//M0//QN1//CS//DL0//EQ

According to Hardy-Weinberg equilibrium, the gene frequency in a population remains constant, but natural selection is one of the main factors affecting this equilibrium. The process of natural selection can affect the distribution of a population in three different ways, as shown in the diagram below:
(1) Stabilizing selection (Figure-a) - In which more individuals acquire mean character value.
(2) Directional (Figure-b) - More individuals acquire value other than the mean character value.
(3) Disruption (Figure-c) - More individuals acquire peripheral character value at both ends of the distribution curve.
(i) During the Industrialisation, the number of white-winged moths in England decreased and the population of black-winged (melanised) moths increased. Which type of selection does this phenomenon show in the given diagram ?
(a) Figure-a - Stabilizing selection
(b) Figure-b - Directional selection
(c) Figure-c - Disruptional selection
(d) None of the above
(ii) In a study of birth weight in humans, it has been found that babies with an average weight (3 to 4 kg) have the highest chance of survival, while babies with very low or very high weight are more likely to die. What type of this graph would produce ?
(a) Figure (a) - Peak gets higher and narrower
(b) Figure (b) - Peak shifts in one direction
(c) Figure (c) - Two peaks form
(d) irregular graph
(iii) Which of the following is correct regarding disruptive selection shown in 'figure (c)'?
(a) In this, nature promotes only mean character value.
(b) In this, the population grows in one direction.
(c) In this, more individuals acquire peripheral character value other than the mean character value.
(d) It always keeps the gene pool of the population at the equilibrium.
(iv) When an antibiotic is used in a population of bacteria, some resistant bacteria survive and form a new population. Over the time, the entire population becomes resistant. Which graph is suitable with this example ?
(a) only figure (a)
(b) only figure (b)
(c) only figure (c)
(d) Figure (a) and (c) both

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(no answer)