Final answer:
Jordan's Law relates to island biogeography and a genus with a variety of genetic traits has a higher chance of survival after a volcanic eruption. Genetic drift occurs more rapidly on islands due to smaller population sizes.
Step-by-step explanation:
The Law of Geminate species (Jordan's Law) relates to island biogeography. Island biogeography is the study of life on island chains and how their geography interacts with the diversity of species found there. After a volcanic explosion changes the ecosystem on an island, the genus with the highest probability of surviving the disaster would likely be the one with a wide variety of genetic traits.
Pertaining to the second question on genetic drift, it would happen more quickly on an island due to a smaller population size and lower genetic variation compared to the mainland. Genetic drift can lead to the elimination of alleles from a population by chance.