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:
“What quarrel, what harshness, what unbelief in each other can subsist in the presence of a great calamity, when all the artificial vesture of our life is gone, and we are all one with each other in primitive mortal needs?”
—George Eliot [Mary Ann (or Marian)
“Beyond the horizon, or even the knowledge, of the cities along the coast, a great, creative impulse is at work—the only thing, after all, that gives this continent meaning and a guarantee of the future. Every Australian ought to climb up here, once in a way, and glimpse the various, manifold life of which he is a part.”
—Vance Palmer (1885–1959)
“What makes saintliness in my view, as distinguished from ordinary goodness, is a certain quality of magnanimity and greatness of soul that brings life within the circle of the heroic.”
—Harriet Beecher Stowe (1811–1896)