Logistic growth would be a slow increase of the population, then there is a sudden exponential growth, then a carrying capacity is reached causing growth to level out. Limited resources have caused polar bears to become endangered. The loss of space has led to the environment reaching its carrying capacity (the maximum number of individuals of a particular species that the environment can normally and consistently support). The melting of the polar ice caps is making the carrying capacity smaller because there is less space for the population to live.
Births: The amount of births in the population would increase a population. If there are enough resources (and mates) available for the polar bears, the population would keep increasing until it reaches the carrying capacity.
Deaths: If there are a lot of deaths in a population, it would definitely decrease a population. Polar are endangered due to less resources, like space and food, so their population has been decreasing (and might lead to extinction of this species). However, more deaths can lead to more resources being made available for the new polar bears.
Immigration: The movement of individuals (polar bears) to an area where there are more resources would increase the population. If there is more food and space available somewhere, polar bears would immigrate to that area to survive (increasing that population).
Emigration: The movement of individuals (polar bears) out of an area where resources are low would decrease that population. If there is less fish, ice, and mates available polar bears can decide to leave their population and emigrate to another (therefore decreasing their original population size).
Density-Dependent Factors: Disease would influence the size of the population in a negative way by wiping out part of the population. Competition would also have a negative impact on a population because when polar bears compete for resources, the ones who can't gain the resources will die off and decrease the population.
Density-Independent Factors: Habitat disruption has had a major negative impact on the polar bear population because their habitat is melting and this causes them to have less space to live and survive. Temperature also affects the size of a population; if an area is too warm, polar bears are forced to emigrate because they can't live in that environment (therefore decreasing a population).