EVOLUTION OF WILD TOBACCOBACKGROUND:Today we’ll be exploring how natural selection produces evolutionary change in populations.EXERCISES (do on carbonless paper):EVOLUTION OF WILD TOBACCOBACKGROUND:Today we’ll be exploring how natural selection produces evolutionary change in populations.You were given a packet containing a “population” of wild tobacco plants and a sheet of graph paper. The population is really a set of cards, and each card represents one individual tobacco plant. On each card is a picture of the tobacco plant’s flower. Spread the cards out and look at each flower. You can see that the individuals in this population vary in the length of their flower. We’ve measured each flower and included the measurement on the card so you can see exactly how long each flower is. There is other important information on the card. Each plant will produce a certain number of seeds (depicted by circles), and these seeds will grow up to become the next generation of flowering tobacco plants. The number inside the circle is the flower length each of these offspringwill have when they germinate and become the next generation of flowering tobacco plants.EXERCISES ( do on carbonless paper ):1. Think about what consequences variation in floral traits might have for plant fitness. Write down your ideas.2. Calculate the average corolla length for your wild tobacco population.3. Use the graph paper to plot the relationship between flower length and fitness. Be sure to label both axes of the graph. 3a. What kinds of variables are flower length and fitness (continuous or categorical)?3b. What kind of graph will you make (bar or scatter plot)?3c. Which variable is independent and which is dependent?4. Is flower length under natural selection in your population? Why or why not? Hypothesize what environmental factors, if any, might be selecting on flower length.5. What do you think the next generation of plants will look like? Predict whether the average flower length of the next generation will be smaller, larger or the same as the current generation.6. Calculate the flower length of the next generation. Was your prediction accurate? If not, why not?7. Predict what this population will look like in 20 generations? Why?Rubric Fall 2007Part I1. Think about what consequences variation in floral traits might have for plant fitness. Variation in flora traits may lead to variation in fitness. In other words, flowers with certain versions of traits have higher fitness compared to plants with other versions of those traits.2. Calculate the average corolla length for your wild tobacco population. a) white:b) yellow:c) green:3. Use the graph paper to graph the relationship between corolla length and fitness.Independent variable: corolla lengthDependent variable: Fitness (# of offspring)Green population0246810120 10 20 30 40 50 60 70 80Parent Corolla Length (mm)Fitness (Number of offspring)White population 01234560 10 20 30 40 50 60 70 80Parent Corolla Length (mm)Fitness (Number of Offspring)Yellow population0246810120 10 20 30 40 50 60 70 80Parent Corolla Length (mm)Fitness (Number of Offspring)4. Is flower length under natural selection in your population? Why or why not? Hypothesize what, if any, the selective agents might be.a) white population: NO. - Flower length is not under selection because there is no relationship between corolla length and fitness.- There is no selective agent acting on corolla length here.b) yellow population: YES.- Flowers with shorter corolla length have greater fitness compared with flowers with longer corolla length. In other words, as the corolla length increases, fitness increases.- Flowers with shorter corolla length can be visited by many more different kinds of pollinators (ones with short and long proboscises) than flowers with longer corolla length (only ones with long proboscises), and therefore have more opportunities to be pollinated and have greater fitness.c) green population: YES.- Flowers with shorter corolla length have lower fitness compared with flowers with longer corolla length. In other words the corolla length increases, fitness decreases.- Flowers with longer corolla length only can be reached by pollinators with long proboscises, leading to greater fidelity between pollinators and flowers, leading to less pollen wasted on flowers of a different species. Thus, flowers with longer corolla length will have greater fitness than flowers with shorter corolla.5. What do you think the next generation of plants will look like? Predict whether the average corolla length of the next generation will be smaller, larger, or the same as the current generation. a) white population: 4.7 cm.The average corolla length will stay the same.b) yellow population: 4.7 cm.The average corolla length will be longer than that of the parent population.c) green population: 4.7 cm.The average corolla length will be shorter than that of the parent population.6. Calculate the corolla length of the next generation. Was your prediction accurate? a) white population: 4.67 cm. Yes.b) yellow population: 5.50 cm. Yes.c) green population: 3.86 cm. Yes.7. What do you think this population will look like in 20 generations? Why? [1/2 pt for each part of the answer]a) white population: The average corolla length will stay the same b/c there's no selection on corolla length.b) yellow population: The average corolla length will continue to get longer b/c flowers with longer corolla have greaterfitness (think, however: is there a limit to how long the corolla length will become? So how mightyou modify your answer?).c) green population: 3.86 cm.The average corolla length will continue to get shorter b/c flowers with shorter corolla have greater fitness (think, however, is there a limit to how short the corolla length will become? So, how might you modify your answer?).Part II 1. Copy their graphs and return to your team. 2. Discuss the following questions: a. Predict which population(s) are experiencing natural selection.Yellow and Green b. What is a possible selection agent?Different pollinators with different pollinating strategiesc. Which population(s) might look different in 20 generations?\Yellow and GreenPart III In which tobacco populations will evolution likely occur over the course of 20 generations?Base your answer on: 1. the definition of evolution given above 2. your data and predictions1. One is likely to see evolution in the
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