What is Nature Harmony Exercises in Class 8 Science NCERT?

The Class 8 Science NCERT Chapter 12 — How Nature Works in Harmony exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions. It includes multiple-choice questio…

What does the NCERT Class 8 Science How Nature Works in Harmony exercise section cover?

The Class 8 Science NCERT Chapter 12 u2014 How Nature Works in Harmony exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the How Nature Works in Harmony exercises?

Class 8 students should approach the How Nature Works in Harmony exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and ecosystem questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these How Nature Works in Harmony questions competency-based as per NEP 2020?

Yes, the How Nature Works in Harmony exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 12 exercises?

The Chapter 12 u2014 How Nature Works in Harmony exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science How Nature Works in Harmony exercise set present two statements u2014 an Assertion (A) and a Reason (R) u2014 and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting How Nature Works in Harmony exercises is to read through all theory parts of NCERT Curiosity Chapter 12 once, write down the key terms such as NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions u2014 first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

What does the NCERT Class 8 Science How Nature Works in Harmony exercise section cover?

The Class 8 Science NCERT Chapter 12 — How Nature Works in Harmony exercise section tests students on all the key concepts covered in the chapter, including NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions. It includes multiple-choice questions (MCQs), assertion-reason questions, short-answer questions, long-answer questions, and competency-based questions that align with the NCERT Curiosity textbook. Working through these exercises helps Class 8 students reinforce their conceptual understanding, prepare for classroom assessments, and build exam readiness for CBSE school tests. Each question links back to a specific section of the chapter so students can revise the theory alongside the practice.

How should Class 8 students approach the How Nature Works in Harmony exercises?

Class 8 students should approach the How Nature Works in Harmony exercises by first revising the main theory and definitions from each part of the chapter, especially around NCERT exercises and ecosystem questions. Start with the MCQs and assertion-reason questions to quickly test recall, then attempt the short-answer questions that need a one or two-line explanation, and finally tackle the long-answer and competency-based questions that require applying concepts to new situations. Write neat diagrams wherever the question involves a process, cycle, or setup, and always use NCERT-style vocabulary in your answers to match CBSE marking schemes.

Are these How Nature Works in Harmony questions competency-based as per NEP 2020?

Yes, the How Nature Works in Harmony exercise set follows the NEP 2020 competency-based education (CBE) framework used by CBSE and NCERT for Class 8 Science. Instead of only asking students to recall definitions, many questions are scenario-based and require applying the concept to real-life situations, analysing data, or evaluating claims. This matches Bloom's Taxonomy levels L3 (Apply), L4 (Analyse), and L5 (Evaluate), going beyond rote learning. Students practising these questions build the higher-order thinking skills that modern CBSE school exams increasingly assess, and also prepare well for competitive foundation tests in later years.

Which NCERT Curiosity sections are tested in Chapter 12 exercises?

The Chapter 12 — How Nature Works in Harmony exercise set systematically tests every major section of the NCERT Curiosity Class 8 Science textbook for this chapter. Topics covered include NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions. Every in-text question, activity-linked question, and end-of-chapter question from the Curiosity book is represented, so students can be confident that completing this exercise set gives them full coverage of the NCERT syllabus. Teachers also frequently pick questions from these sections for school unit tests and half-yearly exams, making thorough practice essential for strong performance.

How do assertion-reason questions work in this Class 8 Science chapter?

Assertion-reason questions in the Class 8 Science How Nature Works in Harmony exercise set present two statements — an Assertion (A) and a Reason (R) — and ask students to judge whether each is true and whether R correctly explains A. Students pick from four standard options: both true with R explaining A, both true but R not explaining A, A true and R false, or A false. This format tests whether Class 8 learners genuinely understand the cause-and-effect relationships behind NCERT exercises, not just surface facts. Mastering this format is valuable because CBSE Class 10 board exams use the same pattern.

What is the best revision strategy before attempting these exercises?

The best revision strategy before attempting How Nature Works in Harmony exercises is to read through all theory parts of NCERT Curiosity Chapter 12 once, write down the key terms such as NCERT exercises, ecosystem questions, cycle questions, biodiversity questions, competency-based questions in your own words, and then re-do all activities mentally to understand the underlying concept. Next, make a one-page mind map linking the main ideas. Only then attempt the exercise questions — first without looking back, then self-correcting. This active-recall approach builds much stronger long-term memory than repeatedly re-reading the textbook, and is widely recommended by CBSE teachers for Class 8 Science preparation.

