Organizing Functions

We can think of "levels of organization" not only in terms of structure, but also in terms of function. A good way to think about this is to ask: What must organisms do to stay alive and survive as a species? 

Consider the function of moving an arm or leg. Many small steps are involved in completing this action. To determine the levels in our example, one approach is to take a top-down look at the steps involved in a body function. In movement, for example, there must be:

• Commands from the brain to tell the body which parts to move, where to move and how fast to move. 

• Contraction of the correct muscles that will create joint movements. 

• Movement of proteins in cells that cause the whole muscle to contract.

• Exchange of carbon dioxide for oxygen in the air we breathe by way of lungs and blood.

• Chemical reactions that make energy by combining oxygen with food chemicals.

   Cell Function: How do we find out?

Two approaches have been mentioned for learning about cells and their functions:

1. Culturing them
2. Looking at them with microscopes

Other ways to study cells include:

1. Putting electrodes in cells to learn about electrical charges
2. Injecting chemicals that glow when certain kinds of chemical reactions take place
3. Grinding cells up, separating and identifying their chemical components, and testing for kinds of reactions that these chemicals perform
4. Growing them in cultures and using chemicals to change growth