MS-LS4-6
The standard
Use mathematical representations to support explanations of how natural selection may lead to increases and decreases of specific traits in populations over time.
Next Generation Science Standards
What this standard means
Students need to connect numbers to natural selection. They should use tables, graphs, percentages, ratios, or simple probability statements to show how a trait becomes more or less common in a population across generations. The focus is not gene math. It is explaining a trend with evidence.
Mastery looks like a student saying, “The darker beetles increased from 20% to 75% after the habitat darkened, so that trait likely helped survival.” Common sticking points are mixing up individuals and populations, assuming organisms choose traits, and describing change without using the data.
Ways to teach it
- Hands-on activity: Give students colored beans on different fabric backgrounds and have them graph which colors survive after each predator round.
- Discussion or writing prompt: Ask, “Which trait increased, what evidence shows it, and why might that trait help survival in this environment?”
- Quick assessment: Show a three-generation trait table and have students write one percentage comparison and one natural selection explanation.
- Real-world connection: Use antibiotic resistance data to explain why resistant bacteria become a larger share of the population after treatment.
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