Classroom Activity: The Airfare of Migration

| Materials | Preparation | Procedure | Evaluative Questions | Extensions |

Objective:

Students will use graphs to calculate the energy costs in calories required for traveling great distances.

Concept:

Different modes of locomotion require different amounts of energy. Migrating can be energetically expensive.

Time:

One to two hours.

Materials:

For each pair of students: calculator, pencil and paper, copies of the Energy Cost of Locomotion graphs (Running, Swimming, and Flying).

Preparation:

Copy and enlarge the locomotion graphs. Make overheads of graphs if possible.

Procedure:

1. Students work in pairs for this activity. Review with students the concept of migration, emphasizing both its costs and benefits as discussed in the Mystery of Migration
   
   
2. Discuss with students how they are able to obtain energy from their environment (i.e., they eat food). In what form do they get energy from food? (Answer: in the form of calories.) Remind students that all animals need calories for energy.
   
   
3. Let students know that they will be using the metric system. Review the metric measurements for mass (grams) and for distance (meters) on the graphs. Use conversion figures if necessary.

One kilogram = 2.2 lbs.
One pound = .453 kg
One kilometer = 0.621 miles
One mile = 1.6093 km





4. Distribute the graph titled Running to student teams. Along the bottom is the mass (weight) of the animal in kilograms (kg). The vertical axis is the number of calories an animal must burn to travel one kilometer per gram of that animal's mass (cal/g/km). This value gets smaller as the animal gets larger due to higher efficiency of travel.
   
   
5. Present to the students the following general formula for calculating the energy costs of traveling:
   
   

   Calories for  X  Body Mass  X  Distance  =  Energy Cost
   Locomotion
   ____________     _________     ________     ___________ 
     cal/g/km           g            km            cal

This is the formula students will use to compute the energy costs of different types of locomotion.

Guide students through the following calculation:

If a fox that weighed 4 kg ran 100 km, how many calories would it burn?



1. Convert 4 kg to 4,000 g (1 kg = 1,000 g).
   
   
2. From the graph for Running, locate 4,000 g on the bottom (Body Mass) axis.
   
   
3. Go straight up until you intersect with the sloped line, then directly left to the vertical (Energy Cost) axis. You should arrive at about 1.2 cal/g/km.
   
   
4. Plug this value into the above formula: 1.2 cal/g/km x 4,000 g x 100 km = 480,000 calories! (The final units are calories, since the grams and kilometers cancel out.)
   
   

6. Now distribute the graphs for Swimming and Flying. Challenge students to locate the correct cal/g/km values for a 4 kg salmon and a 4 kg Greater Sandhill Crane.
   (Answer: salmon = 0.5 cal/g/km, crane = 0.8 cal/g/km.) Check their answers.
   
   
7. Now let students calculate how many calories each of these 4 kg animals would burn on a migration of 5,000 km using the formula in step 5.
   (Answer: fox = 24,000,000 cal, salmon = 10,000,000 cal, crane = 16,000,000 cal.)
   
   
8. The way calories are usually listed for food that we eat is in kilocalories (1 kcal = 1,000 cal). So, to calculate the number of kcals, divide the answer to the above equation by 1,000.
   (Answer: fox =24,000 kcal, salmon =10,000 kcal, crane = 16,000 kcal.)
   
   
9. Just for fun, calculate the number of hamburgers each animal would need to eat in order to complete a 5,000-km migration (assuming they could digest them!). Simply divide the above kcal figures by 550 kcal, the average number of kcals in one hamburger.
   (Answer: fox = 44, salmon = 18, crane = 29.) Students have just converted kcals into hamburger units!
   
   

Evaluative Questions:

Which mode of locomotion appears to be the most expensive (in calories)?

Which mode was the least expensive?

Why would traveling in water require fewer calories than running or flying?

Extensions:

• Using the formula, calculate the cal/g/km cost for each of the four other species featured in the Wild Wings: Heading South broadcast. Body masses (weights) of these species and distances of migration can be found in a fact box in the Sandhill Crane and Snow Goose profile information. How many hamburgers would they each require for their migrations?
  
  
• Using the Running graph, estimate the energetic cost in cal/g/km for your own body weight. Then follow the same procedures above to calculate the number of calories and the number of hamburgers it would take for you to make the same 5,000-km trip.
  (Answer: a 45-kg student = 1.0 cal/g/km, so 1.0 cal/g/km x 45,000 g x 5,000 km = 225,000,000 cal; divided by 1,000 = 225,000 kcal; divided by 550 = 409 hamburgers!)
  
  
• For Advanced Students: Have students calculate their own energetic expenditures of their daily travels to and from school, to friends' houses, etc. Then have them calculate the number of calories (and hamburgers!) for these trips.
  
  
• Convert the values for kilometers and grams to miles and pounds. Work out the energy cost formula for each animal using these units.