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WBCHSE HS Environmental Science study materials
WBCHSE HS Environmental Science study resources

WBCHSE HS Environmental Science practice questions

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Question 1Environmental Science: scope, components and ecosystems

In the standard ecological hierarchy used in environmental science, which sequence correctly arranges levels of biological organisation from simplest to most complex?

  1. Organism → community → population → biome → ecosystem
  2. Population → organism → ecosystem → community → biome
  3. Biome → ecosystem → community → population → organism
  4. Organism → population → community → ecosystem → biome Correct answer.

Explanation

Ecological organisation builds upward: individual organisms of one species form a population, interacting populations form a community, and the community plus its abiotic surroundings forms an ecosystem; biomes are broad climatic groupings of ecosystems. The reverse ordering describes increasing simplification rather than increasing integration.

Question 2Environmental Science: scope, components and ecosystems

The term 'environment' in the WBCHSE Environmental Science syllabus is best understood as covering which set of components?

  1. Only the abiotic factors such as air, water and soil
  2. The physical, chemical, biological and social conditions that surround and influence an organism Correct answer.
  3. Exclusively the natural resources that humans extract for industry
  4. Only the living organisms surrounding a human settlement

Explanation

Environment is a composite concept: it includes abiotic factors (air, water, soil, light), biotic factors (other organisms), and for humans also social, cultural and economic conditions. Narrow definitions that pick only one of these strands miss the integrated scope of the subject.

Question 3Environmental Science: scope, components and ecosystems

Which statement most accurately describes the relationship between environmental science and ecology?

  1. Ecology is a branch of environmental science that studies only pollution
  2. Ecology deals only with animals while environmental science deals only with plants
  3. Environmental science draws on ecology along with physical and social sciences to study environmental problems Correct answer.
  4. Ecology and environmental science are identical in scope and methods

Explanation

Ecology is the scientific study of interactions between organisms and their surroundings, while environmental science is interdisciplinary, combining ecology with chemistry, physics, economics, sociology and policy to address environmental issues. Ecology is therefore a core input to, not a synonym for, environmental science.

Question 4Environmental Science: scope, components and ecosystems

In the ecosystem concept, the abiotic component is best illustrated by which group?

  1. Solar radiation, soil minerals and dissolved oxygen Correct answer.
  2. Detritivores breaking down leaf litter
  3. Bacteria, fungi and earthworms in the soil
  4. Grasses, shrubs and grazing herbivores

Explanation

Abiotic components are the non-living physical and chemical factors of an ecosystem, such as light, temperature, water, minerals and gases. All the other options list living organisms, which belong to the biotic component.

Question 5Environmental Science: scope, components and ecosystems

A pond contains algae, water fleas, small fish, herons, aquatic plants and decomposer bacteria, together with dissolved nutrients, sunlight and water. Which statement correctly identifies the functional components of this pond ecosystem?

  1. Algae and aquatic plants are producers; water fleas and fish are consumers; bacteria are decomposers Correct answer.
  2. Algae are decomposers; aquatic plants are consumers; bacteria are producers
  3. Only the fish and herons are consumers; all plants are decomposers
  4. Dissolved nutrients are producers; sunlight is a consumer

Explanation

In any ecosystem the functional components are producers (photosynthetic autotrophs), consumers (heterotrophs feeding on other organisms) and decomposers (saprotrophs breaking down dead matter). Algae and aquatic plants fix energy as producers, the animals consume, and bacteria recycle nutrients.

Question 6Environmental Science: scope, components and ecosystems

Which of the following best defines a biome?

  1. A large terrestrial region with a characteristic climate and dominant vegetation type Correct answer.
  2. The total number of species present in one habitat
  3. The non-living part of an ecosystem
  4. A single pond with its associated organisms

Explanation

A biome is a large-scale terrestrial unit defined by climate, especially temperature and precipitation, and by the dominant plant life, such as tropical rainforest, grassland or tundra. It is broader than an ecosystem and is not defined by species counts or abiotic material alone.

Question 7Environmental Science: scope, components and ecosystems

Sunlight is described as an essential abiotic factor for most ecosystems. Which reason best explains this?

