Definition of Life
How do we know if something is alive? The answer might seem obvious but it is actually a very complicated question to answer.
Some areas of ambiguity include:
- Crystals grow and multiply, but are they alive?
- Fire consumes, grows and even reproduces itself, but is it alive?
- Viruses attack organisms and use their host to reproduce themselves, but are they actually living?
The answer is "no" according to Wikipedia which states:
"There is no universal agreement on the definition of life, the generally accepted biological manifest- ations are that life exhibits the following phenomena:
- Organization - Living things are comprised of one or more cells, which are the basic units of life.
- Metabolism - Metabolism produces energy by converting nonliving material into cellular components (synthesis) and decomposing organic matter (catalysis). Living things require energy to maintain internal organization (homeostasis) and to produce the other phenomena associated with life.
- Growth - Growth results from a higher rate of synthesis than catalysis. A growing organism increases in size in all of its parts, rather than simply accumulating matter.
- Adaptation - Adaptation is the accommodation of a living organism to its environment. It is fundamental to the process of evolution and is determined by the individual's heredity.
- Response to stimuli - A response can take many forms, from the contraction of a unicellular organism when touched to complex reactions involving all the senses of higher animals. A response is often expressed by motion: the leaves of a plant turning toward the sun or an animal chasinvg its prey.
- Reproduction - The division of one cell to form two new cells is reproduction. Usually the term is applied to the production of a new individual (either asexually, from a single parent organism, or sexually, from two differing parent organisms), although strictly speaking it also describes the production of new cells in the process of growth
Food for Thought |
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Our oceans are 99% unexplored. In the past 30 years, we have discovered 3 ecosystems that don't directly depend on light for their survival. We never even guessed these ecosystems were possible. What other surprises will we find as we continue to explore the ocean floor?
A Trivial Point |
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The Italian astronomer, Giovanni Schiaparelli, described "canali" appearing on the surface of Mars. An American enthusiast, Percival Lowell, mistranslated the term Schiaparelli used as "canal".
Lowell himself observed Mars through a telescope (with a heavy dose of wishful thinking ) and claimed to have seen these canals, as well as his theory they were evidence of Martian civilizations. This speculation inspired many science fiction writers of the day, including H.G. Wells who wrote the notorious "War of the Worlds".
