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:
“We [actors] are indeed a strange lot! There are times we doubt that we have any emotions we can honestly call our own. I have approached every dynamic scene change in my life the same way. When I married Charlie MacArthur, I sat down and wondered how I could play the best wife that ever was.... My love for him was the truest thing in my life; but it was still important that I love him with proper effect, that I act loving him with great style, that I achieve the ultimate in wifedom.”
—Helen Hayes (1900–1993)
“The man who is aware of himself is henceforward independent; and he is never bored, and life is only too short, and he is steeped through and through with a profound yet temperate happiness. He alone lives, while other people, slaves of ceremony, let life slip past them in a kind of dream.”
—Virginia Woolf (1882–1941)