Question

In relation to Gross primary productivity and Net primary productivity of an ecosystem, which one of the following statements is correct?

• A. Gross primary productivity is always less than net primary productivity.
• B. Gross primary productivity is always more than net primary productivity.
• C. Gross primary productivity and Net primary productivity are one and same.
• D. There is no relationship between Gross primary productivity and Net primary productivity.

Answer 1

The Correct Option is B

To answer the question regarding the relationship between Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) in an ecosystem, we need to understand these two terms.

1. Gross Primary Productivity (GPP) is the total amount of chemical energy as biomass that primary producers (plants, algae) create in a given amount of time. This includes all the energy produced through photosynthesis before any is used up by the organism for its metabolic needs.
2. Net Primary Productivity (NPP) is the remaining amount of energy that is stored as biomass after the primary producers use some of the energy during respiration to maintain and reproduce themselves. Mathematically, it is defined as:
   NPP = GPP - R
   where R refers to the energy used in respiration by plants.

From this, it is clear that NPP will always be less than GPP because the energy used for respiration (R) is subtracted from the gross amount of energy produced.

Now, let's evaluate the given options:

• Option 1: Gross primary productivity is always less than net primary productivity. - This is incorrect because GPP includes all energy produced, making it greater than the energy remaining after respiration, which is NPP.
• Option 2: Gross primary productivity is always more than net primary productivity. - This is the correct answer as explained above.
• Option 3: Gross primary productivity and Net primary productivity are one and the same. - This is incorrect because the two are related but not identical; NPP is always less than GPP due to plant respiration.
• Option 4: There is no relationship between Gross primary productivity and Net primary productivity. - This is incorrect as there is a definite mathematical relationship between them, where NPP is derived from GPP.

Therefore, the correct statement regarding the relationship between Gross Primary Productivity and Net Primary Productivity is: "Gross primary productivity is always more than net primary productivity."