Question

Which of these is a premating isolating mechanism?
A.Habitat isolation
B.Temporal isolation
C.Gamete isolation
D.All of the above

Answer 1

Hint: In order for different species that diverge from common ancestors and driven to evolution – a reproductive isolation must take place. One of the major types of reproductive isolation is called prezygotic isolation. It happens before fertilization takes place. If an individual cannot reproduce with other individuals from the same species, they are not considered to be different species and make a branch in the phylogenetic tree that describes divergence on the tree of life.

Complete step by step answer:
The common description of the above-mentioned terms:
-Habitat isolation- Every species has a preference of their habit and reproduction. Habitat isolation can be defined as the non compatibility of the preferred locations for the reproductive events to the actual habitat of the animal. If individuals of two different species live together, there will be no opportunity to reproduce and thus reproductive isolation will lead to speciation.
-Temporal isolation- Different species have different breeding seasons. Temporal isolation can be described as the timing of when females are fertile. For example, a female of one species is fertile during a particular month of the year but the males of that same species may not be able to reproduce at that time of the year – which leads to reproductive isolation. Thus, we can say similar species may be physically compatible to reproduce with each other but may still not reproduce as the mating seasons are different during the year.
-Gametic isolation- It is a well-known fact that the female ovum is fused with the male sperm during fertilization and a zygote develops. Suppose, the sperm and egg are not compatible with each other, then the fertilization will not produce any zygote. Sometimes, the sperm are not attracted to the egg as the chemical signals are released by the egg at the time of fertilization. Again, the sperm cannot penetrate the vitelline membrane of the egg. These reasons are sufficient enough to stop the fertilization and formation of zygote and lead to reproductive isolation.

So, the correct answer is option D. All of the above.

Note:
There is another isolating mechanism known as mechanical isolation that can be described as the simplest concept that keeps an individual from being able to reproduce offspring with each other from the same species. Mechanical isolation deals with the incompatibility of sexual organs. In the case of plants mechanical isolation is different than that of animals – as the size and shape are irrelevant to the reproductive system in plants. Mechanical isolation is usually different due to the use of different pollinators present for the plants.