biology : class12 Net Secondary Productivity : Primary Productivity, Secondary Productivity, Gross Productivity, Net Productivity : Productivity MCQ Questions and Answers
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Net Secondary Productivity
MCQ questions and answers.
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MCQ Questions
1. What does net secondary productivity represent in an ecosystem?
A.
The rate at which producers capture solar energy
B.
The rate of biomass gain by consumers after respiratory losses
C.
The total amount of sunlight received by plants
D.
The rate at which decomposers break down dead matter
Correct Answer:
The rate of biomass gain by consumers after respiratory losses
Explanation:
Net secondary productivity is the rate at which consumers add biomass after subtracting the energy they use in respiration.
2. Net secondary productivity is mainly associated with which organisms?
A.
Consumers
B.
Green plants only
C.
Abiotic soil components
D.
Sunlight-absorbing pigments
Correct Answer:
Consumers
Explanation:
Net secondary productivity measures biomass production by consumers after their respiratory energy expenditure.
3. If a consumer assimilates 100 units of energy and uses 40 units for respiration, what is its net secondary productivity in energy terms?
A.
40 units
B.
60 units
C.
100 units
D.
140 units
Correct Answer:
60 units
Explanation:
Net secondary productivity equals assimilated energy minus respiratory loss: 100 − 40 = 60 units.
4. Which process reduces net secondary productivity in consumers?
A.
Respiration
B.
Biomass formation
C.
Growth
D.
Tissue production
Correct Answer:
Respiration
Explanation:
Respiration uses part of the assimilated energy, leaving less energy available for biomass gain and therefore lowering net secondary productivity.
5. If respiratory loss increases while assimilation remains constant, what happens to net secondary productivity?
A.
It increases
B.
It decreases
C.
It remains unchanged in every case
D.
It becomes equal to primary productivity
Correct Answer:
It decreases
Explanation:
Greater respiratory loss leaves less assimilated energy available for growth and biomass formation, so net secondary productivity decreases.
6. A consumer assimilates 80 kJ of energy and loses 20 kJ through respiration. What is its net secondary productivity?
A.
20 kJ
B.
60 kJ
C.
80 kJ
D.
100 kJ
Correct Answer:
60 kJ
Explanation:
Net secondary productivity is calculated as assimilated energy minus respiratory energy loss: 80 − 20 = 60 kJ.
7. Which equation correctly expresses net secondary productivity?
A.
Assimilated energy + respiratory loss
B.
Assimilated energy − respiratory loss
C.
Respiratory loss − assimilated energy
D.
Primary productivity − sunlight received
Correct Answer:
Assimilated energy − respiratory loss
Explanation:
The energy available for consumer biomass production is the assimilated energy remaining after respiratory expenditure.
8. When a consumer uses assimilated food energy to produce new body tissue, this contributes to its:
A.
Net secondary productivity
B.
Gross primary productivity
C.
Solar radiation
D.
Respiratory loss
Correct Answer:
Net secondary productivity
Explanation:
The formation of new consumer biomass is the main outcome measured by net secondary productivity.
9. A consumer has an assimilated energy input of 50 units and a respiratory loss of 50 units. What is its net secondary productivity?
A.
0 units
B.
50 units
C.
100 units
D.
25 units
Correct Answer:
0 units
Explanation:
When respiratory loss equals assimilated energy, no energy remains for biomass gain, so net secondary productivity is zero.
10. Which change would most directly increase net secondary productivity if food assimilation is unchanged?
A.
A decrease in respiratory loss
B.
An increase in respiratory loss
C.
A decrease in biomass formation
D.
An increase in energy used for maintenance
Correct Answer:
A decrease in respiratory loss
Explanation:
Lower respiratory expenditure leaves more assimilated energy available for consumer growth and biomass production, increasing net secondary productivity.
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