  1. It provides the energy that autotrophs capture to synthesise organic matter Correct answer.
  2. It supplies minerals directly to plant roots
  3. It carries oxygen into aquatic habitats
  4. It regulates the rate of decomposition in soil

Explanation

Light is the ultimate energy source for most ecosystems because photosynthetic autotrophs convert light energy into chemical energy stored in organic compounds, which then flows through food chains. Minerals come from soil, decomposition depends on temperature and microbes, and oxygen enters water mainly by diffusion and mixing.

Question 8Environmental Science: scope, components and ecosystems

In a grassland food chain, grass → grasshopper → frog → snake → hawk, what is the trophic level of the frog?

  1. Secondary consumer Correct answer.
  2. Primary consumer
  3. Tertiary consumer
  4. Primary producer

Explanation

Grass is the producer (first trophic level), the grasshopper eating it is the primary consumer, and the frog eating the grasshopper is the secondary consumer. Each feeding step moves one trophic level up the chain.

Question 9Environmental Science: scope, components and ecosystems

In a food web, removing a top predator is often followed by a chain of changes in lower trophic levels. This phenomenon is best described as:

  1. A trophic cascade Correct answer.
  2. Biological magnification
  3. Primary succession
  4. Nitrogen fixation

Explanation

A trophic cascade is the indirect effect that a change at one trophic level produces on other levels, for example when removing a predator releases herbivores to overgraze producers. It is a specific consequence of food-web linkage, not a chemical or successional process.

Question 10Environmental Science: scope, components and ecosystems

A forest ecosystem receives 100,000 kJ of solar energy, of which producers capture 1,000 kJ as gross primary production. If ecological efficiency between trophic levels is about 10%, how much energy is theoretically available to secondary consumers?

  1. 10 kJ Correct answer.
  2. 100 kJ
  3. 1,000 kJ
  4. 10,000 kJ

Explanation

With 1,000 kJ at the producer level, primary consumers receive about 10% (100 kJ) and secondary consumers about 10% of that (10 kJ). The 10% rule reflects energy lost as heat through respiration at each transfer.

Question 11Environmental Science: scope, components and ecosystems

Why are food chains in nature rarely longer than four or five trophic levels?

  1. Because decomposers remove all energy before it can be transferred
  2. Because higher trophic levels cannot obtain water
  3. Because predators refuse to eat organisms at higher levels
  4. Because energy is progressively lost as heat at each transfer, leaving too little to support further levels Correct answer.

Explanation

Energy transfer between trophic levels is inefficient, with roughly 90% lost mainly as heat through respiration and other metabolic activities. After several transfers the remaining energy is too small to sustain viable populations of additional consumers.

Question 12Environmental Science: scope, components and ecosystems

In the carbon cycle, which process returns carbon dioxide to the atmosphere from the biotic component?

  1. Cellular respiration by living organisms Correct answer.
  2. Absorption of carbonates by shells
  3. Photosynthesis by green plants
  4. Nitrogen fixation by rhizobia

Explanation

Cellular respiration oxidises organic carbon compounds and releases carbon dioxide to the atmosphere, balancing the carbon fixed by photosynthesis. Photosynthesis removes carbon dioxide, while the other options concern nitrogen or calcium carbonate rather than gaseous carbon return.

Question 13Environmental Science: scope, components and ecosystems

Leguminous plants such as pea and gram improve soil fertility mainly because:

  1. Symbiotic bacteria in root nodules fix atmospheric nitrogen into ammonia compounds Correct answer.
  2. Their roots absorb atmospheric nitrogen directly through root hairs
  3. They convert soil nitrates into atmospheric nitrogen
  4. Their leaves release nitrogen gas into the soil during decomposition

Explanation

Rhizobium bacteria living in nodules on legume roots reduce atmospheric nitrogen to ammonia, which the plant uses and which enriches the soil when residues decay. Plants cannot use nitrogen gas directly, and denitrification is a separate bacterial process.

Question 14Environmental Science: scope, components and ecosystems

Which description correctly matches the phosphorus cycle?

