Urgent : view the screenshot below

Gene flow

Explanation:

Gene flow describes the process where genetic information migrates to another population, introducing new alleles into the gene pool and increasing the variation in that population.

Having physical barriers would prevent this exchange of information. For example, two populations separated by a mountain range or body of water would have far less chances to interact and exchange genetic material. This would make it difficult for gene flow to occur.

answer; hydrologic cycle;