Species
In biology, a species (plural: species) is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, the difficulty of defining species is known as the species problem. Differing measures are often used, such as similarity of DNA, morphology, or ecological niche. Presence of specific locally adapted traits may further subdivide species into "infraspecific taxa" such as subspecies (and in botany other taxa are used, such as varieties, subvarieties, and formae).
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Famous quotes containing the word species:
“Thus all probable reasoning is nothing but a species of sensation. ‘Tis not solely in poetry and music, we must follow our taste and sentiment, but likewise in philosophy, When I am convinc’d of any principle, ‘tis only an idea which strikes more strongly upon me. When I give the preference to one set of arguments above another, I do nothing but decide from my feeling concerning the superiority of their influence.”
—David Hume (1711–1776)
“The question that will decide our destiny is not whether we shall expand into space. It is: shall we be one species or a million? A million species will not exhaust the ecological niches that are awaiting the arrival of intelligence.”
—Freeman Dyson (b. 1923)
“As kings are begotten and born like other men, it is to be presumed that they are of the human species; and perhaps, had they the same education, they might prove like other men. But, flattered from their cradles, their hearts are corrupted, and their heads are turned, so that they seem to be a species by themselves.... Flattery cannot be too strong for them; drunk with it from their infancy, like old drinkers, they require dreams.”
—Philip Dormer Stanhope, 4th Earl Chesterfield (1694–1773)