Natural Selection Problem Goals: Students will be able to 1. Design a testable hypothesis 2. Analyze and interpret a simulation about an ecological problem 3. explain how evolution actually works.

Pre-test: Explain the changes that occurred in the tree and animal Pre-test: Explain the changes that occurred in the tree and animal. Use your current understanding of evolution by natural selection.

Pre-test Analyses Instructor read responses to assess students’ prior knowledge and misconceptions. Responses will be coded and compared with post-test writings. Analysis pending…

Hummingbird Video www.pbs.org What are the four processes required for natural selection?

Sex and the Single Guppy www.pbs.org

Introduction to the Question In pools with many predators, male guppies are drab colored. In pools with few predators, male guppies have bright coloration. Why is there a difference?

Guppy Gallery

Design a Testable Hypothesis In your groups, develop a hypothesis to explain the observed pattern of fish coloration in the pools. Design an experiment to test your hypothesis.

Experimental Simulation Before each simulation begins, predict what will happen, based on your hypothesis. As the simulation is running, your group will record data for each generation.

Simulation 1

Results - Simulation 1

Data Table - Simulation 1

Simulation 2

Results - Simulation 2

Data Table - Simulation 2

Data Analysis On your carbonless paper, plot a line graph of the changing proportions of color pattern over time. What is the independent variable? Which axis should you plot it on? Which is the dependent variable? Which axis should you plot it on?

Low Predation

High Predation

Analysis Do these data match your prediction (support your hypothesis)? Why or why not?

Questions for Discussion What determines the color pattern of an individual guppy? What role(s) does color play in guppy survival and reproduction? Explain the results in terms of fitness and natural selection. Describe how sexual selection and natural selection push in opposite directions.

Questions for Assessment (from Anderson et al., 2002) A typical natural population of guppies consists of hundreds of guppies. Which statement best describes the guppies of a single species in an isolated population? a. The guppies share all of the same characteristics and are identical to each other. b. The guppies share all of the essential characteristics of the species; the minor variations they display don’t affect survival c. The guppies are all identical on the inside, but have many differences in appearance. d. The guppies share many essential characteristics, but also vary in many features.

Student Responses on Midterm (n=176)

Questions for Assessment (from Anderson et al., 2002) Fitness is a term often used by biologists to explain the evolutionary success of certain organisms. Which feature would a biologist consider to be most important in determining which guppies were the “most fit”? a. large body size and ability to swim quickly away from predators b. excellent ability to compete for food c. high number of offspring that survived to reproductive age d. high number of matings with many different females

Student Responses on Midterm (n=176)

Questions for Assessment (from Anderson et al., 2002) In guppy populations, what are the primary changes that occur gradually over time? a. The traits of each individual guppy within a population gradually change. b. The proportions of guppies having different traits within a population change. c. Successful behaviors learned by certain guppies are passed on to offspring. d. Mutations occur to meet the needs of the guppies as the environment changes.

Student Responses on Midterm (n=176)

Final Exam Assessments Analogous questions from Anderson et al., 2002 - Canary Island Lizards The final exam was optional; 72 of 182 students chose not to take the final The following data are from the 110 who took the final

Questions for Assessment (from Anderson et al., 2002) Fitness is a term used by biologists to explain the evolutionary success of certain organisms. Below are descriptions of four fictional lizards. Which lizard would a biologist consider to be the “most fit?” a. Very healthy, strong, and clever - 10 offspring surviving to adulthood b. Has mated with many lizards - 28 offspring surviving to c. Dark colored and very quick - 22 offspring surviving to d. Has the largest territory of all the lizards - 26 offspring surviving to adulthood

Student Responses on Final (n=110)

Questions for Assessment (from Anderson et al., 2002) According to the theory of natural selection, where did the variations in body size in the three species of lizards most likely come from? a. The lizards needed to change in order to survive, so beneficial new traits developed b. The lizards wanted to become different size, so beneficial new traits gradually appeared in the population. c. Random genetic changes and sexual recombination both created new varieties. d. The island environment caused genetic changes in the lizards.

Student Responses on Final (n=110)

Questions for Assessment (from Anderson et al., 2002) What would cause one species to change into three species over time? a. Groups of lizards encountered different island environments so the lizards needed to become new species with different traits in order to survive. b. Groups of lizards must have been geographically isolated from other groups and random genetic changes must have accumulated in the lizard populations over time. c. There may be minor variations, but all lizards are essentially alike and are members of a single species. d. In order to survive, different groups of lizards needed to adapt to the different islands, and so all organisms in each group gradually evolved to become new lizard species.

Student Responses on Final (n=110)

Final Exam: Explain the changes that occurred in the tree and animal Final Exam: Explain the changes that occurred in the tree and animal. Use your current understanding of evolution by natural selection. Analysis pending…