This activity was created for students to complete on their own during the Covid-19 pandemic. Hardy Weinberg equilibrium can be a difficult concept, even with class guidance, so I’ve attempted to break it down into small bite-sized pieces.
The activity starts with a description of North American squirrels, which are mostly gray in color. Black squirrels can be found in some areas. Students use the Hardy Weinberg equation to determine the frequency of black squirrels (black is a dominant allele) and use the results to determine if the populations show evidence that evolution has occurred.
A khan academy video is embedded in the lesson to explain how to uses the equation. If we were in class, I would probably explain it and show examples, but the video does makes it fairly simple for students to try to get it on their own.
The last section of the activity requires students to use a deck of cards to see if the HW equation can accurately predict the frequency of red and black cards in the deck. Students draw twenty cards at random, with black representing the dominant (B) allele and red representing the recessive (b) gray allele. After drawing 20 cards, they can use the equation to see if they get close to a 50/50 ratio on black and red alleles. If students don’t have a deck of cards they are advised they can use other types of cards, or even use an online card simulator.
Students can also do the Hardy Weinberg Problemset, but at this point, I’m not sure I’ll require it for my students during this time. The Squirrel activity is meant to just give them a basic introduction to the Hardy Weinberg equilibrium and the opportunity to work with the equation.
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Abby Hongsermeier
Hello, the 50/50 assumption at the beginning of this lab in not correct. Alleles do not occur at 50/50 frequencies often, and this is not a reason wether evolution has occurred. We actually cannot tell wether evolution has occurred because we only have on set of frequencies and nothing to compare it to. Hope this help improve this HW practice!
Admin
I get what you are saying. Students are checking for changes in frequency, not a mythical 50/50 ratio. This is a difficult concept – the equilibrium part of the equation. I think I can make a minor adjustment. Thanks!
Sarah
This blog from Nature.org reports that 1% of the grey squirrel population have the black coat phenotype. However they don’t cite a source! https://blog.nature.org/science/2021/10/11/whats-up-with-white-squirrels-and-black-squirrels/