Animal

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:

    You don’t want to be an animal, you want to observe your own animal functions, so as to get a mental thrill out of them. It is all purely secondary—and more decadent than the most hide-bound intellectualism.
    —D.H. (David Herbert)

    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 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 (1778–1830)