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Every NCERT book that matters for UPSC — open a book, then a chapter. Learn each chapter's concepts, then how UPSC tests them — with diagrams, flowcharts and the past questions to attempt.
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← Our Environment — all chaptersHuman Environment Interactions: The Tropical and the Subtropical Region
Start here: why this chapter matters
In simple wordsTwo families: one lives where it rains every afternoon and the forest is so thick that the ground is always in shade; the other lives on a wide, flat, crowded plain where everything depends on the summer rains. Both need food, clothes and a home — but the place decides how they get them. This chapter visits both: the Amazon rainforest and the Ganga–Brahmaputra plains.
About this chapter (edition note)In the current book (reprint 2024-25) Chapter 6 is ‘Human Environment Interactions: The Tropical and the Subtropical Region’; its QR code (0762CH08) still carries its old number. The pre-2022 chapter ‘Natural Vegetation and Wildlife’ was removed in NCERT's rationalisation. Vegetation and wildlife are still here — rainforest, deciduous, coniferous and mangrove forests and their animals — and are taught fully in kegy105 (natural vegetation of India), kegy214 (biodiversity) and hess402 (Class 8 resources).
This is Chapter 6 of Our Environment (Class 7 Geography): 10 pages (39–48). It opens with a story — Renuka and her uncle, a wildlife photographer, looking at pictures of people from deserts, frozen lands and rainforests (Fig. 6.1) — and then studies two regions in turn. The Amazon basin (Fig. 6.2): its climate, its rainforest and wildlife (Figs 6.3–6.5), its people and their slash-and-burn farming, and the destruction of the forest (Fig. 6.6). The Ganga–Brahmaputra basin (Figs 6.7–6.8): landforms, monsoon climate, population, crops (Figs 6.9–6.10), vegetation and wildlife (Figs 6.11–6.12), a case study of an ox-bow lake fishery, cities and pollution (Fig. 6.13), transport and tourism (Fig. 6.14). It has two maps, two glossaries, seven ‘Do you know?’ boxes, two ‘Let's do’ boxes, an activity box, a case study and seven exercises ending in a soil activity.
- Builds on gess201 (environment: natural and human; people and nature interacting) and gess203 (ox-bow lakes, flood plains, deltas). Next: gess207 (Life in the Deserts) — the same human–environment lens on the hottest and coldest dry lands.
- Goes further in: kegy105 (India's forest types — tropical evergreen, deciduous, montane, mangrove), kegy214 (biodiversity and its loss), kegy211 (world climates — the equatorial type), kegy103 (the Ganga and Brahmaputra systems), hess402 and hess403 (Class 8 land, soil, forests; agriculture — shifting cultivation, paddy, jute, tea), legy104 (primary activities — shifting cultivation) and legy201 (India's population density).
- UPSC, honestly: Prelims tests the rainforest repeatedly — what makes equatorial forests special (2013), epiphytes (2001), the equatorial daily weather (2015), the rainforest biome (2021), and why its soil is poor once cleared (2003, 2011, 2023) — plus deforestation and soil erosion (1986), biodiversity threats (1993), terraces (1991), paddy and jute in the lower Gangetic plain (2011), the Ganges river dolphin (2014) and the one-horned rhino (2019). Mains GS3 2015 asked about Namami Gange. We link 14; several jhum, soil-erosion and Ganga-basin questions are already linked to three chapters.
| Word | What it means here |
|---|---|
| Equatorial region | The belt close to the equator — the book takes 10°N to 10°S; hot and wet all year |
| Sub-tropical region | In the book, the belt from 10°N to 30°N, where the Ganga–Brahmaputra basin lies |
| Tributary | A smaller river that joins a main river |
| River basin (catchment area) | The area drained by a main river and all its tributaries |
| Mouth | The place where a river flows into another body of water — a sea, lake or bigger river |
| Rainforest | Thick forest of heavy-rainfall regions, with a dense roof (canopy) of leaves |
| Epiphyte † | A plant that grows on another plant for support only, making its own food — orchids, bromeliads |
| Slash and burn | Cutting and burning a patch of forest, farming it for a few years, then moving on while it recovers |
| Manioc (cassava) | A plant with starchy underground roots; the staple food of the Amazon peoples (tapioca is made from it †) |
| Maloca | A large shared house with a steeply slanting roof, home to several families |
| Population density | The number of people living in one square kilometre |
| Terrace farming | Cutting steps into a slope to make flat strips for crops, so water does not run off fast |
| Sericulture | Rearing silkworms to produce silk |
| Mangroves | Salt-tolerant trees of coasts and deltas — the Sundarbans |
| Ox-bow lake (maun) | A crescent lake left when a river bend is cut off (gess203); called a maun in Bihar |
Reading the chapter opening and Fig. 6.1 (page 39)
- Header art: the cartoon sun over a blue band with the number 6 and the title in two lines; a QR code marked 0762CH08 (the old chapter number).
- Fig. 6.1, ‘People from various parts of the world’: a photo collage of children and adults in many styles of dress — a man in braces and a feathered hat, a woman with a lace shawl and fan, children in school clothes, an elderly man with a long white beard, a young man in a powdered wig and red coat, a woman in a bright headscarf. The point the uncle makes: people look different, but they share the same basic needs — food, clothing and shelter, and their children play, sing and help at home like Renuka.
- The story: Renuka's uncle, a wildlife photographer, explains that people in forests learn early to fish and to collect what the forest gives. The point: the way people meet their needs depends on their environment — the theme of the chapter.
At a glance — the six ideas to carry away
- Two basins, two environments: the Amazon (book: ‘equatorial’, 10°N–10°S) and the Ganga–Brahmaputra (book: ‘sub-tropical’, 10°N–30°N). A river basin = a main river + all its tributaries; the Amazon's is the largest in the world.
- Amazon climate: hot and wet all year, rain almost every day, humid nights. Rainforest: a dense leafy roof, a dark damp floor; orchids and bromeliads on branches (epiphytes — the book says ‘parasites’).
- Amazon life: toucans, hummingbirds, macaws; monkeys, sloths, tapirs; anaconda, boa; piranha. People: slash and burn; staple manioc (cassava); cash crops coffee, maize, cocoa; malocas with steep roofs.
- Change: the Trans-Amazon highway (1970), aircraft; indigenous people pushed out; development clears forest; rain washes the bare topsoil away (Fig. 6.6; the three-can activity).
- Ganga–Brahmaputra: monsoon rain mid-June to mid-September. Mountains thinly peopled; plains very densely peopled (Bihar 1,102 vs Uttarakhand 189 per sq km). Paddy main crop; jute, sugarcane, tea (W. Bengal, Assam), silk (Bihar, Assam); terraces on slopes.
- Vegetation and wildlife: conifers in the hills, sal–teak–peepal and bamboo in the plains, mangroves in the delta; one-horned rhino (Brahmaputra plain), Bengal tiger and crocodiles (delta), Susu dolphin; rohu, catla, hilsa. Cities pollute rivers; Namami Gange, Swachh Bharat (2 October 2014).
