1 2 3

Bio 220 Lecture 18 Notes: Circulation Campbell, 5th, 811-815 I. Exchange of food/waste and O2/CO2 A. No circulatory system

41.9, 42.1

Cells ´environment

Many marine invertebrates manage to have most of their cells in contact or in close proximity with the environment. The cells exchange material directly by diffusion. 1. Strategies that facilitate direct exchange a. Flat bodies b. Large, branched internal cavities (gastrovascular systems) 2. Problems a. doesn't work in air b. doesn't work if more than a few cells thick B. Circulatory systems In these cases, cells exchange materials with a surrounding interstitial fluid. Some sort of circulatory system is required to facilitate exchange with the environment. Cells ´interstitial fluid ´environment

C. Open vs closed circulatory systems

42.2

Found in arthropods most mollusks annelids vertebrates

Motive force heart(s) pump

Fluid hemolymph = interstitial blood

Contained no

Rate slow

Open

Closed

heart(s) pump

yes

fast

1. Advantages of closed system a. more rapid, - able to deliver enough O2for high metabolic activity (insects require a second system for gas exchange)