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:
“The boxer’s ring is the enjoyment of the part of society whose animal nature alone has been developed.”
—Ralph Waldo Emerson (1803–1882)
“Nobody can misunderstand a boy like his own mother.... Mothers at present can bring children into the world, but this performance is apt to mark the end of their capacities. They can’t even attend to the elementary animal requirements of their offspring. It is quite surprising how many children survive in spite of their mothers.”
—Norman Douglas (1868–1952)
“Most men would feel shame if caught preparing with their own hands precisely such a dinner, whether of animal or vegetable food, as is every day prepared for them by others. Yet till this is otherwise we are not civilized, and, if gentlemen and ladies, are not true men and women. This certainly suggests what change is to be made.”
—Henry David Thoreau (1817–1862)