1. Two regions, two river basins
In simple wordsPour water on a sloping roof with gutters: every little stream runs into a bigger gutter, and all of it leaves through one down-pipe. A river basin works the same way — small rivers (tributaries) feed a main river, and everything leaves through its mouth into the sea. The whole roof is the basin.
The chapter compares two regions. The tropical region the book studies lies very close to the equator, between 10°N and 10°S, so it is called the equatorial region; the River Amazon flows through it, from the mountains in the west to the Atlantic Ocean in the east. The place where a river flows into another body of water is its mouth. Numerous tributaries join the Amazon to form the Amazon basin — the largest river basin in the world (glossary) — which drains portions of Brazil, parts of Peru, Bolivia, Ecuador, Colombia and a small part of Venezuela. The second region, the Ganga–Brahmaputra basin in the Indian subcontinent, lies in the sub-tropical region, which the book places between 10°N and 30°N.
| Fig. 6.2 in words (no map drawn) | What the book's map shows |
|---|---|
| Where | the north of South America, the Amazon basin shaded green across the equator |
| The river | rises in the mountains in the west (the Andes †) and flows east to the Atlantic Ocean; many tributaries join from north and south |
| Countries of the basin (text) | Brazil (most of it), Peru, Bolivia, Ecuador, Colombia, a small part of Venezuela |
| Countries the equator crosses (in-text question) † | Ecuador, Colombia and Brazil |
| Oceans | Pacific to the west of the continent, Atlantic to the east |
Reading Fig. 6.2, the glossary and the ‘Do you know?’ (page 40)
- Fig. 6.2, ‘The Amazon Basin in South America’: a political map of South America with latitude and longitude lines, a scale bar and country names; the basin is shaded green with the main river and its tributaries in blue. The point: the basin straddles the equator and drains several countries into the Atlantic. Converted into the table above; we draw no map.
- Glossary — tributaries: small rivers joining the main river; the main river and all its tributaries form a river basin or catchment area; the Amazon basin is the largest in the world.
- Do you know? — the name: Spanish explorers who met local people wearing headgear and grass skirts were reminded of the legendary women warriors called the Amazons, and named the river after them. (The Amazons are figures of ancient Greek legend; the book says ‘Roman Empire’ — see the note below.)
NCERT details to read carefully — the two regions
- ‘Tropical’: geographers call the whole belt between the Tropic of Cancer and the Tropic of Capricorn (about 23½°N and S) the tropics †. The book's 10°N–10°S is the narrower equatorial belt. Its ‘sub-tropical’ 10°N–30°N band straddles the Tropic of Cancer; most of the Ganga–Brahmaputra basin lies north of it. In an exam, say ‘the Amazon basin lies in the equatorial region’.
- The Amazons belong to ancient Greek mythology, not the ‘Roman Empire’. The river was named by Spanish explorers in the sixteenth century †.
- Spelling: the book's ‘Columbia’ is Colombia (the country).
- Largest basin (area drained) is the Amazon's — a safe, standard fact. Which river is longest (Nile or Amazon) depends on how it is measured †; the book does not say.
2. The Amazon: climate, rainforest and wildlife
In simple wordsThink of a crowded hall where everyone holds an umbrella up high: the umbrellas touch, and the floor below is in deep shade. In the rainforest the umbrellas are the crowns of tall trees. Above them it is bright and wet; below them it is dim, damp and still — and every plant is trying to reach the light.
Lying right on the equator, the Amazon basin is hot and wet throughout the year. Days and nights are almost equally hot and humid; the skin feels sticky. It rains almost every day, often without much warning. Days are hot with very high humidity; at night the temperature falls but the humidity stays high. With such heavy rain, thick forests grow (Fig. 6.3) — so thick that the dense ‘roof’ of leaves and branches stops sunlight reaching the ground, which stays dark and damp; only shade-tolerant plants grow there. Orchids and bromeliads grow on the trees. The forest is rich in animals: birds such as toucans (Fig. 6.4), hummingbirds and macaws, with brilliant feathers, oversized bills and loud calls; monkeys, sloths and tapirs (Fig. 6.5); reptiles and snakes — crocodiles, pythons, anaconda, boa constrictor; thousands of insect species; and fish including the flesh-eating piranha. The basin is ‘extraordinarily rich in the variety of life’.
⤵ Why the forest floor is dark (pp. 40–41)
On the equatorthe sun is high all year, so it is hot every day
Rain almost dailyhot, moist air rises and pours rain, often without warning
Thick forestplenty of heat and water all year let trees grow tall and close together
A roof of leavesthe crowns join and block most of the sunlight
Dark, damp flooronly shade-tolerant plants grow below; others perch on branches to reach the light
| Group | What the book names | Note |
|---|---|---|
| Plants | thick forest; shade-tolerant plants on the floor; orchids, bromeliads | orchids and bromeliads are epiphytes — they grow on trees for support (UPSC 2001) |
| Birds | toucans, hummingbirds, macaws | brilliant plumage, oversized bills, loud calls |
| Mammals | monkeys, sloths, tapirs | tapirs eat leaves and fruit † — not ants (see the note) |
| Reptiles | crocodiles, snakes, pythons, anaconda, boa constrictor | ‘various species… thrive’ |
| Insects | thousands of species | a large part of the forest's variety |
| Fish | several species, including the flesh-eating piranha | in the river |
Reading Figs 6.3–6.5, the bromeliad box and the ‘Let's do’ (page 41)
- Fig. 6.3, ‘The Amazon Forest’: a photograph of a thick, moss-covered branch crowded with small leafy plants growing on it, in dim green light. The point: in the rainforest even the branches carry plants — the epiphytes.
- Fig. 6.4, ‘Toucans’: a drawing of a black bird with a huge orange-and-yellow bill and a white throat, perched upright. The point: the oversized bill the text mentions.
- Fig. 6.5, ‘Tapir’: a drawing of a stocky brown animal with a short, flexible snout, walking. The point: a large forest mammal unlike any in India.
- Do you know? — bromeliads: special plants that store water in their leaves; frogs lay eggs in these pockets of water.
- Let's do: watch wildlife documentaries on TV and share the experience with the class — outline in the activities section.
NCERT details to read carefully — the rainforest
- The book says orchids and bromeliads ‘grow as plant parasites’. They are epiphytes: they grow on trees for support only and make their own food by photosynthesis; parasites take food from their host. UPSC asked exactly this (2001: epiphytes depend on other plants for mechanical support).
- ‘Ant-eating tapirs’: tapirs are plant-eaters (leaves, fruit, shoots) †. The ant-eaters of South America are a different animal (the anteater). Write ‘tapirs’ without ‘ant-eating’.
- The book's word is ‘roof’; the standard term is canopy — UPSC 2013 described ‘tall, closely set trees with crowns forming a continuous canopy’ as an equatorial-forest trait.
