Ways Natural Selection Affects Distribution of Phenotypes?

If a phenotype isn't suited for a particular environment, the number of individuals in the next generation are less likely to have it than the previous one. Say, for example, that there is a super windy island with big and little birds. Then most of the big birds are blown away, so when the birds mate, the next generation has more little birds than big ones because there were more little birds that passed on the little gene. (this kind of example is called selective pressure~ when the environment 'acts' on a certain trait- ie, the wind got rid of many big-birds and their big bird genes). Competition and sexual selection are other kinds of natural selection too~ those terms might be in your textbook and it might help.

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Organisms reproduce more offspring than could possibly survive.

Organisms and their offspring have variation in their phenotypes and genotypes.

Favorable variations survive and are passed on to offspring.

Modification with descent by natural selection happens.