Evolving Populations

SCCS AP Biology Name: Evolving Populations

In this lab, we will model how different scenarios affect evolution. According to the Hardy-Weinberg theory, there are five factors that can cause evolution: 1) Natural selection. 2) Non-random mating. 3) Mutation. 4) Small population size. 5) Migrations. In this lab, we will look at three of these factors: natural selection, small population size, and migrations. The model we will use in class is a simplified version of real and complex situations. In building our model population, the following assumptions will be made: 1) All members of the population mate randomly. 2) All matings will produce the same number of offspring (2).

If the frequency of alleles in a population does not vary from one generation to another, we say the population is in GENETIC EQUILIBRIUM (i.e., no evolution is occurring). If there is a change in the frequency of alleles, then the population is said to be evolving!

PART I: GENETIC EQUILIBRIUM Once upon a time, there were happy little Skittles creatures in the world. They were happy because they lived on an island with no predators. There were three variations of Skittles creatures: X______, Y______, and Z______. No color of Skittles creature had any advantages over the other. They were all equal.

1. On the table, you will find containers with three types of Skittles. The color of the creature represents the genotype of the individual: X______= RR Y______= Rr Z______= rr In each container there should be 10 X______, 20 Y______, and 10 Z______Skittles creatures. Thus, we are starting with 25% RR, 50% Rr, and 25% rr. Determine and record the initial p and q values (p = frequency of R alleles and q = frequency of r alleles). Compare all your hypotheses to these values! 2. Before you begin this experiment, review the expected results of the following crosses. Using 6 half sheets of paper, draw the Punnett square for each of the possible matings – one Punnett square on each half sheet. Record the number of expected offspring (out of 4) in the EXPECTED RESULTS chart on your data sheet. 3. ** Make your hypothesis regarding final p and q values. Record your hypothesis on the chart.** Randomly draw out two Skittles creatures. We will assume that the two creatures mate and produce 2 offspring. To select which of the possible offspring they have, one partner spins the Punnett square on the half sheet of paper around and the other partner points to the paper while closing their eyes. The offspring in the Punnett square closest to where you point is the offspring you have. Repeat to determine the genotype of the second offspring. Use tally marks in Table 1 to indicate the type of offspring they will have. 4. Continue to draw out all of the Skittles creatures two at a time and indicate the type of offspring in your chart with tally marks. 5. Total your tally marks in each column, calculate and record the final frequency of R alleles (p) and the final frequency of r alleles (q). 6. Return all 40 Skittles creatures to the container.

PART II: NATURAL SELECTION One day, a population of Hot Tamales Creatures moved to the island. The Hot Tamales creatures were friendly enough, but they brought with them a terrible disease. Fortunately, most of the Skittles creatures were immune to the disease. However, the Z______Skittles creatures were not. They all died. ** Make your hypothesis regarding final p and q values. Record your hypothesis on the chart.** 1. Remove all of the Z______(rr) creatures from your population to simulate their deaths (don’t eat them – we will need them again later). This represents NATURAL SELECTION. 2. Again, randomly draw out each of the Skittles creatures by pairs and mate them as you did in part one to determine genotypes of offspring. If you create a Z______offspring, that offspring dies. If that happens, mate again until you have 2 viable offspring. Record the genotypes of the viable offspring in Table 2: Natural Selection. 3. Total your tally marks in each column, calculate and record the final p and q for part 2. 4. Return all 40 Skittles creatures to the container.

PART III: GENETIC DRIFT There was a major catastrophe on Skittles island! An earthquake caused a small piece of land from the island to break off and drift out to sea. Those who were standing on that piece of land at the time became isolated from the rest of the group. ** Make your hypothesis regarding final p and q values. Record your hypothesis on the chart.** 1. To simulate this isolation, randomly remove 30 Skittles creatures from the container. DO THIS WITHOUT LOOKING TO MAKE SURE IT IS RANDOM! The remaining 10 represent those stuck on the drifting piece of land. 2. Again, randomly draw out each of the 10 remaining Skittles creatures by pairs. Record the genotypes of their offspring in Table 3: Genetic Drift. Random fluctuations in the percentage of genotypes in a small population is referred to as GENETIC DRIFT. 3. Total your tally marks in each column, calculate and record the final p and q for part 3. 4. Return all 40 Skittles creatures to the container.

Part IV: MIGRATION Skittles creatures located on the mainland learned how to build a boat. A group of 10 X______Skittles creatures migrate over to the island. ** Make your hypothesis regarding final p and q values. Record your hypothesis on the chart.** 1. To simulate the migration, add an additional 10 X______Skittles creatures to your container. 2. Again, randomly draw out each of the Skittles creatures by pairs. Record the genotypes of their offspring in Table 4: Migration. 3. Total your tally marks in each column, calculate and record the final p and q values for part 4.

A pblueator moves to the island! This pblueator is VERY smart—it understands evolution and the concept of genetic equilibrium. S/he is so cunning that he eats ALL of the Skittles creatures on the island and the Skittles creatures go extinct! To simulate this portion of the model, eat all the Skittles creatures. SCCS AP Biology Name ______

Period______Date______

DATA SHEET – EVOLVING POPULATIONS

EXPECTED RESULTS Parents Offspring Genotype Phenotypes RR Rr rr RR x RR X x X Table 3: Genetic Drift RR x Rr X x Y Hypothesis for Final p______RR x rr X x Z Hypothesis for Final q______Rr x Rr Y x Y Offspring Rr x rr Y x Z RR Rr rr rr x rr Z x Z

Initial p_____ Initial q_____

Table 1:Genetic Equilibrium Final p_____ Final q_____ Hypothesis for Final p______Hypothesis for Final q______Offspring Table 4: Migration RR Rr rr Hypothesis for Final p______Hypothesis for Final q______Offspring RR Rr rr

Final p_____ Final q_____ TOTAL

Final p_____ Final q_____ Table 2: Natural Selection Hypothesis for Final p______Hypothesis for Final q______Offspring RR Rr rr

Final p_____ Final q_____ LAB WRITE-UP Type your responses to the following questions. Use complete sentences (subject + verb) for full credit. Diagrams may be included, but must be accompanied by an explanation of the diagram. Submit finished assignment on www.turnitin.com by the due date: ______

1. In your own words, explain what we investigated in this lab activity. Include your hypotheses that you formed in the course of the lab.

2. State whether or not your hypotheses were supported by the data. Explain what misconceptions changed and what new concepts you learned as a result of doing this activity.

3. Evolution occurs whenever allelic frequencies change from one generation to the next. Discuss each part of this activity, explaining whether or not evolution occurred and why (which H-W conditions were/were not met?)

4. Compare your results to other groups – were your results always the same? Why or why not?

5. Explain a real-world example where either non-random mating or mutation could lead to evolution.

6. How can this knowledge make us better stewards of our bodies and/or the world that we live in?

7. If we could investigate this phenomenon further, what aspects could we explore?