The most likely reason for the development of resistance against pesticides in insects damaging a crop is :-
A
Genetic recombination
B
Directed mutations
C
Acquired heritable changes
D
Random mutations
The answer is D.
Solution
In a large insect population, some individuals already carry random mutations that make them resistant to a pesticide. These mutations arise by chance, not because the pesticide is present. When the pesticide is sprayed, the susceptible insects die, while the resistant ones survive and reproduce. This is natural selection. Over a few generations, the resistant individuals make up most of the population. The idea that the pesticide directly causes useful changes (directed mutations or acquired heritable changes) is Lamarckian and is not accepted. Recombination only reshuffles existing alleles. So the most likely reason is random mutations (followed by selection).
ConceptPre-existing random variation selected by pesticide
Evolution in past papers
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