EEB 3407 Test Questions with Correct Answers
Explain why ecosystem functioning and ecosystem services are not the same.
Ecosystem functioning includes all chemical, physical, and biological processes in an
ecosystem. Ecosystem services are only the subset of those functions that directly benefit
humans. For example, nutrient cycling is an ecosystem function, while water purification that
benefits people is an ecosystem service.
Explain why nitrogen is often limiting even though the atmosphere contains lots of
nitrogen.
Most atmospheric nitrogen is N2, which has a strong triple bond and cannot be used directly
by most organisms. Organisms need reactive nitrogen such as nitrate, nitrite, or ammonium.
Because nitrogen fixation requires energy, usable nitrogen can be limited.
Explain eutrophication.
Eutrophication occurs when excess nutrients enter aquatic ecosystems. Nutrients increase
algal growth. When algae die, decomposers break them down and use oxygen, causing low
oxygen that can harm fish and reduce biodiversity.
Explain how biodiversity can increase ecosystem functioning.
Biodiversity can increase ecosystem functioning through complementarity, where species use
resources differently, and through selection effects, where diverse communities are more
likely to contain highly productive species. Redundancy can also protect functions if species
are lost.
Explain how biodiversity can increase ecosystem stability.
Explain why ecosystem functioning and ecosystem services are not the same.
Ecosystem functioning includes all chemical, physical, and biological processes in an
ecosystem. Ecosystem services are only the subset of those functions that directly benefit
humans. For example, nutrient cycling is an ecosystem function, while water purification that
benefits people is an ecosystem service.
Explain why nitrogen is often limiting even though the atmosphere contains lots of
nitrogen.
Most atmospheric nitrogen is N2, which has a strong triple bond and cannot be used directly
by most organisms. Organisms need reactive nitrogen such as nitrate, nitrite, or ammonium.
Because nitrogen fixation requires energy, usable nitrogen can be limited.
Explain eutrophication.
Eutrophication occurs when excess nutrients enter aquatic ecosystems. Nutrients increase
algal growth. When algae die, decomposers break them down and use oxygen, causing low
oxygen that can harm fish and reduce biodiversity.
Explain how biodiversity can increase ecosystem functioning.
Biodiversity can increase ecosystem functioning through complementarity, where species use
resources differently, and through selection effects, where diverse communities are more
likely to contain highly productive species. Redundancy can also protect functions if species
are lost.
Explain how biodiversity can increase ecosystem stability.
