Download Teddy Graham Evolution Lab

You are a mysterious, bear-eating predator found only in the forests of Tedditopia.
There are two kinds of bears in the forest that you like to eat: polar bears and brown
bears.
During hibernation, new bears are born every year; the birth rate is one bear for every
bear that survives the winter.
Part 1: Natural Selection Simulation
1. Get with a partner from your square group, wash your hands, and obtain 10
polar bears and 10 brown bears. Place your population on a paper towel on
your desk.
2. Record the number of polar bears and brown bears, and the total population
in your data table below. This population is your first generation.
3. Eat the three easiest to catch bears based on their environment. Do not just
pick your favorite kind of bear 
4. Obtain a second generation of bears equal to the surviving population. Add
these new bears to your old ones and chart the population numbers.
5. Repeat steps 3 and 4 until you have four generations recorded in your data
table.
6. Calculate the percentage of polar bears and brown bears for each generation
and enter these calculations in your data table.
7. On a single graph, plot your data comparing generation and percentage of
bears.
Part 1 Data Table
Generation
Brown Bears
Polar Bears
1
2
3
4
Flip the
paper over!
Total Bears
% Brown Bears
% Polar Bears
Part 2: Hardy-Weinberg Calculations
After extensive genetic studies, it has been determined that the polar bear and brown
bear are actually of the same species. The coloration difference is a result of genes in
which the recessive gene expresses a lack of pigment. The polar bear then has a
genotype of dd. The pigmented trait is dominant, therefore that brown bears have a
genotype of either DD or Dd.
Use your data from Part 1 and the Hardy-Weinberg formula to determine the data for
your data table in Part 2. Find p2, 2pq, q2, p and q for each of the four generations.
Remember that:
p2 + 2pq + q2 = 1 and p + q = 1
Example:
If you have 4% polar bears, then q2 = 0.04 and q = 0.2
Since p + q = 1, then p = 0.8
If p = 0.8, then p2 = 0.64
2pq = 2(0.8)(0.2) = 0.32
To check that your calculations are correct: p2 + 2pq + q2 = 1
0.64 + 0.32 +0.04 = 1
Part 2 Data Table
Generation
q2
q
p
p2
2pq
p2 + 2pq + q2
1
2
3
4
Analysis Questions
1. Explain which trait is favorable and explain why.
2. Which phenotype is reduced in the population?
3. What specifically happens to the genotypic frequencies from generation one to
generation four?
4. Make a second graph showing p and q versus generation. Did p and q stay
constant over time? Explain your results with detail.
5. What occurs when there is a change over time of the gene frequencies?
6. What happens to the recessive gene over the generations?
7. Explain why the recessive gene does not disappear from the population.
8. Explain, over time, what would happen if the selection pressure changed, and the
recessive gene was positively selected for. What conditions would favor the
recessive gene?
9. What would happen if it were better to be heterozygous? Will there still be
homozygous bears? Explain.
10. What requirements need to be met to observe the Hardy-Weinberg equilibrium?
11. Why don’t the Teddy Grahams follow the Hardy-Weinberg equilibrium?