Organisms can be classified in the same species by morphology and

a. variation
b. dichotomy
c. reproductive isolation

Answer : The correct answer for the blank is- C.reproductive isolation.

According to the biological species concept given by Ernst Mayor, species can be described as a group of organisms that are capable of interbreeding among themselves and produce viable and fertile offspring. Organisms from different species are thus reproductively isolated from members of other species. In other words, members from different species can not interbreed to produce viable and fertile offspring.

Thus, by morphology and reproductive isolation, organisms can be classified in the same species.

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.