"You Are What You Eat": Tracing Carbon Isotopes through the Modern American Food Chain

This is a unit designed to be taught early in a one year Living Environment course. I am aligning my curriculum for Living Environment next year around two major topics: We will study a variety of issues related to food in the first semester and then in the second semester move on to studying human disease with a particular focus on an extended student investigation of asthma in the local area. This "You Are What You Eat" unit is designed to be the opening module for the Fall semester focused on food and will introduce a variety a themes and investigations that students will continue to explore throughout that semester. It will also introduce in a more structured and guided way much of the knowledge, skills, and mindsets required for the extended student work to be completed independently later in the year.

This year I found that many of my students struggled with connecting and synthesizing the different ideas in biology that we had studied throughout the course. They had trouble remembering previously taught material and failed to discriminate in their recall and application of prior material when attempting to solve novel problems presented out of context of the unit to which they related. I attribute many of these issues to my linear presentation of material in highly segregated conceptual units. Two weeks on evolution here, three weeks on cell structures there, just as the state curriculum and textbook recommended with little to no meaningful connections built between.

This "You Are What You Eat" unit integrates material from multiple areas of study within biology around a real-world issue. The content first encountered here will then be continually revisited throughout the year at increasingly complex levels of understanding and interaction. By taking advantage of a variety of community resources, it is hoped that the material in this unit will be better able to come alive for students in such a way that it doesn't just add to their knowledge of an academic subject area but actually changes the way in which they perceive their natural environment.

