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
Consider the function of moving an arm or leg. Many
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.
Function: How do we find out?
Two approaches have been mentioned for
learning about cells and their functions:
- Culturing them
- Looking at them with microscopes
Other ways to study cells include:
- Putting electrodes in cells to learn about
- Injecting chemicals that glow when certain
kinds of chemical reactions take place
- Grinding cells up, separating and identifying their
chemical components, and testing for kinds of reactions that these chemicals
- Growing them in cultures and using chemicals to