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:
“To revolt is a natural tendency of life. Even a worm turns against the foot that crushes it. In general, the vitality and relative dignity of an animal can be measured by the intensity of its instinct to revolt.”
—Mikhail Bakunin (1814–1876)
“Come into animal presence.
No man is so guileless as
the serpent. The lonely white
rabbit on the roof is a star
twitching its ears at the rain.”
—Denise Levertov (b. 1923)
“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)