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:
“All things are flowing, even those that seem immovable. The adamant is always passing into smoke. The plants imbibe the materials which they want from the air and the ground. They burn, that is, exhale and decompose their own bodies into the air and earth again. The animal burns, or undergoes the like perpetual consumption. The earth burns, the mountains burn and decompose, slower, but incessantly.”
—Ralph Waldo Emerson (1803–1882)
“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)
“The African race evidently are made to excel in that department which lies between the sensuousness and the intellectual—what we call the elegant arts. These require rich and abundant animal nature, such as they possess; and if ever they become highly civilised, they will excel in music, dancing and elocution.”
—Harriet Beecher Stowe (1811–1896)