Survival of the Fittest: Natural Selection - Student Handout

NGSS Alignment: HS-LS4-3

Performance Expectation: Apply concepts of statistics and probability to support explanations that organisms with an advantageous heritable trait tend to increase in proportion to organisms lacking this trait.

Part 1: Engage (Anchoring Phenomenon)

Consider the case of the Peppered Moth.

• Tree bark turned dark due to industrial soot.
• Moths changed from light-gray to mostly black within decades. The Question: Did the moths “decide” to change color, or was something else happening?

Part 2: Explore (Simulation Investigation)

Open the Natural Selection Simulation. Track the average color of the population over 20 generations.

Experimental Data Table:

| Generation | Trial A (Light Base: 200) | Trial B (Dark Base: 50) | Trial C (Shift at Gen 10) | | :— | :— | :— | :— | | 0 (Initial) | | | | | 10 | | | | | 20 | | | |

Part 3: Explain (Sensemaking)

1. Identify Patterns: How did the average population color relate to the Environment Color over time?
2. Probability: If an organism is color 150 and the environment is 50, is it more or less likely to be eaten than an organism with color 60?
3. The Mechanism: Does the simulation show individuals changing, or certain individuals being “filtered out”?
4. Evidence-Based Claim: Support the statement: “Organisms with an advantageous heritable trait tend to increase in proportion over time.”

Part 4: Elaborate/Evaluate

1. Mutation: If Mutation Rate is 0%, can the population adapt to a new background? Why?
2. Pressure: How does lowering the Predation Level to 10% affect the speed of evolution?
3. Application: How might a new reflective city building act as a selective pressure on local birds?

Part 5: Summary

Construct a 3-sentence summary using the terms: Variation, Inheritance, and Selection.