A change in the gene pool of a population form one generation to the next that does not necessarily result in speciation is an example of

Genetic Drift

Explanation:

Genetic drift is a mechanism of evolution in which allele frequencies of a population change over generations due to chance or sampling error.  Genetic drift occurs in all populations of non-infinite size, but its effects are strongest in small populations.  This process may result in the loss of some alleles (including beneficial ones) and the fixation, or rise to 100% frequency, of other alleles.  It also have major effects when a population is sharply reduced in size by a natural disaster (bottleneck effect) or when a small group splits off from the main population to found a colony (founder effect).

type 2 happens when excess consumption of high-sugar foods flood the blood supply with glucose and reduce the production and effectiveness of insulin. if a person has prediabetes, they can reduce the risk of full diabetes through regular exercise and a balanced, low-sugar diet.

explanation:

on disadvantage of hydroelectric power is the cost. another disadvantage of using hydroelectric power is finding a water source powerful enough to harvest hydroelectric power.