Question

how does natural selection change allele frequencies in populations?
natural selection has no control over allele frequency changes.
natural selection selects alleles that improve fitness.
natural selection controls the rate of mutations.

Explanation:

To solve this, we analyze each option:

1. The first option is incorrect because natural selection does influence allele frequencies by favoring traits (and their associated alleles) that increase survival and reproduction (fitness).
2. The second option is correct. Natural selection acts on phenotypes, and alleles that code for traits (phenotypes) which improve an organism's fitness (ability to survive and reproduce) are more likely to be passed on to the next generation. Over time, this leads to an increase in the frequency of these beneficial alleles in the population.
3. The third option is incorrect. Natural selection does not control the rate of mutations. Mutations are random changes in the DNA, and natural selection acts on the existing genetic variation (including mutations) by selecting for or against the phenotypes they produce.

Answer:

The correct option is: Natural selection selects alleles that improve fitness.