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The Charcteristics of Life

All Living Things:

1) Are composed of cells. All living things are composed of one or more cells. This is true whether its bacteria, plants, amoeba, the frog shown above or humans. The structure of a virus is not considered to be a cell.

2) Contain genetic information. Living things contain genetic information in the form of DNA which encodes the information to make new living things of the same species.

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3) Grow and reproduce A living cell must contain all the information and “machinery” necessary to create new members of the same species. They do not require the machinery of another species to reproduce.

4) Use energy Living organims are able to efficiently utilize energy in their environment and use this energy to build organic molecules needed. Plants harvest the energy from sunlight, while animals can harvest the energy stored in sugars.

5) Respond to their environment All living organisms are able to sense important details about their environment and respond accordingly to maintain the homeostatis of their internal environment. Bacteria can sense the presence of different sugars and upregulate enzymes necssary for utilizing them.

6) Have order and organization Living things have a complex and genetically determined organizational structure. This is true from the subcellular structures of bacteria up to the larger organs of humans.

What about viruses? There is often some debate about viruses. They do contain genetic information in the form of DNA or RNA. They however are not able to reproduce without using the cellular machinery of a host cell (like a bacterial or human cell). They also are not considered to be composed of cells. The instead have genetic material wrapped in a protein coat (or capsid).

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