Q.The rate of formation of new organic matter by consumers, and the biomass available for consumption of herbivores as well as decomposers are referred to as: (A) Gross primary productivity and Net primary productivity (B) Net primary productivity and Secondary productivity (C) Secondary productivity and Net primary productivity (D) Secondary productivity and Gross primary productivity
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Start your 14-day free trial to unlock the full solution →Secondary productivity measures the rate at which consumers (herbivores, carnivores) form new organic matter, while net primary productivity represents the biomass actually available to herbivores and decomposers after plants have used some energy for their own respiration.
The question asks us to match two distinct ecological concepts: the productivity of consumers and the biomass available for the next trophic level. Understanding these terms requires clarity about how energy flows through an ecosystem and how we measure productivity at different levels.
Gross primary productivity is the total rate at which producers (plants, algae) capture solar energy and convert it into chemical energy through photosynthesis. Think of it as the gross income of the ecosystem—the entire amount of organic matter synthesized before any deductions.
Net primary productivity is what remains after plants subtract their own respiratory losses from gross primary productivity. The formula is simple: NPP = GPP – Respiration by plants. This is the actual biomass available to herbivores and decomposers—the net income, if you will. It represents the stored energy in plant tissues that can be consumed by the next trophic level.
Now, when herbivores eat plants and carnivores eat herbivores, they too produce new organic matter in their own bodies. This rate of formation of new organic matter by consumers—whether herbivores, carnivores, or any heterotroph—is called secondary productivity. It's analogous to primary productivity but occurs at the consumer level rather than the producer level.
The term "secondary" doesn't mean less important; it simply indicates that this productivity depends on primary producers. Consumers cannot synthesize organic matter from inorganic sources—they must consume existing organic matter and convert it into their own biomass. …
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