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Animal Circulatory Systems

An efficient circulatory system has: This creates a problem:

The Fish Heart

Most fishes have never solved this problem, which is probably why most of them are "cold-blooded".

While obviously adequate to the fish's needs, this is not a very efficient system. The pressure generated by contraction of the ventricle is almost entirely dissipated when the blood enters the gills.

The Squid Hearts

This group of marine invertebrates has solved the problem by having separate pumps:

Three Chambers: the Frog and Lizard

The Frog Heart

The frog heart has 3 chambers: two atria and a single ventricle.

The Lizard Heart

Four Chambers: Birds, Crocodiles, and Mammals

The septum is complete in the hearts of birds, crocodiles, and mammals providing two separate circulatory systems: The efficiency that results makes possible the high rate of metabolism on which the endothermy ("warm-bloodedness") of birds and mammals depends.

Link to these illustrated discussions of the human (mammalian) circulatory system.

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22 December 2010