BIOL 364 Population Biology Fairly testing the theory of evolution by natural selection with playing cards

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1 BIOL 364 Population Biology Fairly testing the theory of evolution by natural selection with playing cards Game I: The Basics Scenario: Our classroom is now a closed population (no immigration or emigration) at carrying capacity (population growth rate 0; adults replace themselves). We ll follow the fate of a phenotype determined by a single genetic locus with 12 possible alleles (standard deck of playing cards without the jokers). 1) You are born! Forage for your genetic identity! Haphazardly select two playing cards that constitute your allelic identity at the locus we re following. Because the effects of these alleles act in an additive fashion, add them together and put the sum on the worksheet (genetic score). In this first scenario, your genetic score your phenotypic score. 2) Time flies and you are now an adult. Forage for a mating card (labeled M1A or M1B ), and find your mate (there are pairs of each number). Once you find your mate, figure out what your average phenotype is and write it on the worksheet. 3) Next, each partner should place their genotype FACE DOWN (these are your gametes) and select one from their partner. Because we re at carrying capacity, all the parents in our population die off and you are now an individual in the second generation. Your individual # is the same as before, but now you probably have a new genetic score and phenotypic score. Write those on the worksheet 4) We can now use the population data to calculate the heritability of this trait. Think about what you predict it should be and why 5) Now we re going to select against about one-third of our population Think about what you predict the evolutionary response to this selection will be in the next generation and why 6) Those that survived, grab another mating card (labeled M2A or M2B ), find your mate, swap gametes, and become the next generation. Don t worry about calculating your average value just record your new genetic and phenotypic score below.

2 Natural selection on a deck of cards Adding a tweak Game II: Random environmental effects Scenario: Same as before, except there are now things to eat in our environment. Every time you need to calculate your phenotypic score, you will forage for an environmental score and add or subtract it from your genetic score to get your phenotype. These environmental effects have a mean of 0 in our population and a variance of about 14 with values ranging from 6 to -6. 1) You are born! Forage for your genetic identity! Haphazardly select two playing cards that constitute your allelic identity at the locus we re following & select an environment card (labeled ENV A or ENV B ). Because the effects of these alleles act in an additive fashion, add them together and put the sum on the worksheet (genetic score). Your genetic environmental score your phenotypic score. 2) Time flies and you are now an adult. Forage for a mating card (labeled M1A or M1B ), return your E card, and find your mate (there are pairs of each number). Once you find your mate, figure out what your average phenotype is and write it on the worksheet. 3) Next, each partner should place their genotype FACE DOWN (these are your gametes) and select one from their partner. Because we re at carrying capacity, all the parents in our population die off and you are now an individual in the second generation. Your individual # is the same as before, but now you probably have a new genetic score and phenotypic score. Forage for a new environmental score ( E ) and write your values on the worksheet. 4) We can now use the population data to calculate the heritability of this trait. Think about what you predict it should be (more or less than before) and why 5) Now we re going to select against about one-third of our population Think about what you predict the evolutionary response to this selection will be in the next generation (more or less than before) and why 6) Those that survived, grab another mating card (labeled M2A or M2B ), find your mate, swap gametes, become the next generation, and forage for a new environment score ( E2 Kids A or E2 Kids B ). Don t worry about calculating your average value just record your new genetic and phenotypic score on the worksheet.

3 Natural Selection on a Deck of Cards - Dominance and Epistasis Game III: Dominance 1) In this game there are two loci, red and blue, represented by the red and blue decks of cards 2) The genotypic score of the RED locus is always completely additive (take the sum) as before 3) For each individual we will keep track of two phenotypes a. Additive sum of alleles at the red and blue loci b. Dominant sum of alleles at the red locus rules of the blue locus c. The genotypic score of the BLUE locus follows these rules under dominance: alleles are dominant over the red alleles i. If 2 red then the genotypic score redred ii. If 2 then the genotypic score iii. If red/ then the genotypic score 2() Additive red deck blue deck Dominance or 2() 4) MATING: a. Forage for a random mating number (in BLACK) b. Calculate the additive and dominant mid-parent value for your mating pair c. Place your cards face-down and exchange one card from each locus with your mate d. You are now the offspring with one allele from each parent at each locus 5) Calculate your new additive and dominant genotypic score 6) As a class we will determine the heritability of this trait using a mid-parent offspring regression 7) SELECTION a. Roughly one-third of the class will survive 8) The survivors forage for a random mating number (in RED) and proceed through steps 5-7 above As a class we will determine the observed response to selection and compare it to the predicted response to selection

4 Game IV: Epistasis This game is played identical to the previous game with a single modification. In determining the epistatic phenotype, the effect of the blue locus on the genotypic score depends on the alleles at the red locus. If there are 2 red cards at the RED locus then the total epistatic phenotype is the sum of the alleles at the red locus minus the sum of the alleles at the blue locus. Additive Epistatic red red red deck red red blue deck - If there are 2 cards at the RED locus then the total epistatic phenotype is the sum of the alleles at the red locus plus the sum of the alleles at the blue locus. Additive red deck blue deck Epistatic If there is a red and a card at the RED locus, then the total epistatic phenotype is the sum of the alleles at the red locus alone. Additive red deck blue deck Epistatic red red

5 GAME I Individual number Parent Genotype Environment Mating Mid-parent mean phenotype Offspring genotype Offspring environment Offspring phenotype Selection: If you make it to the next generation... Offspring genotype Offspring environment Offspring phenotype

6 GAME II add w/ env Individual number Parent Genotype Environment Mating Mid-parent mean phenotype Offspring genotype Offspring environment Offspring phenotype Selection: If you make it to the next generation... Offspring genotype Offspring environment Offspring phenotype

7 GAME III add w/ dom Individual number Parent Score at the blue locus (dominant) Additive phenotype Dominant phenotype Mating Additive mid-parent mean Dominant mid-parent mean Score at the blue locus (dominant) F1 additive phenotype F1 dominant phenotype Selection: If you make it to the next generation... Score at the blue locus (dominant) Additive phenotype Dominant phenotype

8 GAME IV Individual number add w/ epi Parent Score at the blue locus (epistatic) Additive phenotype Epistatic phenotype Mating Additive mid-parent mean Epistatic mid-parent mean Score at the blue locus (epistatic) F1 additive phenotype F1 epistatic phenotype Selection: If you make it to the next generation... Score at the blue locus (epistatic) Additive phenotype Epistatic phenotype