Why is reproductive isolation required for a speciation to occur ?

Explanation:

Option A is right If populations can interbreed, they are considered as one species.

Speciation is the formation of new and distinct species in the course of evolution. It involves the splitting of a single species into two or more genetically independent species, even if they cannot mate each other due to their physical barrier.

Reproductive isolation means the given group cannot mate with each other because of their physical barrier.

Reproductive isolation is required for speciation to avoid mating because natural selection want them to evolve differently.

white blood cells or wbc s are mainly 2 types-

1.agranulocytes

2.granulocytes

the monocytes or macrophages of agranulocytes , dendritic cells which are accessory leucocytes, and b cells which is one type of lymphocytes   identify the antigens present on the pathogen's surface. these three cells are called antigen presenting cells(apc) which are phagocytes and destroy the antigens by secreting antitoxins. besides this leukocyte is always plays vital role in the immunity of the body.

these muscles maintain the blood pressure in the vessels. the smooth muscles are innervated by nerves of the autonomic nervous system. when the muscles contract, they cause vasoconstriction of the vessels and increase blood pressure. when the muscles relax, they enable vasodilation of the   blood vessels hence reduce blood pressure.