In a population of organisms, certain individuals pass on their alleles with more frequency than...
In a population of organisms, certain individuals pass on their alleles with more frequency than other individuals. What type of selection would increase or decrease a trait, such as size, in an entire population over generations?
- A. Competition
- B. Disruptive selection
- C. Directional selection
- D. Stabilizing selection
Correct Answer: C. Directional selection
Explanation
The correct answer is directional selection. Directional selection is when, over multiple generations, an entire population shifts its phenotype towards one extreme. Stabilizing selection is when the extremes of that trait decrease in frequency compared to the less extreme phenotypes. In the example of size, the extreme phenotypes are very small and very large. Disruptive selection is when the different extremes of a trait in a population become more frequent than the less extreme version, eventually forming different populations of organisms. If disruptive selection continues long enough, the differences between the two populations can accumulate to the point when they cannot breed with each other. This is speciation.