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 evolution, as it provides the raw material for natural selection to act upon. Without genetic variation, a population cannot adapt to changing environments, which can lead to extinction. 2. The 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 mutagens. Mutations can introduce new alleles (versions of a gene) into a population, which can lead to new traits.

• Types of Mutations:
• Point mutations: A single nucleotide change (e.g., A to G).
• Insertions and deletions: Adding or removing nucleotides, which can alter the reading frame of a gene.
• Chromosomal mutations: Larger-scale changes that can affect multiple genes.

Mutations are the only source of new genetic material. While other mechanisms can shuffle existing genetic variation, they do not create new genetic information. 3. Why Other Options Are Incorrect or Weaker:

• A. Natural Selection:
• Natural selection is a process that acts on existing genetic variation. It favors individuals with advantageous traits, leading to an increase in those traits in the population over time. However, it does not create new genetic variation; it merely selects for traits that already exist.
• B. Genetic Drift:
• Genetic drift is a random process that can lead to changes in allele frequencies in a population, especially in small populations. While it can result in the loss of genetic variation, it does not introduce new genetic variation. Instead, it can lead to the fixation or loss of alleles purely by chance.
• D. Gene Flow:
• Gene flow, or gene migration, occurs when individuals from one population migrate to another and breed, introducing new alleles into the gene pool. While gene flow can increase genetic diversity, it relies on the presence of existing genetic variation in the migrating individuals. It does not create new genetic variation on its own.

Summary of Key Points

• Mutation is the primary source of new genetic variation in a population, introducing new alleles through changes in DNA.
• Natural selection, genetic drift, and gene flow do not create new genetic variation; they act on existing variation.
• Understanding these mechanisms is crucial for grasping how populations evolve and adapt over time.

Revision Summary

• Mutation introduces new genetic variation by altering DNA sequences.
• Natural selection acts on existing variation, favoring advantageous traits.
• Genetic drift randomly changes allele frequencies, often reducing variation.
• Gene flow mixes genetic material between populations but does not create new variation.