Biology and Then Some

We have rolled into our third Biology unit (body systems).  Last week we started with nutrition (I know, technically not a body system) and yesterday we did the digestive system.

This was great!  Knowing the hows and whys of your digestive system is always news you can use!

We actually got sidetracked at first by daylight savings time and circadian rhythms (did you know the human clock is 25 hours long?  This helps us continually adjust to changes in day length, and it makes adding an hour really easy, but it also makes subtracting an hour really painful!).

We talked about the changes in circadian rhythm that happen in the teenage years (there's a reason it's hard to fall asleep, and it's hard to get up!) and why that was an advantage when humans needed round the clock guarding from predators.

Oh yeah, then we talked about the digestive system!

We talked about physical digestion: breaking food into smaller pieces.  We ground up some bath salt crystals in a mortar and pestle, and tried dissolving equal amounts of large crystals and ground up small crystals.  We talked about the importance of maximizing surface area  for chemical reactions.

We talked about chemical digestion: breaking food down into absorbable nutrients.

We did a couple of experiments here.  One was to try iodine on a wide variety of foods.  Based on their observations, I asked them to come up with which nutrient the iodine reacted with.  They correctly said, "Complex carbohydrates!"  I love these kids!!

We also did an emulsification experiment.  Each kid  had a jar of 1/4 cup of oil and 1/4 cup of water, and we tried 5 different possible emulsifiers: whole egg, egg yolk, egg white, mustard, and liquid soap.  Emulsification is pretty critical.  If oils and fats aren't broken down into smaller particles, they tend to coat the food and disallow digestion and absorption.

And, of course we talked about all the parts and pieces of the system as shown here: