Life
Evidence suggest that life on Earth has existed for about 3.7 billion years. All known life forms share fundamental molecular mechanisms, and based on these observations, theories on the origin of life attempt to find a mechanism explaining the formation of a primordial single cell organism from which all life originates. There are many different hypotheses regarding the path that might have been taken from simple organic molecules via pre-cellular life to protocells and metabolism.
Although there is no universal agreement on the definition of life, scientists generally accept that the biological manifestation of life is characterized by organization, metabolism, growth, adaptation, response to stimuli and reproduction. Life may also be said to be simply the characteristic state of organisms. In biology, the science of living organisms, "life" is the condition which distinguishes active organisms from inorganic matter, including the capacity for growth, functional activity and the continual change preceding death.
A diverse array of living organisms (life forms) can be found in the biosphere on Earth, and properties common to these organisms—plants, animals, fungi, protists, archaea, and bacteria—are a carbon- and water-based cellular form with complex organization and heritable genetic information. Living organisms undergo metabolism, maintain homeostasis, possess a capacity to grow, respond to stimuli, reproduce and, through natural selection, adapt to their environment in successive generations. More complex living organisms can communicate through various means.
Read more about this topic: Natural Environment
Famous quotes containing the word life:
“The moment one accosts a stranger or is accosted by him is above all in this life the moment of drama.... Whoever we meet watches us intently at the quick, strange moment of meeting, to see whether we are disposed to be friendly.”
—Haniel Long (1888–1956)
“There was a heavy power in her eyes which laid hold of his whole being, as if he had drunk some powerful drug. He had been feeling weak and done before. Now the life came back into him, he felt delivered from his own fretted, daily self.”
—D.H. (David Herbert)
“The secret of the truly successful, I believe, is that they learned very early in life how not to be busy. They saw through that adage, repeated to me so often in childhood, that anything worth doing is worth doing well. The truth is, many things are worth doing only in the most slovenly, halfhearted fashion possible, and many other things are not worth doing at all.”
—Barbara Ehrenreich (b. 1941)