--- title: "Ecosystem Energy Budgets: GPP, NPP and Transfer Efficiency" description: "Gross primary production is what producers capture, net primary production is what remains after their own respiration, and only a small share reaches the next trophic level. The numbers are why food " canonical: https://lightmysky.com/learn/science/ecosystem-energy-budgets-gpp-npp-and-transfer-efficiency-mt_D81CKcOdBI source: https://lightmysky.com/learn/science/ecosystem-energy-budgets-gpp-npp-and-transfer-efficiency-mt_D81CKcOdBI.md retrieved: 2026-11-12 --- > **Agent view.** This is the Markdown twin of the page, for tools and assistants. > When to use this site, and the call that answers each job: https://lightmysky.com/agent-instructions.md > API description (OpenAPI 3.1): https://lightmysky.com/openapi.json · Authentication: https://lightmysky.com/auth.md > Pricing: https://lightmysky.com/pricing.md · Catalog: https://lightmysky.com/llms.txt · Full catalog: https://lightmysky.com/llms-full.txt > Every machine-readable file on this domain: https://lightmysky.com/.well-known/ai-catalog.json > Ask for Markdown with `Accept: text/markdown`, a `.md` address, or `?mode=agent`. # Ecosystem Energy Budgets: GPP, NPP and Transfer Efficiency Gross primary production is what producers capture, net primary production is what remains after their own respiration, and only a small share reaches the next trophic level. The numbers are why food chains stay short. Subject: Science · Area: Organisms & Life Processes · Ages 17 to 18 Page: https://lightmysky.com/learn/science/ecosystem-energy-budgets-gpp-npp-and-transfer-efficiency-mt_D81CKcOdBI ## Ready when they can - Calculates net primary production from gross production and respiratory loss. - Works out percentage energy transfer between two trophic levels from given data. - Explains where the energy that fails to transfer actually goes. ## Lesson: Where the Energy Goes GPP is the total chemical energy producers fix per area per time. Plants respire too, releasing energy from glucose as other cells do, and that respiration burns some of what they fix just to keep them alive. NPP equals GPP minus respiration, and NPP feeds every herbivore and everything above. *(drawing: NPP is what is left of GPP after the plants' own respiration: 15000 minus 6000 is 9000.)* Each feeding step in a food chain is a trophic level. Only about a tenth of the energy at one level becomes new biomass at the next. A rabbit burns most of the energy in its grass in respiration, losing it as heat. More leaves in urine and faeces, and the roots are never eaten. Short chains and narrow pyramid tops follow. **Example.** Work the transfer as a percentage: energy in new biomass above, divided by energy available below, times 100. Grass holding 24000 units with 1800 reaching new rabbit tissue gives 1800 divided by 24000, times 100, which is 7.5 percent. Use a chain for the maths and the web for the full story. One grass plant feeds rabbits, grasshoppers and voles while the fox eats all three, so removing one species ripples in several directions. **Recap.** Subtract respiration from GPP for NPP, expect about a tenth to move up, and trace the rest to heat, waste, and uneaten parts. ## Practice 8 questions on this page, each with its working shown. ## Needs first - [Anaerobic Routes and the ATP Yield Compared](https://lightmysky.com/learn/science/anaerobic-routes-and-the-atp-yield-compared-mt_LBZ4laMfqb) ## Optional connections - [Energy Loss Between Levels](https://lightmysky.com/learn/science/energy-loss-between-levels-mt_BOG5zRYtQz) - [Respiration: Energy Yield, Oxygen Debt and Fermentation](https://lightmysky.com/learn/science/respiration-energy-yield-oxygen-debt-and-fermentation-mt_mvnCjThdTH) ## Opens up - [The Nitrogen Cycle and the Microbes That Drive It](https://lightmysky.com/learn/science/the-nitrogen-cycle-and-the-microbes-that-drive-it-mt__K1J47NhWj) - [Optimal foraging and the currency of a behavioural decision](https://lightmysky.com/learn/science/optimal-foraging-and-the-currency-of-a-behavioural-decision-mt_9iNYB7d1Rh)