Animal
Animals are a major group of multicellular, eukaryotic organisms of the kingdom Animalia or Metazoa. Their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later on in their life. Most animals are motile, meaning they can move spontaneously and independently. All animals are also heterotrophs, meaning they must ingest other organisms or their products for sustenance.
Most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago.
Read more about Animal: Etymology, Characteristics, Origin and Fossil Record, Model Organisms, History of Classification, Ethics
Famous quotes containing the word animal:
“The most threatened group in human societies as in animal societies is the unmated male: the unmated male is more likely to wind up in prison or in an asylum or dead than his mated counterpart. He is less likely to be promoted at work and he is considered a poor credit risk.”
—Germaine Greer (b. 1939)
“Man is the only animal that laughs and weeps; for he is the only animal that is struck with the difference between what things are and what they ought to be.”
—William Hazlitt (1778–1830)
“Man is the Religious Animal. He is the only Religious Animal. He is the only animal that has the True Religion—several of them.”
—Mark Twain [Samuel Langhorne Clemens] (1835–1910)