- Rich forest, poor soil: heavy rain and rapid decay mean the nutrients sit in the living plants, not in the soil †. This is why cleared rainforest soon loses fertility (section 4; UPSC 2003, 2011, 2023).
Beyond NCERT — the rainforest in brief
- Equatorial climate (kegy211): high temperatures with a small annual range, and rain in every month, often in afternoon thunderstorms — UPSC 2015 quoted exactly this daily pattern (clear morning, heat, clouds, thunder, brief rain) and asked which region it describes: equatorial.
- Other equatorial rainforests: the Congo basin in Africa and South-East Asia; in India, tropical evergreen forests of the Western Ghats, the north-east and the Andaman and Nicobar Islands (kegy105).
- The biome (iest202): leaf litter decomposes faster than anywhere else, so the ground is often almost bare; climbers and epiphytes reach up into the canopy (UPSC 2021).
3. People of the rainforest: farming, food and homes
In simple wordsImagine a garden you use for three years until the soil tires, then leave to grow wild while you dig a new one; years later you come back and the old one is rich again. That is how many forest peoples farm: they borrow a patch from the forest, use it, and give it back to heal.
People of the rainforest grow most of their food in small areas cleared in the forest. In the book's account, men hunt and fish along the rivers while women look after the crops — and, since hunting and fishing are uncertain, it is the women's vegetables that keep families fed. They mainly grow tapioca, pineapple and sweet potato, by slash and burn agriculture. The staple food is manioc, also called cassava, which grows under the ground like the potato. They also eat queen ants and egg sacs. Cash crops — coffee, maize and cocoa — are grown too. The forest gives wood for houses: some families live in thatched houses shaped like beehives; others in large, apartment-like houses called malocas, with a steeply slanting roof.
| Need | How it is met (book) | Why it suits the place |
|---|---|---|
| Food | small cleared plots; manioc (staple), sweet potato, pineapple; fish and game; queen ants and egg sacs | thick forest leaves little open land; rivers and forest supply protein |
| Farming | slash and burn; plots used for a few years, then left to recover | the ash gives nutrients the poor soil lacks; fallow restores it |
| Cash | coffee, maize, cocoa | for sale outside the community |
| Shelter | thatched beehive-shaped houses; large malocas with steep roofs | forest wood and leaves; steep roofs shed the daily rain |
| Work | men hunt and fish; women tend crops (book's account) | a division of labour the book describes; it differs between communities † |
| How to judge slash and burn? (attributed; no verdict) | Who | Position |
|---|---|---|
| A self-renewing system | the book's own box | fallow lets young trees grow back and soil fertility is restored; people can return and cultivate again |
| Sustainable only at low pressure | ecologists and geographers generally † (legy104, hess403) | works when land is plentiful and fallows are long; shorter fallows under growing population degrade soil and forest |
| A threat to biodiversity | a standard textbook and exam view † (UPSC 1993, 1999) | clearing and burning destroy habitat; UPSC 1993 grouped ‘shifting cultivation’ with habitat destruction as a strong threat |
Reading the ‘Do you know? — Slash and Burn’ box (page 42)
- The box explains the method step by step: farmers clear land by slashing trees and bushes, burn them to release nutrients into the soil, grow crops for a few years, abandon the patch when the soil loses its nutrients, and clear another; meanwhile young trees grow in the old field and fertility is restored, so people can return to it. Drawn as our cycle above.
NCERT details to read carefully — farming and food
- Tapioca and manioc are listed as if different; tapioca is the starch made from manioc (cassava) roots † — one plant. Exercise 1(ii) accepts tapioca/manioc, sweet potato, pineapple, and the cash crops coffee, maize and cocoa.
- Manioc ‘grows under the ground like the potato’: its edible part is a swollen root; the potato is a swollen underground stem (a tuber) † — similar use, different organ.
- Exercise 2(ii): manioc is the staple food of the (c) Amazon peoples (in the book's three options).
- Exercise 3(ii): maloca — (d) slanting roof.
- Words: the book's ‘looses’ means loses. Use neutral terms — ‘indigenous peoples’, ‘communities’ — and avoid labels such as ‘primitive’.
4. A changing Amazon: roads, people and a shrinking forest
In simple wordsA quiet village reachable only by boat gets a highway. Trucks arrive, then sawmills, farms and settlers. The road brings goods and jobs to some — and pushes the old residents out and the forest back. Without its trees, the land under the heavy rain is like a sandcastle under a garden hose.
Life in the Amazon basin is slowly changing. In the past, the heart of the forest could be reached only by river. In 1970 the Trans-Amazon highway opened the rainforest to road traffic (the book says ‘all parts’); aircraft and helicopters are also used. The indigenous population was pushed out and forced to settle in new areas, where they continued their own way of farming. Developmental activities are gradually destroying the biologically diverse rainforests; a large area disappears every year. The destruction has wider effects (Fig. 6.6): when the trees go, the topsoil is washed away by the rain and the lush forest becomes a barren landscape. The exercise activity with three cans of soil shows why (Exercise 7).
⤵ How a road changed the rainforest (p. 42)
River onlythe forest's heart could be reached only by boat
1970: the highwaythe Trans-Amazon highway opens the forest to roads; aircraft and helicopters follow
People pushed outindigenous people are moved to new areas, where they keep farming their own way
Forest cleareddevelopmental activities remove a large area of forest every year
Soil lostrain washes the bare topsoil away; lush forest becomes barren land
| Development or forest? (attributed; no verdict) | Who | Position |
|---|---|---|
| Roads and development | the reasoning behind highways and settlement schemes † | roads connect remote areas, open land for farming, mining and settlement, and bring services and markets |
| Forest and biodiversity | the book; conservation scientists † | development is destroying a biologically diverse forest; the cleared soil turns barren |
| The people of the forest | the book; indigenous organisations † | the indigenous population was pushed out; their land and way of life are at stake |
Reading Fig. 6.6, ‘Gradual Destruction of Forests’ (page 42)
- Three painted blocks of land rising diagonally up the page, linked by orange arrows: first a dense green forest; then the forest cut back to one side, with ploughed fields, a farmhouse and a road; finally a bare, brownish slope with a few stumps and gullies. The point: forest is cleared bit by bit, and the end is barren land with its topsoil gone. Redrawn as our three panels.
NCERT details to read carefully — change
- 1970 is when work on the Trans-Amazon highway began † (it opened in stages from 1972); much of it is still unpaved, so ‘made all parts of the rainforest accessible’ overstates it.
- The book gives no figure for forest loss (‘a large area… annually’) — do not invent one.
- Why cleared rainforest fails as farmland: its soil is poor in nutrients — they are held in the plants, and heavy rain leaches the soil once the cover goes. So UPSC 2003's assertion (cleared rainforest yields productive farmland for years without fertiliser) is false, while its reason (high primary productivity) is true; 2011: it regenerates slowly because the soil is deficient in nutrients; 2023: ‘rich in nutrients’ is incorrect, fast decomposition is correct.
