This MCQ module is based on: Earth as a System: Energy, Matter, and Life — NCERT Exercises
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Earth as a System: Energy, Matter, and Life — NCERT Exercises
🎓 Class 9
Science
CBSE
Theory
Ch 13 — Earth as a System: Energy, Matter, and Life
⏱ ~13 min
🌐 Language: [gtranslate]
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Chapter Summary — Earth as a System
- Earth is a single, integrated system made of four overlapping spheres: geosphere (rocks, soil, interior — crust, mantle, core), hydrosphere (oceans 97%, glaciers, groundwater, rivers, lakes), atmosphere (78% N₂, 21% O₂, layered into troposphere, stratosphere, mesosphere, thermosphere) and biosphere (the zone of life).
- The Sun is the chief external source of energy, driving the water cycle, winds, ocean currents and photosynthesis. Earth's internal heat drives volcanoes and plate movement.
- Matter moves repeatedly through Earth in biogeochemical cycles: water, carbon, nitrogen and oxygen.
- The water cycle involves evaporation, transpiration, condensation, precipitation, infiltration and runoff. The Indian monsoon is a continental-scale water cycle.
- The carbon cycle moves carbon between atmosphere (CO₂), plants (photosynthesis), animals and decomposers (respiration), oceans, and fossil fuels (combustion).
- The nitrogen cycle depends on bacteria — fixation by Rhizobium and Azotobacter, nitrification, ammonification and denitrification. Lightning fixes a small amount.
- The oxygen cycle is a mirror image of the carbon cycle — photosynthesis releases O₂, respiration and combustion consume it.
- An ecosystem = biotic + abiotic components. Producers, consumers and decomposers are linked by food chains and food webs; only ~10% of energy passes to the next trophic level.
- Weather = short-term atmospheric state; climate = long-term average. The south-west monsoon (June–Sept) and the retreating north-east monsoon (Oct–Dec) shape Indian climate.
- Human activities — burning fossil fuels, deforestation, pollution, over-fertilising — disrupt every cycle, leading to climate change, global warming, melting glaciers, rising seas and extreme weather.
- Sustainable development, the 3 R's (Reduce, Reuse, Recycle), renewable energy and conservation movements like the Chipko Movement and the Bishnoi tradition show how communities can live in balance with the spheres.
Keyword Grid
Geosphere
Hydrosphere
Atmosphere
Biosphere
Crust
Mantle
Core
Troposphere
Stratosphere
Ozone Layer
Water Cycle
Evaporation
Condensation
Precipitation
Infiltration
Carbon Cycle
Photosynthesis
Respiration
Decomposition
Combustion
Fossil Fuels
Nitrogen Cycle
Nitrogen Fixation
Rhizobium
Nitrification
Denitrification
Oxygen Cycle
Ecosystem
Biotic
Abiotic
Producer
Consumer
Decomposer
Food Chain
Food Web
10% Law
Weather
Climate
Monsoon
Greenhouse Effect
Global Warming
Climate Change
Pollution
Deforestation
Biodiversity
Sustainability
Renewable Energy
3 R's
Chipko Movement
Bishnoi
Exercises
1Name the four spheres of the Earth and write one example of each.
Geosphere — Himalayan rocks; Hydrosphere — Ganga river; Atmosphere — air we breathe; Biosphere — a banyan tree.
2Why is the Sun called the master driver of Earth's system?
Sunlight evaporates water for the water cycle, heats air to drive winds and monsoons, fuels photosynthesis that supplies food and oxygen, and warms ocean currents. Almost every flow of energy in Earth's spheres can be traced back to solar radiation.
3Distinguish between weather and climate using one example from your own state.
Weather is the short-term state of the atmosphere — for example, "It is cloudy and raining in Pune today." Climate is the long-term average over many years — for example, "Pune has a tropical wet-and-dry climate with a strong south-west monsoon."
4Draw a labelled flow diagram of the water cycle. Mention the role of the Sun.
Cycle: Sun → evaporation from oceans/rivers + transpiration from plants → vapour rises → condensation into clouds → precipitation as rain/snow → infiltration into soil and runoff into rivers → back to oceans. The Sun supplies the energy that lifts water from the surface and keeps the cycle running.
5List four ways carbon enters the atmosphere as CO₂ and two ways it is removed.
Adds CO₂: respiration of plants/animals, decomposition, combustion of fossil fuels, volcanic eruptions. Removes CO₂: photosynthesis by green plants and absorption by ocean water/phytoplankton.
6Why are leguminous plants important for soil fertility?
Their root nodules house Rhizobium bacteria that fix atmospheric N₂ into ammonia, enriching the soil with usable nitrogen for the next crop. That is why farmers rotate wheat with chana, moong or groundnut.
7Explain the 10% law of energy transfer in a food chain with an example.
Only about 10% of the energy at one trophic level is stored in the body of the next level. Example: 1000 J in grass → 100 J in deer → 10 J in tiger. The rest is lost as heat through respiration. This is why food chains rarely have more than 4–5 links.
8Differentiate between a food chain and a food web.
A food chain is a single straight line of who eats whom (grass → deer → tiger). A food web is a network of many interconnected food chains because most organisms eat several kinds of food. Real ecosystems are food webs, not isolated chains.
9Describe the Indian south-west monsoon. How is it different from the retreating monsoon?
The south-west monsoon (June–September) blows from the Arabian Sea and Bay of Bengal towards a hot, low-pressure Indian land mass, bringing rain to most of the country. The retreating (north-east) monsoon (October–December) blows from the cool land out to sea, picks up moisture over the Bay of Bengal and gives rain mainly to Tamil Nadu and parts of Andhra Pradesh.
