General Studies | Food Chains and Energy Pyramids: Tutor Lesson Plan

2026-11-04

Tutor lesson-prep guides · Primary General Studies

Every child can say “big fish eats small fish”, but ask why there are fewer tigers than sheep and they answer “because tigers are bigger”. This lesson turns the ten-percent rule into a sum they can do.

Objectives — Students can: (1) order a four-link food chain and label producers, consumers and decomposers; (2) apply the 10% rule to each level of the pyramid; (3) say which links break when one species is removed.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Percentages	What is 10% of 100?	10
Large numbers	How many ten-thousands in 100000?	10
Categories	Which is producer, consumer, decomposer?	Grass, cow, bacteria

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0–5 min	Hook with one question	Ask how many tigers one grassland can hold	Guess a number and justify
5–12 min	Quick prerequisite check	Three quick questions, repair on the spot	Answer orally, copy if wrong
12–22 min	Act 1 The three roles	Draw grass, locust, frog, snake, bacteria	Label each box
22–30 min	Act 2 Energy pyramid	Compute 10% down from 100000 kJ	Work out the fourth level
30–36 min	Act 3 Food web	Overlay three chains, remove one species	Name the links that break
36–50 min	Timed practice (14 min)	Two questions, seven minutes each	Work independently
50–55 min	Peer review	Swap and ask for each role	Spot a missing decomposer
55–60 min	Exit check	Three oral questions	Redraw if wrong

03 Teaching script (read it out)

Scene 1: Three roles, one line

Write “grass” on the left and “snake” on the right, leave the middle blank. Ask what belongs between them: children say “rabbit”. Then ask who makes its own food and who must eat. Write producer and consumer on the board.
Ask where a dead snake goes. Most say the bin. Point out that bacteria and fungi break the body down so nutrients return to the soil, which is why decomposers close the loop.

Students restate: plants produce, animals consume, microbes decompose.

Scene 2: Ten percent per level

Write 100000 kJ under the grass. Ask how much of that becomes locust body. About a tenth; the rest is spent on respiration, heat and waste.
Compute down: 10000, 1000, 100. Then ask again why tigers are fewer than sheep: at levels three and four only 1% and 0.1% of the original energy remains, so the habitat cannot support many large predators.

Students compute 100 from 1000 and say “nine tenths is lost”.

Scene 3: A web, not a line

Draw three chains that share the grass. Overlap them and mark the crossings. Remove the frog: the first chain breaks but the snake still has mice. Remove the grass: every chain fails.
The lower the species sits, the bigger the effect of losing it.

Students state that removing grass breaks all three chains.

04 Question types and worked steps

Type	Example	Steps	Answer
Order a chain	Grass, locust, frog, snake	Start at the producer, arrow to the eater	Grass→locust→frog→snake
Compute a level	Grass 100000 kJ, third level?	Multiply by 0.1 each level	1000 kJ
Add the decomposer	What is missing at the end of a chain?	Who handles dead matter?	Bacteria and fungi
Find broken links	Remove one species, what breaks?	Check each chain for a gap	Any chain containing it

Sanity check (teach this): Check the numbers: each level keeps 10%, so 100000 kJ becomes 10000, then 1000, then 100 kJ across 4 levels, losing 90% each time. One frog eats 8 locusts a day and each locust eats 20 g of grass, so 160 g of grass per day. Lesson 60 min = 5 + 7 + 24 + 14 + 5 + 5.

05 Independent practice (3 questions)

Question	Answer	What to watch
Order one	Order grass, mouse, snake, hawk and label roles	Arrows and role names correct
Compute one	Grass 100000 kJ, how much at the snake?	Must reach 100 kJ
Find a break	Remove the mouse from the web	Note one chain still reaches the hawk

06 Common mistakes and what to say

Mistake	Student writes	Say this
Mixed roles	“A snake is a producer because it finds food”	“A producer makes its own food; a snake must eat, so it is a consumer.”
Reversed arrows	“Snake→frog→locust”	“The arrow points to the eater, the direction energy flows.”
Missing decomposers	Chain stops at the snake	“Where does the snake go? Without microbes nutrients never return.”
Size explains numbers	“Fewer tigers because they are big”	“Only one percent of the energy reaches level three, so few can live there.”

07 Homework (paper, section and question numbers)

P5 General Studies paper — Science and technology short answers: ordering chains
P6 General Studies paper — Data questions: explain population change with a web
Primary General Studies index — All chapters and matching papers

08 Exit check (last 5 minutes)

Question	Answer	Decision
Name the three roles.	Producer, consumer, decomposer	Missing decomposer means re-teach
How much energy passes up one level?	One tenth; nine tenths is lost	Any other answer gets the sum again
What happens if the grass goes?	All three chains fail	Redraw the web if unsure

09 Tutor FAQ

Should children memorise many chain names?

No; the roles and the energy direction matter more than the names at primary level.

Why are there always fewer predators?

Nine tenths of the energy is lost at each step, so fewer individuals can be supported.

Are decomposers a kind of consumer?

No; they break down dead matter and return nutrients to the environment.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.