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CBSE · Class 8 · Science

How Nature Works in Harmony

Standard difficulty · 20 questions · 40 marks

Name: Date: Score: ____ / 40

Show your working for Sections B and C. Answers are on the last page — try every question first!

Section A — Choose the correct answer8 × 1 = 8 marks
1.
The living parts of an ecosystem are called:
  1. minerals
  2. climate
  3. abiotic components
  4. biotic components
2.
In a food chain, a deer is a:
  1. decomposer
  2. omnivore
  3. herbivore
  4. carnivore
3.
What kind of relationship is this: a louse on a person's head?
  1. decomposition
  2. commensalism
  3. mutualism
  4. parasitism
4.
Which of these is an ABIOTIC part of a pond ecosystem?
  1. rocks
  2. fish
  3. grass
  4. algae
5.
In the food chain grain → mouse → owl, what does the owl eat?
  1. owl
  2. sunlight
  3. grain
  4. mouse
6.
Four 1 m × 1 m quadrats had 14, 19, 9, 25 grass plants. What is the average number per square metre?
  1. 25 plants
  2. 67 plants
  3. 16.75 plants
  4. 33.5 plants
7.
On average there are 16 plants of a kind in each square metre. About how many are there in a field of 69 m2?
  1. 1,120 plants
  2. 85 plants
  3. 1,104 plants
  4. 69 plants
8.
Which of these is a DECOMPOSER?
  1. an earthworm's gut bacteria
  2. a crow
  3. grass
  4. a leopard
Section B — Short answer8 × 2 = 16 marks
9.
What is an ecosystem?
10.
Is each a producer, herbivore, carnivore, omnivore or decomposer? (a) a leopard (b) a crow
11.
Name the relationship (mutualism, commensalism or parasitism): (a) Rhizobium in a bean plant's roots (b) a bee and a flower
12.
Write "biotic" or "abiotic": (a) temperature (b) grass
13.
In algae → small fish → big fish → kingfisher, if the number of small fish falls sharply, what happens to the numbers of algae and of big fish?
14.
Five quadrats counted 18, 5, 15, 17, 6 clover plants. Find the total and the average per quadrat.
15.
A field has about 693 grass plants, 38 grasshoppers and 2 snakes. Arrange them as a pyramid of numbers from the base up. Which level has the fewest?
16.
Why is each important in nature? (a) decomposers (b) pollinators
Section C — Word problems4 × 4 = 16 marks
17.
Explain how removing frogs from a food chain affects other organisms.
18.
Look at the food chain leaves → goat → leopard. (a) Name the producer and the top consumer. (b) What would happen if the goat disappeared? (c) Why is a food web more stable than this single chain?
19.
Students placed four 1 m × 1 m quadrats in a 300 m2 meadow and counted 21, 16, 13, 21 daisies. (a) What is the average per square metre? (b) Estimate the total number of daisies. (c) Why use several quadrats, not one?
20.
Explain the relationship in (a) a louse on a person's head and (b) Rhizobium in a bean plant's roots: who gains, and who is harmed, if anyone?
AmbifulWorksheets
Practice that never repeats
CBSE · Class 8 · Science

Answer key

How Nature Works in Harmony · AW-8S-NWH-2026-V1 · For parents — fold back or tear off before handing the sheet to your child.

QAnswerWorking
1(d) biotic components—
2(c) herbivore—
3(d) parasitism—
4(a) rocks—
5(d) mouse—
6(c) 16.75 plants67 ÷ 4 = 16.75
7(c) 1,104 plants16 × 69 = 1104
8(a) an earthworm's gut bacteria—
9All the living things in an area together with the non-living things around them.—
10(a) carnivore (b) omnivore—
11(a) mutualism (b) mutualism—
12(a) abiotic (b) biotic—
13The algae increases (less is eaten); the big fish decreases (less food).—
1461; 12.261 ÷ 5
15grass (693) → grasshoppers (38) → snakes (2); snakes are fewest—
16(a) return nutrients to the soil (b) help plants make seeds—
17In grass → grasshopper → frog → snake, removing frogs means grasshoppers increase and eat more grass, while snakes have less food and decrease. This happened in India when frogs were over-caught in the 1980s and insect pests rose.—
18(a) Producer: leaves; top consumer: leopard (b) The leaves would increase and the leopard would lose food and decrease. (c) In a web, animals have other foods, so the loss of one does not break everything.—
19(a) 17.75 (b) About 5325 (c) Plants are not spread evenly; several quadrats give a fairer average.—
20(a) parasitism (b) mutualism—