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How Nature Works in Harmony — Exercises

🎓 Class 8 Science CBSE Theory Ch 12 — Sound ⏱ ~21 min

🌐 Language: [gtranslate]

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This MCQ module is based on: How Nature Works in Harmony — Exercises

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Chapter 12 — In a Nutshell

In this chapter we explored how the living and non-living parts of Earth fit together into a finely balanced whole. Every forest, pond and paddy field is an ecosystem humming with activity. Energy from the Sun flows through food chains, nutrients spin through water, carbon, oxygen and nitrogen cycles, and countless species weave the fabric of biodiversity. Humans can disturb this harmony — but we can also choose to protect it.

🔑 Big Ideas at a Glance

Ecosystem = living (biotic) + non-living (abiotic) components interacting continuously.
Producers (green plants) trap sunlight by photosynthesis; consumers eat; decomposers recycle.
Food chains show straight-line energy flow; food webs are interlinked chains — far more stable.
Only ~10% of energy passes from one trophic level to the next — that is why food chains are short.
The Sun is the ultimate energy source for every food chain on Earth.
Matter moves in loops: water, carbon, oxygen and nitrogen cycles keep Earth habitable.
Photosynthesis removes CO₂; respiration, burning and decomposition return it. Together they stabilise the atmosphere.
Air is 78% N₂, but plants depend on Rhizobium and other nitrogen-fixing bacteria (and lightning) to make it usable.
Biodiversity = the variety of life: genetic, species and ecosystem levels.
India is a megadiverse country; Western Ghats, Eastern Himalayas, Indo-Burma and Sundaland are its four hotspots.
Human pressures — deforestation, pollution, hunting, climate change, habitat fragmentation — push species towards extinction.
Conservation tools: national parks, wildlife sanctuaries, biosphere reserves, Project Tiger, Project Elephant.
Indigenous wisdom (Bishnoi, sacred groves, Chipko) shows that culture and conservation are natural partners.
Sustainable living is within every student's reach — save energy, save water, reduce-reuse-recycle, compost, plant, walk.

🗝️ Keywords to Remember

Ecosystem

Living + non-living components interacting in a place.

Biotic / Abiotic

Living / non-living factors of an ecosystem.

Producer

Green plants that make food by photosynthesis.

Consumer

Organisms that eat plants or other animals.

Decomposer

Bacteria/fungi that break down dead matter.

Food Chain

Linear sequence showing energy flow.

Food Web

Interconnected food chains; more stable.

Trophic Level

Each step of a food chain.

Water Cycle

Evaporation → condensation → precipitation → runoff.

Carbon Cycle

CO₂ moving through plants, animals, soil, fossil fuels.

Nitrogen Cycle

N₂ fixed, used, released back by bacteria.

Rhizobium

Nitrogen-fixing bacterium in legume root nodules.

Biodiversity

Variety of life at genes, species, ecosystem levels.

Hotspot

Species-rich, threatened region (e.g. Western Ghats).

Extinction

Permanent disappearance of a species.

Conservation

Planned protection of nature for future generations.

Project Tiger

1973 flagship programme to save Bengal tigers.

Elephant Corridor

Forest strip linking larger habitats for safe movement.

Sacred Grove

Community-protected forest patch with religious value.

Sustainable Living

Meeting needs today without harming tomorrow.

📝 Exercises — Test Yourself

Read each question carefully. Try to answer on paper first, then click Show Solution to check yourself.

Q1. Define an ecosystem. Give two examples — one terrestrial and one aquatic.

Solution: An ecosystem is a natural unit in which living organisms (biotic components) and non-living surroundings (abiotic components) interact, exchanging energy and nutrients. Terrestrial example: a forest (such as the Bandipur forest). Aquatic example: a pond, a river or the Chilika lake.

Q2. Classify the following into biotic and abiotic components: earthworm, sunlight, river water, peepal tree, air, bacteria, rock, tiger.

Solution:
Biotic: earthworm, peepal tree, bacteria, tiger.
Abiotic: sunlight, river water, air, rock.

Q3. Construct one food chain each for: (a) a pond ecosystem and (b) a grassland ecosystem. Show arrows in the correct direction.

Solution:
(a) Pond: Algae → Small fish → Big fish → Kingfisher.
(b) Grassland: Grass → Grasshopper → Frog → Snake → Eagle.
Arrows point from the eaten to the eater, showing the direction of energy flow.

Q4. Explain why a food web is more stable than a single food chain.

Solution: In a food web, most consumers have more than one food source. If one species declines, consumers can shift to an alternative food and survive. In a single food chain, the removal of any link starves everything above it. Multiple connections give the web its resilience — which is why preserving species variety keeps ecosystems healthy.

Q5. State the role of decomposers. What would happen to a forest if they disappeared?

Solution: Decomposers (bacteria, fungi, earthworms) break down dead plants, animals and waste, returning nutrients to the soil. If they vanished, dead leaves and bodies would pile up, locking away nutrients. Soil would lose fertility, producers would starve, and eventually consumers would collapse. The entire cycle of matter would halt.

