Personal Energy Use

 

STUDENTS WILL BE ABLE TO:
- Identify their daily caloric needs.
- Determine their daily caloric intake.
- Calculate the amount of land necessary to support their diets for one year.

GUIDING QUESTIONS:
How much energy do we use?
What are our sources of energy?

MATERIALS:
Day 1:
- My Energy Use worksheet: Part 1
Day 2:
- My Energy Use worksheet: Part 2
- Computers with Internet access for each student
- Calorie calculator website or sheet (determines how many calories are burned in a certain activity)
- Calorie counter website or book (determines how many calories are contained in various foods)
- Calculators (if not using computers)
Day 3:
- Calculators
- Yardsticks or measuring tapes
- Flags for marking a large land area
- Camera (optional)
Optional Extension:
- Bomb calorimeter and associated lab equipment

CLASS ACTIVITIES:
Day 1:
1. Assign homework: Students should track what they eat and what they do for the next 3 days. Students can use the My Energy Use worksheet.

Day 2:
1. Students should calculate how many total calories they consumed, using a book or website listing how many calories (link to glossary) are in various foods. Have them complete Diet: Part 2 of the worksheet. Many calorie counters can be found on the Internet; http://www.caloriecountercharts.com/chart1a.htm is one example.
Note: While this lesson can have useful health implications, instructors should also be aware of the prevalence of eating disorders in teenagers. The calorie counters can be helpful instructional tools, but teachers should emphasize the distinction between healthy and unhealthy use of the calculators. Remind students that while animals (including people) rely upon food for energy, they also need food for nutrients, protein, etc., and that it is possible to have enough (or too many) calories while still having a shortage of nutrients.
2. Make sure to clarify to your students that when referring to foods, the term "calories" is used, when in fact the energy quantified is kilocalories.
3. Next, students should complete the Activity: Part 2 section of the worksheet. In order to do this, they will need a calorie calculator that tells students how many calories are burned in a specific activity.

• A basic calorie calculator can be found at this site: http://primusweb.com/fitnesspartner/jumpsite/calculat.htm. This website will tell students how many calories they use for each activity based on their weight; they will still have to add their results together to get their final calorie use. If your class has limited access to computers, you can print a handout listing how many calories are burned per hour for each activity by listing "60" in the "Duration" box. Because the amount of calories used are determined by weight, it may be helpful to print about ten handouts, so that students may select the one most appropriate for themselves.
  
• Other calorie calculators are available, such as this one: http://www2.vhihealthe.com/topic/calburncalc. Many of these will take into account whether the students are male or female and will complete the calculations for students, displaying their total calorie use for each activity. However, teachers should be aware that sex is one of the listed activities on this and other sites.
  

Day 3:
1. On this day, students will calculate the amount of land that it takes to support their diets for a year. (This is referred to as their "footprint.") Students should first complete at least the first five questions of the Global Land Use section of the worksheet.
2. Take your class outside to a large space. A football field is ideal. Using the markings on the field, each student should map out the area that must be in cropland or grazing land to support his or her diet for a year (as determined by the Global Land Use worksheet). If a field with markings is not available, use a long [10 m or more] measuring tape and flags to mark the area in 100 m2 increments prior to class.
3. Standing at the 0 m mark (in the end zone if you are using a football field), take a photo of your class showing how much land each student uses.

The Gorge Ecology Institute thanks Phil Camill, Assistant Professor of Biology at Carleton College, who designed this section of the lesson. A more elaborate version of this lesson, which allows students to incorporate items such as transportation into their ecological footprint, can be found at: http://ublib.buffalo.edu/libraries/projects/cases/footprint/footprint.html
http://ublib.buffalo.edu/libraries/projects/cases/footprint/footprint_notes.html (teaching notes)

Day 4:
1. Hold a Round Table, and discuss the following questions:

• Which students had the smallest footprint? Which students had the largest? What about their diets created the variations in their respective footprints?
  
• C4 plants use water more efficiently during photosynthesis. For instance, many grasses in arid areas are C4 plants. Was there a difference in the amount of energy (calories) that these plants could produce per area of land?
• How much land does it take to support the average diet in your class? Assuming that this is also the average diet of your town, how much land would it take to feed your town for a year? How about your state?
  

2. Introduce the term carrying capacity. Discuss the implication of carrying capacity on the distribution of organisms in your local ecosystem. Why have your students found more plants than plant consumers, and more plant consumers than animal consumers?

Optional Extension:
1. If you have access to a bomb calorimeter or equivalent laboratory equipment, conduct a lab allowing your students to measure the amount of calories in foods that they have eaten. Then compare student measurements with those in calorie counters. Are they the same? Why might differences exist?