Biology: Sensational Skin

This week we investigated a type of cell called the sensory receptor. These receptors are found in our skin and allow us to feel pressure, pain, heat, and cold. The kids made pressure probes (see photo), which were used to test 4 different areas of the body: fingertip, forearm, cheek, and calf. The idea was to GENTLY poke these areas with the probe, gradually decreasing the distance between the 2 toothpicks until the subject could only feel 1 prick. The area with the smallest 2-point discrimination was the area that was most sensitive and was assumed to contain the highest number of sensory receptors for pressure. The kids were surprised to find quite a great deal of variation. Subjects could distinguish 2 distinct pricks at an average of 2.5 mm on their fingertips, while the 2-point discrimination was much larger for the calf and forearm - as much as 7 mm.

We concluded by discussing why it might be adaptive for some areas to be more sensitive than others.

General Science and Biology: Which chip is the greasiest?

This week in science we asked the following questions: which brand of potato chip is the greasiest and more importantly, how can I be sure?

We went about answering them by carrying out 3 tests. The first 2 were a touch and a taste test in which the kids rated the chips on a scale from 1-5, with 5 being the greasiest. Then the kids were challenged to come up with a more quantitative test, one based on measurement. Some kids crushed equal amounts of each chip on a piece of graph paper and then compared the sizes of the different oil stains. Others compared the weight of the chips before and after crushing; the assumption being, the greasier the chip, the more oil lost in the act of being crushed on a piece of paper. Another test consisted of soaking different chips in water, removing them, and then comparing the amount of oil observed sitting on top of the water.

After carrying out our tests, we tested our tests. We read the nutritional information on the packages and reviewed our data to see which test was actually the best. Finally the kids thought about how they could improve their tests in the future.

Biology: How small is small?

This week we learned a technique for measuring specimens under the microscope. The kids measured the lengths of ants and even actual cells. You can be sure we weren't measuring in meters or even centimeters. The kids got some practice with micrometers, 1000 of which make a millimeter.

How did we do this? Using a ruler, the kids measured the field of view. Then they converted this number to micrometers (so much easier to work with when you're measuring cells and such). They estimated how many times a specimen would fit within the field of view, did some simple math and came up with a measurement that was within 100 micrometers (.1mm of the accepted answer). Not bad for a day's work!