Class 8 Science Curiosity Chapter 12 Solutions (NCERT 2026–27) – How Nature Works in Harmony

These Class 8 Science Curiosity Chapter 12 solutions cover How Nature Works in Harmony from the new NCF-2023 textbook (2026–27), with every “Keep the curiosity alive” question answered step by step.

Class: 8 Subject: Science Book: Curiosity Chapter: 12 Exercise: Keep the curiosity alive (9 Qs) Session: 2026–27
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Class 8 Science Curiosity Chapter 12 Solutions – Overview

Chapter 12 of Curiosity, How Nature Works in Harmony, explains how living and non-living parts of the environment depend on one another. It introduces habitats, biotic and abiotic components, and the levels of organisation — individual, population, community and ecosystem. It explores feeding relationships through food chains, food webs and trophic levels, the roles of producers, consumers and decomposers, and interactions such as competition, mutualism, commensalism and parasitism. It also looks at how one change can cascade through nature, the importance of biodiversity and conservation (the Sundarbans, protected areas), and sustainable farming. These Class 8 Science Curiosity Chapter 12 solutions answer every textbook question step by step.

Key Concepts & Definitions

Habitat: the place that provides the right conditions for an organism to live and grow (e.g. a pond, a forest, even the bark of a tree).

Biotic components: the living parts of a habitat (plants, animals, microbes). Abiotic components: the non-living parts (air, water, soil, sunlight, temperature).

Levels of organisation: Individual → Population (same kind in one place) → Community (different populations together) → Ecosystem (community + abiotic components interacting).

Producers (autotrophs): green plants that make food by photosynthesis. Consumers (heterotrophs): herbivores, carnivores, omnivores. Decomposers (saprotrophs): fungi and bacteria that break down dead matter and recycle nutrients.

Food chain: a linear “who eats whom” sequence. Food web: interlinked food chains forming a network. Trophic level: the position of an organism in a food chain.

Interactions: competition, mutualism (both benefit), commensalism (one benefits, the other unaffected) and parasitism (one benefits, the other is harmed).

“Probe and Ponder” & In-text Answers

How might the loss of forest cover and changes in rainfall patterns lead to elephants to enter human farms and villages?

ANSWERCutting trees and changes in rainfall and temperature dry up and shrink the forest, so food and water become scarce in the elephants’ natural habitat. Driven by hunger and thirst, elephants wander into nearby farms and villages in search of food such as bananas and sugarcane, leading to crop damage and human–wildlife conflict.

Imagine you are a tree in a dense forest. What kind of relationships would you have with water, sunlight, other animals, and other components of the forest?

ANSWERAs a tree I would absorb water and nutrients from the soil and use sunlight, carbon dioxide and water to make food by photosynthesis. I would provide oxygen, food, shade and shelter to animals, birds and insects, and my roots would hold the soil and retain moisture. Insects and birds would pollinate my flowers and disperse my seeds — a web of give-and-take with every component of the forest.

Do you think the Earth can thrive without humans? Can humans survive without the Earth?

ANSWERThe Earth can thrive without humans — ecosystems flourished for millions of years before people existed. But humans cannot survive without the Earth, because we depend on it for air, water, food, soil and shelter. This shows how closely human well-being is tied to a healthy planet.

If two kinds of birds compete for the same fruit, how might their way of living change over time?

ANSWERCompetition for the same fruit would pressure the two birds to differ over time — one might shift to feeding at a different time, in a different part of the tree, or on a slightly different food, reducing the overlap. This lets both populations survive and keeps the ecosystem balanced.

Can human actions cause natural disasters?

ANSWERYes. Human actions such as deforestation, pollution and overuse of resources disturb nature’s balance and can trigger or worsen disasters — for example, cutting mangroves leaves coasts exposed to floods and storm surges, and removing forest cover increases soil erosion, landslides and flooding.

(Activity 12.5) How do plants get their food, and how are organisms classified by what they eat?

ANSWER Plants make their own food by photosynthesis, so they are producers (autotrophs). Organisms that cannot make food and depend on others are consumers (heterotrophs). By diet, consumers are herbivores (eat only plants, e.g. deer, hare), carnivores (eat only animals, e.g. leopard) and omnivores (eat both, e.g. crows, foxes, mice).

