"Natural selection is the obvious fact that some varieties of creatures are going to be more successful than others, and so they will contribute more offspring to future generations.
A favorite example of natural section is the peppered moth of England, Biston betularia. As far as anyone knows, this moth has
always existed in two basic varieties, speckled and solid black. In pre-industrial England, many of the tree trunks were light in color. This provided a camouflage for the speckled variety, and the birds tended to prey more heavily on the black variety. Moth collections showed many more speckled than black ones. When the Industrial Age came to England, pollution darkened the tree trunks, so the black variety was hidden, and the speckled variety was conspicuous. Soon there were many more black moths than speckled.
As populations encounter changing environments, such as that described above or as the result of migration into a new area, natural selection favors the combinations of traits which will make the creature more successful in its new environment. This might be considered as the positive role of natural selection. The negative role of natural selection is seen in eliminating or minimizing harmful mutations when they occur."
As populations encounter changing environments, such as that described above or as the result of migration into a new area, natural selection favors the combinations of traits which will make the creature more successful in its new environment. This might be considered as the positive role of natural selection. The negative role of natural selection is seen in eliminating or minimizing harmful mutations when they occur."
CMI
