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:
“Most vices ... demand considerable self-sacrifices. There is no greater mistake than to suppose that a vicious life is a life of uninterrupted pleasure. It is a life almost as wearisome and painful—if strenuously led—as Christian’s in The Pilgrim’s Progress.”
—Aldous Huxley (1894–1963)
“I have no doubt that they lived pretty much the same sort of life in the Homeric age, for men have always thought more of eating than of fighting; then, as now, their minds ran chiefly on the “hot bread and sweet cakes;” and the fur and lumber trade is an old story to Asia and Europe.”
—Henry David Thoreau (1817–1862)
“Their rebukes have never made me angry, because I have always wondered why they did not rebuke me more. They should have. Their friendly praise has been one of the sweetest, most warming things in my life in the theater. I do go on the stage unafraid of them and with love in my heart for them.”
—Minnie Maddern Fiske (1865–1932)