10What is the greenhouse effect? Why is it both essential and dangerous?
It is the trapping of outgoing infrared heat by gases like CO₂, CH₄ and water vapour in the atmosphere. The natural greenhouse effect keeps Earth's average temperature about 33 °C warmer than it would be — without it the planet would freeze. The danger comes from the enhanced greenhouse effect, when humans add too much CO₂ and methane, raising temperatures and causing climate change.
11List four observable effects of climate change in India.
(i) Retreating Himalayan glaciers like Gangotri; (ii) rising sea levels threatening Mumbai, Sundarbans and Kolkata; (iii) more intense floods in Kerala and Assam, droughts in Marathwada; (iv) erratic monsoon — fewer but heavier rain spells, longer dry periods.
12How does deforestation affect the water cycle and the carbon cycle simultaneously?
Trees release water vapour through transpiration; cutting them reduces local rainfall and disturbs the water cycle. They also lock up carbon by photosynthesis; removing them releases that stored carbon as CO₂ and removes a major sink, accelerating global warming.
13Explain the 3 R's with one example each from your daily life.
Reduce: switch off lights when leaving a room. Reuse: carry a refillable steel water bottle instead of plastic. Recycle: hand over old newspapers and metal cans to the kabadiwala for recycling.
14Write a short note on the Chipko Movement and its importance.
The Chipko Movement began in 1973 in the Garhwal region of Uttarakhand. Villagers led by figures like Sunderlal Bahuguna and Gaura Devi hugged trees ("chipko" = "to stick") to stop contractors from cutting them. The movement led to a 15-year ban on commercial logging in the region, protected fragile Himalayan slopes from erosion and inspired environmental movements across India and the world.
15Suggest five practical actions a Class IX student can take to support sustainability.
(i) Walk, cycle, or use public transport for short trips; (ii) save electricity by switching off fans, lights and chargers when not in use; (iii) avoid single-use plastic — carry a cloth bag and steel bottle; (iv) plant and care for trees on World Environment Day; (v) segregate waste at home into wet, dry and hazardous, and educate younger siblings and neighbours about why it matters.
Frequently Asked Questions — NCERT Exercises & Intext Questions
How do I solve NCERT Class 9 Science Chapter 13 (Earth as a System: Energy, Matter, and Life) exercise questions for the CBSE board exam?
Solve NCERT Chapter 13 — Earth as a System: Energy, Matter, and Life — exercise questions by first reading the question carefully, writing down the given data, recalling the relevant concepts like spheres of earth, biogeochemical cycles, ecosystem, and applying them step by step. This Part 4 covers every intext and end-of-chapter exercise from the NCERT textbook. Write balanced equations, label diagrams clearly and show each step — CBSE Class 9 examiners award step marks even if the final answer has a small slip. Practising these solutions strengthens conceptual clarity and builds speed for both the school exam and the upcoming Class 10 board exam.
Are the NCERT intext questions from Earth as a System: Energy, Matter, and Life important for the Class 9 Science exam?
Yes, NCERT intext questions for Chapter 13 Earth as a System: Energy, Matter, and Life are highly important for the CBSE Class 9 Science exam. Many questions in school and competitive papers are directly lifted or only slightly modified from these intext questions, and they test the foundational concepts — spheres of earth, biogeochemical cycles, ecosystem — that chapter-end questions and the Class 10 board build on. Attempt every intext question first, then move on to the exercises. This practice ensures complete NCERT coverage, which is the CBSE syllabus's primary source.
What types of questions from Earth as a System: Energy, Matter, and Life are asked in the Class 9 Science exam?
The Class 9 Science paper (CBSE pattern) asks a mix of question types from Earth as a System: Energy, Matter, and Life: 1-mark MCQ and assertion-reason, 2-mark short answers, 3-mark explanations, 5-mark long answers with diagrams or derivations, and 4-mark competency-based / case-study questions. These test understanding of spheres of earth, biogeochemical cycles, ecosystem, climate change. Practising every NCERT exercise and intext question prepares you to answer all of these formats with confidence.
How many marks does Chapter 13 — Earth as a System: Energy, Matter, and Life — typically carry in the Class 9 Science paper?
Chapter 13 — Earth as a System: Energy, Matter, and Life — is part of the CBSE Class 9 Science syllabus and typically contributes 5–9 marks in the annual paper, depending on the year's weightage. Questions are drawn from definitions, reasoning, numerical/descriptive problems and diagrams on topics like spheres of earth, biogeochemical cycles, ecosystem. Solving the NCERT exercises in this part is essential because CBSE directly references the NCERT Exploration textbook for question design.
Where can I find step-by-step NCERT solutions for Chapter 13 Earth as a System: Energy, Matter, and Life Class 9 Science?
You can find complete, step-by-step NCERT solutions for Chapter 13 Earth as a System: Energy, Matter, and Life Class 9 Science on MyAiSchool. Every intext and end-of-chapter exercise question is solved with full working, labelled diagrams and CBSE-aligned mark distribution. Solutions highlight key points about spheres of earth, biogeochemical cycles, ecosystem that examiners look for. This makes revision quick and exam-focused for Class 9 CBSE students.
What is the best way to revise Earth as a System: Energy, Matter, and Life for the Class 9 Science exam?
The best way to revise Earth as a System: Energy, Matter, and Life for the CBSE Class 9 Science exam is a three-pass approach. First pass: skim the chapter and note down key terms like spheres of earth, biogeochemical cycles, ecosystem in a one-page mind map. Second pass: solve every NCERT intext and exercise question without looking at the solution, then self-check. Third pass: attempt sample papers and competency-based questions under timed conditions. This structured revision secures full marks for this chapter.
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