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Question
Answer the following question.
Describe the inter-relationship between productivity, gross primary productivity, and net productivity.
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Solution
The rate of biomass production per unit area, over a time period by plant during photosynthesis is called productivity.
- It is expressed (kcal m-2)yr-1or g/m2/yr or g m-2y-1.
- The amount of biomass or organic matter produced per unit area over a time period in plants during photosynthesis is called primary production.

| * It is the rate of production of organic matter during photosynthesis in an ecosystem. | * It is the weight of the organic matter stored by the produces in a unit area/volume per unit time. |
| * Some of GPP is utilized in respiration. |
NPP = GPP - R |
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RELATED QUESTIONS
What is primary productivity?
State the relation between gross and net primary productivity.
Explain what does the equation given below show:
NPP = GPP – R
Productivity is the rate of production of biomass expressed in terms of ______.
Justify the following statement in terms of ecosystem dynamics. “Nature tends to increase the gross primary productivity, while man tends to increase the net primary productivity”.
Which of the following ecosystems will be more productive in terms of primary productivity? Justify your answer. A young forest, a natural old forest, a shallow polluted lake, alpine meadow.
Use the information provided in the table given below to answer the following questions:
| Tropic level | Net Production(KJm-2y-1) | Respiration (KJm-2y-1) |
| Top Carnivore | 50 | 35 |
| Carnivores | 420 | 378 |
| Herbivores | 4490 | 4041 |
| Producers | 45000 | 40,367 |
- Calculate the gross primary productivity.
- Analyze the trend in the Net Production from Producers to Top Carnivore. Give a reason for your observation.
What is the rate at which biomass is synthesised by a trophic level per unit area per unit time called?
Which human activity indirectly reduces ecosystem productivity?
Why is CO₂ concentration considered a factor affecting productivity?
