The bottleneck effect occurs when a. large groups of individuals leave their home population and establish new settlements, mating only among themselves b. many members of a population die, resulting in a great loss of genetic diversity c. many members of a population reproduce causing too much genetic diversity within the population d. small groups of individuals leave their home population and establish new settlements, mating only among themselves.

B. many members of a population die, resulting in a great loss of genetic diversity

Explanation:

When certain environmental fluctuations such as reduced food supply or an outbreak of disease result in a sudden decrease in the population size, the population is said to be going through a bottleneck. Bottleneck reduces genetic diversity due to the loss of alleles/genes from the population. Therefore, the death of many members of a population due to some adverse environmental factors and the resultant reduction in genetic diversity represents the bottleneck effect.