- Exercise 4(i): rainforests are depleting because of developmental activities — roads, settlement, clearing for farms — and the bare soil then washes away.
Beyond NCERT — why the Amazon matters beyond South America
- Forests store carbon; clearing and burning them releases it and adds to climate change (kegy214, kegy211).
- Deforestation is a leading cause of soil erosion (UPSC 1986) and of biodiversity loss (UPSC 1993; kegy214).
- India's own tropical forests face the same pressures; protected areas such as national parks and sanctuaries are one response (kegy105; Mains GS1 2023 asked about sanctuaries in India's rainforest regions — linked there).
5. The Ganga–Brahmaputra basin: rivers, land and climate
In simple wordsPicture a staircase that ends in a huge, flat courtyard by the sea. The top steps are the Himalayan mountains, steep and cold; the courtyard is the great plain, built from mud the rivers carried down; at its edge, where the rivers meet the sea, is a maze of channels and mangroves — the delta.
The tributaries of the Ganga and the Brahmaputra together form the Ganga–Brahmaputra basin in the Indian subcontinent (Fig. 6.8), in the book's sub-tropical belt (10°N–30°N). Ganga tributaries such as the Ghaghra, Son, Chambal, Gandak and Kosi, and the tributaries of the Brahmaputra, drain it. Its main features are the plains of the Ganga and the Brahmaputra, the mountains and foothills of the Himalayas, and the Sundarbans delta; ox-bow lakes dot the plain. The climate is monsoon: rain from mid-June to mid-September, hot summers and cool winters. The basin's topography varies, and the environment strongly shapes where people live.
| Fig. 6.8 in words (no map drawn) | What the book's map shows |
|---|---|
| The Ganga | rises in the Himalayas in the north-west of the basin and flows south-east across the plain to the Bay of Bengal, joined by many tributaries from the north (Himalayan) and the south (peninsular) |
| The Brahmaputra | flows east across Tibet (China) north of the Himalayas, turns south and west through north-east India (Assam) and south into Bangladesh |
| Where they meet | in Bangladesh, before reaching the Bay of Bengal through the delta |
| Neighbours shown | Nepal and Bhutan (on the northern side of the basin), Bangladesh, China (Tibet), Myanmar; the Tropic of Cancer crossing the lower basin |
| Map-skills content as tables (Exercise 5-i) † | Ganga | Brahmaputra |
|---|---|---|
| Source | Gangotri glacier (as the Bhagirathi); joined by the Alaknanda at Devprayag (kegy103) | Chemayungdung glacier near Lake Mansarovar in Tibet (kegy103) |
| Important tributaries | Yamuna (with the Chambal), Ramganga, Gomti, Ghaghara, Gandak, Kosi (north bank); Son (south bank) | Subansiri, Manas, Teesta (right bank — from the Himalayas); Dibang, Lohit, Dhansiri (left bank) |
| Names along the way | Bhagirathi–Hooghly in West Bengal; Padma in Bangladesh | Tsangpo (Tibet), Siang or Dihang (Arunachal Pradesh), Brahmaputra (Assam), Jamuna (Bangladesh) |
| Mouth | the Bay of Bengal, through the Ganga–Brahmaputra (Sundarbans) delta, after joining the Brahmaputra and then the Meghna | the same |
Reading Figs 6.7–6.8 and the ‘Let's do’ (pages 43–44)
- Fig. 6.7, ‘Brahmaputra river’: a photograph of a wide, calm river at sunset, the sky and water orange, a small boat in the middle and hills on the far bank. The point: the Brahmaputra is a very broad river.
- Fig. 6.8, ‘Ganga–Brahmputra Basin’: a map of India and its neighbours with the basin shaded green and the two river systems in blue, arrows showing the direction of flow; Nepal, Bhutan, Bangladesh, China (Tibet) and Myanmar labelled; the Tropic of Cancer dotted. The point: two great river systems join to drain the north and north-east of the subcontinent. Converted into the tables above; we draw no map.
- Let's do: the Brahmaputra has different names in different places — outline in the activities section.
- In-text tasks: name some Brahmaputra tributaries (p. 43) and the states in which the basin lies (p. 44) — outlines in the activities section.
NCERT details to read carefully — rivers and climate
- The Chambal is named as a Ganga tributary; it joins the Yamuna, which joins the Ganga at Prayagraj (Allahabad) † — so it is in the basin, but as a tributary of a tributary.
- Brahmaputra drainage is antecedent — older than the Himalayas it cuts through (UPSC 1989, linked to kegy103).
- ‘Monsoon’ means a seasonal reversal of winds (UPSC 2014 — on kegy104, kegy211): here most rain falls in about three months, mid-June to mid-September.
- Spellings: ‘Brahmputra’ (caption), ‘difference places’ (Let's do) — read Brahmaputra, different places.
6. People, crops and population density
In simple wordsWhere would you build a house: on a steep, rocky hillside or on flat, soft, well-watered ground near a river? Most people choose the flat ground — so it fills up. That simple choice, made by millions over centuries, is why the Ganga plain is one of the most crowded places on earth while the mountains above it are thinly peopled.
Mountain areas with steep slopes have inhospitable terrain, so fewer people live there. The plains provide the most suitable land: the soil is fertile, and agriculture is the main occupation where flat land is available. The population density of the plains is very high. The main crop is paddy (Fig. 6.9); because paddy needs plenty of water, it is grown where rainfall is high. Wheat, maize, sorghum, gram and millets are also grown, with cash crops — sugarcane and jute. Bananas grow in parts of the plain; tea grows in plantations in West Bengal and Assam (Fig. 6.10); silk comes from rearing silkworms in parts of Bihar and Assam. In the mountains and hills, where slopes are gentle, crops are grown on terraces.
⤵ Why paddy is the main crop of the plains (Exercise 4-ii)
Monsoon rainheavy rain from mid-June to mid-September
Flat landfields can be bunded and flooded; water stands in them
Fertile soilriver-laid alluvium renewed by floods (gess203)
Enough waterpaddy needs plenty of water, so it is grown where rainfall is high
Rice on every platefish and rice become the staple; many people can be fed from little land
| Activity | Where (book) | Note |
|---|---|---|
| Paddy | the plains (main crop) | needs plenty of water; high rainfall areas |
| Wheat, maize, sorghum, gram, millets | the plains | other food crops |
| Sugarcane, jute | the plains (cash crops) | jute grows best in the hot, humid lower Gangetic plain † (UPSC 2011: paddy and jute) |
| Bananas | some areas of the plain | plantations |
| Tea | West Bengal and Assam (plantations) | on well-drained slopes † (hess403, legy203) |
| Silk (sericulture) | parts of Bihar and Assam | Assam's muga and Bihar's Bhagalpur tussar are well-known silks † |
| Terrace farming | mountains and hills, on gentle slopes | flat steps slow the water (UPSC 1991: on slopes of mountains) |
Reading Figs 6.9–6.10, the glossary, the activity and the terrace box (pages 44–45)
- Fig. 6.9, ‘Paddy Cultivation’: a photograph of people bent over a flooded field, transplanting bright green rice seedlings in rows. The point: paddy grows in standing water — it needs plenty of rain.
