Unit Plan 31 (Grade 7 Science): Natural Selection
Natural selection acts on variation so advantageous traits become more common over generations, leading populations to adapt to their environments.
Focus: Construct explanations, based on evidence, that natural selection acting on variation in traits leads to adaptation of populations to their environments.
Grade Level: 7
Subject Area: Science (Life Science — Biological Evolution & Adaptation)
Total Unit Duration: 5 sessions (one week), 50–60 minutes per session
I. Introduction
In this unit, students investigate how natural selection can change the makeup of a population over many generations. They begin by exploring variation in traits and how different environments create selective pressures. Using a simple natural selection simulation (e.g., tools as “beaks” or colored “prey” on different backgrounds), students collect data on which traits help organisms survive and reproduce. They then analyze results, connect them to real-world examples (e.g., camouflage, beak shape, antibiotic resistance), and construct explanations showing how natural selection leads to adaptation. The unit culminates in a Natural Selection & Adaptation Explanation aligned with MS-LS4-4.
Essential Questions
- How does variation in traits within a population affect which individuals are more likely to survive and reproduce?
- How do environmental conditions and selective pressures influence which traits become more common over time?
- In what way does natural selection explain how populations become adapted to their environment?
- Why is it important to distinguish between changes in individual organisms and changes in the population over generations?
II. Objectives and Standards
Learning Objectives — Students will be able to:
- Describe variation in traits within a population and identify which traits may be advantageous in a particular environment.
- Conduct or analyze a natural selection simulation and collect data on which traits increase or decrease over several “generations.”
- Use graphs, tables, and observations to explain how differential survival and reproduction change the frequency of traits in a population.
- Construct a written or oral explanation, supported by evidence, that shows how natural selection leads to adaptation of populations.
- Apply the idea of natural selection to at least one real-world example (e.g., camouflage, beak shape, antibiotic resistance), clearly linking variation → selection → adaptation.
Standards Alignment — 7th Grade (NGSS-based custom)
- MS-LS4-4 — Construct an explanation based on evidence that natural selection leads to adaptation of populations.
- Example: Use data from a simulated or real population to show how one trait becomes more common when it improves survival or reproduction.
Success Criteria — Student Language
- I can describe how individuals in a population vary and why that matters for survival.
- I can use data from a simulation or example to show how some traits help organisms survive and reproduce more than others.
- I can explain how natural selection changes the frequency of traits in a population over generations.
- I can connect natural selection to adaptation, showing how populations become better suited to their environment.
- I can write or present an explanation that uses specific evidence, not just opinion.