  1. It depends on bacteria to convert phosphate into a gas
  2. It is mainly a sedimentary cycle with its main reservoir in rocks and minerals Correct answer.
  3. It is a gaseous cycle with a large atmospheric reservoir
  4. It has no involvement of living organisms

Explanation

Phosphorus has no significant gaseous phase; it cycles mainly through rocks, soil, water and organisms, with weathering releasing phosphate and sedimentation returning it. This makes it a sedimentary cycle with a comparatively slow turnover.

Question 15Environmental Science: scope, components and ecosystems

The role of decomposers in an ecosystem is best described as:

  1. Fixing atmospheric nitrogen within root nodules
  2. Converting solar energy into chemical energy
  3. Breaking down dead organic matter and releasing inorganic nutrients for reuse Correct answer.
  4. Transferring energy directly to top predators

Explanation

Decomposers such as bacteria and fungi mineralise dead organic matter, releasing nutrients like nitrogen, phosphorus and carbon back into the soil and water where producers can reuse them. This recycling role keeps ecosystems functioning despite continuous nutrient loss.

Question 16Environmental Science: scope, components and ecosystems

Two ecosystems receive similar rainfall, but one is a tropical rainforest and the other a temperate deciduous forest. Which factor most strongly explains the difference in their productivity?

  1. Difference in mean temperature and growing-season length Correct answer.
  2. Difference in soil colour
  3. Difference in the number of decomposer species only
  4. Difference in latitude alone, independent of climate

Explanation

Net primary productivity depends heavily on temperature and the length of the growing season, which control photosynthetic rates and plant growth. Tropical rainforests remain warm and productive year-round, whereas temperate forests have a cold dormant season.

Question 17Environmental Science: scope, components and ecosystems

Gross primary productivity (GPP) and net primary productivity (NPP) are related how?

  1. NPP equals GPP minus energy lost through plant respiration Correct answer.
  2. NPP equals GPP plus the energy consumed by herbivores
  3. GPP equals NPP minus plant respiration
  4. GPP and NPP are always numerically equal

Explanation

Net primary productivity is what remains after autotrophs use some fixed carbon for their own respiration, so NPP = GPP − respiration. Only this net amount is available to consumers and decomposers.

Question 18Environmental Science: scope, components and ecosystems

In an ecological pyramid of numbers, an inverted shape is most likely when:

  1. Decomposers outnumber producers
  2. Many small plants support a few large herbivores
  3. A predator population is larger than its prey
  4. A single large tree supports many insects Correct answer.

Explanation

A pyramid of numbers counts individuals, so one tree (one producer) supporting hundreds of insects produces a narrow base and a wide upper tier, an inverted pyramid. In most other situations numbers decrease at higher levels.

Question 19Environmental Science: scope, components and ecosystems

Why is a pyramid of energy always upright, unlike pyramids of numbers or biomass?

  1. Because energy is created anew at each trophic level
  2. Because larger animals always contain more energy than smaller ones
  3. Because decomposers add energy to the top of the pyramid
  4. Because energy transfer is inefficient, so each level contains less energy than the one below Correct answer.

Explanation

The second law of thermodynamics means energy is lost as heat at every transfer, so each successive trophic level holds less energy than the one below. This makes the energy pyramid invariably upright regardless of the numbers or biomass involved.

Question 20Environmental Science: scope, components and ecosystems

Biological magnification of a persistent pesticide such as DDT is expected to be greatest in which organism of a food chain?

  1. Fish-eating birds at the top Correct answer.
  2. Small fish feeding on zooplankton
  3. Small zooplankton feeding on phytoplankton
  4. Phytoplankton at the base

Explanation

Persistent, fat-soluble substances are not readily excreted and accumulate in body tissues, so their concentration rises at each trophic transfer. The highest concentration therefore occurs in the top consumer, here the fish-eating birds.

Question 21Environmental Science: scope, components and ecosystems

Which pair correctly matches an ecosystem type with a distinctive feature of its abiotic environment?

