The document discusses various form and functions of invertebrates including different types of digestion, circulatory systems, skeletons, and reproduction. It outlines intracellular and extracellular digestion, open and closed circulatory systems, hydrostatic skeletons, exoskeletons, and endoskeletons. The document also covers external and internal fertilization and discusses trends in the evolution of the nervous system in invertebrates.

1. 29-2 Form and Function in Invertebrates

2. Intracellular digestion Process in which food is digested inside cells

3. Extracellular digestion Process in which food is broken down outside the cells in a digestive tract.

4. Open circulatory System System in which blood is not always contained within a network of blood vessels

5. Closed circulatory System System in which blood is contained within a network of blood vessels

6. Hydrostatic skeleton Layers of circular and longitudinal muscles, together with the water in the gastrovascular cavity, that enable movement.

7. Exoskeleton External skeleton; tough external covering that protects and supports the body of many invertebrates.

8. endoskeleton Structural support located inside the body of an animal

9. External fertilization Process in which eggs are fertilized outside the female’s body.

10. Internal fertilization Process in which eggs are fertilized inside the female’s body.

11. Key Concept The simplest animals break down food primarily through intracellular digestion, but more complex animals use extracellular digestion.

12. Key concept Respiratory organs have large surface areas that are in contact with the air or water. Also, for diffusion to occur the respiratory surfaces must be moist.

13. Key Concept Most complex animals move blood through their bodies using one or more hearts and either an open or a closed circulatory system.

14. Key Concept Most animals have an excretory system that rids the body of metabolic wastes while controlling the amount of water in the tissues.

15. Key concept Invertebrates show three trends in the evolution of the nervous system: centralization, cephalization, and specialization.

16. Key Concept Invertebrates have one of three main kinds of skeletal systems: hydrostatic skeletons, exoskeletons, or endoskeletons.

17. Key concept Most invertebrates reproduce sexually during at least part of their life cycle. Depending on environmental conditions, however, many invertebrates may also reproduce asexually.