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:
“As the twentieth century ends, commerce and culture are coming closer together. The distinction between life and art has been eroded by fifty years of enhanced communications, ever-improving reproduction technologies and increasing wealth.”
—Stephen Bayley (b. 1951)
“I love, cherish, and respect women in my mind, in my heart, and in my soul. This love of women is the soil in which my life is rooted. It is the soil of our common life together. My life grows out of this soil. In any other soil, I would die. In whatever ways I am strong, I am strong because of the power and passion of this nurturant love.”
—Andrea Dworkin (b. 1946)
“Like children, the elders are a burden. But unlike children, they offer no hope or promise. They are a weight and an encumbrance and a mirror of our own mortality. It takes a person of great heart to see past this fact and to see the wisdom the elders have to offer, and so serve them out of gratitude for the life they have passed on to us.”
—Kent Nerburn (20th century)