The natural selection that acts against change in form and keeps the population constant through the time is `:`

Options

A. Disruptive
B. Directional
C. Not acting
D. Stabilizing

Answer

To solve the question regarding the type of natural selection that acts against change in form and keeps the population constant through time, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Natural Selection**:
- Natural selection is a process in evolution where organisms better adapted to their environment tend to survive and produce more offspring. This process leads to changes in the traits of populations over time.

**Hint**: Remember that natural selection is about survival and reproduction based on adaptability.

2. **Identifying Types of Natural Selection**:
- There are three main types of natural selection: stabilizing selection, directional selection, and disruptive selection.
- **Stabilizing Selection**: This type favors the average traits and selects against extreme traits.
- **Directional Selection**: This type favors one extreme trait over others, leading to a shift in the population's traits.
- **Disruptive Selection**: This type favors both extreme traits and selects against average traits.

**Hint**: Think about how each type affects the traits within a population.

3. **Analyzing Stabilizing Selection**:
- In stabilizing selection, the average traits are preserved while extreme traits are eliminated. This results in a population that remains relatively constant over time.
- The graph representing stabilizing selection typically has a higher and narrower peak, indicating that most individuals have average traits.

**Hint**: Visualize the graph of stabilizing selection to see how it maintains the population's characteristics.

4. **Eliminating Other Options**:
- **Disruptive Selection**: Incorrect, as it promotes extreme traits and leads to a diverse population.
- **Directional Selection**: Incorrect, as it shifts the population towards one extreme trait.
- **Natural Selection**: This is a general term and does not specify the type that maintains constancy.

**Hint**: Compare the effects of each type of selection on the population's traits to find the correct answer.

5. **Conclusion**:
- The type of natural selection that acts against change in form and keeps the population constant through time is **Stabilizing Selection**.

**Final Answer**: The correct answer is **Stabilizing Selection**.