Download Using Wooly Worms to Model Natural Selection Lab (Recovered)

Natural Selection Model and Analysis
Purpose, Background and Procedures
Worms are pieces of yarn of various colors distributed in a random manner over a designated area. You will
simulate the feeding by avian predators that have just arrived in the ecosystem. You will feed on (collect) as
many worms in a timed session as you can by using chopsticks as model beaks. The collected worms are
counted and recorded and a Chi-square test is used to determine if the yarn pieces were collected randomly or
by a selection process. Hands may not be used at any time during the feeding process. These predators work in
pairs. Worms will be preyed upon by one bird of a bird pair only.
Various colors should blend into the environment differently which might offer an adaptive advantage to alleles
that code for better blending colors. This 1000 worm population is equally distributed into 5 phenotypic colors
red, black, sage green, turquoise and dark blue. The red allele is recessive to the other 4 alleles. The expression
of the other alleles is controlled by various gene regulation mechanisms that result in equal probability of
expression regardless of whether the worm is heterozygous for multiple dominants, heterozygous for dominantrecessive or homozygous dominant. If the cryptic coloration of some genotypes yields a meaningful adaptive
advantage, then you would expect to see a change in allele frequency from what you would expect with
continued Hardy-Weinberg genetic equilibrium. Use the paired Hardy-Weinberg equations to determine the
magnitude of the change in allele frequency and the chi square test to see if the change that you observe could
be due to chance.
We will also be interested in predicting the future of this population. If there is an adaptive advantage that not
only allows increased survival of the various phenotypes, then there may also be variation in the survivor’s
reproductive rate. Assume that pairs of worms of the same color have differential reproductive rates according
to the following scenario. The color with the greatest survival reproduces at a rate of 5 offspring per pair per
year, the next highest survival color reproduces at the rate of 4 offspring per year, then 3, 2 and 1 for the
remaining phenotypes. Assume that the survival pattern continues indefinitely. Determine how many
generations it would take for the population of the most stressed phenotype to drop below 5% of its original
portion of the population.
You will also propose how this model might be used to test for differences in chopstick skills that might occur
in the human population.
You will need a null hypothesis to serve as a testing baseline for each of these investigations.
Your conclusion will not only address your data but will also address the effectiveness of this model for
investigating the impact of natural selection on phenotypic variation in populations.
Process
Choose bird predator teams, as many possible. If an odd person exists they will help to make sure that only
beaks are used.
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Natural Selection Model and Analysis
Spread worms as randomly across the designated area as possible
Have predators feed for 90 seconds by picking up worms with chopsticks and depositing them in a plastic bag
held by the partner bird back at the starting line.
Return to class to tabulate individual and class data.
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