Answer:
Variation, overproduction, adaptation, descent with modification.
Step-by-step explanation:
Variations occur within members of a population. these variations arise by chance and from within the individual. Another observation is that the offspring by far outnumber(overproduction) the parental generation but only a few survive to adulthood and are able to reproduce. Individuals with advantageous variations are well adapted to the environment. The gradual accumulation of small variations from generation to generation over a long period of time leads to emergence of new species.