What is a population bottleneck, and what risk does it pose?

A  This describes a population that transitions through a small effective population size. It will either collapse or recover. Maintaining sufficient genetic diversity (standing variation) is a concern during this transition.

B  This describes a very large population that drifts towards its environmental capacity until it cannot expand more (bottleneck). For example, the Tyranosarus rex could not increase further in population due to insufficient mammuts present as prey.

C  Bottleneck describes a deleterious mutation of the 9th cervical vertebra of tetrapods due to inbreeding. This neck was charactersitic of the Habsburg Royal family in northern Rheinland (France). It is believed the Notredamme story is based on the Habsburg neck.