CHAPTER 42: ECOSYSTEMS AND ENERGY
1. What is an ecosystem?
Concept 42.1 – Physical laws govern energy flow and chemical cycling in ecosystems.
2. Define the following laws and explain the importance of each.
a. The First Law of Thermodynamics
b. The Second Law of Thermodynamics
c. The Law of Conservation of Mass
3. Label the diagram below and include the definition of each term.
KEY
Concept 42.2 – Energy and other limiting factors control primary production in ecosystems.
4. What is primary production? Distinguish between gross primary production and net
primary production.
5. Write an equation here that shows the relationship between gross and net primary
production.
6. Biomass is the total mass of all individuals in a trophic level. Another way of defining net
primary production is as the amount of new biomass added in a given period of time. Why is
net primary production, or the amount of new biomass/unit of time, the key measurement
to ecologists?
7. How do light limitations and nutrient limitations impact primary production in aquatic
ecosystems?
8. What is eutrophication? What are factors that contribute to eutrophication?
9. What are the main factors controlling primary productivity in terrestrial ecosystems?
Concept 42.3 – Energy transfer between trophic levels is typically only 10% efficient.
10. Define the following:
a. production efficiency
b. trophic efficiency
Concept 42.4 – Biological and geochemical processes cycle nutrients and water in ecosystems.
11. Use the figure below to describe the water cycle. Specify the roles of evaporation,
transpiration, and rainfall.
KEY
12. Use the figure below to describe the carbon cycle. In doing so, explain how carbon enters
the living system and how it leaves, and identify the reservoir for carbon.
13. Write the equation for photosynthesis: __________________________________________
14. Write the equation for cellular respiration: _______________________________________
15. Use the figure below to describe the nitrogen cycle. In doing so, indicate the role of
microorganisms in nitrogen fixation, nitrification, and denitrification.
16. Use the figure below to describe the phosphorus cycle.