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.
Famous quotes containing the word animal:
“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 (17781830)
“To the men of this world, to the animal strength and spirits, to the men of practical power, whilst immersed in it, the man of ideas appears out of his reason. They alone gave reason.”
—Ralph Waldo Emerson (18031882)
“Labor came to humanity with the fall from grace and was at best a penitential sacrifice enabling purity through humiliation. Labor was toil, distress, trouble, fatiguean exertion both painful and compulsory. Labor was our animal condition, struggling to survive in dirt and darkness.”
—Shoshana Zuboff (b. 1951)