Natural Selection – Wild Tobacco ExercisePage 1EVOLUTION 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 graphpaper. The population is really a set of cards, and each card represents one individual tobaccoplant. On each card is a picture of the tobacco plant’s flower. Spread the cards out and look ateach 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 exactlyhow long each flower is.There is other important information on the card. Each plant will produce a certain number ofseeds (depicted by circles), and these seeds will grow up to become the next generation offlowering tobacco plants. The number inside the circle is the flower length each of theseoffspring will have when they germinate and become the next generation of flowering tobaccoplants.EXERCISES (do on carbonless paper):1. Think about what consequences variation in floral traits might have for plant fitness. Writedown 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 labelboth 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? Hypothesizewhat 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 averageflower 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, whynot?7. Predict what this population will look like in 20 generations? Why?Natural Selection - Wild Tobacco ExercisePopulation 1Page 2Natural Selection - Wild Tobacco ExercisePopulation 1Page 3Natural Selection - Wild Tobacco ExercisePopulation 2Page 4Natural Selection - Wild Tobacco ExercisePopulation 2Page 5Natural Selection – Wild Tobacco ExercisePopulation 3Page 6Natural Selection – Wild Tobacco ExercisePopulation 3Page
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