Natural Selection Problem

Goals: Students will be able to 1. Design a testable hypothesis2. Analyze and interpret a simulation

about an ecological problem3. explain how evolution actually

works.

Hummingbird Videowww.pbs.org

What are the fourprocesses requiredfor natural

selection?

Sex and the Single Guppywww.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 ofa single species in an isolated population?

a. The guppies share all of the same characteristics andare identical to each other.

b. The guppies share all of the essential characteristicsof the species; the minor variations they display don’taffect survival

c. The guppies are all identical on the inside, but havemany differences in appearance.

d. The guppies share many essential characteristics, butalso vary in many features.

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a b c d

Answer Choice

Questions for Assessment(from Anderson et al., 2002)

Fitness is a term often used by biologists to explain theevolutionary success of certain organisms. Which

featurewould a biologist consider to be most important indetermining which guppies were the “most fit”?

a. large body size and ability to swim quickly away from predatorsb. excellent ability to compete for foodc. high number of offspring that survived to reproductive aged. high number of matings with many different females

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a b c d

Answer Choice

Questions for Assessment(from Anderson et al., 2002)

In guppy populations, what are the primary changes thatoccur gradually over time?

a. The traits of each individual guppy within a populationgradually 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.

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a b c d

Answer Choice

% of Students