This MCQ module is based on: Ecosystems, Climate and Human Impact
TOPIC 49 OF 50
Ecosystems, Climate and Human Impact
🎓 Class 9
Science
CBSE
Theory
Ch 13 — Earth as a System: Energy, Matter, and Life
⏱ ~19 min
🌐 Language: [gtranslate]
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This assessment will be based on: Ecosystems, Climate and Human Impact
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Introduction: From a Single Pond to a Whole Planet
A village pond in Bihar contains lily pads, fish, frogs, water beetles, mud, dissolved oxygen, sunlight and warmth. Each living thing depends on the others and on the non-living conditions around it. Zoom out and you find the same kind of mutual dependence in a forest, a desert, a coral reef, or the entire planet. Understanding these relationships — and how humans are upsetting them — is the central concern of environmental science.
13.13 What Is an Ecosystem?
An ecosystem has two parts working together:
- Biotic components — every living thing: plants, animals, microbes.
- Abiotic components — the non-living surroundings: sunlight, temperature, water, air, soil, minerals.
Roles within an ecosystem
| Role | What they do | Examples |
|---|---|---|
| Producers | Make their own food using sunlight (photosynthesis) | Grass, mango tree, phytoplankton |
| Consumers | Eat producers or other consumers | Deer (herbivore), tiger (carnivore), human (omnivore) |
| Decomposers | Break down dead matter, recycling nutrients | Bacteria, fungi, earthworms |
13.14 Food Chains, Food Webs and the 10% Rule
A simple food chain shows who eats whom in one straight line, energy flowing from one link to the next.
The 10% law
When energy passes from one level of the food chain to the next, only about 10% of it is stored in the next organism's body. The other 90% is used up in respiration, lost as heat, or remains undigested. This is why food chains are usually only 3–4 links long — there isn't enough energy for further levels.
Food web: Real ecosystems have many criss-crossing food chains because most animals eat several kinds of food. The interconnected network is called a food web. A grass-cricket-frog-snake-eagle-kite chain in a paddy field shares organisms with several other chains.
13.15 Weather, Climate and the Indian Monsoon
Many people use the words "weather" and "climate" as if they mean the same thing. They do not.
| Weather | Climate |
|---|---|
| Day-to-day state of the atmosphere | Average pattern of weather over many years (usually 30+) |
| "It is raining in Mumbai today." | "Mumbai has a tropical wet climate." |
| Changes by the hour | Changes very slowly |
The Indian monsoon
India's most important weather phenomenon is the monsoon.
- South-West Monsoon (June – September): The land heats up faster than the sea in summer. Hot, low-pressure air rises over India and moist winds rush in from the Arabian Sea and Bay of Bengal, bringing the rains that fill our wells and fields.
- North-East (Retreating) Monsoon (October – December): The land cools, the wind reverses, and dry winds blowing out to sea pick up moisture over the Bay of Bengal before bringing rain to the Coromandel coast (Tamil Nadu, parts of Andhra).
13.16 Climate Change and Global Warming
The atmosphere naturally traps some of the Sun's heat — the so-called greenhouse effect. This is what keeps the planet warm enough for life. The trouble begins when humans add extra greenhouse gases — mainly CO₂ and methane — much faster than nature can absorb them. The result is global warming: a steady rise in average temperatures.
🌡️ Greenhouse Effect Analyser — Click each part to compare its role L4 Analyse
Click incoming sunlight, the reflected/trapped heat arrows, and each greenhouse-gas molecule (CO₂, CH₄, H₂O) to analyse how each contributes to natural warming and to human-driven global warming.
Click any arrow or molecule above to compare its role in the natural greenhouse effect and the enhanced (human-driven) effect.
Visible effects in India
- Melting Himalayan glaciers — Gangotri and other glaciers that feed our rivers are retreating year by year.
- Rising sea levels threaten coastal cities like Mumbai, Kolkata and Chennai, and low-lying islands such as the Sundarbans.
- Extreme weather events — more intense cyclones, floods in Kerala and Assam, heatwaves in northern plains, droughts in Marathwada.
- Erratic monsoon — total rainfall may be similar but is concentrated into fewer, heavier downpours.
13.17 Pollution — Spoiling the Spheres
| Type | Major Indian sources | Effects |
|---|---|---|
| Air pollution | Vehicles, coal power plants, stubble burning, brick kilns, dust | Smog, respiratory disease, acid rain |
| Water pollution | Sewage, industrial effluents, fertiliser run-off, plastic waste | Polluted Ganga and Yamuna, fish kills, unsafe drinking water |
| Soil pollution | Pesticides, plastic, e-waste, untreated waste dumps | Falling soil fertility, food chain contamination |
| Noise pollution | Traffic, loudspeakers, construction | Hearing damage, stress, sleep loss |
13.18 Deforestation
India's forest cover faces continuous pressure from agriculture, mining, dam projects and urban expansion. Cutting trees:
- removes a huge carbon sink, raising atmospheric CO₂;
- destroys habitats — driving species like the great Indian bustard towards extinction;
- causes soil erosion and floods because tree roots no longer hold the soil;
- reduces local rainfall because forests release water vapour through transpiration.
