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 goal in raising one’s child is to enable him, first, to discover who he wants to be, and then to become a person who can be satisfied with himself and his way of life. Eventually he ought to be able to do in his life whatever seems important, desirable, and worthwhile to him to do; to develop relations with other people that are constructive, satisfying, mutually enriching; and to bear up well under the stresses and hardships he will unavoidably encounter during his life.”
—Bruno Bettelheim (20th century)
“The truth is, I do indulge myself a little the more in pleasure, knowing that this is the proper age of my life to do it; and, out of my observation that most men that do thrive in the world do forget to take pleasure during the time that they are getting their estate, but reserve that till they have got one, and then it is too late for them to enjoy it.”
—Samuel Pepys (1633–1703)
“The married are those who have taken the terrible risk of intimacy and, having taken it, know life without intimacy to be impossible.”
—Carolyn Heilbrun (b. 1926)