Today I got to work with one of my students, Eric, on his ninth grade biology homework assignment covering natural selection and evolution.  He has a quiz coming up so his homework reviewed the sections in the book.  While working through the problems, Eric and I had a great discussion about each of his answers.  We came up with lots of examples for the different terms he had to know.  The example that stuck most with Eric was how the finches that flew to the Galapagos Islands represented the founder effect of genetic drift.  By geographically isolating a small population of a species, the genetic variation is limited causing the species to change and adapt to the new environment.  He enjoyed thinking up other situations in which the founder effect could be applied.

The one topic that confused Eric was the Hardy-Weinberg principle for genetic equilibrium.  This is a tough concept to understand because it theoretical and complex.  First off, we had to memorize the conditions that are necessary for this equilibrium to take place: very large population, random mating, no natural selection, no immigration/emigration, and no mutation. We talked about why those criteria are necessary for keeping the allele frequencies constant and that helped him remember each of those restrictions.  After establishing the basis for the Hardy-Weinberg principle, we went over how to calculate allele and genotype frequencies.  This uses two different equations and can be confusing at first.  After showing him how to use the equations to solve for the frequencies, I gave him some practice problems.  After a rough start, he did really well by getting the last three questions right.

After a quick review at the end of the session, Eric was much more confident about the material that was on his quiz.  We got a lot done during the session and he improved a lot!