Natural Selection

The dramatic increase in the frequency of dark moths, and corresponding decrease in the frequency of light moths, in 19th-century England's peppered moth population define the investigative phenomenon. To answer the driving question, students read about the phenomenon in the pre-lab and make an initial claim about it. Students model 5 generations of moths, gathering evidence of genotype and allele frequencies as environmental variables change. They compare calculated Hardy-Weinberg frequencies for a population in genetic equilibrium with the observed frequencies of their model. After their statistical analysis, students revise their claim about the cause of the phenomenon.

Time Requirement
Total, 195 minutes. Teacher prep and pre-lab, 65 minutes. Investigation, 100 minutes. Assessment, 30 minutes.

Digital Resources
Includes 1-year access to digital resources that support 3-dimensional instruction for NGSS. Digital resources may include a teacher manual and student guide, pre-lab activities and setup videos, phenomenon videos, simulations, and post-lab analysis and assessments.

Performance Expectation(s)
HS-LS4-3 and HS-LS4-4

Crosscutting Concepts
Patterns

Disciplinary Core Ideas
LS4.B: Natural Selection

Science and Engineering Practices
Analyzing and Interpreting Data

Learning Objectives

• Model how natural selection affects a population's genetic equilibrium when an environmental change is introduced.
• Apply concepts of statistics and probability to calculate and analyze allele, genotype, and phenotype frequencies in a population.
• Use mathematical reasoning to evaluate whether a population is in the process of natural selection.
• Make a claim, supported by evidence, about changes in the distribution of traits in the peppered moth population.

Prerequisite Knowledge and Skills
Students should understand basic Mendelian genetics. They should be familiar with the following terms: traits, genes, alleles, recessive, dominant, homozygous, heterozygous, genotype, and phenotype. They should also be able to solve polynomial equations and simultaneous algebraic equations.