Explain 3 different situation as explained about variation by taking examples of population of beeteles
Answers
Consider a group of twelve red beetles. They live, let us assume, in some bushes with green leaves. Their population will grow by sexual reproduction, and therefore, can generate variations. Let us imagine also that crows eat these beetles. The more beetles the crows eat, the fewer beetles are available to reproduce. This produces difficulty for the survival of the beetles. Hence, natural selection helps in producing changes which may help in the survival of this particular species.
First Case - Natural Selection:
A colour variation arises during reproduction, so that there is one beetle that is green in colour instead of red. This beetle, moreover, can pass the colour on to its progeny, so that all its progeny beetles are green. Crows cannot see green-coloured beetles on the green leaves of the bushes, and therefore cannot eat them.
This is useful for the survival of the beetles and thus eventually, the red variant gene disappears and all beetles are green.
Second Case - Natural Calamity:
A colour variation arises during reproduction, but now it results in a beetle that is blue in colour instead of red. This beetle can also pass the colour on to its progeny, so that all its progeny beetles are blue. Crows can see blue-coloured beetles in the green leaves of the bushes as well as they can see red ones, and therefore can eat them.
Natural selection does not opt for this, as the colour blue is seen just as well as red in the grass. The progeny keeps inheriting the colour blue, but red beetles also exist alongside.
Suppose, an elephant comes by, and stamps on the bushes where the beetles live. This kills most of the beetles. By chance, the few beetles that have survived are mostly blue. The beetle population slowly expands again, but now, the beetles in the population are mostly blue.
Third Case - Inherited vs. Acquired Traits:
The beetle population begins to expand, the bushes start suffering from a plant disease. The amount of leaf material for the beetles is reduced. The beetles are poorly nourished as a result. The average weight of adult beetles decreases from what it used to be when leaves were plentiful, but there is no genetic change occurring.
When this disease is eradicated, the beetles return back to their weight returns to normal. As the reproductive cells are not affected by these changes (here, weight loss) these changes are acquired and thus are not passes on to their progeny.