AP® Environmental Science: Duckweed Population Study

Product Details

Overview 
In this inquiry lab, students explore how populations change over time, what affects the size of a population, and what limits growth. Students grow duckweed (Lemna minor) in Petri dishes, counting fronds weekly over 10–12 weeks to observe exponential and logistic growth patterns firsthand. Students analyze population data, identify density-dependent and density-independent limiting factors, evaluate carrying capacity, and design their own follow-up experiments to test additional variables. 

AP® Course and Exam Description Alignment 
This activity is aligned to the 2024 AP® Environmental Science Course and Exam Description, Unit 3: Populations.  

Learning Objectives addressed: 
● ERT-3.B: Identify differences between K- and r-selected species. 
● ERT-3.F: Explain how resource availability affects population growth. 

Science Practices addressed:  

SP 1.A, 1.B, 1.C (Describe and explain environmental concepts and processes in applied contexts) 

SP 2.A (Describe characteristics of an environmental concept represented visually) 

SP 4.A, 4.B, 4.D (Identify testable hypotheses, research methods, and make observations) 

SP 5.A, 5.C, 5.E (Describe patterns, explain trends, and explain what data implies about environmental issues) 

Exam Connect questions are included, featuring both free-response and multiple-choice questions aligned to Unit 3 topics and science practices. 

Key Features 

Real sample data included. Kit instructions always include real sample data—never made up! Teachers have a complete 12-week group and class data table with sample answers to guide expectations. 

Tested and optimized. Each experiment has been thoroughly tested, retested, and optimized to guarantee safety and success. 

Prelab questions build foundational understanding, guided procedures walk students through setup and weekly observations, and post-lab questions progress from description to analysis to experimental design. 

Flexible and adaptable. Students can design their own follow-up experiments to test variables such as light intensity, nutrient availability, water temperature, pH, or salinity on duckweed growth. 

Teacher Notes 
Estimated Time: Initial setup requires 20–30 minutes. Students check duckweed daily to replace evaporated water and count the population weekly for 10–12 weeks. 

Kit accommodates 15 groups of students. 

Materials: Kit includes planting mix, Petri dishes, and fertilizer. 

Additional Materials: Dissecting needle or forceps; distilled or spring water; graduated cylinder; live duckweed plants (available separately); marking pen. 

Note: Duckweed is required and available separately. 

Safety: The materials used in this laboratory exercise are considered relatively nonhazardous. However, chemical splash goggles and chemical-resistant gloves should be worn. Wash hands thoroughly with soap and water before leaving the laboratory.