Tuesday, December 11, 2007



Animals such as pinnipeds, sea otters and polar bears are amphibious. In aquatic environments, it is difficult for warm-blooded mammals to survive. Most mammals have a natural insulator, blubber, that helps keep them warm and buoyant. Another way mammals control their body temp. is through a process called vasodilation. This involves them controlling their blood flow to and from peripheral vessals near the surface of their flippers and fins. This heat exchange enables cold blood returning to the body to warm up.
Mammals need air to breathe. Whales and dolphins breathe through blowholes on the back of their heads. When they reach the surface, they inhale the air and relax their muscular flap to close it so that they can return to dive. Under water, blood is driven away from the tissues that can handle low O2 levels and moves it toward the heart&brain where it is needed.
Their smooth skin allows them to swim well, creating less friction.