Cross River gorilla is listed as critically endangered species. With only 35 of these gorillas in the world, they are at risk of extinction largely due to poaching and loss to diseases such as Ebola. Genetic studies of the remaining gorillas show very little variability, because several alleles were likely lost due to .

Genetic drift

Explanation:

Genetic drift occurs as a result of random changes that may be dude to chance which leads to large changes in the population size over a short period of time. When an allele's frequency tends to drift up and down over time continuously, the allele can become lost. And there will be little to no variability seen.

Option A, Genetic drift

Explanation:

Options for the question

a.genetic drift

b. gene flow

c. increased rate of spontaneous mutations

d. adaptive radiation

Solution

Genetic drift is an evolutionary mechanism in which the random fluctuations occur in the gene pool of a given population. In general, this variation of allele frequency continues till the allele is lost or it persists as the only allele in the population.  

Due to such changes in the allele population, the genetic diversity reduces as is the case with the cross river gorilla whose gene pool has reduced due to fluctuations such as poaching and Ebola disease.

Hence , option A is correct

a. the production of carbon dioxide through the process of photosynthesis

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