Human Factors
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Humans can impact animal and plant populations. When humans develop land for houses and buildings, they cut down trees and change animal and plant habitats. Some animals like the raccoon and the skunk can adapt, but other animals can't adapt and their populations are affected.
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The common loon nests on land near large lakes. Some loon nesting places have been taken over by human development and the loon population has decreased. Pollution can also hurt animal and plant populations. Sometimes hunting can impact animal populations. Whale populations have been lowered because of overhunting.
Natural Balance
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Predator/prey relationships play a big role in animal populations. If the balance between predator and prey is changed, populations are changed. The
white-tailed deer population in some areas has grown too large because there are no natural predators. Mountain lions and wolves are the natural predators of the white-tailed deer. Wolf and mountain lion populations have been lowered due to overhunting and habitat loss. This loss of a natural predator for the white-tailed deer, along with other factors, has led to overpopulation of the white-tailed deer in some areas.