Try each question on your own first. Use the Show Answer button only after you have selected your option, then read the explanation and revise the related concept from your chapter notes.
A. Biotic and abiotic components interacting together
B. Only the living organisms present in an area
C. Only the non-living physical components of an area
D. Only the producer organisms present in an area
Answer: A. Biotic and abiotic components interacting together
Explanation: An ecosystem includes both the living community of organisms (biotic) and the physical, non-living environment (abiotic) with which they interact.
2. The primary source of energy that sustains almost all ecosystems on Earth is:
A. The Sun
B. Decomposers
C. Consumers
D. Nutrients present in the soil
Answer: A. The Sun
Explanation: Solar energy is captured by producers through photosynthesis, forming the foundational energy input for nearly all ecosystems.
3. Organisms capable of producing their own food using sunlight are known as:
A. Producers (autotrophs)
B. Primary consumers
C. Decomposers
D. Secondary consumers
Answer: A. Producers (autotrophs)
Explanation: Producers, such as green plants and certain bacteria, synthesize organic compounds from inorganic materials using light energy.
4. A food chain in which energy flows from living green plants to grazing herbivores and then on to various carnivores is called a:
A. Grazing food chain
B. Detritus food chain
C. Parasitic food chain
D. Decomposer food chain
Answer: A. Grazing food chain
Explanation: The grazing food chain begins with living plant material being consumed directly by herbivores, in contrast to the detritus food chain.
5. Organisms that break down dead organic matter, thereby recycling essential nutrients back into the ecosystem, are called:
A. Decomposers
B. Producers
C. Primary consumers
D. Secondary consumers
Answer: A. Decomposers
Explanation: Decomposers such as bacteria and fungi convert complex organic matter from dead organisms into simpler inorganic substances.
6. According to the ten percent law of energy transfer, approximately how much energy is passed on from one trophic level to the next?
A. 10%
B. 50%
C. 90%
D. 100%
Answer: A. 10%
Explanation: Only about ten percent of the energy at one trophic level is typically available and transferred to the next higher trophic level.
7. A pyramid that represents the total number of individual organisms present at each trophic level is called a:
A. Pyramid of numbers
B. Pyramid of biomass
C. Pyramid of energy
D. Pyramid of productivity
Answer: A. Pyramid of numbers
Explanation: The pyramid of numbers illustrates how the count of individual organisms generally changes from one trophic level to the next.
8. Gross Primary Productivity (GPP) of an ecosystem refers to the:
A. Total rate of production of organic matter through the process of photosynthesis
B. Rate of energy loss occurring solely through respiration
C. Rate at which decomposition of matter occurs
D. Rate at which nutrients are cycled through the ecosystem
Answer: A. Total rate of production of organic matter through the process of photosynthesis
Explanation: GPP represents the total amount of energy fixed by producers, before any losses due to their own respiration are subtracted.
9. The continuous process by which nutrients move from the abiotic environment through living organisms and back again is called:
A. Nutrient (biogeochemical) cycling
B. Ecological succession
C. Primary productivity
D. Energy flow
Answer: A. Nutrient (biogeochemical) cycling
Explanation: Biogeochemical cycles, such as the carbon and nitrogen cycles, describe the continuous movement of essential nutrients through an ecosystem.
10. Ecological succession that begins in an area which has never previously been colonized by living organisms, such as bare rock, is called:
A. Primary succession
B. Secondary succession
C. Cyclic succession
D. Regressive succession
Answer: A. Primary succession
Explanation: Primary succession starts essentially from scratch in a lifeless environment, gradually building up a community of organisms over time.
11. The pyramid of energy in virtually any ecosystem is always:
A. Upright, since a significant amount of energy is progressively lost at each successive trophic level
B. Inverted, in every type of ecosystem without exception
C. A straight horizontal line, with no variation
D. Completely absent in aquatic ecosystems
Answer: A. Upright, since a significant amount of energy is progressively lost at each successive trophic level
Explanation: Because energy is lost as heat at each trophic transfer, the amount of energy available necessarily decreases at higher trophic levels, giving an upright pyramid.
12. Decomposition of complex organic matter into simpler inorganic substances typically involves processes such as:
A. Fragmentation, leaching, catabolism, humification and mineralization
B. Only the process of photosynthesis
C. Only the process of respiration
D. Only the process of transpiration
Answer: A. Fragmentation, leaching, catabolism, humification and mineralization
Explanation: These sequential processes together break down detritus, ultimately releasing simple inorganic nutrients back into the soil and environment.
