Lesson 4.3 - Where Did the Energy Go?

The rule of ten in energy flow indicates that only about 10% of the energy from one level is transferred to the next level.  Where does the other 90% of the energy go?  You just have to look at your own body and daily activities to answer the question. 

All organisms have to expend a great deal of energy to live.  Predators use much energy chasing after their prey.  Prey use much energy running away from their predators.  Primary consumers have to use much energy looking for food.  All warm-blooded animals have to spend a lot of energy just keeping warm.  None of that energy is available to the next level in the ecological pyramid, the energy is wasted as heat. 

Read What Happens to the Energy on page 247. Then, answer the following questions.

 

Question 1. List seven ways that organisms use energy that is then not available to the next level in the energy pyramid.

Question 2. What happens to the energy of the organisms that are not eaten?

Question 3. Are energy transformations always 100% efficient?

Question 4. Answer questions 1 to 4 of Check Your Understanding on page 247.

 

Check your answers with those that follow.

 

 

 

 

 

 

 

 

 

 

 

 

Answers to Questions:

Question 1. List seven ways that organisms use energy that is then not available to the next level in the energy pyramid.

Seven ways that organisms use energy that is not available to the next level in the energy pyramid are the following:

      1. Predators chasing prey.
      2. Prey running away from predators.
      3. Organisms looking for food.
      4. Organisms keeping warm.
      5. Organisms using energy for growth.
      6. Organisms using energy for reproduction.
      7. Organisms using energy for body functions such as digestion and circulation.

Question 2. What happens to the energy of the organisms that are not eaten?

The decomposers extract the remaining energy from the bodies of the the organisms that are not eaten but die from natural causes.  Some of the energy can be stored as fossil fuels.

Question 3. Are energy transformations always 100% efficient?

No energy transformations are 100% efficient.  Some energy is always wasted as heat.

Question 4. Answer questions 1 to 4 of "Check Your Understanding" on page 247.

      1. twigs, lease, and bark → moose → wolves
      2. Two animals that are both primary and secondary consumers are birds (robins, sparrows, and many others) and humans.
        seeds and fruit → sparrows
        green plants → insects → sparrows
        seeds and fruit → humans
        green plants → cattle → humans
      3. The rule of 10 tells you that only 10% of the energy available to the next energy level. Large carnivores require large amounts of energy and must eat other large animals to get enough energy. Because fewer large animals are available as food, the populations of large carnivores must be even smaller.
      4. a. The longest chain will lose the most heat because each level loses 90% of the energy from the previous level.
        b.  The shortest food chain provides the maximum amount of energy because it will waste the least amount of energy.


Now, do Assignment 12D.  Page forward to access it.