In a given area, insects live by making burrows in the bark of a tree. These insects are fed upon by a population of birds in the same area. The most correct explanation for the increase in the beak size of the bird population is

Increased fitness of the birds, leading to speciation

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Decreased fitness of the insects, allowing the birds to catch them more easily

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Increased fitness of large-beaked birds, leading to evolution

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Decreased fitness of small-beaked birds, leading to speciation

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Random mutation and genetic recombination

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Solution

The correct option is B Increased fitness of large-beaked birds, leading to evolution
The insects live in the burrow in the tree bark and mutation in the beak size leading to increasing in its size conferred the survival advantage to the birds having this mutation. This is because large beak size enables them to trap the insects from inside of the burrow. Natural selection favoured this mutation owing to survival advantage and gradually the number of birds having this mutation increased i.e., the evolution of the birds having large beak size.
Thus, the correct answer is option C.

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