Why does evolution acts on populations and not individuals?

Answer 1

it's better to explain it using an example. say there are two types of moths - black and white. the black allele and the white allele together make up the gene pool (all of the alleles together) for the moth species. then say that there are only black trees in the habitat of these moths. in the eyes of a predator, it is much easier to see the white moths on the black trees than the black ones, so they continually get eaten. therefore, the allele frequency of the white moths goes down. because the moths are being eaten and there are less and less of them, we say they are being selected against and eventually the white moths die off, because they are not adapted to their environment

Answer 2

Well, let's give an example. Suppose you use pesticides on an insect population. At first, it seems to be working and most of the insects died. Those who survived somehow carried the genes that has pesticide resistance. These insects with the genes for pesticide resistance quickly reproduced and passed on their genes. Over time, natural selection occured, and the pesticide resistance became less effective. Note that environmental change doesn't create new alleles that are benefitial in the environment, but rather, natural selection select alleles from a population's gene pool that will be benefitial. Thus, natural selection acts on a population and its gene pool rather than the individual.

Answer 3

The reason it works on populations is because evolution is a change in the allele frequency over time. That only happens in populations, not individuals.

Answer 4

Individuals die. So any germ line mutations/variations need to be passed on to progeny for the change in allele frequency in populations of organisms that defines evolution.

Answer 5

Evolution of populations happens as new individuals are born and old individuals die. Thus populations evolve and individuals do not.