Which of the following is a true statement concerning genetic variation?
Select one:
A. It must be present in a population before natural selection can act upon.
B. It arises in response to changes in the environment.
C. It tends to be reduced by the processes involved when diploid organisms produce gametes.
D. It is created by the direct action of natural selection.
E. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.
The correct answer and explanation is :
The correct answer is A. It must be present in a population before natural selection can act upon.
Explanation:
Genetic variation refers to the differences in the genetic makeup among individuals in a population. This variation is crucial for the process of natural selection, as it provides the raw material for evolutionary changes. Let’s break down each option to understand why A is the correct choice:
- A. It must be present in a population before natural selection can act upon.
This is the correct answer. Genetic variation exists in populations as differences in DNA sequences, which can lead to differences in physical traits or behaviors. Natural selection can only act on traits that are already present in the population. For example, if a population of organisms has individuals with varying levels of resistance to a disease, natural selection can favor those with higher resistance. However, the variation must already be there; natural selection does not create variation but acts on it by selecting for beneficial traits and against harmful ones. - B. It arises in response to changes in the environment.
This statement is not true. Genetic variation arises primarily through mutations, gene flow, and sexual reproduction. While environmental pressures can influence which traits are selected for or against, genetic variation itself does not arise as a direct response to environmental changes. It is more of a random process (e.g., mutations) that may be influenced by the environment. - C. It tends to be reduced by the processes involved when diploid organisms produce gametes.
This is incorrect. When diploid organisms produce gametes (through meiosis), genetic variation is shuffled and redistributed through recombination, which actually increases genetic diversity, not reduces it. - D. It is created by the direct action of natural selection.
Natural selection does not create genetic variation; it merely acts on the existing variation. The variation is generated through mechanisms like mutations, genetic recombination, and migration. - E. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.
This statement is incorrect. Heterozygosity refers to the presence of different alleles at a genetic locus. A higher average heterozygosity indicates more genetic variation within a population, not less.
In summary, genetic variation must exist in a population before natural selection can act on it. The other options either misrepresent the nature of genetic variation or confuse the relationship between variation and natural selection.