Question

Assertion: The "biological species" concept helps us to ask how species are formed.
Reason: The concept of biological species focuses our attention on the question of how reproductive isolation comes about.
A. Both Assertion and Reason are correct and Reason is the correct explanation for Assertion.
B. Both Assertion and Reason are correct but Reason is not the correct explanation for Assertion.
C. Assertion is correct but Reason is incorrect.
D. Both Assertion and Reason are incorrect.

Answer 1

Biological species concept was given by Theodosius Dobzhansky in 1935. The concept states that organisms belonging to the same species or different whether they can interbreed to give rise to fertile organisms.

Complete answer:
Biological species concept emphasizes on species are a group of interbreeding populations that are isolated from each other. This is called speciation. Species are groups of individuals that breed together. Members breed with others that can give birth to potential organisms not according to their physical appearance.
The members of species exhibit following features
Reproductive Community: the individual recognises each other in terms of potential mate which can give rise to fertile organism.
Ecological unit: individuals differ from each other in many ways but live and coordinate together as a unit in the environment.
Genetical unit: organisms which belong to the same genetic pool, but cannot breed due to reproductive isolation.
Reproductive isolation can include mechanical barrier, geographical barrier, behavioural barrier, ecological barrier, zygotic barrier.

So here both Assertion and Reason are correct but Reason is the correct explanation for Assertion. So option A is the correct answer.

Note:
Ernst Mayr gave the biological species concept, which explains species as groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups.