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:
“Perhaps life is just that ... a dream and a fear.”
—Joseph Conrad (1857–1924)
“When I was in high school I thought a vocation was a particular calling. Here’s a voice: “Come, follow me.” My idea of a calling now is not: “Come.” It’s like what I’m doing right now, not what I’m going to be. Life is a calling.”
—Rebecca Sweeney (b. 1938)
“Professors of literature, who for the most part are genteel but mediocre men, can make but a poor defense of their profession, and the professors of science, who are frequently men of great intelligence but of limited interests and education, feel a politely disguised contempt for it; and thus the study of one of the most pervasive and powerful influences on human life is traduced and neglected.”
—Yvor Winters (1900–1968)