Question 5
How does an insertion occur in a chromosome?

It refers to insertion of longer sequence in chromosomes and occurs due to cross over in meiosis.

Explanation:

Or we can say it occurs when one portion of chromosomes is deleted from its normal place and insert into another chromosome

All of these models apply to the scenario equally well.

Explanation:

Firstly, the male crabs battle each other for territory using their greatly enlarged claws. This clearly depicts male-male competition.Secondly, Females choose to mate with only those male who are fit to survive in stress full condition. Thus female look for good genes that would enable her offspring to survive in stressful condition. Here Good gene mechanism applies.Thirdly, The presence of large claws make it more noticiable to female and stronger to compete with other males. Thus this is a direct benefit.Lastly, we see that female crab have a tendency to look up for their prey and this tendency is well exploited by male crabs who raise their claws to a heigh so that they get noticed by the female.