Tundra ecosystems are considered to be fragile because of

Tundra ecosystems are considered to be fragile because the short growing season.

Explanation:

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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).

you can have just about every answer you can think of