What is natural selection? What is genetic drift?

Answer 1

Natural selection is a broader, evolutionary mechanism that works over a very long period of time where traits (and the genes that code for those traits) are selected upon that offers an organism some adaptive advantage in their environment and allows them to survive, reproduce and pass on those traits. It results in adaptation where certain traits of very similar organism, species, are selected upon by non-random mechanisms like food availability or type of food, geographical location and isolation, and so forth, and after some time, that trait become more common in the species and eventually become a dominant genotype for that species. Genetic drift, on the other hand, is a very random process and does not depend on the beneficial or deleterious affects of alleles for that organism. Genetic drift is more pronounced in smaller populations and is where alleles are lost or gained due more to chance, or "sampling error" when organism reproduce and a new generation arises. Genetic drift may very well result in a "new species," but their is not really an impetus for this because it is not a consequence of organism trying to survive, adapt, and acclimate to their environment.