Natural Selection: Fur verses Furless Rabbits

Revised Spring 2010

Background

In this lab, you will simulate natural selection in a small population of wild rabbits. Evolution, on a genetic level, is a change in the frequency of alleles in a population over a period of time. Breeders of rabbits have long been familiar with a variety of genetic traits that affect the survivability of rabbits in the wild, as well as in breeding populations. One such trait is the trait for furless rabbits. This trait was first discovered in England in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a definite selection force against the furless trait.

In this lab, F represents the dominant allele for normal fur, and f represents the recessive allele for no fur. Bunnies that inherit two F alleles (FF) or one F and one f allele (Ff) have fur, while bunnies that inherit two f alleles (ff) have no fur.

The purpose of this lab is to observe the impact that genetics can have on the natural selection of a population of organisms.

Procedures:

1.  Write your hypothesis for the lab. (Hint: How many generations will it take for the “white allele” to completely disappear from the population?)

2.  The red beans represent the allele for fur, and the white beans represent the allele for no fur. The Ziplock bag represents the English countryside, where the rabbits randomly mate.

3.  Count all of the red beans and all of the white beans. You MUST begin the simulation with 50 red beans and 50 white beans!

4.  Place the 50 red and 50 white beans (alleles) in the Ziplock bag and shake up to “mix” the alleles.

5.  Without looking at the beans, select two at a time. Place the “rabbits” into the appropriate cup: FF, Ff, or ff. Continue drawing pairs of beans until all beans have been selected and sorted. (Note: The total number of individuals will be half the total number of beans because each rabbit requires two alleles.)

6.  Count the number of FF individuals and record the number in your data table. (Column 2)

7.  Count the number of Ff individuals and record the number in your data table. (Column 3)

8.  Count the number of ff individuals and record the number in your data table. (Column 4)

9.  Count the number of F alleles (all red beans in the FF and Ff cups) and record in your data table (Column 5).

10.  Count the number of f alleles (all white beans in the ff and Ff cups) and record in your data table (Column 6).

11.  Determine the total number of alleles present in the generation by adding the results of column 5 & 6 and record in your data table (Column 7).

12.  The ff bunnies are born furless. The cold weather kills them before they reach reproductive age, so they can’t pass on their alleles. Place the beans from the ff container into the “dead” cup after you have recorded the alleles and before beginning the next round.

13.  Place the alleles of the surviving rabbits from the FF and Ff cups back into the Ziplock bag and “mate” them again to get the next generation.

14.  Repeat steps 4 through 13 to obtain Generations 2 through 10.

15.  Determine the Allele Frequency of the F Allele by the formula:

16.  Determine the Allele Frequency of the f Allele by the formula:

17.  Graph the Allele Frequencies. Prepare a line graph with the horizontal axis as the generation and the vertical axis as the frequency in decimals. Plot BOTH allele frequencies on one graph. Use a red line for the F allele and a blue line for the f allele.

Directions for Writing the Lab Report

5 pts NEATNESS: Your lab report must be written in blue or black ink. DO NOT write your lab report in pencil.

5 pts HEADING: Write your first and last name, teacher’s name, class period, and date (MLA format) in the upper left corner of your lab report.

5 pts TITLE: Write a descriptive, scientific title for your lab report. It may NOT be the same as the one at the top of this page and it may not be the same as your classmates’.

5 pts HYPOTHESIS: Write your hypothesis in correct form for this lab.

5 pts PURPOSE: Write the purpose for this lab.

20 pts DATA TABLE:

a.  15 points for your data table with correct results

b.  5 points for a descriptive, scientific title for your data table

25 pts GRAPH (each item is worth 5 points)

a. Correctly set up axes and increments

b. Label axes

c. Correctly plot points

d. Correctly label lines

e. Give your graph a scientific TITLE

30 pts ANALYSIS QUESTIONS: Answer each of the following questions in complete sentences and in your own words. YOU MUST WRITE YOUR ANSWERS IN COMPLETE SENTENCES in order to receive FULL credit.

1.  Define evolution in terms of genetics. (Read the first paragraph of the background information.)

2.  Based on your graph, describe what happened to the frequency of the Fur allele and what happened to the frequency of the furless allele?

3.  Why were the alleles for the ff genotype placed in the “dead cup” instead of returning them to the bag at the end of each generation?

4.  Predict what would happen to the furless allele if the rabbits were born in Costa Rica instead of in England. Explain (justify) your answer!

5.  In a real rabbit habitat new rabbits often come into the habitat (immigrate) and other rabbits leave the area (emigrate). How might emigration affect the frequency of F and f alleles in this population of rabbits? Be Specific. (Which rabbits might leave? Why?)

6.  In a real rabbit habitat new rabbits often come into the habitat (immigrate) and other rabbits leave the area (emigrate). How might immigration affect the frequency of F and f allele in this population of rabbits? (Which rabbits might move in? Why?)

7.  Was your hypothesis supported or rejected? Explain.