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:
“Man, became man through work, who stepped out of the animal kingdom as transformer of the natural into the artificial, who became therefore the magician, man the creator of social reality, will always stay the great magician, will always be Prometheus bringing fire from heaven to earth, will always be Orpheus enthralling nature with his music. Not until humanity itself dies will art die.”
—Ernst Fischer (1899–1972)
“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)
“Power is, in nature, the essential measure of right. Nature suffers nothing to remain in her kingdoms which cannot help itself. The genesis and maturation of a planet, its poise and orbit, the bended tree recovering itself from the strong wind, the vital resources of every animal and vegetable, are demonstrations of the self-sufficing and therefore self-relying soul.”
—Ralph Waldo Emerson (1803–1882)