Question

Following is the diagrammatic representation of the operation of natural selection on different traits. Which of the following options correctly identifies all the three graphs A, B and C.

• A. (A) Directional (B) Stabilizing (C) Disruptive
• B. (A) Stabilizing (B) Directional (C) Disruptive
• C. (A) Disruptive (B) Stabilizing (C) Directional
• D. (A) Directional (B) Disruptive (C) Stabilizing

Answer 1

The correct option is B (A) Stabilizing (B) Directional (C) Disruptive

The given graphs represent the operation of natural selection on different traits.

• Graph A shows a selection of intermediate or heterozygous phenotypes while the extreme phenotypes (both dominant and recessive) tend to reduce in number. This type of natural selection is called stabilizing.
  
• Graph B shows a directional shift in the peak, implying favouring and select of a particular phenotype. This type of natural selection is directional.
• Graph C shows no presence of a particular peak, but two peaks signifying selection of extreme characters, both dominant and recessive. Also, the depression between the two peaks shows elimination or disfavoring of intermediate or heterozygous characters or phenotypes. This type of natural selection is disruptive.

So, the correct option is (A) Stabilizing, (B) Directional (C) Disruptive'.