Biology · 35 minutes
Suggested grades 9–10 · Unit 3: Populations and Biological Evidence · Lesson 1 of 2
Build an Ecosystem Energy Budget
Use proportional data while keeping energy conservation distinct from biomass transfer.
Mr. S Teaches · Original starter lesson · HS-BIO-05 · Grade range is planning guidance.Watch, notice, discuss
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Food Webs and Energy Pyramids: Bedrocks of Biodiversity
By Amoeba Sisters
Interpret the energy pyramid before computing the lesson’s transfer fractions; the ten-percent pattern is approximate, not universal.
Open on YouTube: Food Webs and Energy Pyramids: Bedrocks of Biodiversity (opens a new tab) ↗Ecosystem Ecology: Links in the Chain - Crash Course Ecology #7
By CrashCourse
Compare trophic-level energy transfer with the lesson’s numerical budget and account for respiration and unconsumed material.
Open on YouTube: Ecosystem Ecology: Links in the Chain - Crash Course Ecology #7 (opens a new tab) ↗What idea from the video helps you calculate two transfer fractions and account for energy not stored as new biomass at the next level? Identify one useful example and one limit of the video's model or explanation.
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Learning objective
Calculate two transfer fractions and account for energy not stored as new biomass at the next level.
Before you begin
- Use percentages and define a system boundary.
Gather your materials
- Paper or notebook
- Pencil; calculator optional for numerical work; all task data supplied below
Language to know
- trophic level
- A feeding position in an ecosystem model.
- production
- Energy stored in newly formed biomass over a stated interval.
- transfer efficiency
- The proportion of one level’s production appearing as production at the next.
Understand the concept
Fictional annual meadow budget: producers store 20,000 kJ in new biomass; primary consumers store 2,400 kJ; secondary consumers store 180 kJ. Not all biomass is eaten, and consumed energy also supports respiration, movement and other processes or leaves as waste. The energy not appearing as next-level production is not destroyed. Matter in remains and wastes can enter decomposer pathways. The supplied figures describe one model, not a universal ten-percent rule.
Teach it step by step
- Convert the prose budget into a labeled trophic diagram with annual kJ units.
- Calculate primary-consumer production divided by producer production.
- Calculate secondary-consumer production divided by primary-consumer production and compare the fractions.
- Add arrows for uneaten matter, wastes and thermal transfers; explain how the budget avoids inventing missing energy.
Make the thinking visible
Worked example or model response
The first modeled fraction is 2,400/20,000 = 0.12, or 12%. The second is 180/2,400 = 0.075, or 7.5%. Unequal percentages show why a fixed ten-percent shortcut is not a measured law for every food web.
Guided practice
Together identify the 17,600 kJ difference between producer and primary-consumer production and explain why it cannot all be labeled “heat” without more evidence.
Independent practice
Create a proportional budget and a five-sentence account of matter and energy pathways. State one measurement needed to divide the untransferred amount among uneaten biomass, respiration and waste.
Quick assessment
Can 12% transfer efficiency be interpreted as 88% of the energy disappearing?
Answer key & assessment criteria
Answers and teaching guidance
- Guided: The difference is 17,600 kJ, but several pathways contribute; the provided production totals do not separate them.
- Independent: Require 12% and 7.5%, correct units, decomposer/matter pathways and an additional measurement such as consumption or respiration.
- Quick check: No. Energy leaves the selected production pathway through other transfers; conservation still applies.
Look for: Assess the stated objective using the concrete criteria and explanations in the answer key. Invite an alternative supported solution; distinguish a model’s prediction from an established observation.
Make it work for your learner
More support
Provide a ratio template and use bars scaled to the producer total before drawing arrows.
Extension challenge
Add a hypothetical 60% consumption fraction and determine which further measurements would be needed to estimate assimilation efficiency.
Verified references · Selected contributions
Standards connections
Selected NGSS high school-band contribution; full performance requires additional evidence and instruction.
Subject-content standards
These records identify the part of a subject standard practiced here. Course placement is instructional guidance; the source’s category or band remains authoritative.
Contributes to NGSS performance expectation
HS-LS2-4
NGSS · High school band
Use proportional representations of ecosystem matter and energy transfers.
Read the official performance expectation ↗The activity uses selected annual production data and proportional reasoning. It does not quantify all matter cycles, organisms or energy pathways in a real ecosystem.
Verified 2026-11-04. Selected contribution, not full attainment.
Supporting literacy connections
These records apply to the specified reading, writing or communication task. They do not establish subject-content alignment.
Supporting Common Core literacy connection
RST.9-10.7
Common Core · Grades 9–10
Translate technical prose into visuals and explain mathematical or visual information.
Read the official standard ↗The activity explicitly analyzes the provided technical text, table or model. It contributes selected literacy practice rather than complete grade-band reading coverage or independent subject-content alignment.
Verified 2026-11-04. Selected contribution, not full attainment.