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:
“Both classically- and romantically-minded spirits—inasmuch as these two species always exist—occupy themselves with a vision of the future: but the former do so out of a strength of their age, the latter out of its weakness.”
—Friedrich Nietzsche (1844–1900)
“Prostitution is the most hideous of the afflictions produced by the unequal distribution of the world’s goods; this infamy stigmatizes the human species and bears witness against the social organization far more than does crime.”
—Flora Tristan (1803–1844)
“Any reading not of a vicious species must be a good substitute for the amusements too apt to fill up the leisure of the labouring classes.”
—James Madison (1751–1836)