The multiple choice questions have five answer choices — one (and only one) is correct in each case.
Which of the following correctly explains how a favorable genetic trait can increase in frequency in a population?
Select an Answer
Segregation of alleles
The correct answer is natural selection, (B). Favorable traits increase in a population over time because the organisms bearing those favorable traits have some advantage over other members of the population, and thus leave more surviving offspring than do individuals without the trait. This is sometimes called "survival of the fittest" but it is important to realize that survival alone is only part of the equation; the gene frequency is most influenced by the differential reproductive success of these survivors (that is, by the fact that individuals with the trait leave more offspring than individuals without the favorable trait).
Lamarck, (while a very important man in his time, and one who struggled to come up with an explanation that made sense) has been shown to have been wrong about the inheritance of acquired characteristics, so choice (A) is clearly wrong. Adaptive radiation involves the spread of organisms into open niches and subsequent speciation, so (C) is not a correct choice. Genetic recombination is part of sexual reproduction, whether or not gene frequencies are changing, so (D) is not a correct choice. And finally, segregation of alleles does not explain a change in gene frequency over time. Choice (E) is not correct.