Class 8 Science Curiosity Chapter 12 Solutions — Keep the Curiosity Alive

1. Refer to the given diagram (Fig. 12.19) and select the wrong statement. (i) A community is larger than a population.(ii) A community is smaller than an ecosystem.(iii) An ecosystem is part of a community.

ANSWER The wrong statement is (iii) “An ecosystem is part of a community.” The correct order from smallest to largest is population → community → ecosystem. So a population is part of a community, and a community is part of an ecosystem — not the other way round. Statements (i) and (ii) are correct.

2. A population is part of a community. If all decomposers suddenly disappear from a forest ecosystem, what changes do you think would occur? Explain why decomposers are essential.

ANSWER If all decomposers disappeared, dead plants, dead animals and waste would pile up instead of breaking down. Nutrients locked in the dead matter would not return to the soil, so the soil would lose fertility and plants (producers) would struggle to grow. With weaker plant growth, food for consumers would fall and the whole food web would be disturbed. Decomposers are essential because they break down complex substances into simpler ones and recycle nutrients back into the soil, keeping the ecosystem running. In nature, nothing is wasted — decomposers make that possible.

3. Selvam from Cuddalore district, Tamil Nadu, shared that his village was less affected by the 2004 Tsunami compared to nearby villages due to the presence of mangrove forests. This surprised Sarita, Shabnam, and Shijo. They wondered if mangroves were protecting the village. Can you help them understand this?

ANSWER Yes, the mangroves protected Selvam’s village. Mangrove forests grow thickly along the coast with dense roots and stems that act as a natural barrier. During the tsunami, this barrier slowed down the strong waves and winds and reduced their force before they reached the village, so there was less damage. This is the same reason the Sundarbans protect the coast during storms and floods. It shows how a healthy ecosystem directly benefits and protects humans.

4. Look at this food chain: Grass → Grasshopper → Frog → Snake. If frogs disappear from this ecosystem, what will happen to the population of grasshoppers and snakes? Why?

ANSWER Grasshoppers would increase. Frogs eat grasshoppers; with no frogs to control them, the grasshopper population would grow unchecked and damage more grass. Snakes would decrease. Snakes feed on frogs; losing their food source, the snake population would fall (unless they find other prey). This shows how removing one link disturbs the whole food chain — the level below increases and the level above decreases.

5. In a school garden, students noticed fewer butterflies the previous season. What could be the possible reasons? What steps can students take to have more butterflies on campus?

ANSWER Possible reasons: fewer flowering plants (less nectar), use of pesticides/insecticides that kill butterflies and caterpillars, loss of host plants on which they lay eggs, pollution, or changes in weather. Steps to attract more butterflies: plant more nectar-rich flowers and host plants, stop or reduce the use of chemical pesticides, keep a shallow water source, and avoid disturbing caterpillars — creating a small butterfly-friendly garden.

6. Why is it not possible to have an ecosystem with only producers and no consumers or decomposers?

ANSWER An ecosystem needs all three groups to keep nutrients cycling. With only producers, dead plant matter would accumulate and the nutrients in it would never return to the soil. Without decomposers, dead matter would not be broken down and recycled, so the soil would soon run out of nutrients for plants. Without consumers, plant populations would not be controlled and energy would not flow through higher trophic levels. So the producers, consumers and decomposers depend on one another — an ecosystem cannot work with producers alone.

7. Observe two different places near your home or school (e.g., a park and a roadside). List the living and non-living components you see. How are the two ecosystems different?

ANSWER Example observations:
PlaceLiving (biotic) componentsNon-living (abiotic) components
ParkGrass, trees, flowers, butterflies, birds, squirrels, earthwormsSoil, water, air, sunlight, stones
RoadsideA few hardy grasses/weeds, stray dogs, crows, antsConcrete, dust, air (often polluted), sunlight, little soil
Difference: the park is richer and more balanced, with more plants, more animals and fertile soil, so it supports greater biodiversity. The roadside has fewer living things, poorer soil and more pollution, so it supports far less life.

8. ‘Human-made ecosystems like agricultural fields are necessary, but they must be made sustainable.’ Comment on the statement.