Unit Outline:
0. Collecting Hair - During the first week of school (approximately 1 month before this unit begins), I will select 2 students at random from each of my living environment classes to have a sample of their hair collected (if they agree) and mailed to Prof. Stephen Macko of the University of Virginia. Prof. Macko has very graciously agreed to run isotope analyses of these samples and share the results with us in the form of raw data, videoconference discussion, and personal certificates indicating what percentage of the carbon in each student comes from corn.
1. King Corn
- As the kickoff to this unit, students will watch excerpts from the documentary film "King Corn" using a loosely structured viewing and discussion guide. Prominent in these clips is a scene in which Prof. Macko tests the filmmakers' hair for its composition of different carbon and nitrogen isotopes. By interpreting this data, he is able to show that most of the carbon in their bodies originally came from corn. Later clips explore the reasons for this finding and its implications, as well chronicling the filmmakers' attempt to grow their own acre of corn in a small town in Iowa.
2. The Energy Pipeline, Part 1 - Next, students will be given a common kinesthetic experience that introduces many of the difficult concepts they will be studying throughout the unit. I modified this activity from a Project Wild game designed for middle-schoolers, refocusing it on the movement of carbon as well as energy through a simple food chain. In the first part, students are divided into producer, herbivore, carnivore, and decomposer teams and move energy tokens along from their source as sunlight through the different levels of the food chain. Upon completion of the first round of the game, students will complete a reflection guide, at first through teacher-led instruction and then independently.
3. The Energy Pipeline, Part 2 - After students have experienced the basic version of the simulation in which only energy is tracked, they are then exposed to a more complicated iteration that incorporates in the movement of some key organic and inorganic material. This time, by assigning more specific roles within each team (such as a cell membrane role on the bacteria team or a stomate role on the corn team) and tracking different atoms using colored paperclips, they are able to see a more complete picture of the process by which energy flows through an ecosystem and materials are recycled.
4. Organic v. Inorganic
- Using the inductive model of concept attainment described in Bruce Joyce's Models of Teaching book, this activity will challenge students to create their own working definition of organic and inorganic compounds from a series of already classified compounds from the Energy Pipeline activity and beyond. As different definitions begin to emerge from the student teams, the class will evaluate each definition's success at classifying new molecules and decide as a class what is the most useful definition of these terms.
5. Introduction to Food Journaling - As a homework the night before this activity, students will be required to bring in a food label or package from one of their favorite foods or drinks. I will then model how to set up a food journal and complete an entry that would meet the criteria of the rubric for this extended homework project. Students will track their food and drink consumption using this rubric and project guide for 1 week.
6. Farm to Fork Field Trip - This all day field trip, will consist of a morning trip to Eagle St. Rooftop Farm in Greenpoint, Brooklyn and afternoon visits to a live poultry market and a grocery store in Canarsie, Brooklyn.
  • 6a. Rooftop Farm
    • My four Living Environment sections will travel together with their classmates between two major stations. One of these stations will consist of a 90 minute presentation by the Farm's education staff. This standard presentation will take place on the rooftop farm and angled sitting area and will discuss the planting, growing, and harvesting of various plants as well as the care required for the small number of chickens on the farm. The rooftop farm's compost system will also be introduced during this presentation.
    • For the other station, the two classes will separately attend two 45 minute sessions that begin to set up the conceptual foundations and material equipment for later units of study in our semester long investigation of food. One of these sessions will involve the construction of a class bucket-based compost system that will later be used to study the process of decomposition (including the culturing of different bacterial species from this system). The other session will introduce a long-term team competition to grow the hairiest plant using a kit from the Wisconsin "Fast Plant" system. At this session, samples of the many edible relatives of these "Fast Plants" will also be present for students to investigate.
  • 6b. Local Markets
    • In the afternoon we will travel back to Canarsie to visit the Saba Live Poultry Market near the Rockaway Parkway train station as well as a small grocery store around the corner. Students will be in two groups, alternating between activities at the poultry market and the grocery store. The halal poultry market claims to sell chicken, pigeon, turkey, duck, rabbit, lamb, goats, and roosters, but when I was there to visit, only chicken, lamb, and goats were present. One of the store owners agreed to take our group on a tour of the facility during which he would explain where they get their animals, how they take care of them, including how much food and water they require. He agreed to set up a mound of corn feed equal to the amount required to grow 1 chicken (estimated at about 45 pounds of grain), which will serve to show the loss of energy that occurs with movement up the food chain that students saw earlier in the “energy pipeline” activity.
    • The students who are not at the poultry market will be around the corner completing the grocery store scavenger hunt, one key task of which will be finding as many different corn-based products on the ingredients lists of as many different items from across the entire store.
7. Grocery Store Graphing, Part 1 - Following the field trip, students will prepare for a return visit to a grocery store (this time to the one across the street from our school). The aim of this activity will be reinforce graphing skills while simultaneously looking at some of the reasons why we end up eating so many food products made from corn and what the implications of these eating habits may be. In the first part of this activity, all students will participate in collecting data for the construction of a line graph comparing the relationship between calorie content and price for foods containing processed corn products and those that don’t. All students will also collect data for a bar graph comparing the average "Food Facts" health score values of foods containing processed corn products and for those that don’t. The practice of creating these two graphs together will provide an opportunity to review the key skills necessary for creating and interpreting graphs setting them up for success in designing their own grocery store question to analyze.
8. Grocery Store Graphing, Part 2 - In addition, to the two class-wide grocery store graphs, each student team will be responsible for coming up with their own testable question, hypothesis, and procedure for collecting data. Students will then spend a class period in the grocery store collecting data to answer their own questions which they will then graph, interpret, and present to the class for discussion and peer review. Students will be free to select any question they want to test, but will also be provided with some ideas, such as a line graph comparing the relationship between distance from eye level a food item is on the shelf and its price per calorie, or a bar graph comparing products that do or do not make health claims and their actual nutritional score.
9. Hairy Results, Part 1 - I will lead a direct instruction lesson on the experimental techniques used by Prof. Macko to determine the trophic level of the organism from which the sample came from and the relative proportion of C3 and C4 plants in their diet. This lesson will incorporate the use of classroom clickers and partnered discussions at many points throughout to check for students' understanding and to extend their thinking. It will also link heavily back to the investigations students have done so far.
10. Hairy Results, Part 2 - The following day students will receive the complete set of analyzed student hair data and will perform some simple algebraic calculations to determine the proportion of heavy to light carbon isotope in their hair and from that, they will use an equation to calculate the percent to which they are composed of carbon originally found in corn. Connections will be made to the food journals of the student participants and how that informs our interpretations and insights. Following this data investigation, we will have a class discussion with student's scientific and emotional reactions. I will then present students with the certificates that Prof. Macko creates with their official corn percentages.
11. The Ice Man Cometh, Part 1 - Students will read and react to an article published in the New Scientist by Prof. Macko called "Beyond the Fringe." This article describes how Macko applies the same isotope analysis used on our class participants' hair to the mysterious Ice Man in order to figure out his prehistoric diet. To differentiate for different level readers without socially embarrassing those who struggle, the article will be completed in a jigsaw format in which different student groups are assigned different passages to focus on and become "experts." The written questions to go along with each passage will be similarly aligned to meet and stretch different students' abilities.
12. The Ice Man Cometh, Part 2 - Students will be given real data Macko has collected from experiments with prehistoric hair samples to analyze. In addition to the isotope data they should now be familiar with, students will also have photographs of different teeth wear patterns of the specimens, artifacts they were found with, and any preserved plant or animal material found at the same site. Using all of this information, students will be required to reconstruct the probable diets of the two different individuals and to comment on the changes in diet that occurred in the time that separated them. This will link to the next unit we will be studying on agricultural developments and the green revolution.
13. Prof. Macko "Visits" the Classroom - Students will share the conclusions their teams came to regarding the prehistoric samples and will have a chance to hear Prof. Macko talk about his work. Prof. Macko has significant experience using videoconferencing technology for distance learning, so we will be using his standard protocols for connecting. This will be the students' chance to interact "scientist to scientist" with Macko without me as a filter or interpreter.