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 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)
“The moose will, perhaps, one day become extinct; but how naturally then, when it exists only as a fossil relic, and unseen as that, may the poet or sculptor invent a fabulous animal with similar branching and leafy horns ... to be the inhabitant of such a forest as this!”
—Henry David Thoreau (1817–1862)
“The screech and mechanical uproar of the big city turns the citified head, fills citified ears—as the song of birds, wind in the trees, animal cries, or as the voices and songs of his loved ones once filled his heart. He is sidewalk- happy.”
—Frank Lloyd Wright (1869–1959)