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 boxer’s ring is the enjoyment of the part of society whose animal nature alone has been developed.”
—Ralph Waldo Emerson (1803–1882)
“The animal merely makes a bed, which he warms with his body, in a sheltered place; but man, having discovered fire, boxes up some air in a spacious apartment, and warms that.... Thus he goes a step or two beyond instinct, and saves a little time for the fine arts.”
—Henry David Thoreau (1817–1862)
“There is an animal inside me,
clutching fast to my heart,
a huge crab.”
—Anne Sexton (1928–1974)