Final answer:
Demographic stochasticity is the term for random year-to-year variations in birth and death rates affecting populations, particularly influential in small or isolated groups.
Step-by-step explanation:
The random variation in birth and death rates that occur in populations from year to year is known as demographic stochasticity. This type of stochastic variation can affect population dynamics significantly, especially in small and isolated populations. These stochastic effects can result from fluctuations in the environment, like changes in rainfall and food sources, or catastrophic events such as wildfires, which can drastically alter birth and death rates.
Demography, the statistical study of population changes over time, is critical to understanding how birth rates, death rates, and life expectancies impact population sizes. Significant factors in demography include genetic variation losses due to inbreeding and genetic drift, environmental variation, and the effects of natural disasters and competition for resources on species' populations.