Q.60 Match the types of ecological energy productivity in Group 1 with their respective definitions in Group 2.

(A) P–iii, Q–ii, R–iv, S–i

(B) P–ii, Q–i, R–iii, S–iv

(C) P–ii, Q–i, R–iv, S–iii

(D) P–iv, Q–i, R–ii, S–iii

Correct matching is: P–ii, Q–i, R–iv, S–iii, so the right option is (C).​

Concept review of each term (Group 1)

• Net primary productivity (NPP)

  • NPP is the energy or biomass stored by autotrophs after subtracting respiratory losses from gross primary productivity.​

  • Mathematically, $\text{NPP}=\text{GPP}-\text{Respiration}$, and it represents energy available to herbivores in the next trophic level.​

  • Therefore NPP matches definition (ii) Amount of energy stored by autotrophs after respiration.

• Gross primary productivity (GPP)

  • GPP is the total amount of energy fixed by autotrophs through photosynthesis per unit area per unit time, before any loss to respiration.​

  • It is essentially the total primary production of an ecosystem by producers like green plants and phytoplankton.​

  • Hence GPP matches (i) Total amount of energy produced by autotrophs.

• Net productivity

  • In ecological energy flow, net productivity for a trophic level is the portion of assimilated energy that remains after accounting for respiration and waste, and becomes available to the next trophic level.​

  • When referring to heterotrophs, this is the energy not used up by them and that can move upward in the food chain.​

  • This aligns with (iv) Unused amount of energy after consumption by heterotrophs.

• Secondary productivity

  • Secondary productivity is the rate at which consumers (heterotrophs) convert ingested organic matter into their own biomass.​

  • It reflects the net energy gain of herbivores and other consumers after energy losses via respiration, feces and excretion.​

  • Therefore it matches (iii) Net gain of energy by the consumers after energy loss.

Explanation of all options (A–D)

• Option (A): P–iii, Q–ii, R–iv, S–i

  • P–iii is wrong because NPP concerns plants, not net gain of energy by consumers.​

  • Q–ii is wrong because “energy stored after respiration” describes NPP, not GPP.​

  • R–iv is acceptable for net productivity, but S–i is wrong because secondary productivity is due to heterotrophs, not “total energy produced by autotrophs.”​

• Option (B): P–ii, Q–i, R–iii, S–iv

  • P–ii and Q–i are correct as argued above.​

  • R–iii is incorrect because “net gain of energy by consumers” is secondary productivity, not general net productivity of a level.​

  • S–iv is incorrect because “unused energy after consumption by heterotrophs” refers to what passes on or is left as waste, not the rate of biomass formation in consumers.​

• Option (C): P–ii, Q–i, R–iv, S–iii

  • P–ii correctly defines net primary productivity.​

  • Q–i correctly defines gross primary productivity.​

  • R–iv is suitable for net productivity at the consumer level as “unused energy” that can move to higher trophic levels.​

  • S–iii correctly describes secondary productivity as net gain of energy by consumers.​

  • Hence Option (C) is correct.

• Option (D): P–iv, Q–i, R–ii, S–iii

  • P–iv is wrong because NPP is plant‑level, not “unused energy after consumption by heterotrophs.”​

  • R–ii is wrong because “energy stored by autotrophs after respiration” is again NPP, not generic net productivity.​

  • Only Q–i and S–iii are correct matches here.​

Short SEO‑optimized introduction

Ecological energy productivity explains how energy flows from autotrophs to heterotrophs through gross primary productivity, net primary productivity, net productivity and secondary productivity. Understanding these linked productivity terms is crucial for analyzing ecosystem efficiency, trophic levels and exam questions that ask you to match each type of ecological energy productivity with its precise definition.​