  1. Coral reef ecosystem - cold, dark water with no light penetration
  2. Grassland ecosystem - permanently waterlogged anaerobic soil
  3. Desert ecosystem - high rainfall with leached soils
  4. Mangrove ecosystem - saline, waterlogged soils with low oxygen Correct answer.

Explanation

Mangroves grow in tidal, saline, waterlogged mud where oxygen is scarce, and they show adaptations such as aerial roots. The other pairings contradict the defining conditions of those ecosystems.

Question 22Environmental Science: scope, components and ecosystems

In the context of ecosystem services, the pollination of crops by insects is classified as:

  1. A supporting service
  2. A cultural service
  3. A regulating service Correct answer.
  4. A provisioning service

Explanation

Pollination regulates ecological processes that maintain ecosystem functioning and agricultural output, so it is classed as a regulating service. Provisioning services are the tangible products such as food and timber, cultural services are non-material benefits, and supporting services underpin the others, such as nutrient cycling.

Question 23Environmental Science: scope, components and ecosystems

A scientist argues that a wetland should be conserved because it absorbs floodwater, filters pollutants and supports fish breeding. This argument rests primarily on which concept?

  1. Aesthetic value of the landscape
  2. Intrinsic value of individual species
  3. The rarity of wetland plants alone
  4. Ecosystem services provided by wetland functions Correct answer.

Explanation

Flood buffering, water purification and nursery habitat are functions that benefit humans and are described as ecosystem services, both regulating and supporting. The argument is therefore utilitarian and functional rather than based on intrinsic worth or appearance.

Question 24Environmental Science: scope, components and ecosystems

Two islands of equal area lie at the same latitude; one is close to the mainland and the other is 500 km away. According to island biogeography theory, which prediction is most reasonable?

  1. Species richness will depend only on the age of the islands
  2. Both islands will have identical species richness because area is equal
  3. The near island will support more species because immigration rates are higher Correct answer.
  4. The distant island will support more species because competition is lower

Explanation

The theory of island biogeography holds that species richness reflects a balance between immigration and extinction; closer islands receive more colonists, so at equilibrium they hold more species than distant ones of the same size. Area and distance act together, so equal area alone does not equalise richness.

Question 25Natural resources and their conservation

In the context of natural-resource classification used in environmental science, which resource is best described as non-renewable on a human time scale?

  1. Solar radiation
  2. Tidal energy
  3. Wind
  4. Coal Correct answer.

Explanation

Coal forms from buried plant remains over millions of years, so the rate of formation is negligible compared with the rate of human consumption. Wind, solar radiation and tides are continuously replenished by natural processes and are therefore treated as renewable.

Question 26Natural resources and their conservation

Which pair correctly matches a forest product with the category of resource use it represents?

  1. Fuelwood collected for cooking - indirect non-consumptive use
  2. Scenery viewed by a trekker - direct consumptive use
  3. Pollination by wild bees - direct consumptive use
  4. Timber from a felled tree - direct consumptive use Correct answer.

Explanation

Consumptive use removes or depletes the resource, as when a tree is felled for timber. Pollination and scenery are services obtained without removing the organism or the landscape, so they are non-consumptive uses.

Question 27Natural resources and their conservation

The chief physical factor that makes groundwater a more reliable dry-season resource than surface streams in the plateau region of West Bengal is that groundwater

  1. is replenished only by glacial meltwater
  2. evaporates more rapidly than river water
  3. flows entirely above the ground surface throughout the year
  4. is stored in the pore spaces and fractures of rock and released slowly Correct answer.

Explanation

Groundwater occupies voids in soil and rock, forming a reservoir that discharges gradually, so wells and springs keep yielding after streams dry up. Surface flow depends on immediate rainfall and declines quickly in the dry season.

Question 28Natural resources and their conservation

In soil-conservation practice, contour ploughing reduces soil loss mainly because it

  1. increases the gradient of the cultivated slope
  2. exposes bare subsoil to direct raindrop impact
  3. cuts across the slope so runoff is slowed and trapped between furrows Correct answer.
  4. removes the topsoil before the rains begin

Explanation

Ploughing along the contour creates ridges and furrows at right angles to the slope, which shorten the path of runoff and give water time to infiltrate. Reduced runoff velocity means less detachment and transport of soil particles.