- Fig. 6.10, ‘Tea Garden in Assam’: a photograph of women plucking leaves among waist-high tea bushes, one carrying a large basket on her back, with shade trees behind. The point: tea is a plantation crop of Assam and West Bengal.
- Glossary — population density: the number of persons living in one sq km — Uttarakhand 189, West Bengal 1,029, Bihar 1,102. Drawn as our bar chart.
- Activity: collect jute, bamboo and silk handicrafts and find where they were made — outline in the activities section.
- Do you know? — terraces (p. 45), with a photograph of a hillside cut into many narrow green steps: terraces create flat surfaces on steep slopes so that water does not run off rapidly. The point: people reshape the land to farm the mountains.
NCERT details to read carefully — population and crops
- The densities have no year in the book. They match the Census 2011 provisional totals; the final Census 2011 figures are Bihar 1,106, West Bengal 1,028, Uttarakhand 189 (India 382) † (legy201). Quote the year with any figure.
- Bihar is the most densely peopled large state in Census 2011 †; in Census 2001 West Bengal led (UPSC 2003 — on legy201).
- Exercise 3(iv): silk worm — (c) sericulture; Exercise 3(v): Kaziranga — (a) Assam.
- Terraces reduce soil erosion on slopes; it is deforestation that causes it (UPSC 2014 — on hess402, jess101, keec107).
7. Vegetation, wildlife and a lake that feeds a village
In simple wordsWalk from a cold hill town down to the sea: pine trees give way to sal and teak, then to bamboo thickets, and at the coast to trees that stand in salt water on stilt-like roots. The animals change with them — and in the river itself swims a dolphin that tells you, just by being there, whether the water is healthy.
The vegetation changes with the landform. In the Ganga and Brahmaputra plains, tropical deciduous trees grow, along with teak, sal and peepal; thick bamboo groves are common in the Brahmaputra plain. The delta is covered with mangrove forests. In parts of Uttarakhand, Sikkim and Arunachal Pradesh, coniferous trees — pine, deodar and fir — grow because the climate is cool and the slopes steep. Wildlife is varied: elephants, tigers, deer and monkeys are common; the one-horned rhinoceros lives in the Brahmaputra plain (Fig. 6.11); in the delta are the Bengal tiger and crocodiles (Fig. 6.12). Fresh rivers, lakes and the Bay of Bengal are rich in fish — rohu, catla and hilsa are the most popular, and fish and rice are the staple diet. In the Ganga and Brahmaputra lives a dolphin, the Susu or ‘blind dolphin’, whose presence shows that the river is healthy; untreated industrial and urban waste is killing it. A case study tells of Binod, a fisherman of Matwali Maun village in Bihar, who with fellow fishermen cleaned the maun (ox-bow lake) to farm fish fed on lake weeds, and grows paddy, maize and pulses on the fertile land around it, ploughing with buffaloes — enough fish to eat and to sell, as long as pollutants from nearby towns stay out.
| Zone | Vegetation (book) | Wildlife (book) |
|---|---|---|
| Mountains (Uttarakhand, Sikkim, Arunachal Pradesh) | coniferous: pine, deodar, fir — cool climate, steep slopes | — |
| Ganga plain | tropical deciduous; teak, sal, peepal | elephants, tigers, deer, monkeys |
| Brahmaputra plain | tropical deciduous; thick bamboo groves | one-horned rhinoceros |
| Delta | mangrove forests | Bengal tiger, crocodiles |
| Rivers, lakes, Bay of Bengal | lake weeds (Vallisneria, Hydrilla) feed the fish | rohu, catla, hilsa; the Susu dolphin |
⤵ The ox-bow lake fishery (case study, pp. 45–46)
Clean the maunBinod and fellow fishermen clear the ox-bow lake
Weeds feed fishlocal lake weeds are food for the fish they raise
Fertile fields aroundpaddy, maize and pulses, ploughed with buffaloes
Food and incomefish to eat, to sell, and to supply the neighbouring town
One conditionpollutants from nearby towns must not reach the lake
Reading Figs 6.11–6.12, the case study and the dolphin box (page 45–46)
- Fig. 6.11, ‘One horned rhinoceros’: a photograph of a grey, armour-plated rhino crossing a forest track, a small white circle drawn round its single horn. The point: the animal's one horn — the Brahmaputra plain's best-known animal.
- Fig. 6.12, ‘Crocodiles’: a photograph of pale crocodiles resting in tall grass by water. The point: crocodiles of the delta.
- Case study, ‘Lake: A source of livelihood’, with two photographs — ‘A clean lake’ (green water under bamboo and trees, people at the edge) and ‘A Polluted Lake’ (a shrunken, weedy lake with boats pulled up on a muddy bank). The point: a clean ox-bow lake supports a whole village; pollution threatens it.
- Do you know? — Susu, with a photograph captioned ‘Blind Dolphin’ showing a grey dolphin's long, thin beak rising from muddy water. The point: the dolphin is an indicator of the river's health, and chemical waste is killing it.
NCERT details to read carefully — wildlife
- The Bengal tiger is not a delta-only animal: it is the tiger subspecies of the whole subcontinent †, and the book's own Fig. 6.14 shows a tiger in Manas, in the Himalayan foothills. Exercise 2(v)'s expected answer is (b) delta area — the book's text — but know the wider fact.
- The one-horned rhinoceros lives in the Brahmaputra plain (Kaziranga holds the largest population †) and also in the Terai of Nepal † — so it is not found in India only (UPSC 2019).
- The Susu is the Ganges river dolphin; ‘blind’ because its eyes are very poorly developed and it finds food by echolocation †. It was declared India's National Aquatic Animal in 2009 †. UPSC 2014 asked the reasons for its decline other than poaching: dams and barrages, accidental capture in fishing nets, and farm chemicals — not crocodiles.
- Deodar and fir are coniferous trees (Exercise 2-iv: (a)); teak and sal are tropical deciduous (kegy105). Piranha — (g) fish (Exercise 3-iii).
- Spelling: ‘vallineria’ is Vallisneria.
Beyond NCERT — protected areas the book names
- Kaziranga and Manas in Assam are both national parks and UNESCO World Heritage Sites (1985); Manas is also a tiger reserve (kegy105, jess102).
- The Sundarbans — the world's largest mangrove forest, shared by India and Bangladesh — is a tiger reserve and a World Heritage Site (kegy105).
