Apopulation of fish in an enclosed lagoon was threatened with overpopulation and a stressed food supply until a number of predators discovered the population. after a time, there were fewer fish, but the average swimming speed of the population of fish had increased. this is a good illustration of .

This is a good illustration of Natural Selection.

Explanation: Also known as (a.k.a.) "survival of the fittest". The fish who are more alert and faster swimmers, will naturally escape capture by the various predators, and continue to live and breed, passing along their genes and characteristics. The slower fish are caught and eaten and are, therefore, unable to breed to pass on their own genes and characteristics. Over time, the concentration of the characteristics that make the fish faster swimmers, is enhanced in the genes of the population, as there is less "watering down" of these genes by the slower swimmers.

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