SAT Subject Biology Practice Question 37: Answer and Explanation

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Question: 37

1. Which of these form the basis of natural selection?

I. Random mating

II. Limited environmental resources

III. Stable genotype frequencies over time

A. I only
B. II only
C. III only
D. I and II
E. II and III

Correct Answer: B

Explanation:

A principle of natural selection is that environmental resources are limited and cannot support an infinitely growing population. Therefore, individuals with certain phenotypes are more likely to pass on their alleles (that is, they have greater fitness). Random mating and stable genotype frequencies characterize a population in Hardy-Weinberg equilibrium, in which natural selection is not acting.

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