
(a) Animals with radial symmetry lack a well-defined head. Any plane that passes through the central axis divides the body into mirror-image halves.

4. Blind Digestive Tract with Mouth/Anus
Open Digestive Tract with Mouth and Anus

5. Hydrostatic Skeleton
Exoskeleton
Endoskeletons

6. Circular and Longitudinal Muscles move Elongated Bodies
Flexors and Extensors move Jointed Skeletons

7. Porifera asymmetrical body plan lack true tissues and organs
internal skeleton made of spicules

8. Cnidaria radial symmetry jellylike mesoglea
bag-like digestive tract with a single opening
tentacles equipped with stinging cells

9. Platyhelminthes bilateral symmetry
digestive tract with a single opening
mesenchyme tissue

10. Annelida bilateral symmetry
digestive tract with two openings (mouth and anus)
coelom functions as a skeleton
longitudinal and circular muscles
body segmented
closed circulatory system

11. Mollusca bilateral symmetry soft body usually with a shell
digestive tract with two openings
circular and longitudinal muscles

12. Nematoda bilateral symmetry
digestive tract with separate mouth and anus
longitudinal muscles only

13. Arthropoda bilateral symmetry paired, jointed appendages
body divided into segments
exoskeleton which must be molted
flexor and extensor muscles

14. Echinodermata adults have pentaradial symmetry
possess an endoskeleton that sends projections through the skin
unique tube foot locomotory system