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Name: Jason C.
Status: educator
Age: 20s
Location: N/A
Country: N/A
Date: 3/26/2004


Question:
I would like to know why it is that different species of owls have different color eyes? I know that the two main colors are brown as in the barred owl and yellow in the great horned and orange in European owls. I also know that melanin is what determines the color but why is the color determined by species? I have been researching this for a while and have not been able to find a solid answer, just the same speculations as I came up with. Any information on this topic would be most appreciated.


Replies:
First off...melanin is not the only determinant of eye color. In humans, eye color is not simply a dominant recessive association of the two alleles. If it was, then how would humans have the many shades of brown, the many shades of blue and green. The thickness of the iris plays a role also, which is certainly polygenic. I think rather than asking, " why it is that different species of owls have different color eyes", perhaps a more appropriate question is, "what advantage is there for the different species to have those colors?" As a biologist, I ask this question when I am wondering why a certain trait exists. There must be some evolutionary advantage. Also, I would reframe the question, "why is color determined by species" to what advantage in a certain species would a certain eye, or skin color serve?" A species no more determines the color of its eyes any more than a human being, because it is a homo sapiens, determines that it has mammary glands, is bipedal and communicates with spoken language. The traits we recognize in species help us define and recognize a species but these traits do not in statically determine the species. The species accumulates these traits through evolution because the environment has placed a selective pressure on the evolving species to survive with those traits.

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