A Future Without Coffee

NSTA Playlist

A Future Without Coffee

Storylines start with an anchoring phenomenon that raises questions or introduces a problem. Each step in a playlist or unit is then driven by students’ questions that arise from the phenomenon.

In this case, the anchoring phenomenon is that 60% of coffee species are threatened with extinction. That number is high compared with a global figure of 22% for all plants. Students contemplate why there might be a future without coffee and can we do anything about it?

The first day of the playlist allows students to consider what a future without coffee might look like and consider who would be impacted by this. Students watch a video and look closer at the scientific study that shows that wild arabica coffee is being negatively impacted by environmental changes such as climate change, disease, and deforestation. This gives students a reason to investigate how arabica coffee populations are changing and how they could become extinct in the future. In doing so, they will make sense of Disciplinary Core Ideas related to genetics, natural selection, artificial selection, and evolution.

Lesson Plan 1

Why might there be a future without coffee, and can we do anything about it?

High school students, as scientists, investigate changes in coffee plant populations in order to answer the following driving question: Why might there be a future without coffee and can we do anything about it? Students figure out that there are a number of environmental changes that have threatened coffee plants. Students will explore more about a disease called Coffee Leaf Rust (CLR) that is becoming more common in coffee plants. Students will learn that some coffee plants are more resistant to rust than others. Students will model their initial ideas about how wild and cultivated coffee populations are changing and why the future of these populations looks bleak. Students will create a list of ideas about what we would need to know about coffee plants in order to protect them in the future.

Time: One 50-minute class period

Lesson Plan 2

Do all of the coffee varieties have these alleles?

Students wonder why the trait for resistance to rust disease has different frequencies in different coffee growing areas. They decide to create a model to help them explain this difference. They notice this trait has a lot more variation than they thought and decide to first model a simpler example. They learn about variation in populations of rock pocket mice and create a model that explains how the distribution of the trait changes over time and reflect on the model to identify the components of Natural Selection. Students use this model to return to the initial phenomenon to explain how that changes over time.

Time: One 50-minute class period

Lesson Plan 3

Where did the different alleles come from?

Students investigate an example of new traits arising in populations by watching a video that shows the growth of bacteria on increasingly high concentrations of antibiotics as the bacterial genome accumulates mutations that confer antibiotic resistance. Students wonder how these mutations can develop so quickly. Students create a mathematical representation of bacterial reproduction to model the speed at which these populations grow to figure out that while mutation rates make it seem like mutations are very rare, they are instead quite common due to the rate at which bacterial populations reproduce. They extend this to the rock pocket mouse model and see that in a case where organisms do not reproduce as quickly, the sheer size of an organism’s genome and the number of offspring produced in a generation still guarantee mutations will accumulate over time. Finally, students return to their consensus models and use them to make predictions about what would happen in the case of specific mutations in different environments. Then they test their predictions using a computer simulation and consider the affordances of one type of model over another.

Time: One 50-minute class period

Lesson Plan 4

How does reduced genetic diversity impact survival and reproduction?

High school students as scientists investigate genetics, natural selection, and evolution to answer the following driving question: How does reduced genetic diversity impact survival and reproduction? Students analyze a graph to see that genetic diversity varies in different crops, but all populations do have some degree of genetic diversity. After analyzing genetic diversity across different species worldwide, students wonder why some populations have higher levels of genetic diversity than others and if this difference is significant. Next, students read two different articles about artificial selection and monocultures to look for patterns between the case studies. Students use this new information to discuss why scientists are concerned that both wild and cultivated arabica coffee populations have low genetic diversity. They then use what they have learned throughout this unit to explain how genetic diversity is maintained in populations and why genetic diversity is important, and they think about how they want to use this information to learn more and to help educate others. Then students return to their initial Driving Question Board to determine which questions they had can now be answered.

Time: One 50-minute class period