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.

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)