Question

The relationship between birth weight and degree of survival $ (log \frac{ 𝑠𝑢𝑟𝑣𝑖𝑣𝑜𝑟𝑠 }{ 𝑛𝑜𝑛−𝑠𝑢𝑟𝑣𝑖𝑣𝑜𝑟𝑠})$ in 6908 human births in an obstetric hospital is shown in the figure below. The mode of selection for birth weight is

• A. directional
• B. disruptive
• C. diversifying
• D. stabilizing

Answer 1

The Correct Option is D

The problem involves understanding the mode of selection based on the relationship between birth weight and the degree of survival in human births. The graph provided illustrates the degree of survival on the y-axis and birth weight on the x-axis.

Let's analyze the graph and the given options:

1. **Directional Selection**: This refers to a selection mode where one extreme of a trait is favored over others, leading to a shift in the population mean. The graph would show a continuous increase or decrease in survival with birth weight.
2. **Disruptive Selection**: This involves favoring both extremes of a trait while selecting against the intermediate. The graph would show two peaks with a trough in the middle.
3. **Diversifying Selection**: This is similar to disruptive selection, where multiple phenotypes are favored. The graph would again display more than one peak.
4. **Stabilizing Selection**: This type of selection favors the average individuals in the population. The graph would show a single peak at the intermediate birth weight.

Conclusion: The graph displayed in the question shows a single peak at an intermediate birth weight, indicating that newborns with an average birth weight have a higher survival rate compared to those at either extreme. This pattern is characteristic of stabilizing selection, where the average phenotype is preferred, reducing variation in the population.

Therefore, the correct answer is: Stabilizing