Question

Natural selection can lead to
(a) stabilisation
(b) genetic drift
(c) directional change
(d) disruption
Choose the correct answer from the options given below :

• A. (a) and (c) only
• B. (a) only
• C. (a), (c) and (d) only
• D. (a), (b), (c) and (d)

Hint:

Stabilising selection narrows the phenotypic distribution curve around the mean. Directional selection shifts the peak of the curve toward one side. Disruptive selection produces two distinct peaks at the extreme ends of the phenotypic range, which can lead to speciation.

Answer 1

The Correct Option is C

Step 1: Understand the question.
We must pick which outcomes natural selection can produce from the list: (a) stabilisation, (b) genetic drift, (c) directional change, (d) disruption.
Step 2: Recall the modes of selection.
Natural selection works in three modes: stabilising, directional, and disruptive.
Step 3: Test (a) stabilisation.
Stabilising selection favours intermediate types and reduces variation. This is a real mode, so (a) is correct.
Step 4: Test (c) and (d).
Directional selection shifts the mean toward one extreme (directional change), and disruptive selection favours both extremes (disruption). So (c) and (d) are correct.
Step 5: Test (b) genetic drift.
Genetic drift is random change in allele frequencies due to chance, not a result of natural selection. So (b) is NOT an outcome of natural selection.
Step 6: Conclude.
The correct outcomes are (a), (c), and (d), which is option (3).
\[ \boxed{\text{(a), (c) and (d) only}} \]