What are some examples of biochemical and physiological evidence for evolution?

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Degrees of similarity in the structure of biomolecules of organisms, and in the physiology of systems in organisms help to show how closely those organisms are related to each other.

One of the major biochemical evidences for evolution is the universal genetic code. All organisms have the same four nucleic...

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Degrees of similarity in the structure of biomolecules of organisms, and in the physiology of systems in organisms help to show how closely those organisms are related to each other.

One of the major biochemical evidences for evolution is the universal genetic code. All organisms have the same four nucleic acids that code for amino acids; the amino acid sequence created determines the type of protein produced. When we study the amino acid sequence of various vital proteins, we can estimate how far back in time different organisms diverged from each other. For example, proteins that are vital for cellular respiration are common to most organisms, and the structures are similar. But the structure for, say, cytochrome C in humans may differ by only a few amino acids from that of chimpanzees, more from that of a horse, and differ by even more from that of an oak tree. All, however, are coded for by the same four nucleic acids, showing they all evolved from a common ancestor.

Physiology refers to how an organism's systems function. Similarities are obvious if you look at the respiratory, circulatory, cardiovascular, reproductive and digestive systems of mammals. It is one of the reasons they are grouped together in the same class. Reptiles and amphibians split off from the evolutionary "tree" before mammals differentiated further; although they have the same systems, there are marked differences. 

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