Evolution of the Heart Image 2
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Evolution of the Heart (Image 2)

July 28, 2010
The three-chambered frog heart mixes oxygenated and deoxygenated blood in the ventricle. Therefore, the body never receives fully oxygen-rich blood. In turtles, where a septum begins to form and separate the ventricles, the body receives slightly richer blood in oxygen. It is only in the warm-blooded model, in birds and mammals, that the two circulatory systems become fully separate sending low-pressure pumping to the lungs, and a high-pressure flow of blood to the rest of the body. In this model, the animal's muscles receive fully oxygenated blood. Recent research has found the first genetic link in the evolution of the heart from three-chambered to four-chambered, illuminating part of the puzzle of how birds and mammals became warm-blooded.

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