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Vertebrate Hearts
12 years ago
The hearts of vertebrate animals give a strong indication that random processes, not preconceived design, was the factor in the development of circulatory systems over millions of years. Let us examine the various forms:

Fish: Their hearts are two chambered, with the blood going first to the gills to be oxygenated and then to the rest of the body under low pressure. It is a slow and very inefficient process.

Amphibians: Their hearts are three chambered, with two atria and one ventricle, enabling the blood to be pumped twice through the heart per round trip rather than once like in a fish. But oxygenated blood from the lungs is constantly mixed with deoxygenated blood from the rest of the body as the heart beats. It's the sort of thing you would expect if a mutation merely added an third chamber to a fish heart, instead of an ideal heart design for amphibians.

Reptiles: They have hearts that are four chambered, but the two ventricles are still connected by an opening between them, allowing some mixing of oxygenated and deoxygenated blood. Again, a simple mutation would account for this, not intelligent design.

Although the hearts of fish, amphibians, and reptiles are poor in design, they in fact are adequate for these animals because they are cold-blooded and need less oxygen than birds and mammals, which are warm-blooded.

Birds and mammals:  Their hearts are completely devided into four chambers, two atria and two ventricles, and under normal conditions at no point is oxygenated and deoxygenated blood allowed to mix except in the liver.
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