Question 29Natural resources and their conservation

Which statement best explains why the 'tragedy of the commons' is often used to describe over-exploitation of open-access grazing land or fishing grounds?

  1. Users of common resources are legally barred from any extraction
  2. Open-access resources are unlimited, so depletion cannot occur
  3. Common-property resources are always owned by a single private individual
  4. Each user gains the full benefit of extra extraction while the cost of depletion is shared by all users Correct answer.

Explanation

When access is open, an individual who takes more keeps the entire gain but bears only a fraction of the resulting depletion, so rational individual behaviour produces collective loss. This divergence between private benefit and shared cost drives over-exploitation.

Question 30Natural resources and their conservation

Which of the following is a recognised in-situ method of biodiversity conservation?

  1. Breeding orchids in a botanical garden
  2. Storing seeds in a cryogenic gene bank
  3. Rearing endangered fish in hatchery tanks
  4. Maintaining a biosphere reserve around a natural habitat Correct answer.

Explanation

In-situ conservation protects species within their natural habitat, and a biosphere reserve does exactly that by conserving the ecosystem in place. Gene banks, hatcheries and botanical gardens maintain organisms away from their natural habitat and are ex-situ measures.

Question 31Natural resources and their conservation

A student argues that a hydroelectric project is a 'clean' renewable option with no environmental cost. Which observation most directly weakens that argument?

  1. Rainfall recharges the catchment every monsoon
  2. Hydropower does not involve combustion of fuel
  3. Reservoirs submerge forest and displace people, and downstream flow regimes are altered Correct answer.
  4. Water passing through turbines is converted to electricity

Explanation

Although hydropower avoids fuel combustion, impoundment floods terrestrial habitat, causes displacement and changes sediment and flow patterns downstream. These ecological and social costs mean the technology is not impact-free.

Question 32Natural resources and their conservation

In the context of Indian forest policy, the term 'joint forest management' refers to

  1. leasing of forest land to private timber companies
  2. complete prohibition of any human entry into forests
  3. sharing of forest protection duties and benefits between the forest department and local communities Correct answer.
  4. nationalisation of all forest land under the central government

Explanation

Joint forest management is a participatory arrangement in which village communities help protect and regenerate degraded forest land in return for a share of the produce. It recognises local users as partners in conservation rather than as trespassers.

Question 33Natural resources and their conservation

Which cropping practice is most effective for restoring nitrogen fertility in a degraded field without heavy use of synthetic fertiliser?

  1. Flood-irrigating the field throughout the year
  2. Continuous monoculture of a cereal crop
  3. Burning crop residue after every harvest
  4. Growing a legume in rotation with a cereal Correct answer.

Explanation

Legumes form symbiotic associations with nitrogen-fixing bacteria in root nodules, which add combined nitrogen to the soil. Rotating them with cereals therefore replenishes nitrogen while interrupting pest cycles.

Question 34Natural resources and their conservation

The main reason why over-extraction of groundwater near a coastal aquifer leads to saline intrusion is that

  1. rainfall over the sea becomes more saline
  2. the water table rises above sea level
  3. the freshwater head falls and seawater moves inland through the aquifer Correct answer.
  4. coastal soils lose all their clay content

Explanation

Fresh groundwater normally forms a lens that holds back denser seawater at the coast. Pumping lowers the freshwater head, so the seawater interface migrates inland and contaminates wells.

Question 35Natural resources and their conservation

Which of these is a direct outcome of deforestation on a hill slope?

  1. Increased soil organic matter
  2. Increased surface runoff and accelerated soil erosion Correct answer.
  3. Permanent rise in groundwater recharge
  4. Higher infiltration and reduced peak discharge

Explanation

Tree cover intercepts rainfall and roots maintain soil structure and permeability. Removing it increases the volume and speed of surface runoff, which detaches and carries away soil.

Question 36Natural resources and their conservation

A farmer wants to reduce wind erosion on a sandy field in an arid tract. Which combination is most appropriate?

