(i) Speciation: Origin of new species from preexisting ones.
Role of Genetic drift and natural selection:
Natural selection is phenomena in which the best and the fittest is selected.
Genetic drift is a process in which the change in the types of the gene occurs
By the help of both phenomena the new generation is created. For example, there were giraffes with small necks, these giraffes could not reach the top leaves of the trees and thus got extinct while the best type with long neck survived and moved forward to next generation.