- Ox-bow lakes and other wetlands are protected under the Ramsar Convention; Kanwar Taal in Bihar, an ox-bow lake of the Burhi Gandak, became Bihar's first Ramsar site in 2020 (gess203).
8. Cities, pollution, transport and tourism
In simple wordsA river through a city is like a long kitchen sink shared by everyone downstream. If each town pours its dirty water into it, the next town drinks it, the fish die, and the river's own animals vanish. The same river also carries boats, draws pilgrims and tourists, and links cities — so keeping it clean pays back in many ways.
The Ganga–Brahmaputra plain has many big towns and cities. Allahabad, Kanpur, Varanasi, Lucknow, Patna and Kolkata, each with more than ten lakh people, are named as lying along the Ganga (Fig. 6.13). Wastewater from towns and industries is discharged into the rivers, polluting them. All four kinds of transport are well developed: roads and railways in the plains, waterways especially along the rivers — Kolkata is an important port on the River Hooghly — and many airports. Tourism is important: the Taj Mahal on the Yamuna at Agra; Allahabad at the confluence of the Ganga and Yamuna; Buddhist stupas in Uttar Pradesh and Bihar; Lucknow with its Imambara; Assam with Kaziranga and Manas wildlife sanctuaries (Fig. 6.14); and Arunachal Pradesh with its distinctive tribal culture. Two boxes name government programmes: the Swachh Bharat Mission, launched by the Prime Minister on 2 October 2014 for universal sanitation, and the Namami Gange programme to conserve the Ganga.
⤵ From city to river to dolphin (pp. 45–46)
Big cities on the riverseveral cities of over ten lakh people line the Ganga
Wastewater dischargeduntreated sewage and industrial waste flow into the river
Chemicals build upthe river and its lakes are polluted; fisheries suffer
The Susu declinesthe dolphin, the river's health indicator, is being killed
ResponsesNamami Gange for the river; Swachh Bharat for sanitation
| Place (book) | Why visit | Note † |
|---|---|---|
| Agra | the Taj Mahal, on the Yamuna | World Heritage Site |
| Allahabad | the confluence of the Ganga and the Yamuna | renamed Prayagraj in 2018 |
| Uttar Pradesh and Bihar | Buddhist stupas | e.g. Sarnath (UP), Bodh Gaya (Bihar) |
| Lucknow | the Imambara | Lucknow stands on the Gomti, not the Ganga |
| Assam | Kaziranga and Manas wildlife sanctuaries | both national parks today |
| Arunachal Pradesh | a distinctive tribal culture | described as the book does |
Reading Figs 6.13–6.14 and the two programme boxes (page 46)
- Fig. 6.13, ‘Varanasi along the River Ganga’: a photograph of wooden boats moored in the foreground and a long line of steps (ghats), temples and buildings crowding the riverbank under a blue sky. The point: a great city built on the river — and its waste goes into it.
- Fig. 6.14, ‘Tiger in Manas Wildlife sanctuary’: a photograph of a tiger lying in grass, looking at the camera. The point: wildlife as a reason to visit — and a reminder that tigers live in the foothills too.
- Do you know? — Swachh Bharat Mission, launched on 2 October 2014 to speed up universal sanitation coverage.
- Do you know? — Namami Gange: a programme to conserve the river Ganga.
NCERT details to read carefully — cities and programmes
- Lucknow is on the Gomti, a tributary of the Ganga †, not on the Ganga itself — of the six cities, five lie on the Ganga or (Kolkata) its distributary the Hooghly. Exercise 1(iv): name Allahabad (Prayagraj), Kanpur, Varanasi, Patna and Kolkata, and note Lucknow's river.
- Exercise 2(iii): Kolkata is on the (b) Hooghly. The Hooghly is the lower course of the Bhagirathi — the ‘Bhagirathi–Hooghly’ † — so (c) is a near-miss; the book's answer is (b).
- The box's wording: ‘put fours on sanitation’ means put focus on sanitation; ‘acceletrate’ is accelerate; ‘Bay of Bengal Sea’ is simply the Bay of Bengal.
- Namami Gange: approved as a flagship programme of the Union Government in June 2014 †, run by the National Mission for Clean Ganga (NMCG) — UPSC Mains GS3 2015 asked about both (kegy103, legy204).
9. Two basins side by side
In simple wordsSame question, two answers: how do people get food, homes and a living from where they are? Line the two basins up feature by feature and the chapter's lesson appears — the environment sets the limits, people choose within them, and their choices change the environment back.
| Feature | Amazon basin | Ganga–Brahmaputra basin |
|---|---|---|
| Location | South America, on the equator (book: 10°N–10°S) | Indian subcontinent (book: 10°N–30°N) |
| Climate | hot and wet all year; rain almost daily | monsoon: rain mid-June to mid-September; hot summers, cool winters |
| Vegetation | thick rainforest; dense roof; epiphytes | conifers (hills), tropical deciduous — teak, sal, peepal; bamboo; mangroves (delta) |
| Wildlife | toucans, macaws, hummingbirds, monkeys, sloths, tapirs, anaconda, piranha | elephants, tigers, deer, monkeys, one-horned rhino, crocodiles, Susu; rohu, catla, hilsa |
| Farming | slash and burn; manioc staple; coffee, maize, cocoa for sale | settled farming; paddy main crop; wheat, jute, sugarcane, tea, silk; terraces |
| People | indigenous communities in the forest; fewer people | very dense on the plains, sparse in the mountains |
| Change and threats | highway (1970), displacement, deforestation, soil loss | city and industrial waste polluting rivers; threat to the Susu and lake fisheries |
| Responses named | — (the book names none) | Namami Gange; Swachh Bharat Mission (2 October 2014) |
⤵ Answer frame for any ‘life in a region’ question
Wherelatitude band, continent, river basin
Climatetemperature and rain through the year
Vegetation and wildlifewhat the climate and landforms allow
How people livefood, farming, homes, occupations, density
Change and responsedevelopment, pollution, conservation — with views attributed
Activities and in-text questions — answer outlines
The in-text questions, the two ‘Let's do’ boxes and the activity box.
Page 40: Name the countries of the Amazon basin through which the equator passes.
Ecuador, Colombia and Brazil. (In South America the equator crosses only these three; all three lie partly in the Amazon basin.)
Let's do, page 41: Watch wildlife documentaries on TV and share your experience with the class.
Note the place (which forest or basin), its climate, the plants and animals shown and how they suit the place (bright birds of the canopy, shade plants of the floor), and any threats mentioned — logging, poaching, pollution. Share one surprising fact and one way people there depend on the forest.
Page 43: Look at the atlas and find names of some tributaries of the River Brahmaputra.
Subansiri, Manas, Teesta (from the Himalayas, on its right bank) and Dibang, Lohit, Dhansiri (on its left bank); also the Kameng (kegy103; UPSC 2016 asked about Dibang, Kameng and Lohit — all three are tributaries).
Let's do, page 44: The River Brahmaputra is known by different names in different places. Find the other names of the river.