  1. Removing all vegetation to expose fresh sand
  2. Deep ploughing to loosen the surface before the dry season
  3. Irrigating with saline water continuously
  4. Planting shelterbelts of trees and keeping crop stubble on the surface Correct answer.

Explanation

Shelterbelts reduce wind velocity at ground level, while stubble protects the soil surface from saltation and creep. Together they lower the wind's capacity to detach and transport sand.

Question 37Natural resources and their conservation

Which statement correctly distinguishes a renewable resource from a non-renewable one?

  1. A non-renewable resource cannot be recycled under any circumstances
  2. A non-renewable resource is always a metal
  3. A renewable resource never depletes regardless of the rate of extraction
  4. A renewable resource is replenished by natural processes at a rate comparable with its use Correct answer.

Explanation

Renewability is a matter of rates: the resource must be regenerated as fast as it is used. If extraction outpaces regeneration, even a biological resource such as groundwater or fish stock can be depleted.

Question 38Natural resources and their conservation

Which of the following best describes the purpose of a 'sacred grove' conserved by many communities in India?

  1. Testing new fertiliser formulations on forest soil
  2. Growing a single commercial timber species for the market
  3. Protecting a patch of natural vegetation and its associated species through customary belief Correct answer.
  4. Storing harvested grain for the village

Explanation

Sacred groves are community-protected forest patches conserved through religious custom, which effectively preserves local biodiversity and soil and water regimes. They are traditional in-situ conservation sites rather than production or storage areas.

Question 39Natural resources and their conservation

In the context of mineral resources, why is 'resource substitution' considered a conservation strategy?

  1. Replacing a scarce material with an abundant alternative reduces pressure on the scarce deposit Correct answer.
  2. It converts a renewable resource into a non-renewable one
  3. It increases the rate of extraction from the scarce deposit
  4. It removes the need for any recycling programme

Explanation

Substitution shifts demand away from a depleting material towards one that is more plentiful or renewable, extending the life of the scarce reserve. It works best when combined with recycling and efficient use.

Question 40Natural resources and their conservation

Which of the following energy sources is classified as a non-conventional renewable source in Indian energy planning?

  1. Biogas from cattle dung Correct answer.
  2. Coal from the Damodar valley
  3. Lignite from Neyveli
  4. Natural gas from offshore fields

Explanation

Biogas produced by anaerobic digestion of cattle dung is a renewable, non-conventional source promoted for rural energy needs. Coal, lignite and natural gas are conventional fossil fuels with finite reserves.

Question 41Natural resources and their conservation

A watershed development programme builds check dams and contour trenches in a catchment. The most direct hydrological benefit is that

  1. the groundwater table is permanently lowered
  2. rainfall in the catchment increases immediately
  3. runoff is retained and infiltrates, raising recharge and extending dry-season availability Correct answer.
  4. evaporation from the soil is eliminated

Explanation

Check dams and trenches slow runoff and hold water on the surface long enough for it to percolate, which raises recharge and sustains wells after the monsoon. They do not alter rainfall totals.

Question 42Natural resources and their conservation

Which practice most directly reduces the pressure on wild populations of a medicinal plant collected from forests?

  1. Collecting the whole plant including the root before flowering
  2. Cultivating the species on farmland and in home gardens Correct answer.
  3. Harvesting from the wild at a rate faster than regeneration
  4. Clearing forest undergrowth to make collection easier

Explanation

Cultivation shifts supply from wild harvest to managed plots, so wild populations are no longer the sole source. Sustainable cultivation also allows controlled harvesting that leaves regeneration intact.

Question 43Natural resources and their conservation

The ecological rationale for protecting a 'corridor' between two forest fragments is that it

  1. allows gene flow and movement of animals between otherwise isolated populations Correct answer.
  2. converts the forest into an agricultural landscape
  3. increases the isolation of each fragment
  4. prevents any movement of animals between the fragments

Explanation

Habitat fragmentation isolates populations, which reduces genetic exchange and raises extinction risk. A corridor reconnects fragments so that individuals and genes can move between them.

Question 44Natural resources and their conservation

Which of the following is the most appropriate definition of 'sustainable use' of a biological resource?

