BIOLOGY SEC. 16-1.

4. Animals that do not have a backbone (makes up 95% of animal species).
5. The movement of blood or nutrients throughout the body.
12. An organism in the phylum Chordata, possessing a notochord at some stage.
13. The outermost germ layer; develops into skin and nervous system.
14. "Cold-blooded"; animals that rely on the environment for body heat.
16. Animals with jointed legs and an exoskeleton (e.g., Insects, Spiders).
18. "Warm-blooded"; animals that generate body heat internally.
23. Plan, The structural design or "blueprint" of an animal's body.
24. The maintenance of a stable internal environment despite external changes.
25. A support system maintained by fluid pressure (e.g., jellyfish, worms).

1. Animals with stinging cells and radial symmetry (e.g., Sea Anemone).
2. Animals that possess a backbone or spinal column.
3. Symmetry, Body parts arranged around a central axis (like a wheel or starfish).
6. The concentration of sense organs and nerve cells at the head end.
7. The middle germ layer; develops into muscles and circulatory system.
8. The ability to change position; can be motile or Sessile (fixed in one place).
9. Simple aquatic animals (Porifera) that lack true tissues or organs.
10. A hard, external support structure (e.g., shells of insects or crabs).
11. Symmetry, Can be divided into two identical halves (left/right) along a single plane.
13. Spiny-skinned marine animals (e.g., Starfish, Sea Urchin).
15. The process by which organisms produce offspring.
17. The exchange of oxygen and carbon dioxide gases.
19. An internal skeleton or supporting framework (e.g., human bones).
20. Animalia, A kingdom of multicellular, eukaryotic organisms that are heterotrophic.
21. The innermost germ layer; develops into the lining of digestive tract.
22. A hollow ball of cells formed during early embryonic development.