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Transcript
NATURAL SELECTION Activity 1: Breeding Bunnies Name: ____________________________ Date: ________________ Block: _______ In this activity, you will examine 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 (naked bunnies). This trait was first discovered in England by W.E. Castle in 1933. The furless rabbit is rarely found in the wild because the cold English winters are a definite selective force against it. In this lab, the dominant allele for normal fur is represented by (F) and the recessive allele for no fur is represented by (f). Bunnies that inherit two (F) alleles or one (F) and one (f) allele have fur, while bunnies that inherit two (f) alleles have no fur. Materials: Red beans represent the allele for fur. White beans represent the allele for no fur. Container representing the English countryside, where the rabbits randomly mate. The clear petri dish is the “cemetery” where rabbits will be discarded. Two dixie cups, labeled FF and Ff Procedures 1. Fill in the hypothesis section of the data form and specific predictions based on that hypothesis. 2. Place the 50 red and 50 white beans (alleles) in the “English countryside” container and shake up (mate) the rabbits. 3. Without looking at the beans, select two at a time, and record the results on the data form next to "Generation 1." a. For instance, if you draw one red (representing a F allele) and one white bean (representing a f allele), place a mark in the chart under "Number of Ff individuals." b. Continue drawing pairs of beans and recording the results in your chart until all beans have been selected and sorted. c. Place the "rabbits" into the appropriate cup: FF, Ff, or the cemetary if they are ff. i. The ff bunnies are born furless and the cold weather kills them before they reach reproductive age, so they can't pass on their genes. These bunnies are placed in the cemetary for this reason 4. Count the actual F and f alleles (beans) that were placed in each of the "furred rabbit" cups in the first round. 5. Record the number in the chart in the columns labeled "Number of F Alleles" and "Number of f Alleles."(This time you are really counting each bean, but don't count the alleles of the ff bunnies because they are dead.) 6. Total the number of F alleles and f alleles for the first generation and record this number in the column labeled "Total Number of Alleles." 7. Place the alleles of the surviving rabbits (which have grown, survived and reached reproductive age) back into the “English Countryside”container and mate them again to get the next generation. 8. Repeat steps three five through seven to obtain generations two through seven on your data table. Calculations 9. Determine the gene frequency of F and f for each generation and record them in the chart in the columns labeled "Gene Frequency F" and "Gene Frequency f." a. To find the gene frequency of F, divide the number of F by the total number of alleles b. To find the gene frequency of f, divide the number of f by the total. i. Express results in decimal form. ii. The sum of the frequency of F and f should equal one for each generation. 10. Graph your frequencies. a. Prepare a graph with the horizontal axis as the generation and the vertical axis as the frequency in decimals. b. Plot all frequencies on one graph. 11. Complete the Discussion Questions form with your group. Pre-Lab Questions: 1. What are the two alleles for fur? a. _____________________________________________ b. _____________________________________________ 2. What are the three possible allele combinations a bunny can inherit for fur? a. _________ b. _________ c. _________ 3. What do the beans represent? a. ref beans: ____________________________________ b. white beans: ____________________________________ 4. Why are furless bunnies rarely found in the wild in England? ______________________________________________________________________________________________ ______________________________________________________________________________________________ 5. Why are the white beans picked as (ff) placed into the “cemetary”? ______________________________________________________________________________________________ ______________________________________________________________________________________________ 6. Why are you not supposed to look at the beans while you are selecting them? ______________________________________________________________________________________________ ______________________________________________________________________________________________ 7. How do you determine the total number of alleles for each generation? ______________________________________________________________________________________________ ______________________________________________________________________________________________ 8. How do you determine the gene frequency for each allele? ______________________________________________________________________________________________ ______________________________________________________________________________________________ 9. When graphing your data, what will go on the horizontal (x) axis? __________________________ 10. When graphing your data, what will go on the vertical (y) axis? __________________________ Problem: How does natural selection affect gene frequencies over several generations? Hypothesis: __________________________________________________________________________________________ __________________________________________________________________________________________ __________________________________________________________________________________________ Data & Calculations ---------------------------------A--------------------------------- ----B---- ----C---- -----D----(B + C) B/D C/D Generation # of FF individuals (2 red beans) # of Ff individuals (1 white bean, 1 red bean) # of ff individuals (2 white beans) # of F # of f TOTAL Gene Gene alleles alleles # of frequency frequency (red (white alleles of F of f beans) beans) 1 2 3 4 5 6 7 Title: ____________________________________ Discussion Questions: 1. What was your original hypothesis? _______________________________________________________________________________________ _______________________________________________________________________________________ 2. Based on your lab data, do you need to change your hypothesis? Explain. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 3. Compare the number of alleles for the dominant characteristic with the number of alleles for the recessive characteristic. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 4. Compare the frequencies of the dominant allele to the frequencies of the recessive allele. _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 5. In a real rabbit habitat new animals often come into the habitat (immigrate), and others leave the area (emigrate). How many emigration and immigration affect the gene frequency of F and f in this population of rabbits? How might you simulate this effect if you were to repeat this activity? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ 6. How are the results of this simulation an example of evolution? Is this population in HardyWeinberg equilibrium? _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________ _______________________________________________________________________________________