  1. Use that eliminates all competing species from the habitat
  2. Use that converts the resource into a non-renewable form
  3. Use that extracts the maximum possible amount in a single season
  4. Use that does not exceed the capacity of the resource to regenerate Correct answer.

Explanation

Sustainability is defined by the balance between harvest and regeneration, so the resource base remains available for future use. Extraction beyond the regeneration rate is by definition unsustainable.

Question 45Natural resources and their conservation

A region has abundant sunshine but scarce water and saline soil. Which renewable energy option is least constrained by these conditions?

  1. Large-scale irrigated biofuel cropping
  2. Solar photovoltaic power generation Correct answer.
  3. Hydropower from a perennial river
  4. Tidal power from a coastal estuary

Explanation

Solar photovoltaics need sunlight and land but very little water, so they suit arid, sunny regions. Biofuel cropping demands irrigation, hydropower needs a perennial river, and tidal power needs a suitable estuary.

Question 46Natural resources and their conservation

In the context of land resources, 'land degradation' is best indicated by

  1. an increase in the area under dense forest
  2. a single season of below-average rainfall
  3. a temporary rise in the water table
  4. a decline in soil organic matter, fertility and vegetation cover over time Correct answer.

Explanation

Land degradation is a persistent decline in the productive capacity of land, shown by loss of organic matter, nutrients and plant cover. A one-off dry spell or a temporary water-table change is a fluctuation, not degradation.

Question 47Natural resources and their conservation

Which sequence correctly orders the steps of a community-based waste-management plan for a residential colony?

  1. Burn all waste first, then segregate the ash, then recycle the unburnt residue
  2. Segregate waste at source, compost the wet fraction, recycle the dry fraction, landfill the rejects Correct answer.
  3. Landfill all waste, then segregate it at the dumping site, then compost the mixed material
  4. Collect mixed waste, dump it in a water body, then treat the water

Explanation

Effective waste management begins with segregation at source, which keeps the biodegradable fraction clean enough for composting and the dry fraction suitable for recycling. Only the residual rejects should reach a landfill.

Question 48Natural resources and their conservation

Which argument best explains why energy conservation is treated as a 'resource' in environmental planning?

  1. Saved energy must be stored in a battery to have any value
  2. Energy conservation increases the total demand for fossil fuel
  3. Every unit of energy saved avoids the extraction of fuel and the emissions that would have produced it Correct answer.
  4. Conservation applies only to non-renewable fuels used in industry

Explanation

Because a saved unit of energy need not be generated, the fuel and the associated environmental impacts are avoided at source. In planning terms this is equivalent to creating a supply of energy without new extraction.

Question 49Biodiversity and wildlife conservation

In the Western Ghats and Eastern Himalaya biodiversity hotspots of India, which feature best explains why these regions support exceptionally high species richness?

  1. Extremely low human population density inside the hotspot boundaries
  2. Uniform year-round temperature with no seasonal variation
  3. Very recent volcanic origin with bare, unweathered soils
  4. High endemism linked to long isolation and steep altitudinal or rainfall gradients Correct answer.

Explanation

Hotspots such as the Western Ghats and Eastern Himalaya combine long evolutionary isolation with steep environmental gradients, producing many endemic species found nowhere else. Their varied rainfall and altitude create diverse habitats that support high richness. Recent volcanism or uniform climate would not generate such endemism.

Question 50Biodiversity and wildlife conservation

A wildlife manager wants to protect a wide-ranging tiger population in a forest landscape fragmented by roads and farms. Which strategy directly addresses genetic and demographic isolation between fragments?

  1. Establishing wildlife corridors linking the forest patches Correct answer.
  2. Removing all native prey species from the fragments
  3. Increasing fertilizer use on the farmland between patches
  4. Converting the forest patches into monoculture plantations

Explanation

Corridors allow individuals to move between fragments, maintaining gene flow and allowing recolonisation after local losses. This reduces the extinction risk caused by isolation. Farming intensification, prey removal and plantation conversion would worsen fragmentation effects rather than relieve them.