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:
“If it were possible to have a life absolutely free from every feeling of sin, what a terrifying vacuum it would be!”
—Cesare Pavese (1908–1950)
“Women are taught that their main goal in life is to serve others—first men, and later, children. This prescription leads to enormous problems, for it is supposed to be carried out as if women did not have needs of their own, as if one could serve others without simultaneously attending to one’s own interests and desires. Carried to its “perfection,” it produces the martyr syndrome or the smothering wife and mother.”
—Jean Baker Miller (20th century)
“I suffer whenever I see that common sight of a parent or senior imposing his opinion and way of thinking and being on a young soul to which they are totally unfit. Cannot we let people be themselves, and enjoy life in their own way? You are trying to make that man another you. One’s enough.”
—Ralph Waldo Emerson (1803–1882)