•Consider the same population of butterflies is in the path of a hurricane. All survive, but 10 are blown to a new location. These 10 start a new population; their progeny will reflect the founder’s gene pool. This is known as the founder effect. Materials
Beaker #1 Beaker #2 Beaker #3
1.What observations can you make regarding the gene pool and gene frequency of the founding individuals? 2.Do these results vary between the populations founded by beakers #1, #2 and #3? Why or why not? 3.What observations can you make about the genetic variation between the parent and founding populations? 4.Suppose you have a population of 300 butterflies. If the population grows by 12% in the following year, how many butterflies do you have? 5.Now suppose you have 300 eggs, but only 70% of those eggs progress to become a cater- pillar, and only 80 of the caterpillar progress to become an adult butterfly. How many butterflies do you have? 6.Suppose you have a population of 150 butterflies, but a wildfire devastates the population and only 24 butterflies survive. What percent does the colony decrease by?
Experiment 4: Natural Selection
Natural selection is a selection pressure that affects phenotypes in one of three ways: •It will create an adaptive advantage.
•It will create an adaptive disadvantage.
•It will remain entirely neutral.
A classic example to illustrate natural selection comes from England. Prior to the Industrial Revolution, the native moths were normally a light color, though darker versions of the same species existed. The lighter color blended with the light bark of the local trees, while the darker moths experienced a higher predation rate – they were easier for birds to spot and fewer survived to reproduce. As England entered the Industrial Revolution they began burning fossil fuels with little regard to the pollutants they were emitting. The trunks of the trees became coated with soot and their color darkened. The lighter moths became more conspicuous and the darker moths were better camouflaged. The proportion of white to dark moths changed. Materials
Red beads, Blue beads, 100 mL Beaker
1.How did the distribution of phenotypes change over time? 2.Is there a selective advantage or disadvantage for the red and/or blue phenotypes? 3.What phenotypic results would you predict if starting with the following population sizes? 4. A. 1000: B. 100: C. 10:
5.Assume that you live in a country with 85 million people that consistently experiences an annual growth rate of 4.2%. If this population continues to grow at the same rate for the next 50 years, how many people will live in the country (round to the nearest whole number).
Experiment 5: Sickle Cell Anemia
Sickle cell anemia is a genetic disease (1 base pair mutation that changes a protein). It is common in those of African ancestry. “S” will represent the normal dominant allele and “s” the recessive sickle allele. They are co-dominant alleles – SS is normal, Ss is not fatal, ss is debilitating, painful and often fatal.
Blue beads, Red beads, 100 mL Beaker
1.What is the remaining ratio of alleles?
2.Have any been selected against?
3.Given enough generations, would you expect one of these alleles to completely disappear from the population? Why or why not? 4.Would this be different if you started with a larger population? Smaller? 5.After hundreds or even thousands of generations both alleles are still common in those of African ancestry. How would you explain this? 6.The worldwide distribution of sickle gene matches very closely to the worldwide distribution of malaria (http://cdc-malaria.ncsa.uiuc.edu/). Is this significant? Why or why not?