Hardy - Weinberg equilibrium is known to be affected by gene - flow, genetic drift, mutation, genetic recombination and:

Options

A. Evolution
B. Limiting factors
C. Saltation
D. Natural selection

Answer

**Step-by-Step Solution:**

1. **Understanding Hardy-Weinberg Equilibrium**: The Hardy-Weinberg equilibrium describes a state in which allele and genotype frequencies in a population remain constant from generation to generation in the absence of evolutionary influences.

2. **Factors Affecting Hardy-Weinberg Equilibrium**: The equilibrium can be disrupted by several factors. The question lists gene flow, genetic drift, mutation, and genetic recombination as known factors.

3. **Identifying the Missing Factor**: We need to identify one more factor that affects Hardy-Weinberg equilibrium. The options provided are:
- Evolution
- Limiting factors
- Saltation
- Natural selection

4. **Analyzing the Options**:
- **Evolution**: This is a broad term and not a specific factor affecting the equilibrium.
- **Limiting factors**: These refer to environmental constraints but do not directly affect allele frequencies.
- **Saltation**: This refers to sudden changes in species, which is not a direct factor in the equilibrium context.
- **Natural Selection**: This is a process where certain traits become more or less common due to their impact on survival and reproduction.

5. **Conclusion**: Among the options, natural selection is the factor that directly affects the Hardy-Weinberg equilibrium by altering allele frequencies based on the reproductive success of individuals with certain traits.

**Final Answer**: Natural selection.

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