What is a living thing?  

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In addition to having similar chemical composition all living things have these characteristics in common:

1. They are made of cells. They can be single-celled, or multi-cellular with various levels of organization such as tissues, organs and organ systems.

2. They obtain and use energy.

3. They eliminate waste.

4. They grow and develop.

5. They reproduce. This can be sexual or asexual.

6. They respond to their environment. For example, plants turn toward sunlight.

7. They adapt over time to their environment.

8. They move. This might be movement within the cell, or movement of an entire organism such as walking or running.

Something that exhibits some but not all of these characteristics, for example a virus, is not considered a living thing.


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