Did you watch that Saturday morning cartoon where the entire house went crazy when the word of the day was spoken?  I’ve always told my students to do the same thing when they hear the word – homeostasis.

There are lots of ways to define it, but balance always seems to be included somewhere in the mix.  For me, homeostasis is the balance between challenges to the system that keeps you alive and the response to offset those challenges.

My quick homeostasis lab.

I always teach homeostasis and the characteristics of life as back to back topics.  That “responds to stimuli” characteristic is a great point to show homeostasis in action.

My favorite quick homeostasis lab is to have students grab a partner and stare at each other’s eyes.  Noting the size of the pupil.  Then I turn off the light and have them close their eyes for 20-30 seconds.  Then turn on the light and have them open their eyes and stare again.  They are looking for the response the pupils make to the change in light.

Then we talk about the bigger question – Why?  Why does the pupil contract and dilate in response to changes in light exposure?  The simple truth is protection.  Light can damage the optic nerve so while we need adequate light in order to see – too much of a good thing, isn’t good.

After this discussion, I have student look at the eyes around the room again.  What is happening and why?  The eyes have returned to normal because the perceived threat wasn’t a threat at all and was within limits.

Homeostasis is about keeping things within limits.

Now that isn’t all there is to teach about homeostasis.  I cover the parts of a feedback loop and the two types: negative and positive feedback.   These can be done through simple notes or questions that students will answer using the resources available to them.

If you are looking for a more formal activity to teach homeostasis, I suggest this Fitness Challenge.  Additionally, for high school level, I love Cornell notes.

My homeostasis resources are on sale from July 31-August 2!