Question

the vicuña is a camel relative found in the andes of south america. suppose that food is exceptionally abundant for several years, resulting in an increase in vicuña population density. this increase in vicuña population density allows pumas, one of the main predators of vicuñas, to find their prey more easily.
is the increased predation on the vicuña population density - dependent or density - independent?
polar bear numbers have been declining over the last decade due to a loss of sea ice on which to hunt seals. the loss of sea ice results in more territorial confrontations between polar bears and the inability of some female bears to feed their cubs.
is the increase in territorial confrontations among polar bears density - dependent or density - independent?
coral reefs are comprised of large numbers of individual corals, which are small animals related to jelly fish. abnormally high water temperatures in the caribbean in 2005 resulted in a massive coral bleaching event. many of the corals subsequently died.
was the bleaching event density - dependent or density - independent?

Explanation:

First Sub - Question (Vicuña and Pumas)

Density - dependent factors are those that depend on the population density. In the case of vicuñas, as their population density increases, pumas (predators) find them more easily, so the predation rate increases with population density. So the increased predation on vicuñas is density - dependent.

The decline in polar bear numbers (leading to a change in density) causes more territorial confrontations. As the population density (in terms of available space and resources per bear) changes, the territorial confrontations increase. So this is a density - dependent factor.

The coral bleaching event was caused by abnormally high water temperatures, which is an abiotic factor that does not depend on the population density of corals. So the bleaching event is density - independent.

Answer:

density - dependent

Second Sub - Question (Polar Bears)