ANSWER Agricultural fields are necessary because they produce the food a growing population needs and are a major livelihood in India. However, unsustainable methods — overuse of synthetic fertilisers and pesticides, excessive groundwater extraction and monoculture — reduce soil fertility, harm useful microbes and pollinators, and damage the environment and human health. So such ecosystems must be made sustainable through organic and natural farming, crop rotation, composting and reduced chemical use, so they keep feeding us without destroying the soil and the environment.

9. If the Indian hare population (Fig. 12.20) drops because of a disease, how would it affect the number of other organisms?

ANSWER In the food web (Sun → grass and plants → hare/deer → fox/eagle), the hare is a herbivore eaten by predators like the fox and the eagle. If hares drop, their predators (fox and eagle) lose a food source, so their numbers may fall — or they may hunt other prey such as deer or mice more heavily, putting pressure on those populations. With fewer hares grazing, the grass and plants they ate may increase. This shows how a change in one population ripples through the whole food web and disturbs its balance.

Common Misconceptions to Avoid

Watch out for these

  • Confusing the order of levels — correct order is population → community → ecosystem, not the reverse.
  • Thinking decomposers are unimportant — without them nutrients are never recycled and the soil loses fertility.
  • Treating a food chain and a food web as the same — a web is many food chains interlinked.
  • Believing only plants are biotic — animals and microbes are also biotic; only air, water, soil, sunlight and temperature are abiotic.
  • Mixing up the interactions — mutualism (both benefit), commensalism (one benefits, other unaffected), parasitism (one benefits, other harmed).
  • Assuming human-made ecosystems run by themselves — unlike natural ones, farms and parks need human care and management.

Extra Practice Questions

Very Short Answer Type Questions

Q1. What is a habitat?

ANSWERA habitat is the place that provides the right conditions for an organism to live and grow.

Q2. What are organisms that break down dead matter called?

ANSWERDecomposers or saprotrophs (e.g. fungi and bacteria).

Q3. Name the two main types of ecosystems in nature.

ANSWERAquatic ecosystems (ponds, rivers, lakes) and terrestrial ecosystems (forests, grasslands, deserts).

Short Answer Type Questions

Q1. Differentiate between biotic and abiotic components with examples.

ANSWERBiotic components are the living parts of a habitat — plants, animals and microbes. Abiotic components are the non-living parts — air, water, soil, sunlight and temperature. The two interact to form an ecosystem.

Q2. What is the difference between a food chain and a food web?

ANSWERA food chain is a simple linear sequence showing ‘who eats whom’ (e.g. grass → grasshopper → frog → snake). A food web is a network formed when many food chains in an ecosystem are interlinked, because most organisms are eaten by more than one kind of organism.

Long Answer Type Question

Q1. Explain mutualism, commensalism and parasitism with one example each.

ANSWER Mutualism: both organisms benefit — e.g. honeybees get nectar while flowers get pollinated. Commensalism: one organism benefits and the other is unaffected — e.g. an orchid growing on a tree gets physical support while the tree branch is not affected. Parasitism: one organism benefits while the other is harmed — e.g. ticks feed on a dog’s blood and the dog gets skin irritation. These interactions are all part of the complex web of life in an ecosystem.

MCQs & Assertion–Reason

1. The living parts of a habitat are called:

(a) abiotic components    (b) biotic components    (c) producers only    (d) trophic levels

2. A group of organisms of the same kind living together in a habitat is a:

(a) community    (b) ecosystem    (c) population    (d) food web

3. Green plants that make their own food are called:

(a) consumers    (b) decomposers    (c) producers    (d) parasites

4. Organisms that eat both plants and animals are:

(a) herbivores    (b) carnivores    (c) omnivores    (d) autotrophs

5. A network of interlinked food chains is called a:

(a) food chain    (b) food web    (c) trophic level    (d) habitat

6. Fungi and bacteria that break down dead matter are:

(a) producers    (b) herbivores    (c) decomposers    (d) carnivores

7. In the relationship between honeybees and flowers, both benefit. This is an example of:

(a) parasitism    (b) commensalism    (c) competition    (d) mutualism

8. The largest mangrove forest in the world, a UNESCO World Heritage Site, is the:

(a) Western Ghats    (b) Sundarbans    (c) Chilika Lake    (d) Manas forest

9. Growing the same crop repeatedly on the same land is called:

(a) crop rotation    (b) monoculture    (c) decomposition    (d) pollination

10. The position an organism occupies in a food chain is called its:

(a) habitat    (b) population    (c) trophic level    (d) community

Answer key: 1-(b), 2-(c), 3-(c), 4-(c), 5-(b), 6-(c), 7-(d), 8-(b), 9-(b), 10-(c).

