How does asexual reproduction limit variation in species?

Asexual reproduction is a cheap and fast method for producing large numbers of propagules having little diversity. The method of cell division is mitosis, which produces identical daughter cells. This is largely advantageous when survival of offspring is dependent, more upon explosive population growth, than on the diversity of each individual. Plankton species are such an example, where to survive they mostly just need to out produce predation.

Most organisms engage in sexual reproduction at some point in their life cycle to introduce diversity when survival is dependent on susceptibility to parasites. Host — parasite coevolution is an arms race accelerated by diversity.

In sexual reproduction, the method of cell division is meiosis, where diversity is introduced through crossing over, independent assortment, and also, random fertilization.

Explanation:

during the process of dna replication, brdu can replace thymidine and incorporate into the newly synthesized dna, cell proliferation thus can be reflected in the extent of brdu incorporation.