What is Extinction?Edit
A species is considered to be extinct once there are zero individuals of that species living on Earth (Primack, 2010).
Natural Selection & ExtinctionEdit
Natural selection- "The process by which plants and animals that can adapt to changes in their environment are able to survive and reproduce while those that cannot adapt do not survive" (Merriam-Webster).
Following this theory, individuals with the best adaptations survive, while those that cannot adapt as well (or as quickly) die. If all of the individuals of a population or species die, it will become extinct.
Amphibians are currently facing an "extinction crisis". Many amphibian species have gone extinct or become endangered as a result of contamination (Primack, 2010) and drought (Pechman, Scott, Semlitsch, Caldwell, Vitt & Gibbons, 1991). These animals are not able to adapt to these changes in their environment, and therefore cannot survive and pass on their genes to a new generation of offspring.
Charles Darwin considered extinction an "engine of imporvement", stating that one species goes extinct so a new and improved species may take its place (Beer, 2009). As much has changed since the 1800's when Darwin introduced his theory of natural selection, this concept is not very commonly supported today. There is some debate over how natural most of today's extinctions are. Many extinctions are considered anthropogenic, or caused by humans (Rolston III, 1995). Is this still natural selection? Some believe that humans are the most evolved animals, and are exercising their evolutionary right to natural resources. The other side argues that part of what makes humans so evolved is their possesion of conscience and morality, which makes them obligated to prevent the extinction of other species (Rolston III, 1995).
Beer, G. (2009). Darwin and the uses of extinction. Victorian Studies, 51 (2), 321-331.
Natural Selection. (n.d.) In Merriam Webster Online Encyclopedia. Retrieved on November 16,
Pechman, J.H.K., Scott, D.E., Semlitsch, R.D., Caldwell, J.P., Vitt, L.J. & Gibbons, W. (1991).
Declining amphibian populations: the problem of separating human impacts from natural
fluctuations. Science, 253, 892-895.
Primack, R. (2010). Habitat destruction, fragmentation, degradation & global change.
Essential of Conservation Biology, 5th Edition. Massachusetts: Sinauer Associates, Inc.
Rolston III, H. (1995). Duties to endangered species. Encyclopedia of Environmental Biology, 1,