Lesson 4.2 - Pyramid of Energy

You might have noticed that the pyramid had about half as many wolves as bison.  This cannot be true; there must be far fewer wolves than bison.  You might remember the rule of ten in energy flow.  Only about 10% of the energy from one level is transferred to the next level. 

A better representation of the energy flow looks something like the following.

           

In the energy pyramid shown, there are fewer buffalo than grass, and fewer wolves than buffalo.  There is about one-tenth of the higher level as the one just below it.  This is a more reasonable ecological energy pyramid.  The next investigation will deal with another way of showing this relationship. 

Read Pyramid of Energy on page 246. Then, answer the following questions.

Question 1. Draw an energy diagram using the rectangles described in the reading and showing the rule of ten.

Question 2. Suppose you had to make another energy level below the first one in the answer to question # 1 as shown above.  How many rectangles would you have to draw?

Question 3. A student made an energy pyramid similar to that in the investigation on page 246.  His energy pyramid had three levels as in the answer to question #1.  His bottom level had 500 rectangles.  How many rectangles must he have in the top energy level?

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. Draw an energy diagram, using the rectangles described in the reading and showing the rule of ten.

Your energy diagram should look similar to the one shown below in which each higher level is 10% of the level below it.
 
                                       

Question 2. Suppose you had to make another energy level below the first one in the answer to question # 1 as shown above.  How many rectangles would you have to draw?

According to the rule of ten, you would have to draw one hundred rectangles below the ten rectangles shown in green in the answer to question #1 above.

Question 3. A student made an energy pyramid similar to that in the investigation on page 246.  His energy pyramid had three levels as in the answer to question #1.  His bottom level had 500 rectangles.  How many rectangles must he have in the top energy level?

He must have 5 rectangles in the top level.  The rule of ten will result in 500/10 = 50 rectangles in the second energy level and 50/10 = 5 rectangles in the top energy level.

 


Go to the next page to continue Lesson 4.