Wednesday, April 6, 2011

Biology: Genetics with a smile

This week the kids carried out a simulation in which they explored how traits are passed down from one generation to the next in the strange but cheerful species, commonly known as "Smiley faces." The kids flipped coins to see which genes the smiley faces would pass on to their offspring. While the kids observed several differences between smiley faces and us - e.g. smileys have eyes that are shaped like stars (maybe that's why they're so happy?), we also noted the basic principles of inheritance we share.
  • individuals carry 2 versions of each trait, one from the mom and one from the dad
  • individuals pass one 1 version of each trait to each offspring
  • an offspring's phenotype (what he looks like) is the combined result of the 2 versions he got from mom and dad - sometimes, but not always following the rules of dominance

General Science: What to feed your pet yeast

Before we do away with all of our חמץ, it seems appropriate to learn something about our tiny unicellular fungal friend, the yeast. After all, we have a lot in common: Like us, yeast eat, reproduce, and respire. That's fancy-talk for releasing carbon dioxide as a result of transforming the energy from food into energy our cells can use. This comes in handy when baking bread. It's the carbon dioxide gas that causes the bread to rise.

This week's question was: What's a yeast's favorite food: salt, sugar, or flour? To know which food was eaten most heartily by our yeast, we prepared bottles of yeast, warm water, and one of the three foods being tested. We covered each bottle with a balloon and then sat back and watched the show. The samples of yeast fed sugar were the happiest, i.e. the balloons inflated the fastest because of the greater production of carbon dioxide. Flour came in second and salt came in last. We discussed how flour, a complex sugar, gets broken down into simpler sugars. A little more work, but when you're hungry, you do what you have to. Yet one more thing we all have in common...LAZINESS and an appreciation for fast food.

Physics: Mirror mirror on the wall

This week in physics the kids completed their periscopes and carried out some experiments with lenses and mirrors. In the first experiment the kids placed an object in front of a set of hinged mirrors. The kids observed how changing the angle between the two mirrors affected the number of images produced and tried to figure out the pattern. Then the kids examined a bunch of different lenses, some convex and some concave and noted how looking through each one affected the size of magazine print. One of the lenses they tried out was a drop of water. Convex or concave...what do you think?