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:
““Mother” is the first word that occurs to politicians and columnists and popes when they raise the question, “Why isn’t life turning out the way we want it?””
—Mary Kay Blakely (20th century)
“Every writer hopes or boldly assumes that his life is in some sense exemplary, that the particular will turn out to be universal.”
—Martin Amis (b. 1949)
“There is a place where we are always alone with our own mortality, where we must simply have something greater than ourselves to hold onto—God or history or politics or literature or a belief in the healing power of love, or even righteous anger.... A reason to believe, a way to take the world by the throat and insist that there is more to this life than we have ever imagined.”
—Dorothy Allison (b. 1949)