Dental Admissions Test (DAT) Practice Test

On which level does natural selection act within a species to allow advantageous traits to survive?

1. Incomplete Dominance

2. Phenotype

3. Selective pressure

4. Zygote

The correct answer is: Selective pressure

Natural selection acts on the phenotype of individuals within a species. The phenotype encompasses the observable traits and characteristics of an organism, which are influenced by both genetics and environmental factors. When certain traits offer a survival advantage and increase an organism's reproductive success, those traits become more common in subsequent generations. While selective pressure is certainly a factor that influences which phenotypes are favored, the mechanism of natural selection specifically targets the phenotypic expression of genes. Therefore, it is the phenotypes that are directly affected by natural selection, allowing for advantageous traits to survive and become more prevalent in the population over time. Incomplete dominance and zygote refer to specific genetic scenarios and developmental stages, which do not directly relate to how natural selection operates. Selective pressure conceptually describes the environmental factors that can influence the survival of certain phenotypes, but the action of natural selection itself is on the phenotypic characteristics present in the organisms.