Question

Artificial selection to obtain cows yielding higher milk output represents :

• A. Directional as it pushes the mean of the character in one direction
• B. Disruptive as it splits the population into two, one yielding higher output and the other lower output
• C. Stabilizing followed by disruptive as it stabilizes the population to produce higher yielding cows
• D. Stabilizing selection as it stabilizes this character in the population

Answer 1

The Correct Option is A

The question is about identifying the type of selection process used in artificial selection to obtain cows with higher milk yield. Let's break down each option to understand which type of selection it reflects.

1. Directional selection: This occurs when a specific trait is favored, and the population mean shifts towards that trait. In this context, selecting cows for higher milk yield represents directional selection, as the trait for high milk output is being pushed in one direction - towards increasingly higher production.
2. Disruptive selection: This type would split a population into two distinct groups, often leading to speciation. For this option to be correct, selection would need to enhance both high and low producers, splitting the population. This is not the case here.
3. Stabilizing followed by disruptive selection: Stabilizing selection maintains a population’s traits around a mean by selecting against extremes; disruptive follows by creating variance. This scenario doesn't fit the method used to achieve higher milk yields.
4. Stabilizing selection: Involves removing extremes in a population to keep it consistent around a mean. This doesn't apply because the goal is not to maintain current traits but to move towards greater milk output.

Based on the definitions above, the correct answer is Directional selection. The objective is to increase milk output over time, thereby changing the population's mean production in one specific direction.