Tsangpo (or Yarlung Tsangpo) in Tibet; Siang or Dihang in Arunachal Pradesh; Brahmaputra in Assam; Jamuna in Bangladesh (where, after joining the Ganga, the combined stream is the Padma and then the Meghna).
Page 44: Find out the states in which the Ganga–Brahmaputra basin lies.
Mainly Uttarakhand, Uttar Pradesh, Bihar, Jharkhand and West Bengal (Ganga), and Arunachal Pradesh and Assam (Brahmaputra); with parts of Himachal Pradesh, Haryana, Delhi, Rajasthan, Madhya Pradesh and Chhattisgarh through the Ganga's tributaries, and of Sikkim, Meghalaya and Nagaland through the Brahmaputra's (kegy103). Use an atlas, not memory, for the boundaries.
Activity, page 44: Collect handicrafts made from jute, bamboo and silk, display them, and find out where they were made.
Jute: bags, mats and rugs — West Bengal and the lower Ganga plain. Bamboo: baskets, furniture, mats — Assam and the north-east, where bamboo groves are common. Silk: Assam's muga and eri, Bihar's Bhagalpur tussar, Varanasi's Banarasi brocade. Link each to the raw material the basin produces.
NCERT exercise — answer outlines
Five short answers, five ticks, a match, two reasons, two map tasks, a collage and a soil activity. Try first, then open.
1 (i) Name the continent in which the Amazon Basin is located.
South America.
1 (ii) What are the crops grown by the people of the Amazon Basin?
Food crops: tapioca/manioc (cassava) — the staple — sweet potato and pineapple, grown by slash and burn. Cash crops: coffee, maize and cocoa.
1 (iii) Name the birds that you are likely to find in the rainforests of the Amazon.
Toucans, hummingbirds and macaws — brightly coloured birds with oversized bills and loud calls.
1 (iv) What are the major cities located on the River Ganga?
Allahabad (Prayagraj), Kanpur, Varanasi, Patna and Kolkata (on the Hooghly) — each with more than ten lakh people. The book also lists Lucknow, which stands on the Gomti, a Ganga tributary.
1 (v) Where is the one-horned rhinoceros found?
In the Brahmaputra plain — for example Kaziranga in Assam.
2. Tick the correct answer: (i) toucans; (ii) manioc staple; (iii) Kolkata's river; (iv) deodars and firs; (v) Bengal tiger.
(i) (a) birds. (ii) (c) Amazon. (iii) (b) Hooghly (the lower Bhagirathi). (iv) (a) coniferous trees. (v) (b) delta area — the book's answer; tigers also live in the foothills (Fig. 6.14, Manas).
3. Match: (i) Cotton textile (ii) Maloca (iii) Piranha (iv) Silk worm (v) Kaziranga — with (a) Assam (b) Terrace farming (c) Sericulture (d) Slanting roof (e) Ganga plain (f) Varanasi (g) Fish.
(ii) Maloca – (d) slanting roof; (iii) Piranha – (g) fish; (iv) Silk worm – (c) sericulture; (v) Kaziranga – (a) Assam. (i) Cotton textile: the chapter never mentions cotton textiles, so there is no answer in the text; of the leftovers (b) terrace farming, (e) Ganga plain and (f) Varanasi, the closest is (f) Varanasi, a historic weaving town — treat it as a weak item.
4 (i) Give reasons: The rainforests are depleting.
Developmental activities: the Trans-Amazon highway (1970) and air transport opened the forest; land is cleared for roads, settlements, farms and timber, and indigenous people are pushed into new areas. Once cleared, the heavy rain washes away the topsoil, which is poor in nutrients, so the forest does not come back and the land turns barren (Fig. 6.6; Exercise 7).
4 (ii) Give reasons: Paddy is grown in the Ganga–Brahmaputra plains.
Paddy needs plenty of water; the plains get heavy monsoon rain (mid-June to mid-September), have flat land that can hold standing water, and fertile alluvial soil; a dense population also supplies the labour paddy needs and eats rice (fish and rice are the staple).
5 (i) Map skills: draw the rivers Ganga and Brahmaputra from source to mouth on an outline map, with important tributaries.
Do this on a printed outline map in class. Checklist (see the table in section 5): Ganga — from the Gangotri glacier (Bhagirathi), joined by the Alaknanda at Devprayag; Yamuna (with the Chambal) at Prayagraj; Ramganga, Gomti, Ghaghara, Gandak, Kosi from the north; Son from the south; Bhagirathi–Hooghly to the sea, Padma in Bangladesh. Brahmaputra — from near Lake Mansarovar as the Tsangpo, east across Tibet, south through Arunachal Pradesh as the Siang, west through Assam (Subansiri, Manas; Dibang, Lohit), south into Bangladesh as the Jamuna; mouth: the Bay of Bengal through the shared delta.
5 (ii) Map skills: draw the equator on a political map of South America and mark the countries through which it passes.
Draw the equator (0°) across the north of the continent; mark Ecuador, Colombia and Brazil. Label the Amazon flowing east to the Atlantic near where the equator meets the coast.
6. For fun: make a collage of places of attraction in India — mountain landscapes, coastal beaches, wildlife sanctuaries and places of historical importance.
Group work: one sheet per theme. From this chapter alone — wildlife: Kaziranga, Manas, the Sundarbans; history and faith: the Taj Mahal (Agra), the Ganga–Yamuna confluence (Prayagraj), Buddhist stupas (Sarnath, Bodh Gaya), Lucknow's Imambara, Varanasi's ghats; mountains: the terraced hills of Uttarakhand and Sikkim, Arunachal Pradesh. Add beaches from your own atlas work, and label each picture with its state.
7. Activity: three cans of soil with coins on top, sprinkled lightly, moderately and heavily. What do you observe?
Unprotected soil splashes out; the heavier the ‘rain’, the more soil is lost — least in the first can, most in the third. Soil under the coins stays. The coins stand for tree cover: if land is cleared completely of vegetation, the soil cover quickly disappears — exactly what happens to cleared rainforest under heavy equatorial rain.
Reading the exercise pages (pages 47–48)
- Exercises 1–6 (p. 47): the cartoon globe heading; short answers, ticks, a match with two spare options, reasons, two map tasks and a collage. The map tasks are answered above as checklists; we draw no map.
- Exercise 7 (p. 48): materials — three small pots or cans, a big can with holes punched in the bottom as a sprinkler, twelve coins or bottle caps, soil — and the steps, ending with the conclusion that cleared land loses its soil fast. A cartoon cloud closes the page. Drawn as our three cans in section 4.
Keys and slips to handle with care
- Stored UPSC keys linked here are all standard: 1986 (a soil erosion), 1991 (b slopes of mountains), 1993 (c habitat destruction and shifting cultivation), 2001 (b mechanical support), 2003 (d: A false, R true), 2011 rainforest (a nutrient-poor soil), 2011 crops (c paddy and jute), 2013 (d 1, 2 and 3), 2014 (c 1, 3 and 4), 2015 (b equatorial), 2019 (a Asiatic lion only), 2021 (d tropical rain forest), 2023 (d: I incorrect, II correct).
