Biology Lesson

Survival of the Fittest: How Natural Selection Shapes Populations Over Time

Shared by A STEM Educator

10th Grade5e-learning-cycle60 min

Learning Objective

Students will be able to explain how heritable trait variation within a population, combined with environmental selective pressures, leads to differential survival and reproduction, and will be able to predict directional changes in allele frequency across multiple generations using simulated and real-world population data.

Lesson Overview

Students investigate how trait variation within a population interacts with environmental pressures to produce differential survival and reproduction, ultimately shifting allele frequencies across generations. Through a hands-on simulation and data analysis, students build a mechanistic understanding of natural selection as the engine of evolutionary change.

Materials

Colored paper squares (red, green, brown — 50 of each color per group)
Green felt or green construction paper (1 large sheet per group, ~60x60 cm, simulating grass habitat)
Brown felt or brown construction paper (1 large sheet per group, simulating leaf-litter habitat)
Plastic cups or small containers (1 per student, acting as 'beak')
Stopwatch or phone timer
Student lab worksheets (printed)
Graph paper or access to Google Sheets / Desmos
Whiteboard and markers for class data compilation
Colored pencils (red, green, brown)
Projector and slides for Engage and Explain phases
Printed 'Population Data Cards' for Elaborate phase (one set per pair)
Exit slip cards (printed or index cards)

Scaffolded Task Progression

1Task 1

Look at the two peppered moth photographs displayed on the board. In your notebook, answer the following:
(a) Describe ONE visible difference between the two moths.(b) Before industrialization, pale moths were common and dark moths were rare. After decades of soot covering trees, dark moths became common and pale moths became rare. The moths did not change color during their lifetime. Write a hypothesis: how could the POPULATION shift from mostly pale to mostly dark without any individual moth changing color? [ Interactive graph / diagram — available in the full lesson ]

2Task 2

SIMULATION DATA RECORDING TASK — Complete the data table below as you run each round of the Colorful Prey Simulation on the GREEN habitat. After Round 3, calculate the PERCENTAGE of each color among survivors.

Generation	Start: Red	Start: Green	Start: Brown	Captured: Red	Captured: Green	Captured: Brown	Survivors: Red	Survivors: Green	Survivors: Brown	Total Survivors
1	15	15	15	?	?	?	?	?	?	?
2	(from prev.)			?	?	?	?	?	?	?
3	(from prev.)			?	?	?	?	?	?	?

After completing the table, answer:
(a) Calculate what percentage of total survivors in Generation 3 are GREEN-colored.(b) Compare your group's Generation 3 percentages with two other groups. Are the results identical? Why or why not?(c) Despite variation between groups, what GENERAL TREND do all groups share regarding green survivors on the green habitat?

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