5.2 LIMITS TO GROWTH
A limiting factor is a factor that causes population growth to decrease. Some of the limiting factors could be food, space, or predators. Density dependent limiting factor is when a limiting factor that depends on the population size. This only happens when a number of organism per unit area reaches a certain level. Density dependent limiting factors include competition, predation, parasitism, and disease. When a population becomes crowded, organism will compete with each other for resources. Competition can also be classified as a density dependent limiting factor. Competition can also occur with different species. This can make organisms evolve. When 2 species compete for the same resource, both species are under pressure to change in ways that decrease their competition, and thus they evolve. They will involve into separate niches because no 2 species can have the same niches in the same place and time.
Predator-prey relationship is one of the best known mechanisms of population control. The picture here shows the relation between the wolf and moose.
Parasites can also limit the growth of a population. These organisms are similar to predators. They take nourishment in their host, and weakening them. This could later lead to death, which means population decrease..
Density independent limiting factors affect all populations in similar ways, regardless of the population size. Unusual weather, natural disasters, seasonal cycles, and certain human activities, such as damming rivers and clear cutting forests are all examples of density independent limiting factors. If this occur, a population crash may happen, after the crash, the population may build up again, or it may slow low for a long time. Environments are always changing and thus the population may shrink or grow to adapt these changes, but major upsets such as human activites can lead to long term declines.
ALL PICTURES ARE FROM GOOGLE IMAGES.