CLEP Biology Ecosystems and Energy Flow 2 — Questions and Answers
Question 1: Which ecological term describes the total mass of living organisms in a given area at a given time?
- Biomass (Correct answer)
- Productivity
- Carrying capacity
- Biodiversity
Correct answer: Biomass
Biomass refers to the total mass of living organic matter in an ecosystem or trophic level.
Question 2: In a food web, detritivores play which role?
- They photosynthesize sunlight into sugars
- They feed on dead organic matter and break it into smaller pieces (Correct answer)
- They fix atmospheric nitrogen into usable forms
- They consume living primary producers
Correct answer: They feed on dead organic matter and break it into smaller pieces
Detritivores such as earthworms and millipedes consume dead organic material, physically breaking it down before decomposers chemically process it.
Question 3: Gross Primary Productivity (GPP) minus plant respiration equals:
- Secondary productivity
- Net Primary Productivity (NPP) (Correct answer)
- Tertiary productivity
- Ecosystem respiration
Correct answer: Net Primary Productivity (NPP)
Net Primary Productivity (NPP) is the energy available to consumers after plants use some GPP for their own cellular respiration.
Question 4: Which biome stores the greatest amount of carbon per unit area in above-ground plant biomass?
- Temperate grassland
- Arctic tundra
- Tropical rainforest (Correct answer)
- Desert scrubland
Correct answer: Tropical rainforest
Tropical rainforests have the highest above-ground plant biomass and therefore store more carbon per unit area than any other terrestrial biome.
Question 5: The 'green world hypothesis' suggests that herbivore populations are kept in check primarily by:
- Competition for plant resources
- Predation and disease (Correct answer)
- Nutrient limitation in plants
- Seasonal temperature changes
Correct answer: Predation and disease
The green world hypothesis proposes that top-down control by predators and parasites prevents herbivores from consuming all available plant material.
Question 6: In an upwelling zone in the ocean, nutrients from deep water rise to the surface. This primarily increases which trophic level most directly?
- Tertiary consumers (fish predators)
- Secondary consumers (zooplankton predators)
- Primary producers (phytoplankton) (Correct answer)
- Apex predators (sharks, seals)
Correct answer: Primary producers (phytoplankton)
Nutrients like nitrates and phosphates from upwelling directly fuel phytoplankton (primary producer) growth, which then supports higher trophic levels.
Question 7: Which process in the nitrogen cycle converts nitrates (NO₃⁻) back into atmospheric nitrogen gas (N₂)?
- Nitrification
- Nitrogen fixation
- Denitrification (Correct answer)
- Ammonification
Correct answer: Denitrification
Denitrification, carried out by anaerobic bacteria in waterlogged soils, converts nitrates back into N₂ gas, completing the nitrogen cycle.
CLEP Biology Ecosystems and Energy Flow 2
Which ecological term describes the total mass of living organisms in a given area at a given time?