Parasitism is a dangerous problem that causes diseases in animals. Over time, the most effective parasites are protozoa, helminths, and some arthropods (Olsen 1962). These parasites have been successful because they move from host to host and some of these parasites, like arthropods, feed on the blood and tissues of animals and humans and deprive their host of nutrients. Often this loss of nutrients will result in severe hemorrhaging of the host's internal organs. For example, “When parasites, such as hookworms in humans or trichostrongyls in cattle and sheep, affect the entire population, the effect of the disease is masked and often unrecognized…injections of these Parasites cause a lot of blood loss through bleeding into the intestine. Additionally, parasites infect their host, leaving an escape route for bacteria and disease to spread. These diseases can be contagious to humans, which is why animals harm the ecosystem by spreading bacteria and pathogens. According to Baucom and de Roode (2011), tolerance or resistance mechanisms in animals can reduce the growth of parasites. Diseases and bacteria aren't the only problems animals face. As the human population increases, animals and humans come into conflict because space and food are limited. To avoid overpopulation, many species are aggressive and have evolved mechanisms to defend their available habitats (Golley 1962). Animals can create major problems because they spread diseases to humans and threaten their way of life. For starters, animals harm humans by transmitting diseases and bacteria. Diseases mainly come from harmful bacteria and parasites. Although some parasites are beneficial to their hosts, many others ...... middle of paper ...... are the occupations of humans. While humans have built many projects and houses to house these animals and have also created restricted spaces that separate them from the animals, so that the animals can live in their habitat without interfering with human populations. Finally, if animals have no boundaries, they can be an intimidating creature. Works Cited Baucom, R. & de Roode, J. (2011). Ecological immunology and tolerance in plants and animals. Functional Ecology, 25(1), 18-28. Castleberry, S. (2005). Mammals. Encyclopedia of Georgia. Retrieved March 19, 2011, from http://www.georgiaencyclopedia.org Golley, F. B. (1962). Mammals of Georgia: a study of their distribution and functional role in the ecosystem. Athens: University of Georgia Press. Olsen, O.W. (1962). Animal parasites; their biology and life cycles. Minneapolis: Burgess Pub.Co.