What are some issues associated with a small population size? (2-3 sentences)
Population size, technically the effective population size, is
related to the strength of drift and the likelihood of inbreeding in the
population. Small populations tend to lose genetic diversity more
quickly than large populations due to stochastic sampling error (i.e.,
genetic drift). This is because some versions of a gene can be lost due
to random chance, and this is more likely to occur when populations are
small. Additionally, smaller population size means that individuals are
more likely to breed with close relatives. In closed populations,
individuals will be more closely related to each other compared to
individuals in the previous generation. For example, in a hypothetical
population consisting of only four individuals, if two pairs each
produced two offspring (meaning that four new individuals are present in
the next generation), the offspring must either mate with a sibling, a
parent, or an individual from the other pair. Assuming they choose the
non-sibling/non-parent option, all of the offspring in the third
generation must mate with individuals that have the same grandparents or
choose to forgo reproduction. Although this example is extreme due to
the very small hypothetical population, the same patterns and forces are
present in larger – albeit still small – populations.