Question

Read the passage carefully and answer the following questions:
A constant input of solar energy is the basic requirement for any ecosystem to function and sustain. Primary production is defined as the amount of biomass or organic matter produced per unit area over a time period by plants during photosynthesis. It is expressed in terms of weight (g m⁻²) or energy (kcal m⁻²). The rate of biomass production is called productivity. It is expressed in terms of g m⁻² yr⁻¹ or (kcal m⁻²) yr⁻¹ to compare the productivity of different ecosystems. It can be divided into gross primary productivity (GPP) and net primary productivity (NPP). Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilised by plants in respiration. Gross primary productivity minus respiration losses (R) is the net primary productivity (NPP).
a. Define gross primary productivity.
b. What is the main requirement of ecosystem functioning?
c. What is the unit of productivity?
d. GPP $-$ Respiration = ________

Hint:

Net Primary Productivity (NPP) is the actual biomass available for the consumption of heterotrophs (herbivores and decomposers).

Answer 1

Step 1: (a) As stated in the passage, Gross Primary Productivity (GPP) of an ecosystem is the rate of production of organic matter during photosynthesis.
Step 2: (b) The passage mentions that a constant input of solar energy is the basic requirement for any ecosystem to function and sustain.
Step 3: (c) The unit of productivity is expressed in terms of $\mathbf{g\,m^{-2}\,yr^{-1}}$ or $\mathbf{(kcal\,m^{-2})\,yr^{-1}}$ to allow for the comparison of different ecosystems.
Step 4: (d) According to the metabolic balance mentioned, GPP minus respiration losses (R) results in Net Primary Productivity (NPP).