V. Respirtation
A. Introduction
Exchange of carbon dioxide and oxygen between an animal and the environment.
1. Animals
a. require a continuos supple of oxygen for aerobic respiration
b. must expel carbon dioxide
c. must have a wet respiratory surface
the exchange of gases requires structures with two basic charachteristics
1. Permeable surface area of sufficient size
2. moist surface area since gases cant normally cross dry membranes
B. Gas exchange Comparisons
1. Protists
Gases are exchanged by diffusion
2. Sponges to annelids
Gases are exchanged by diffusion
3. Mollusks and enchinoderms
Gases are exchanged through gills
4. Arthropoda
Gases are exchanged through trachea, book lungs, or gills
Some organisms, for example, earthworms and frogs, use their entire outer skin as the respiratory organ. The skin needs to be moist, so they live in water or in damp places.