|"Animal." World Book Encyclopedia. 16 vols. Chicago: World Book, 2003.||"So far scientists have named and classified more than 1½ million animals. Over half of these are types of insects and other species are discovered each year. Scientists believe there may be from 2 million to as many as 50 million kinds of animals alive today."||2–50 million|
|1996 IUCN Red List of Threatened Animals. The World Conservation Union (IUCN), 26 May 2003.||"Furthermore, there are currently about 1.5 to 1.8 million named species, but it is estimated that the actual number of species in the world ranges from 5 to 10 million (May et al. 1995)."||5–10 million|
|Wolosz, Thomas. How Many Species are There? Center for Earth & Environmental Sciences, SUNY at Plattsburgh, 1988.||"The most commonly quoted estimate is somewhere between is somewhere between 30 and 50 millions based on Erwin's (1988,1997) study of tropical insects."||30–50 million|
|Just How Many Species Are There, Anyway? Society For Conservation Biology. 26 May 2003.||"'Right now we can only guess that the correct answer for the total number of species lies between 2 and 100 million,' says [Michael] Rosenzweig."||2–100 million|
Taxonomy is a science that directly involves classifying animals, plants, and other organisms into groups of similar characteristics. Scientists have tried for many decades to name and accurately classify all of the species on earth. In order to classify living organisms into groups or families of similar characteristics they follow a method created by Carolus Linnaeus, which provides a two-word Latin name for the species. In his system of classification, the first word is the genus name and the second is usually an adjective describing a particular characteristic, also known as the species name. A species name is given with respect to different external characteristics the organism may possess due to interbreeding. An organism's species name is sometimes referred to as a sub-division of its genus characteristics.
Currently, scientists have named and successfully classified over 1.5 million species. It is estimated that there are as little as 2 million to as many as 50 million more species that have not yet been found and/or have been incorrectly classified. Estimates vary from scientist to scientist because it is close to impossible to truly know whether there are any more species living that are not by the tip of the scientists' noses. As fields such as microbiology progress, scientists of taxonomy become more capable of accurately classifying species of the past and present.
Due to the loss of species and biodiversity scientists are not able to catch up with the rate at which the species are leaving the ecosystem. This loss of biodiversity is usually directly linked with deforestation. Specialists believe that, at the current rate of extinction, during the course of the next half-century one-third of all organisms will be lost.
Felix Nisimov -- 2003
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