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 danger lies in forgetting what we had. The flow between generations becomes a trickle, grandchildren tape-recording grandparents’ memories on special occasions perhaps—no casual storytelling jogged by daily life, there being no shared daily life what with migrations, exiles, diasporas, rendings, the search for work. Or there is a shared daily life riddled with holes of silence.”
—Adrienne Rich (b. 1929)
“In everyone there sleeps
A sense of life lived according to love.
To some it means the difference they could make
By loving others, but across most it sweeps
As all they might have done had they been loved.
That nothing cures.”
—Philip Larkin (1922–1986)
“The changes in our life must come from the impossibility to live otherwise than according to the demands of our conscience ... not from our mental resolution to try a new form of life.”
—Leo Tolstoy (1828–1910)