Cells, up close and personal

This week we continued our investigations with microscopes. Having already gotten some experience last week with the ins and outs of using one, we focused on cells. The kids got a chance to compare plant and animal cells by extracting human cheek cells (sounds much more painful than it actually is) and onion cells (a little smelly, but otherwise no tears). We talked about how animal cells are more "blob-like," and how plant cells have a rigid exterior, which makes them look like boxes or bricks. 

Afterward the kids looked at other specimens under the microscope including: a mosquito (the wings are really interesting up close), a spider (much hairier than you'd think) , a louse (even scarier magnified 100X), a blade of grass, and various leaves.

Biology: Measuring tiny things

This week we learned a technique for measuring the length of tiny things. The kids measured a louse (for the uninitiated that's singular for lice), onion cells, and a human hair. This activity gave new meaning to the question: Do you have thick hair or thin hair?

So what unit do you use when you're measuring something so small? Meters, centimeters, millimeters? At this scale we're talkin' microns, 1000 of which make a millimeter. Using a ruler, the kids measured the field of view. Then they converted this number to microns. After examining a specimen, they estimated how many times it would fit within the field of view, did some simple math, and came up with a measurement that was within 2.5% of the accepted value. Not bad for a day's work!