Th Cell as the Basic Unit of Life
Like cement sets the foundation for a house, the cell theory sets the foundation for biology. Schleiden and Schwann proposed the cell theory, which states that the cell is the basic unit of life and that new cells arise only from the reproduction of already existing cells via cell cycle, in 1839.
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
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