Environmental factors can influence natural selection because they can increase or decrease what

The answer to finish this sentence would be ''the amount of genetic variation in a population'' because environmental factors can either increase or decrease a population.

Answer;

the amount of genetic variation in a population.

Environmental factors can influence natural selection because they can increase or decrease the amount of genetic variation in a population.

Explanation;Natural selection is the process by which organisms with favorable traits are able to adapt to the environment and thus able to carry out reproduction and the traits passed to offspring, while those organisms without the favorable traits are not able to reproduce and thus become extinct.In other words it involves the adaptation of organisms to the environment by having selectively reproducing changes in its genetic composition.Environmental factors may influence natural selection, since natural selection acts on the phenotype which is the result of interaction between the genotype and the environment. For different environment one gene can give different trait as far as the phenotype is concerned.

It's either -limiting factors or -scarce resources but i'd go with my first answer since the food and water are abundant they really aren't scarce