- 2013: some aspirants argue that numerous species and epiphytes also occur in other forests, so are not ‘unique’; the official key counts all three as characteristic. Keep (d).
- Exercise 3(i) (cotton textile) has no answer in the chapter; Exercise 2(v) expects ‘delta area’ though tigers live elsewhere too; Exercise 2(iii): Hooghly, not Bhagirathi, though they are one river system.
What to remember
Numbers
Chapterbook pp. 39–48 (10 PDF pages; QR code 0762CH08 — the old Chapter 8)
Book's equatorial band10°N – 10°S (it calls it ‘tropical’); the tropics proper reach 23½°N and S †
Book's sub-tropical band10°N – 30°N (Ganga–Brahmaputra basin)
Amazon basin countries6: Brazil, Peru, Bolivia, Ecuador, Colombia, Venezuela
Equator in South America †Ecuador, Colombia, Brazil
Amazon basinthe largest river basin in the world; mouth on the Atlantic
Trans-Amazon highway1970 (book; work began then †)
Amazon farmingslash and burn; staple manioc (cassava); cash crops coffee, maize, cocoa
Monsoon rainmid-June to mid-September (about 3 months)
Population density (book, no year)Uttarakhand 189, West Bengal 1,029, Bihar 1,102 per sq km — Bihar ≈ 5.8 × Uttarakhand
Census 2011 final †Bihar 1,106; West Bengal 1,028; India 382
Ganga tributaries (book)Ghaghra, Son, Chambal (via the Yamuna), Gandak, Kosi
Cities over ten lakh (book)Allahabad, Kanpur, Varanasi, Lucknow (on the Gomti), Patna, Kolkata (on the Hooghly)
Fishrohu, catla, hilsa; staple: fish and rice
Swachh Bharat Missionlaunched 2 October 2014
Namami Gange †flagship programme approved June 2014; run by NMCG
Exercise 73 cans × 4 coins = 12 coins
One-liners
- A river basin is the area drained by a main river and all its tributaries; the Amazon's is the largest in the world.
- The Amazon basin lies on the equator and is hot and wet all year, with rain almost every day.
- The rainforest's dense roof of leaves keeps the floor dark and damp; only shade-tolerant plants grow there.
- Orchids and bromeliads grow on trees as epiphytes; bromeliads hold water in which frogs lay eggs.
- Amazon peoples farm by slash and burn; manioc (cassava) is their staple food.
- The Trans-Amazon highway (1970) and development pushed indigenous people out and are shrinking the forest.
- When trees are cleared, rain washes away the topsoil and the forest turns barren.
- In the Ganga–Brahmaputra basin, few people live in the steep mountains and very many on the fertile plains.
- Paddy is the main crop of the plains because it needs plenty of water and the monsoon supplies it.
- Tea grows in West Bengal and Assam; silk comes from Bihar and Assam; terraces are cut on gentle hill slopes.
- Conifers grow in the hills, teak and sal in the plains, and mangroves in the delta.
- The one-horned rhinoceros lives in the Brahmaputra plain; the Susu dolphin shows how healthy the river is.
Traps to avoid
- Orchids and bromeliads are epiphytes (support only), not parasites — the book is wrong here.
- Tapirs eat plants; the book's ‘ant-eating tapirs’ is a slip.
- The Amazons of the legend are Greek, not Roman.
- The tropics reach 23½°N and S; the book's ‘tropical’ 10°N–10°S is the equatorial belt.
- Tapioca is made from manioc (cassava) — one plant, not two crops.
- Lucknow is on the Gomti, not the Ganga; Kolkata is on the Hooghly.
- The Chambal joins the Yamuna, not the Ganga directly.
- Rainforest soil is poor in nutrients; cleared rainforest does not make lasting farmland.
- The one-horned rhino also lives in Nepal; it is not found in India only.
- The book's densities carry no year; Census 2011 final figures are Bihar 1,106 and West Bengal 1,028.
How to strategise
Prelims — what UPSC asks
- From this chapter: the rainforest — what is characteristic of equatorial forests (2013), epiphytes and support (2001), the equatorial daily weather passage (2015), the rainforest biome passage (2021), and its nutrient-poor soil (2003, 2011, 2023); deforestation and soil erosion (1986); habitat destruction and shifting cultivation as threats to biodiversity (1993); terraces on mountain slopes (1991); paddy and jute in the lower Gangetic plain (2011); the Ganges river dolphin's decline (2014); and the one-horned rhino beyond India (2019).
- Elsewhere: jhum cultivation (1979) and eco-friendly farming (1999) on legy104 and others; soil erosion and terraces (2014) on hess402; tropical rain forest regions (1983) on iest202; teak and moist deciduous forests (2015) on kegy105; Brahmaputra tributaries (2016) and antecedent drainage (1989) on kegy103; Census 2001 densities (2003) on legy201. Also asked, not linked: the national aquatic animal (2015) — the book teaches the Susu but not its status.
- Method: learn the rainforest as a cause chain — heat and daily rain → dense canopy → dark floor → epiphytes → rapid decay → poor soil → fails when cleared. Learn each Ganga–Brahmaputra crop, tree and animal with its zone.
Mains — where it appears and how to answer
- From this chapter: GS3 2015 (Namami Gange and the NMCG; why earlier schemes gave mixed results) — the chapter's city-waste-river chain and the Susu as an indicator give the opening; add sewage treatment, industrial effluent, flow and community action from kegy103 and legy204.
- Elsewhere: diversity of natural vegetation and rainforest sanctuaries in India (GS1 2023) on kegy105, kegy214 and iest202; distribution and density of population in the Ganga basin (GS1 2025) on legy201, legy102 and hess405 — this chapter's plains-versus-mountains contrast is a good first paragraph for both.
- In any region answer, use the frame where → climate → vegetation and wildlife → how people live → change and response, and attribute the development-versus-forest positions rather than taking a side.
Self-check
Tap an option. NCERT's own exercise questions come first; the rest test the figures and common confusions.
1. Why does the floor of the Amazon rainforest stay dark and damp?
2. Orchids and bromeliads growing on rainforest trees depend on them for:
3. The staple food of the Amazon peoples, according to the book, is:
4. In slash-and-burn farming, why is a plot abandoned after a few years?
5. Why do fewer people live in the mountain parts of the Ganga–Brahmaputra basin than on its plains?
6. The book gives the population density of Bihar as 1,102 and of Uttarakhand as 189 per sq km. Roughly how many times denser is Bihar?
7. Which of these is NOT a reason UPSC (2014) accepted for the decline of the Ganges river dolphin?
8. Kolkata, an important port, stands on the river:
UPSC questions from this chapter
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