VIRTUAL LAB: NATURAL SELECTION:



VIRTUAL LAB: NATURAL SELECTION:

Go to the website:

Read through the text on the left under “Question: How does natural selection affect allelic frequencies?”

Follow the instructions that are provided.

Choose an Environment (Rocky, Desert, Grasslands & Urban) and be sure to start with each possible allelic frequency provided (A=0.2 and a=0.8, A=0.4 and a=0.6, A=0.5 and a=0.5, A=0.6 and a=0.4). These allelic frequencies tell you the percent of the population that has those particular alleles. For example, “A = 0.2” means that 20% of the population has the “A” allele in their genetic make-up.

Keep track of the environment that you are in, the color of the environment, the starting allelic frequency and how it changes from generation to generation, as well as the number of individuals with the different genotypes.

For example, a table you may use might look like the following:

ROCKY ENVIRONMENT: color of the environment: __________________________

| | | |Before Natural Selection |After Natural Selection |

Generation |A |a |AA |Aa |aa |AA |Aa |aa | |1 | | | | | | | | | |2 | | | | | | | | | |3 | | | | | | | | | |4 | | | | | | | | | |5 | | | | | | | | | |Color of ant selected for: _____________________

Genotype selected for: ___________ Genotype selected against: __________

Allele selected for: _________ Allele selected against: __________

Next, devise a way to graph allelic frequency trends, starting with the four different allelic frequency scenarios.

Finally, answer the lab questions below.

NATURAL SELECTION LAB QUESTIONS:

1) Did either allele A or a disappear from the populations you studied? Why or why not? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2) Did the effect of natural selection vary with different starting allele frequencies in identical environments? Why or why not? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3) A population in which the frequency of alleles remains the same over generations is said to be in genetic equilibrium. Describe one mechanism by which a populations’ genetic equilibrium can be disrupted and result in the process of evolution. ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4) In which of the simulated environments do individuals of the genotype Aa survive best? ____________________________________________________________________________________________________________________________________________________________

5) In which of the simulated environments do individuals of the genotype aa survive best? ____________________________________________________________________________________________________________________________________________________________

6) Which set of data represents a type of natural selection that stabilizes the allele frequencies of the population? ____________________________________________________________________________________________________________________________________________________________

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7) In another population, such as the Peppered Moth population in London during the late 1800’s, there was not an intermediate form of the organism for the heterozygous genotype. For example, ‘BB’ and ‘Bb’ were both black phenotypes which camouflaged well on the soot-covered/lichen-free trees and the ‘bb’ was the white phenotype which camouflaged well on the healthy/lichen-covered trees. In this scenario, if natural selection (lichen-free trees) selected for the dominant ‘B’ allele, would the recessive ‘b’ allele be completely eliminated from the population over time? Why or why not? ____________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

8) There is a theory that humans are creating antibiotic-resistant “superbacteria”. Scientists warn that overuse of antibiotics could result in a strain of bacteria that is resistant to these antibacterial treatments. Explain how this could happen. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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