How would you explain this situation?

A particular species of land snail has a shell that may be brown, yellow, or pink.





a) shell color has not been affected by natural selection.


b) shell color is determined by polygenic inheritance.


c) shell color exhibits a continuous distribution.


d) these snails are polymorphic for shell color.


e) sheel clolor is the result of convergent evolution.

How would you explain this situation?
d) these snails are polymorphic for shell color.


There are different forms ("poly" = many, "morph" = shape or form) -- in this case, three colors.





Why the others are wrong:


a) shell color has not been affected by natural selection.


What if the snails live in an enviroment rich in those three colors -- then it's obvious.


b) shell color is determined by polygenic inheritance.


A single allele could determine shell color:


CC = yellow / Cc = brown / cc = pink


c) shell color exhibits a continuous distribution.


No, there are three distinct colors.


e) shell clolor is the result of convergent evolution.


A single color snail could have diverged to three colors.

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