You just finished learning that the levels of organization are:

cells --> tissues --> organs --> organ systems --> organism

Now it's your turn:

On a sheet of paper, arrange the following in their proper sequence from smallest to largest. 

1. brain          2. human          3. nerve tissue          4. neurons (nerve cells)   

5. central nervous system

Click here to see how well you did.

Now let's compare the properties of higher levels of organization with the properties of the parts of the organism.

An organ, such as the heart, is made up of groups of tissues that work together to perform a specific function. The heart is a pump that keeps blood flowing throughout the body. The heart is primarily made up of muscle tissue, but also contains connective and nerve tissue. However, each of these individual types of tissues has its own primary function which differs from the basic function of the heart.

Without the assistance of the cells in different organs, an entire organism is unable to stay alive. In a similar manner, cells rely on different organs of the organism doing their jobs to keep these cells alive.