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 increasing the distance between the 2 toothpicks until the subject could feel 2 distinct sensations. 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 sensations 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 10-15 mm.

Physics: What color is it really?

This week we did 3 mini-experiments to investigate how we perceive color. The first was with spinning color wheels. The kids compared the patterns of the discs when still to the patterns they saw when the discs were spun. The second mini-experiment involved looking at magazine pictures under the microscope and comparing the images seen with the naked eye to the colors seen at greater magnification. The third was simply giving each kid some red, blue, and yellow paint and letting them go wild...well on paper anyway.

When we physically combine red, blue, and yellow paints in different proportions we can create an enormous range of colors. Similarly the human brain will combine colors that your eyes see when those 2 colors are seen in rapid succession, as in the case of the spinning color wheels or when they are placed very close together, as revealed by a microscopic examination of pictures from a magazine. What is especially cool about the magazine pictures is that no matter what color you "see," when examined under the microscope you realize that the image is made up of just 3 colors: magenta, cyan, and yellow (aka red, blue, and yellow). By producing images that include different ratios of the primary colors, you can get just about any color.

Biology: Testing for organic compounds

This week we discussed organic compounds. First we dispelled any myths about organic compounds being any healthier than regular old compounds. Likewise, if someone tries to charge you more money for an organic compound, don't fall for it! In chemistry, organic means relating to living things and containing lots of carbon atoms.

We used chemical and physical tests to find out whether the 6 foods in question (water, chicken soup, sucrose (table sugar and water), egg, margarine, and bread crumbs solution) contain proteins, fats, or carbohydrates (starches or glucose).

Biology: Carbon

This week we talked about carbon and how its atomic structure gives it so much versatility in forming chemical bonds with other elements. Using the latest in electron microscopy we were able to produce this incredible image of an actual ethane molecule.

Next time we meet we'll investigate the major carbon-containing macromolecules that make up all living things.

General Science: The Right Stuff

This week the kids were charged with designing a spacesuit that could withstand the intensely high temperatures one might find on Venus. Lacking the funding to actually travel to Venus and not wanting to violate the Helsinki Declaration,* we used ice-pops instead of people and hot water instead of Venus. The kids made spacesuits using one of three available materials: tin foil, wax paper, and bubble wrap. Once outfitted with their spacesuits, each ice pop was submerged in a pot of boiling water for one minute. For comparison we also had a control ice pop, meaning an ice pop with no space suit. After a minute the kids opened up each ice-pop and measured how much of it had melted by pouring the liquid into a graduated cylinder. Of the 3 materials, bubble wrap was the best insulator.

*ethical principles for research on human subjects

Biology: Water...more than meets the eye

This week the kids hunted for microorganisms in a sample of pond water taken from Robert and Karen Clements' pond (thanks once again for your annual donation of pond scum!).

To get a sense of what we were looking for, we started off by watching a few short video clips of different microorganisms. Then the kids prepared their slides, making sure to get a sample of pond water that was nice and goopy. After hunting around a bit, the kids turned up some interesting single-celled organisms and even a water flea. What's cool about this little guy is that being transparent means you can WATCH its heart beat!

Biology: Etrog vs Lemon

This week we studied etrogs from a biological perspective. First we classified them as citrus, a type of flowering plant and talked about the role flowers play in helping plants reproduce. Etrog trivia: What part of the flower is the pitom?

Then we asked the question: What's the difference between an etrog and a lemon? The kids started off by making some external observations: shape, color, volume, and weight, and then they opened them up and looked inside. They noted differences in the relative proportions of peel and fruit as well as differences in the volume of juice. They took the pH of each fruit and congratulated themselves on a job well-done to the tune of a tall glass of lemonade. Etrogade, we learned is pretty tough to make given how little juice each fruit contains.