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:
“As a particularly dramatic gesture, he throws wide his arms and whacks the side of the barn with the heavy cane he uses to stab at contesting bidders. With more vehemence than grammatical elegance, he calls upon the great god Caveat Emptor to witness with what niggardly stinginess these flinty sons of Scotland make cautious offers for what is beyond any question the finest animal ever beheld.”
—Administration in the State of Arka, U.S. public relief program (1935-1943)
“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)
“‘Tis said that courage is common, but the immense esteem in which it is held proves it to be rare. Animal resistance, the instinct of the male animal when cornered, is no doubt common; but the pure article, courage with eyes, courage with conduct, self-possession at the cannon’s mouth, cheerfulness in lonely adherence to the right, is the endowment of elevated characters.”
—Ralph Waldo Emerson (1803–1882)