Which of the following is a true statement concerning genetic variation?

a. It must be present in a population before natural selection can act upon the population.

b. It tends to be reduced by the processes involved when diploid organisms produce gametes.

c. It is created by the direct action of natural selection.

d. A population that has a higher average heterozygosity has less genetic variation than one with a lower average heterozygosity.

e. It arises in response to changes in the environment.

a. It must be present in a population before natural selection can act upon the population.

Explanation:

Genetic variation is the difference in the DNA sequences in individuals, which makes a member of a species different from another member of the same species. It can also be said to be the differences in the genetic make up of individuals of a species population.

Genetic variation must be present in a species population before evolutionary mechanisms, such as evolution, can occur. Genetic variation must be present in a population of a species before natural selection can act upon the population, as natural selection can only increase or reduce the frequency of alleles present in the species population already.

Genetic variation in a population of species is important for natural selection to occur.

lysosome is this part of the cell is surrounded by a very thick outer membrane to protect the rest of the cell from its strong enzymes.

d. planting trees

the trees take in carbon to make oxygen.