TeXes Science Practice Test

What is one of the main criteria for natural selection to occur within a population?

1. Migration

2. Genetic variation

3. Mutations

4. Population size

The correct answer is: Genetic variation

Genetic variation is a fundamental criterion for natural selection because it provides the raw material that evolution acts upon. For natural selection to occur, there must be differences among individuals in a population that can affect their survival and reproductive success. When there is genetic variation, some individuals may possess traits that give them an advantage in their environment, allowing them to better survive and reproduce. Over time, these advantageous traits become more common in the population, leading to evolutionary changes. Without genetic variation, all individuals would be genetically similar, and natural selection would have no way to favor one set of traits over another, thereby stifling adaptation. In contrast, factors like migration, mutations, and population size can influence a population's genetic structure or dynamics, but they are not the primary criteria for the process of natural selection itself. Migration can introduce new genes, mutations create new variations, and population size affects genetic drift, but without genetic variation, the mechanism of natural selection cannot operate effectively.