Unit Three: Matter Recycling and Energy Flow
biomass
transpiration
Vocabulary
energy
biogeochemical cycle
fossil fuel
energy quality
aquifer
photosynthesis
trophic level
hydrology
aerobic respiration
--------------------------------------------------------------------------------------------------------------------Thinking about… How is matter recycled in ecosystems and why is energy lost in ecosystems?
Matter cycling in ecosystems (section 3-6, p. 53)
1. How is it possible that nutrient cycles connect living organisms from the past to living
organisms of the present?
2. List two locations where precipitation can end up other than runoff to rivers, lakes, and
oceans.
3. How is water able to transport nutrients between ecosystems?
4. Relate surface runoff to soil erosion.
5. How does the hydrologic cycle purify water?
6. Which kinds of organisms take carbon from the abiotic part of an ecosystem and convert it to
carbon in the biotic part of an ecosystem? What is the source of the abiotic carbon? What is the
process called?
7. What kinds of organisms take carbon from the biotic part of an ecosystem and convert it to the
abiotic part of an ecosystem? What is the source of the biotic carbon? What is the process
called?
8. Carbon can be stored for a long time in fossil fuels. What releases the carbon from fossil
fuels?
9. The atmosphere contains almost 80% nitrogen gas. Why can’t plants and animals use the
nitrogen gas in the atmosphere?
10. How do plants get the nitrogen they need?
11. How do animals get the nitrogen they need?
12. In what ways does nitrogen in the biotic part of an ecosystem return to the abiotic part of an
ecosystem?
13. What are the most important organisms that participate in the nitrogen cycle?
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14. Where is most of the phosphorus in the phosphorus cycle stored? How long can it be stored
there?
15. Why is phosphorus often a limiting factor for producers in land ecosystems and for producers
in freshwater ecosystems?
16. Sulfur passing through the abiotic portion of the sulfur cycle combines with other elements
forming some compounds that are dangerous to living organisms. Why is sulfur an important
element for the biotic portion of an ecosystem?
Energy (section 2-3, p. 29)
17. What kind of energy do plants use to produce the chemicals needed for their growth? From
where does it come?
18. What type of energy do animals use to get the energy they need? From where does it come?
19. Relate the first law of thermodynamics to the following statement: You cannot get more
energy out of a system than you put into the system.
20. Relate the second law of thermodynamics to the following statement: You cannot reuse or
recycle high-quality energy to do useful work.
--------------------------------------------------------------------------------------------------------------------Thinking about… Why does it take more energy to keep a carnivore alive than to keep an
herbivore alive?
Energy flow in ecosystems (section 3-4, p. 46)
21. If primary means first, explain why primary consumers are on the second trophic level.
22. On what trophic level are decomposers?
23. A typical ecosystem has about 10% ecological efficiency. What specific information does
this tell you about the availability of energy in that ecosystem?
24. What type of organisms form the base of energy flow pyramids?
25. Why are animals at the top of food chains more vulnerable than other animals when
ecosystems are disrupted?
26. Many marshes and tropical rainforests are being altered to provide land for cities or crops.
Relate the available net primary productivity of the earth to the degradation of these ecosystems.
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