Q6. Draw and label the carbon cycle. Show at least four processes (photosynthesis, respiration, decomposition, combustion).

Solution: A suitable diagram must include a "CO₂ in atmosphere" box connected to:
• Plants via photosynthesis (arrow from atmosphere to plants).
• Plants and animals via respiration (arrow from organisms to atmosphere).
• Fossil fuels via combustion (arrow from fuels to atmosphere when burned).
• Dead matter & soil via decomposition (arrow from soil microbes to atmosphere).
Refer to Fig 12.5 in Part 2 for the labelled diagram.

Q7. Although the atmosphere is 78% nitrogen, plants often lack nitrogen in the soil. Explain why, and describe how nature solves this problem.

Solution: Atmospheric nitrogen exists as N₂ gas, held by a very strong triple bond that most plants cannot break. So the gas is useless to them directly. Nature solves the problem through nitrogen fixation: (i) Rhizobium bacteria in the root nodules of legumes (moong, tur, gram) convert N₂ into nitrates; (ii) Certain free-living soil bacteria and blue-green algae also fix nitrogen; (iii) Lightning fixes a small amount during thunderstorms. Plants absorb these nitrates and animals obtain nitrogen by eating plants.

Q8. What is biodiversity? Name the three levels at which it is studied and give one Indian example of each.

Solution: Biodiversity is the variety of living organisms at all levels of organisation. The three levels are:
• Genetic diversity — e.g. hundreds of traditional rice varieties in India (Basmati, Sona-Masuri, Red-rice of Kerala).
• Species diversity — e.g. over 500 bird species recorded in Kaziranga.
• Ecosystem diversity — e.g. Himalayan forests, Thar desert, Sundarbans mangroves, coral reefs of Lakshadweep, all within India.

Q9. List any four human activities that threaten biodiversity. For each, suggest one practical step to reduce the harm.

Solution:

Deforestation — enforce afforestation; protect existing forests; adopt agroforestry that combines trees and crops.
Pollution — ban single-use plastics; treat sewage before release; use organic instead of chemical pesticides.
Poaching/hunting — strengthen wildlife laws; involve local communities in anti-poaching patrols; discourage purchase of wildlife products.
Climate change — shift to renewable energy (solar, wind); reduce private vehicle use; plant native trees that store carbon.

Q10. What is an elephant corridor? Why is it important, and how can humans help keep it functional?

Solution: An elephant corridor is a narrow strip of forest or natural habitat that connects two larger forest areas, allowing elephants to move between them safely. It is important because elephants need huge territories for food, water and breeding; isolated populations risk inbreeding and local extinction. Humans can help by (i) identifying and officially protecting corridors, (ii) building wildlife overpasses/underpasses on highways, (iii) preventing new farms and buildings on corridor paths, (iv) reducing conflict by educating local villagers and paying compensation when elephants damage crops.

Q11. Write short notes on any three of the following: (a) Project Tiger, (b) Bishnoi community, (c) Chipko Movement, (d) Sundarbans, (e) Sacred groves.

Solution:

Project Tiger (1973): India's flagship conservation programme launched to save Bengal tigers. It created a network of tiger reserves (like Jim Corbett, Ranthambore, Bandhavgarh). Tiger numbers have climbed from about 1,800 in 1972 to over 3,600 in 2022.
Bishnoi community: A 15th-century Rajasthan community following 29 rules laid down by Guru Jambheshwar. Cutting living trees and harming animals is forbidden. In 1730, Amrita Devi and 362 other Bishnois sacrificed their lives protecting khejri trees.
Chipko Movement (1973): Villagers of Uttarakhand, led by Sunderlal Bahuguna and Gaura Devi, hugged trees to prevent loggers from cutting them, inspiring a nationwide environmental consciousness.
Sundarbans: The world's largest mangrove forest, shared with Bangladesh. Home to the swimming Royal Bengal tigers and a shield for Kolkata against cyclones.
Sacred groves: Forest patches preserved for religious reasons in states like Meghalaya, Maharashtra and Kerala. They have protected rare species for centuries.

Q12. Suggest five sustainable practices a school can adopt, explaining briefly how each helps nature.

Solution:

Rainwater harvesting — collect monsoon water to recharge groundwater and reduce flooding.
Composting kitchen waste — turns waste into manure, cutting landfill load and producing natural fertiliser for the school garden.
School vegetable/herb garden — grows food locally, teaches students about the soil and biodiversity, and reduces packaging waste.
Paperless classes/online assignments — saves trees and reduces garbage; what must be printed is done on both sides.
Tree-plantation drives with native species — planting peepal, neem, jamun, banyan gives food and shelter to birds and insects, while cooling the campus and cleaning the air.

Remember: The Earth is not a warehouse of "resources" to be used up. It is a living, balanced system. When we care for nature, we care for our own future — because we are one thread in the same web.

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