The ultimate source of organic variation is :

Options

A. Mutation
B. Sexual reproduction
C. Natural selection
D. Hormonal action

Answer

**Step-by-Step Solution:**

1. **Understand the Question**: The question asks for the ultimate source of organic variation. Organic variation refers to the differences in the genetic makeup of individuals within a population.

2. **Evaluate the Options**: The options provided are:
- Option 1: Mutation
- Option 2: Sexual reproduction
- Option 3: Natural selection
- Option 4: Hormonal action

3. **Analyze Option 1 - Mutation**:
- Mutation refers to changes in the DNA sequence. These changes can occur due to errors during DNA replication or due to environmental factors. Mutations are the primary source of genetic variation in a population, as they introduce new alleles into the gene pool.

4. **Analyze Option 2 - Sexual Reproduction**:
- Sexual reproduction involves the combination of genetic material from two parents (male and female) to produce offspring. While it does create variation, it does not create new genetic material; it shuffles existing genes.

5. **Analyze Option 3 - Natural Selection**:
- Natural selection is a process that acts on existing variation within a population. It does not create new variation; rather, it favors individuals with advantageous traits, leading to evolutionary change over time.

6. **Analyze Option 4 - Hormonal Action**:
- Hormonal action refers to the influence of hormones on biological processes. While hormones can affect development and behavior, they do not create genetic variation.

7. **Conclusion**: Based on the analysis, the ultimate source of organic variation is **mutation** (Option 1). Mutations introduce new genetic variations that can be acted upon by natural selection, leading to evolution.

**Final Answer**: The ultimate source of organic variation is **mutation**.

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