Question

factors affecting genetic variation
environmental factors can influence natural selection because they can increase or decrease
the number of
chromosomes in a
population.
the amount of
genetic variation in
a population.
the amount of
genetic variation in
an individual.
the number of
chromosomes in an
individual.

Explanation:

To determine the correct answer, we analyze each option:

• The number of chromosomes in a population: Environmental factors don't typically change the chromosome number of an entire population in a way that influences natural selection directly related to genetic variation's increase/decrease for selection.
• The amount of genetic variation in a population: Environmental factors (like climate, availability of resources, predation) can act as selective pressures. For example, a new predator might favor certain genetic traits, leading to changes in the frequency of alleles (thus affecting genetic variation) in the population over time. This ties to natural selection as it's about the population's genetic makeup changing.
• The amount of genetic variation in an individual: Genetic variation in an individual is mostly determined by their genetic inheritance (mutation during their own development is rare and not the main way environmental factors act on "variation amount" in an individual for natural selection's influence).
• The number of chromosomes in an individual: Environmental factors don't usually alter an individual's chromosome number to influence natural selection in terms of increasing/decreasing for selection's sake (chromosomal changes in individuals are often mutations with other implications, not direct environmental influence on selection via this).

So the correct option is the one about the amount of genetic variation in a population.

Answer:

the amount of genetic variation in a population.