For each Assertion–Reason question, choose: (A) Both true and the Reason correctly explains the Assertion; (B) Both true but the Reason is not the correct explanation; (C) Assertion true, Reason false; (D) Assertion false, Reason true.

A-R 1. Assertion: Decomposers are essential for an ecosystem.

Reason: They break down dead matter and recycle nutrients back into the soil.

A-R 2. Assertion: Mangrove forests can protect coastal villages during storms and tsunamis.

Reason: Their dense roots and stems slow down strong waves and winds.

A-R 3. Assertion: A food web is more realistic than a single food chain.

Reason: In nature most organisms are eaten by only one type of organism.

A-R 4. Assertion: Green plants are called producers.

Reason: Plants depend on other organisms for their food.

A-R 5. Assertion: Overuse of synthetic fertilisers and pesticides makes farming unsustainable.

Reason: It reduces soil fertility, harms useful microbes and pollinators, and damages the environment.

Answer key: 1-(A), 2-(A), 3-(C), 4-(C), 5-(A).

Quick Revision Summary

  • A habitat provides the right conditions for an organism to live and grow; it has biotic (plants, animals, microbes) and abiotic (air, water, soil, temperature) components.
  • The interaction of biotic and abiotic components in an area forms an ecosystem — terrestrial (forests, grasslands, deserts) or aquatic (ponds, lakes, seas, oceans).
  • Levels of organisation: individual → population → community → ecosystem.
  • Organisms are producers (plants), consumers (herbivores, carnivores, omnivores) and decomposers (bacteria, fungi) that recycle nutrients.
  • Food chains show who eats whom; food webs show how chains interconnect; positions in a chain are trophic levels.
  • Relationships include mutualism (both benefit), commensalism (one benefits, other unaffected) and parasitism (one benefits, one harmed).
  • Ecosystems give clean air, water, food, medicine and climate regulation; pollution, deforestation, habitat loss and overexploitation threaten them, so conservation (national parks, sanctuaries) is vital.

Real-life Applications

This chapter explains many everyday observations: why mangrove forests like the Sundarbans shield coasts from tsunamis and storms; why over-harvesting Indian bullfrogs led to more crop pests and forced India to ban the export of frog legs; why elephant corridors are marked so herds can move safely without entering villages; and why farmers turn to organic and natural farming to protect soil, pollinators and food security. It also explains how decomposers keep soil fertile and how protecting national parks and biosphere reserves safeguards biodiversity for future generations.

How to score full marks in this chapter

Learn the four levels (individual → population → community → ecosystem) in the correct order. Be able to define producer, consumer and decomposer with one example each, and draw a simple food chain and food web. For “what if” questions (a species disappears), always trace the effect both up and down the chain. Remember one example each of mutualism, commensalism and parasitism, and link conservation to a real case like the Sundarbans.

Frequently Asked Questions

What is Class 8 Science Curiosity Chapter 12 about?

How Nature Works in Harmony covers habitats, biotic and abiotic components, populations, communities and ecosystems, food chains, food webs and trophic levels, producers/consumers/decomposers, interactions like mutualism and parasitism, and conservation of ecosystems such as the Sundarbans.

What is the difference between a food chain and a food web?

A food chain is a single linear ‘who eats whom’ sequence, while a food web is a network of many interlinked food chains, since most organisms are eaten by more than one kind of organism.

How many questions are in the “Keep the curiosity alive” exercise of Chapter 12?

There are 9 questions, all solved on this page along with the “Probe and ponder” and in-text prompts.

Are these Class 8 Science Curiosity Chapter 12 solutions free?

Yes. All ClearStudy NCERT solutions for Class 8 Science Curiosity are free and follow the official NCERT textbook for 2026–27.

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