Which type of selection is industrial melansim observed in moth, Biston betularia?

Options

A. Stabilising
B. Directional
C. Disruptive
D. Artificial

Explanation

**Step-by-Step Solution:**

1. **Understanding Industrial Melanism**: Industrial melanism refers to the phenomenon where darker-colored individuals of a species become more common in industrial areas due to pollution. In the case of the moth Biston betularia, this is a classic example of how environmental changes can affect the coloration of organisms.

2. **Types of Natural Selection**: There are three main types of natural selection:
- **Directional Selection**: This occurs when one extreme phenotype is favored over others, leading to a shift in the population's traits in a specific direction.
- **Stabilizing Selection**: This favors the intermediate variants and acts against extreme phenotypes.
- **Disruptive Selection**: This favors individuals at both extremes of the phenotypic range, leading to two or more contrasting phenotypes in the same population.

3. **Identifying the Type of Selection in Biston betularia**: In the case of Biston betularia, the lighter-colored moths were more visible against the soot-darkened trees in industrial areas, making them more susceptible to predation. As a result, the darker moths had a survival advantage.

4. **Conclusion**: The selection that led to the increase in the frequency of dark-colored moths is an example of **directional selection**. This is because the population shifted towards a specific trait (darker coloration) due to environmental pressures.

**Final Answer**: The type of selection observed in industrial melanism in the moth Biston betularia is **directional selection**.

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