Short videos can be used as case studies by stopping at appropriate time points and asking questions to cue student attention, encourage critical thinking, and make the students part of the story.

This video case study focuses on a real-world problem: declining bee populations. It is appropriate for a range of biology and environmental science courses, including AP/IB Biology, AP Environmental Science, and college-level introductory biology.

Student Learning Targets

• Define the term fungicide and describe how fungicides can have both positive and negative impacts on the environment.
• Given a scientific question, design an investigation that attempts to answer the question.
• Use scientific evidence from an experiment to identify limitations of a study, draw conclusions, and suggest future studies.

Background Information

• Different types of organisms—referred to as pests—attack, damage, and eat crops. Many farmers apply chemicals called pesticides to their crops to control pests. But these pesticides can also have negative effects on other species.
• Pesticides include herbicides to destroy weeds, insecticides to control insect pests, fungicides to prevent the growth of molds and other fungi, and disinfectants to prevent the spread of bacteria.
• Bees are important pollinators of many crops and wild plants. Ecologists have observed that some bee populations are declining. There are likely many reasons for these declines, including the use of certain types of insecticides on crops and flowers. In this video, a scientist explores whether fungicides could also be contributing to bee population declines.
• The video case study is presented in eight modules, each followed by embedded questions. Educators can use the extension questions listed below for additional class discussion or written assessments.

Module 1 describes the different chemicals used in agriculture and how they might be affecting bee populations. It concludes with a question about fungicides.

Extension questions:

• What kinds of chemicals are used in agriculture? Why do we apply them to crops?
• What is the question that the narrator wants to answer?

Module 2 explains the ecological relationship between adult bees, pollen, bee larvae, and yeast; in particular, fungi such as yeast are found in the pollen mixtures eaten by bee larvae. It concludes with a question about how to investigate which bacteria and fungi live with bee larvae.

Module 3 describes a research method for answering the question from Module 2. It shows how the featured scientist isolated and identified the microbes present in the nest with the bee larvae. He discovered that the larvae of some bee species depend on yeast that grows on pollen for food. The module concludes with a question about how to test the hypothesis that fungicides might harm bee larvae. To answer this question, students should think about the data they would need to collect.

Extension question:

• In your own words, explain the logic behind why the scientists think fungicides are causing bee population declines. Are they concerned that the fungicide is directly harming the bees or bee larvae?

Module 4 describes the experiment the scientist used to test the hypothesis from Module 3. It concludes with a question about predicting the results of the experiment using a graph.

Module 5 shows the results of the experiment from Module 4 as a bar graph. The bars compare the average number of bees per colony in control cages without fungicide (orange) to the average number in cages exposed to fungicide (green). This module concludes by asking students to interpret these experimental results.

Note that the error bars on the bar graph represent 95% confidence intervals. The 95% confidence interval estimates the range of values that is likely to include the true average of the population, with a 95% confidence level. In general, if the 95% confidence intervals for two averages do not overlap, they are statistically different from one another.

Extension questions:

• In the bar graph, the error bars (white lines extending above and below each bar) represent 95% confidence intervals. Explain what 95% confidence intervals are and why the scientist may have wanted to show them on this graph.
• Based on the error bars in this graph, are you confident that there is a difference between the control and fungicide plots? Explain your answer.

Modules 6, 7, and 8 summarize the interpretation and application of the experiment’s results, highlighting the need for additional scientific research on the ecological effects of fungicides. They also prompt discussion about society’s role in deciding how to regulate which fungicides are applied to crops, as well as how and when these fungicides are applied. These modules conclude by asking students to consider the results and limitations of the experiment described in this video and to think about the broader relevance of this work.

Extension questions:

• Scientists suggest that bee populations could be helped by changes in policy regarding fungicide use and application. How might a change in policy help solve bee population declines?
• Who regulates policies regarding use and application of pesticides?
• If fungicides have harmful effects, why do we continue to use them?