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 rarest of all things in American life is charm. We spend billions every year manufacturing fake charm that goes under the heading of “public relations.” Without it, America would be grim indeed.”
—Anita Loos (1888–1981)
“Indeed, the life of cattle, like that of many men, is but a sort of locomotiveness; they move a side at a time, and man, by his machinery, is meeting the horse and the ox half-way.”
—Henry David Thoreau (1817–1862)
“The deadly monotony of Christian country life where there are no beggars to feed, no drunkards to credit, which are among the moral duties of Christians in cities, leads as naturally to the outvent of what Methodists call “revivals” as did the backslidings of the people in those days.”
—Corra May Harris (1869–1935)