A-Level Biology OCR A
Blood Single Circulatory Heart Closed Systems Fish Passes
| Front |
Describe the features of single closed circulatory systems using fish as an example. |
| Back |
Single closed circulatory system:- Blood travels only once through the heart for each complete circulation
- Blood passes thru 2 sets of capillaries before returning to heart
- First set - exchanges oxygen and carbon dioxide
- Second set - substances exchanged between blood and cells in diff organ systems
- Blood returns to the heart slowly bc it passes thru 2 sets of very narrow vessels the pressure drops considerably - efficiency of exhange processes relatively low
- Fish have efficient single circulatory system and can be very active bc:
- Countercurrent gas exchange system in gills maintains steep conc gradient for diffusion of oxygen
- Body weight supported by water & they do not maintain their own body temp - lower metabolic demands so no need for double circ
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A-Level Biology OCR A