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:
“Heaven and hell suppose two distinct species of men, the good and the bad. But the greatest part of mankind float betwixt vice and virtue.”
—David Hume (1711–1776)
“The further our civilization advances upon its present lines so much the cheaper sort of thing does “fame” become, especially of the literary sort. This species of “fame” a waggish acquaintance says can be manufactured to order, and sometimes is so manufactured.”
—Herman Melville (1819–1891)
“There are minds so impatient of inferiority that their gratitude is a species of revenge, and they return benefits, not because recompense is a pleasure, but because obligation is a pain.”
—Samuel Johnson (1709–1784)