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:
“... found myself
myself, smaller,
not thin but thinner, nervous,
who hurries without animal calm.”
—Denise Levertov (b. 1923)
“He is blessed who is assured that the animal is dying out in him day by day, and the divine being established.”
—Henry David Thoreau (1817–1862)
“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)