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:
“Thus far women have been the mere echoes of men. Our laws and constitutions, our creeds and codes, and the customs of social life are all of masculine origin. The true woman is as yet a dream of the future. A just government, a humane religion, a pure social life await her coming.”
—Elizabeth Cady Stanton (1815–1902)
“Make me thy Loome: thy Grace the warfe therein,
My duties Woofe, and let thy word winde Quills.
The shuttle shoot. Cut off the ends my sins.
Thy Ordinances make my fulling mills,
My Life thy Web: and cloath me all my dayes
With this Gold-web of Glory to thy praise.”
—Edward Taylor (1645–1729)
“The time comes when each one of us has to give up as illusions the expectations which, in his youth, he pinned upon his fellow- men, and when he may learn how much difficulty and pain has been added to his life by their ill-will.”
—Sigmund Freud (1856–1939)