Over 7,000 species around the world are considered endangered.
Loss of Habitat
Human activity can contribute to a loss of habitat. Development for housing, industry, and agriculture reduces the habitat of native organisms. Loss of habitat can also lead to increased encounters between wild species and people. As development brings people deeper into a species range, they may have more exposure to wild species. As people kill these wild animals, through pesticides, accidents such as collisions with cars, or hunting, native species may become endangered.
Loss of Genetic Variation (diversity found within a species).
Inbreeding is reproduction with close family members. Groups of species that have a tendency to inbreed usually have little genetic variation, because no new genetic information is introduced to the group. Disease is much more common, and much more deadly, among inbred groups. Inbred species do not have the genetic variation to develop resistance to the disease. For this reason, fewer offspring of inbred groups survive to maturity.
Human activity can also lead to a loss of genetic variation. Overhunting and overfishing have reduced the populations of many animals. Reduced population means there are fewer breeding pairs. A breeding pair is made up of two mature members of the species that are not closely related and can produce healthy offspring. With fewer breeding pairs, genetic variation shrinks.