Correct Option: C. Mutation Detailed Explanation 1. Understanding Genetic Variation: Genetic variation refers to the differences in DNA sequences among individuals within a population. This variation is crucial for the process of evolution, as it provides the raw material for natural selection to act upon. The more genetic variation present in a population, the better its chances of adapting to changing environments and surviving over time. 2. Role of Mutation: Mutations are changes in the DNA sequence of an organism's genome. They can occur due to various factors, including errors during DNA replication, exposure to radiation, or chemical influences. Mutations can be classified into several types, such as point mutations (single nucleotide changes), insertions, deletions, and larger chromosomal alterations.

• How Mutations Increase Variation:
• New Alleles: Mutations can create new alleles (variations of a gene). For example, if a mutation occurs in a gene responsible for flower color in a plant, it may result in a new color variant that was not previously present in the population.
• Diversity in Traits: These new alleles can lead to different traits being expressed in individuals, contributing to the overall genetic diversity of the population.

3. Why Other Options Are Incorrect:

• A. Natural Selection:
• Explanation: Natural selection is a process that acts on existing genetic variation within a population. It favors individuals with advantageous traits, leading to their increased survival and reproduction. However, it does not create new genetic variation; rather, it selects from the variation that is already present.
• Conclusion: While natural selection is crucial for shaping the genetic makeup of a population, it does not directly increase genetic variation.
• B. Genetic Drift:
• Explanation: Genetic drift is a random process that can lead to changes in allele frequencies in a population, especially in small populations. It can result in the loss of genetic variation over time, as alleles may become fixed (reach a frequency of 100%) or lost entirely. While it can affect the distribution of existing alleles, it does not introduce new genetic variation.
• Conclusion: Genetic drift can reduce genetic diversity rather than increase it.
• D. Environmental Changes:
• Explanation: Environmental changes can influence the survival and reproduction of individuals within a population, potentially leading to natural selection. However, environmental changes themselves do not create new genetic variation. They may alter the selective pressures on existing traits but do not introduce new genetic material.
• Conclusion: Environmental changes can affect how genetic variation is expressed but do not directly increase the genetic variation itself.

Summary of Key Points

• Genetic Variation: Essential for evolution and adaptation, referring to differences in DNA among individuals.
• Mutations: The primary source of new genetic variation, introducing new alleles and traits into a population.
• Natural Selection: Acts on existing variation but does not create it.
• Genetic Drift: Can reduce genetic variation, especially in small populations, by randomly altering allele frequencies.
• Environmental Changes: Influence selective pressures but do not create new genetic variation.

By understanding these concepts, students can appreciate the mechanisms that drive genetic diversity and the evolutionary processes that shape populations over time.