13.19 Sustainability and Conservation
Sustainable development is the principle of meeting today's needs without robbing future generations. It rests on practical actions:
- Protecting biodiversity — national parks like Jim Corbett, Kaziranga, Gir; tiger reserves under Project Tiger.
- Sustainable agriculture — crop rotation, organic farming, drip irrigation, restoring traditional water harvesting structures (johads, step-wells).
- Renewable energy — solar farms in Rajasthan, wind farms in Tamil Nadu, hydropower, biogas plants.
- 3 R's — Reduce, Reuse, Recycle — using less, using again, and turning waste into raw material.
Indian community movements
Chipko Movement (1973, Uttarakhand): Villagers led by Sunderlal Bahuguna, Gaura Devi and others hugged trees ('chipko' means 'to stick') to stop them from being cut down. The protest forced a government ban on commercial logging in the Himalayan foothills and inspired environmental movements worldwide.
The Bishnoi tradition (Rajasthan): The Bishnoi community has, for over 500 years, lived by 29 principles that include protecting trees and wild animals. In 1730, 363 Bishnois led by Amrita Devi gave their lives to save khejri trees from being felled — possibly the world's first organised conservation sacrifice.
Activity 13.3 — Auditing Your Carbon FootprintL5 Evaluate
Predict first: Which one daily habit at home contributes the most to your family's CO₂ output — lighting, cooking, transport, or appliances?
- For one full day, note every activity that uses electricity, fuel or LPG. Record start time, end time and what was done.
- Group activities into: lighting, cooking, transport, appliances, water heating.
- For each group, estimate the total minutes used.
- List two specific changes (e.g. switching off fans, sharing transport, using a pressure cooker) you could try this week.
- Track for one more day after the changes — did the totals fall?
Sample finding: Most urban Indian families spend the largest share of energy on transport (private vehicle use) and cooling (fans, ACs). Even small changes — using a fan instead of an AC where possible, walking short distances, switching off standby lights — can cut a household's CO₂ output by 10–20%. Multiplied across millions of households, this adds up to an enormous national impact.
Competency-Based Questions L4 Analyse
A class of Class IX students visits a wetland near Bhopal. They count 1000 kg of grass, 100 kg of grasshoppers, 10 kg of frogs and 1 kg of small herons in the area. Their teacher asks them to use this data to explain a key ecological idea.
1. Which ecological law does the data illustrate?
(b) Each higher level holds about 10% of the biomass of the level below — the classic 10% energy transfer rule.
2. Identify the producer and the top consumer in this food chain.
Producer = grass; top consumer = small heron. The grasshopper is the primary consumer and the frog the secondary consumer.
3. Differentiate weather and climate with one Indian example each.
Weather is the short-term state — e.g. a thunderstorm in Delhi this evening. Climate is the long-term average — e.g. Delhi has a hot semi-arid climate with summer monsoon.
4. Fill in the blank: The ____________ Movement of 1973 in Uttarakhand involved villagers hugging trees to prevent felling.
Chipko Movement.
5. Why does cutting forests worsen climate change AND increase soil erosion at the same time?
Trees absorb CO₂ and store carbon — losing them adds CO₂ to the air, accelerating warming. Tree roots also bind soil and slow rainwater runoff; without them, topsoil is washed away by rains.
Assertion–Reason Questions L4 Analyse
Options: (A) Both A and R true, R explains A. (B) Both true, R does not explain A. (C) A true, R false. (D) A false, R true.
A: Food chains rarely have more than four or five links.
R: Only about 10% of the energy at one trophic level passes to the next, so energy soon runs out.
(A) Both correct and the reason directly explains the assertion.
A: The greenhouse effect is harmful and should be eliminated.
R: Greenhouse gases trap outgoing heat radiation in the atmosphere.
(D) The reason is correct, but the assertion is false. The natural greenhouse effect is essential — only the enhanced greenhouse effect from human emissions is harmful.
A: The Bishnoi community of Rajasthan is regarded as one of the earliest conservation movements in the world.
R: Their 29 principles include protection of trees and wildlife, and in 1730 community members died to save khejri trees from being cut.
(A) Both true and the reason directly explains the assertion.
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