Final answer:
Smaller populations face a higher risk of extinction due to lower genetic diversity, higher susceptibility to environmental changes, and human impacts like habitat loss and resource exploitation.
Step-by-step explanation:
The relationship between population size and extinction risk is such that smaller populations have higher extinction risk. Large populations have more genetic diversity and are better able to withstand environmental changes, diseases, and genetic drift. Conversely, small populations can suffer more from inbreeding, reduced genetic diversity, and increased vulnerability to stochastic events. These can lead to decreased population viability and increased extinction risk. Moreover, metapopulation dynamics suggest that interconnected populations with some larger 'mainland' sources have a greater likelihood of persistence due to occasional movements of individuals that increase genetic diversity and enable recolonization after local extinctions. However, all populations, irrespective of size, can be at risk due to human activities. Human-induced habitat loss and resource exploitation dramatically increase extinction rates, affecting both small and large populations, but smaller populations generally suffer the quickest and most severe declines.