Which one of the following features does not represent operation of natural selection?
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Branching
Natural selection can lead to stabilisation, directional change or disruption of a trait. Darwin’s theory has two key concepts: branching descent and natural selection.
(1) Stabilising — A way in which natural selection operates. More individuals acquire the mean value of the trait.
(2) Directional — A way in which natural selection operates. More individuals acquire a value other than the mean, so the curve moves in one direction.
(3) Disruptive — A way in which natural selection operates. More individuals acquire the peripheral values at both ends of the curve.
(4) Branching — Not a way in which natural selection operates. Branching descent is the other key idea of Darwin’s theory. It says that life forms share common ancestors and spread out into different lines. It explains homology. It is not a form of selection.
NCERT Extract:
Hardy-Weinberg Principle – “… Natural selection can lead to stabilisation (in which more individuals acquire mean character value), directional change (more individuals acquire value other than the mean character value) or disruption (more individuals acquire peripheral character value at both ends of the distribution curve) (Figure 6.8).”
Biological Evolution – “… Branching descent and natural selection are the two key concepts of Darwinian Theory of Evolution (Figures 6.7 and 6.8).”
Figure 6.8 Diagrammatic representation of the operation of natural selection on different traits : (a) Stabilising (b) Directional and (c) Disruptive