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Natural Selection Simulation

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Natural Selection Simulation

A population of beetles lives on dark, rocky soil. Some beetles are light-colored and some are dark-colored. Birds can more easily spot beetles that contrast with the soil. In each round, birds eat the more visible beetles. The survivors reproduce, and their offspring usually inherit the parent's color. To keep the simulation simple, each new generation has 20 beetles.

Simulation results

The class repeats the same selection process for three generations. Use the population counts below as evidence. Each row shows the number of beetles at the start of that generation.

Generation

Light-colored beetles

Dark-colored beetles

Analyze the evidence

Answer using the scenario and simulation results.

1.At the start of Generation 0, what fraction of the beetles were dark-colored? Give your answer as a fraction and a percentage.

2.Which beetle color is more likely to be missed by birds on the dark soil, and why?

Light-colored, because it blends into dark soil
Dark-colored, because it blends into dark soil
Both colors, because color cannot affect visibility
Neither color, because birds cannot see beetles

3.Calculate how many more dark-colored beetles than light-colored beetles were in Generation 2.

4.Complete the idea: A trait that helps an organism survive and reproduce in a particular environment is called an trait.

5.True or false: The birds caused individual light-colored beetles to turn dark during their lifetimes.

TrueFalse

6.Match each term to its meaning in the beetle simulation.

Variation
Selection pressure
Inherited trait

Bird predation that affects survival
A feature passed from parents to offspring
Differences in a trait among members of one population

7.Use the table to describe one change in the population from Generation 0 to Generation 2. Include at least two numbers as evidence.

8.Explain how the beetle population changed over generations. In your explanation, connect the soil color, bird predation, survival, and inherited color.

9.Imagine the beetles' habitat changes to pale sand, where light-colored beetles are harder to spot. Predict how the color pattern might change over many generations, and give one reason the prediction might not happen exactly as expected.