Friday, October 23, 2015
Biology: Circulation, Respiration, and Excretion
The fun thing about biology as a general course is that it's a wild ride across all aspects of biology: dipping your toes into the great stream of life!
One thing the kids found very interesting was comparing their heart rates to the heart rates of a gerbil. Yes, Leena's gerbils are now very tame: stranger with a stethoscope? No problem!
They had guessed that larger animals would have faster heart rates because thy have to push their blood so much farther. Actually, the opposite is true: because of the law of cubes, larger hearts push much more blood, and therefore don't need to beat as often.
We also had a good time with respiration. I think I've shown how to do this lung model before, but it's a great way to show how our lungs work on air pressure.
We also used a finger gauge to look at how oxygenated our blood was when we held our breath. They were surprised: our bodies really don't want to let our oxygen levels drop very much at all!
We also talked kidneys, and our secondary excretory system, the skin. I used a little hand sanitizer (alcohol) to illustrate evaporative cooling. Cool!