biology : class12 Heterotrophic Productivity : Primary Productivity, Secondary Productivity, Gross Productivity, Net Productivity : Productivity MCQ Questions and Answers
Practice important
Heterotrophic Productivity
MCQ questions and answers.
Page 1
of
1
|
10
MCQ Questions
1. In a consumer population, which measurement most directly represents heterotrophic productivity?
A.
The total chemical energy ingested from food
B.
The rate at which assimilated energy is converted into new consumer biomass
C.
The total energy lost as respiratory heat
D.
The amount of plant biomass available before feeding
Correct Answer:
The rate at which assimilated energy is converted into new consumer biomass
Explanation:
Heterotrophic productivity is the rate of production of new biomass by organisms that obtain organic matter from other organisms. In consumers, it corresponds to biomass formation after accounting for energy used in respiration and other losses.
2. A herbivore consumes 1,000 kJ of plant material, assimilates 400 kJ, and uses 250 kJ in respiration. What is its production of new biomass?
A.
150 kJ
B.
250 kJ
C.
400 kJ
D.
600 kJ
Correct Answer:
150 kJ
Explanation:
For a heterotroph, production equals assimilated energy minus respiratory expenditure. Therefore, production is 400 kJ − 250 kJ = 150 kJ.
3. Two consumer populations assimilate equal amounts of energy. Population X has a higher heterotrophic productivity than population Y. Which conclusion is most justified?
A.
Population X necessarily consumes more food than population Y
B.
Population X converts a greater fraction of assimilated energy into new biomass
C.
Population X necessarily has a lower respiration rate than population Y in absolute terms
D.
Population X must occupy a lower trophic level than population Y
Correct Answer:
Population X converts a greater fraction of assimilated energy into new biomass
Explanation:
With equal assimilation, higher heterotrophic productivity means that a larger amount of assimilated energy is retained as new biomass rather than being dissipated through respiration or other metabolic costs.
4. A detritivore population has an ingestion efficiency of 60%, an assimilation efficiency of 50%, and a production efficiency of 20%. If it ingests 2,000 kJ of detritus, how much energy becomes new detritivore biomass?
A.
120 kJ
B.
200 kJ
C.
240 kJ
D.
600 kJ
Correct Answer:
120 kJ
Explanation:
The energy assimilated is 2,000 × 0.60 × 0.50 = 600 kJ. Production is 600 × 0.20 = 120 kJ, representing heterotrophic biomass formation.
5. Why is heterotrophic productivity generally lower than the energy intake of a consumer?
A.
All ingested organic matter is immediately converted into structural biomass
B.
Part of the ingested material is unassimilated, and part of assimilated energy is used in metabolism
C.
Consumers cannot assimilate energy from organic compounds
D.
Consumer biomass contains no chemically stored energy
Correct Answer:
Part of the ingested material is unassimilated, and part of assimilated energy is used in metabolism
Explanation:
Heterotrophic production is reduced by egestion of undigested material and by respiratory expenditure after assimilation. Only the remaining assimilated energy contributes to new biomass.
6. A fish population has an annual biomass production of 80 kg and an average standing biomass of 400 kg. What is its annual heterotrophic production-to-biomass ratio?
A.
0.02 per year
B.
0.20 per year
C.
5.0 per year
D.
320 per year
Correct Answer:
0.20 per year
Explanation:
The production-to-biomass ratio is calculated as annual new biomass divided by standing biomass: 80 ÷ 400 = 0.20 per year. This describes the rate of heterotrophic biomass replacement relative to existing biomass.
7. A consumer assimilates 900 kJ from food and produces 180 kJ of new biomass. Which statement correctly describes its heterotrophic production efficiency?
A.
20%, because 180 kJ is one-fifth of assimilated energy
B.
25%, because 180 kJ is one-quarter of ingested energy
C.
50%, because half of assimilated energy is retained
D.
80%, because 720 kJ is lost through respiration
Correct Answer:
20%, because 180 kJ is one-fifth of assimilated energy
Explanation:
Production efficiency is heterotrophic production divided by assimilated energy, multiplied by 100. Thus, (180 ÷ 900) × 100 = 20%.
8. In a grazing food chain, the secondary production of herbivores is best interpreted as:
A.
The total plant biomass eaten by herbivores
B.
The rate at which herbivores generate new biomass from assimilated plant-derived energy
C.
The rate at which plants synthesize organic matter
D.
The total respiratory heat released by plants and herbivores
Correct Answer:
The rate at which herbivores generate new biomass from assimilated plant-derived energy
Explanation:
Herbivores are heterotrophs, so their biomass formation is secondary production. It represents the rate at which assimilated organic energy is incorporated into new herbivore tissue.
9. A change in food quality causes a consumer's assimilation efficiency to decrease while ingestion remains constant. If respiration per unit assimilated energy is unchanged, what is the expected effect on heterotrophic productivity?
A.
It increases because more food is processed
B.
It decreases because less ingested energy becomes available for biomass formation
C.
It remains unchanged because productivity depends only on ingestion
D.
It becomes equal to gross primary productivity
Correct Answer:
It decreases because less ingested energy becomes available for biomass formation
Explanation:
Lower assimilation efficiency means less of the ingested organic matter enters the consumer's assimilated energy pool. With unchanged metabolic expenditure per unit assimilated energy, less energy remains for new heterotrophic biomass.
10. Which experimental approach most accurately estimates the heterotrophic productivity of a consumer population over a defined interval?
A.
Measure only the amount of food ingested
B.
Measure the increase in consumer biomass while accounting for losses caused by mortality and emigration
C.
Measure only oxygen production by the habitat's plants
D.
Measure the total detritus present at the beginning of the interval
Correct Answer:
Measure the increase in consumer biomass while accounting for losses caused by mortality and emigration
Explanation:
Heterotrophic productivity is the formation of new consumer biomass over time. Estimation therefore requires tracking biomass increase and correcting for biomass losses so that production is not underestimated.
Short Questions and Answers
Practice short questions and answers related to
Heterotrophic Productivity
.
Short questions are currently unavailable for this page.