SC.912.L.17.9 Energy Pathways

SC.912.L.17.9 Use a food web to identify and distinguish producers, consumers, and decomposers. Explain the pathway of energy transfer through trophic levels and the reduction of available energy at successive trophic levels.

Students will describe the energy pathways through the different trophic levels of a food web or energy pyramid. 

Students will analyze the movement of matter through different biogeochemical cycles. 

1. A team of ecologists observed feeding patterns of several populations in the desert. The energy pyramid shown below depicts the feeding patterns the ecologists observed. 

Which of the following best explains the difference in the amount of available energy in the trophic levels of the desert ecosystem? 

A. There is less energy available in the producers because their tissues are less dense than those at higher trophic levels. 

B. There is more energy available in the second trophic level because less energy is needed for hunting compared to the higher trophic levels. 

C. There is less available energy in the fourth trophic level because of the loss of energy through metabolism in each of the lower trophic levels. 

D. There is more available energy in the birds of prey because they have greater muscle mass for storing energy than organisms in lower trophic levels have. 

2. What would happen in an ecosystem without herbivores? 

A. The populations of primary consumers would increase.

B. The populations of primary producers would decrease.

C. The populations of secondary consumers would increase.

D. The populations of secondary consumers would decrease.

3. What trophic level has the most energy?

A. producers

B. secondary consumers

C. primary consumers

D. tertiary consumers

4. What is the primary energy source in the food chain?

A. Producers

B. Primary consumers

C. Secondary consumers

D. Sun

5. The food pyramid for the temperate forest is shown above. The pyramid depicts the amount of energy at each trophic level. Which statement best explains the difference in the amount of energy at each trophic level?

1. The producers have less energy because they make their own food through photosynthesis.

2. There is more energy available to the hawk since it needs to hunt its food.

3. The fourth trophic level has less energy because the energy is metabolized at the lower levels.

4. The second tropic level has more energy available because the rabbits do not move as much.

Answer Key:

 1. C - There is less available energy in the fourth trophic level because of the loss of energy through metabolism in each of the lower trophic levels.

2.  D - D. The populations of secondary consumers would decrease. (Primary consumers are herbivores, so the next level up, the secondary consumers (AKA Carnivores) would decrease). 

3. A - Producers; the amount of energy decreases by 90% as you move up each level. 

4. D - The Sun is the primary energy source in food chains and webs (Not primary FOOD source, that would be producers)

5. C - The fourth trophic level has less energy because the energy is metabolized at the lower levels.