Sexual reproduction where a smaller and motile male gamete fuses with larger and motile female gamete known as

Options

A. isogamy
B. anisogamy
C. oogamy
D. heterogamy

Answer

To solve the question regarding the type of sexual reproduction where a smaller and motile male gamete fuses with a larger and motile female gamete, we can analyze the options provided:

1. **Isogamy**: In isogamy, the gametes that fuse are of similar size. Therefore, this option does not apply to our question since we are dealing with gametes of different sizes.

2. **Anisogamy**: Anisogamy refers to sexual reproduction where the gametes are of different sizes. Here, we have a smaller, motile male gamete and a larger, motile female gamete. This fits the description given in the question, making this option a strong candidate.

3. **Oogamy**: Oogamy is a specific type of anisogamy where the female gamete is larger and non-motile, while the male gamete is smaller and motile. Since the question specifies that the female gamete is motile, this option does not apply.

4. **Heterogamy**: Heterogamy refers to the alternation of sexual and parthenogenetic generations, where gametes differ in both size and form. This does not fit the description provided in the question.

Based on this analysis, the correct answer is **Anisogamy**, as it describes the fusion of a smaller and motile male gamete with a larger and motile female gamete.

### Step-by-Step Solution:
1. **Identify the types of gametes**:
- Male gamete: Smaller and motile.
- Female gamete: Larger and motile.

2. **Analyze the options**:
- **Isogamy**: Gametes are of similar size (not applicable).
- **Anisogamy**: Gametes are of different sizes (applicable).
- **Oogamy**: Female gamete is larger and non-motile (not applicable).
- **Heterogamy**: Involves alteration of generations (not applicable).

3. **Conclude the correct answer**:
- The correct answer is **Anisogamy**.