Ecology Of Ecosystem Processes 2 — Questions and Answers
Question 1: Which process converts atmospheric nitrogen into a form usable by plants?
- Denitrification
- Nitrogen fixation (Correct answer)
- Nitrification
- Ammonification
Correct answer: Nitrogen fixation
Nitrogen fixation, performed by certain bacteria like Rhizobium, converts N₂ gas into ammonia that plants can absorb.
Question 2: What term describes the total amount of solar energy fixed by producers in an ecosystem per unit time?
- Net primary productivity
- Gross primary productivity (Correct answer)
- Secondary productivity
- Ecosystem respiration
Correct answer: Gross primary productivity
Gross primary productivity (GPP) is the total rate of photosynthetic energy fixation before any respiratory losses.
Question 3: In the phosphorus cycle, which reservoir holds the largest long-term store of phosphorus?
- Ocean water
- Living biomass
- Sedimentary rock (Correct answer)
- Soil solution
Correct answer: Sedimentary rock
Sedimentary rocks are the primary long-term reservoir of phosphorus, which is released slowly through weathering.
Question 4: What is the fate of most energy that passes through a trophic level?
- It is stored in biomass
- It is transferred to the next level
- It is lost as heat (Correct answer)
- It is recycled through decomposers
Correct answer: It is lost as heat
Roughly 90% of energy at each trophic level is lost as metabolic heat, leaving only ~10% available to the next level.
Question 5: Which nutrient cycle is considered most tightly coupled to the carbon cycle in ecosystems?
- Phosphorus cycle
- Sulfur cycle
- Nitrogen cycle (Correct answer)
- Calcium cycle
Correct answer: Nitrogen cycle
The nitrogen cycle is most tightly coupled to carbon cycling because nitrogen limits primary production and is a key component of proteins and chlorophyll.
Question 6: Which of the following best describes 'ecosystem engineers'?
- Organisms that occupy the top trophic level
- Organisms that physically modify habitat structure (Correct answer)
- Species with the highest biomass in an ecosystem
- Organisms that fix atmospheric gases
Correct answer: Organisms that physically modify habitat structure
Ecosystem engineers like beavers and earthworms physically modify the abiotic environment, creating or maintaining habitats for other species.
Question 7: What process returns organic nitrogen to inorganic ammonium in the soil?
- Nitrification
- Denitrification
- Ammonification (Correct answer)
- Assimilation
Correct answer: Ammonification
Ammonification is carried out by decomposers that break down organic nitrogen in dead matter and waste into ammonium.
Ecology Of Ecosystem Processes 2
Which process converts atmospheric nitrogen into a form usable by plants?