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:
“Every life and every childhood is filled with frustrations; we cannot imagine it otherwise, for even the best mother cannot satisfy all her child’s wishes and needs. It is not the suffering caused by frustration, however, that leads to emotional illness, but rather the fact that the child is forbidden by the parents to experience and articulate this suffering, the pain felt at being wounded.”
—Alice Miller (20th century)
“Pale hands, pink-tipped, like Lotus buds that float
On those cool waters where we used to dwell,
I would have rather felt you round my throat
Crushing out life than waving me farewell!”
—Laurence Hope (1865–1904)
“The authoritarian child-rearing style so often found in working-class families stems in part from the fact that parents see around them so many young people whose lives are touched by the pain and delinquency that so often accompanies a life of poverty. Therefore, these parents live in fear for their children’s future—fear that they’ll lose control, that the children will wind up on the streets or, worse yet, in jail.”
—Lillian Breslow Rubin (20th century)