Which factors characterize ecosystems? a. biotic factors only b. abiotic factors only c. both biotic and abiotic factors d. neither biotic nor abiotic factors

C. both biotic and abiotic factors in earth most ecosystems have both abiotic and biotic systems. They actually need both in order to survive.

C. both biotic and abiotic factors

Explanation:

An ecosystem can be define as biotic community where living beings or biotic  factors of the environment interacts with the non-living components or abiotic factors of the environment. This interaction is necessary for sustaining life on earth as living beings are dependent upon the non-living physical environment for completing their life cycles.

Biotic factors includes the plants, animals, microbes, and other living beings. Abiotic factors includes the soil, water, air and sunlight.

genetic variation can be caused by mutation (which can create entirely new alleles in a population), random mating, random fertilization, and recombination between homologous chromosomes during meiosis (which reshuffles alleles within an organism's offspring).