Genetic variability is beneficial for a species because it enhances that species’ ability to adapt to changing conditions. why, then, do you think that cells go to such great lengths to ensure the fidelity of dna replication?

 Genetic variability  is beneficial for the survival and adaptation. But a flaw in DNA Replication Control or check may leads to the death of cell or may contribute in the disease or cancer.

Explanation:

Almost every species comes with the diversified collection of genes (genome). And some of the diversity comes from the spontaneous mutation but it occurs on a very low frequency. The genes either express constitutively or occasionally for an important task like genes responsible in the generation of ATP by glycolysis, tricarboxylic acid cycle, electron transport chain etc. While some of the genes are inducible that is only activated in a response to an external stimuli. Genetic variations in inducible genes might account for the adaptability or negligible change in a species genetic expression but genetic variation in constitutive or house keeping genes leads to cancer cell formation or even cell death. like mutation occur in p53 genes dysregulate the cell cycle or mutation occur in DNA polymerase enzyme that is responsible for the incorporation of NTPs (nucleotide tri-phosphates) according to wobble base pairing rule in order to make a complementary new strand from the old or parent strand, will eventually leads to cause mutations ultimately results in cell death or cancerous cell formation.

most community's take hundreds of years to become stable

a physical change is being made.