Question

A group of red beetles lives on green leaves of a tree. Beetles multiply through sexual reproduction. One day, few green beetles are seen among the red beetles. Green beetles breed to produce green progeny. Crows on the tree eat beetles. Some green beetles are found among the red beetle because
(A) Beetles turn into green by accumulating chlorophyll from the green leaves that they eat.
(B) Natural variations occur during sexual reproduction.
(C) Red beetles mimic the green colour of leaves when they see crows.
(D) Beetles change colour from red to green with the change of season.

Answer 1

Beetles are sexually reproducing organisms. The appearance of green beetles among the red beetles is a matter of chance, which has occurred due to natural variations. Sexually reproducing organisms tend to show many genetic variations when compared to the asexually reproducing organisms.

Complete answer:
The original population of beetles were all red in colour, which lived on the leaves of the trees. In the due course of time, green beetles started to appear among the red beetles. The population of green beetles started to reproduce and produce progeny of green colour.

The appearance of green beetles among the red beetles is an event of chance, which has taken place due to natural variations. Natural variation is a process, in which the individuals are better adapted to the environment to survive and reproduce. Variations are not always beneficial.

Variations that help the individual to survive and reproduce better in an environment will be selected by nature itself. This is called natural selection. Whereas, those variations that don't contribute to the wellness of the individual will be eliminated gradually.

Variations that occurred due to chance naturally are incorporated in the genes or alleles will be transferred to the next generation. Genetic variation leads to the population acquiring new beneficial characteristics over time. In this case, red beetles will be easily spotted by the crow (predator) and eaten. While, green beetles camouflages itself with the green leaves and survives. This leads to the population with a higher number of green beetles than red beetles, over time.

Understanding the options one by one,
(A) Beetles turn into green by accumulating chlorophyll from the green leaves that they eat.
This is not technically possible. Green beetles don’t take up the colour from chlorophyll. This is not the correct answer.
(B) Natural variations occur during sexual reproduction. Natural variation is a process, in which the individual is better adapted to the environment. Appearance of green beetles is due to natural variations during sexual reproduction. Hence, this is the correct answer.
(C) Red beetles mimic the green colour of leaves when they see crows. The property of mimicry is not observed in beetles, and hence this is not the correct answer.
(D) Beetles change colour from red to green with change of season. Beetles don't have the ability to change colour according to the season. This is not the correct answer.

Therefore, the correct answer is Option (B)

Note: The process of natural variation is the one which leads to occurrence of new characteristics. These are then selected by nature and lead to the formation of new species. It is important to note that these types of natural variations take place more frequently in sexually reproducing organisms than asexually reproducing organisms.