Since the cell is the structural and functional unit of life as the house is for a community, without the house the community would be irritated and would not be stable, the community would therefore cease to exist. Just as there are requirements for a house to be classified as safe, secure and livable, there are 10 requirements for an organism to be classified as living. These 10 characteristics include:
1. The ability to move~ either by using motion or locomotion
2. Ability to respond to short-term environmental changes~ with irritability when detrimental or responsiveness when positive.
3. Ability to adapt to long-term environmental changes~ by making necessary changes to survive. I.e.: evolution
4. Ability to reproduce~ asexual vs. sexual
5. Reaches a point of maturity~ at which point successful reproduction is possible
6. Able to acquire basic nutrients for energy~ through photosynthesis or absorption following a digestive process.
7. Able to convert basic nutrients to a more useable form~ through cellular respiration or synthesis
8. Able to eliminate waste~ the products from the energy transformations
9. Has a limited life span~ will eventually cease to exist and die.
10. Is made up of one or more cells~ and the product of those cells (uni-cellular vs. multi-cellular)
The absence of any single characteristic would mean the organism has a non-living status. The majority of these characteristics aid in the balance of homeostasis and the need for control. As with the second characteristic, there is the need for a reaction to a short-term change in the surrounding environment to aid in maintaining the homeostatic balance. Take for instance the heater
References: http://www.biology.arizona.edu/cell_bio/tutorials/cells/cells3.html http://pespmc1.vub.ac.be/HOMEOSTA.html