Count the number of inhale-exhale movements of your chest for one minute. Write down the number of inhalations you take in one minute.

Now exercise for a few minutes by jumping up and down on one foot. Or two feet. Maybe do a few jumping jacks. Then, sit down and count your inhalations for one minute. Compare that number to your resting respiration rate before exercise. Do you inhale more times after exercise? Why do you think that is? What is it that our bodies need that comes to us with each breath? Oxygen. How long could we live without it? Can we go without oxygen as long as we can go without food?

If you have a classroom pet, count it's inhalations while it is resting. Then, induce it to run around a bit (or maybe do some push-ups), and count it's inhalations. Do fish need to breathe oxygen? How can that be? There isn't any air in the water. How do fish get oxygen from the water?

How many animals can you name that do not require oxygen?