I85PREP
⌘ K
WBCHSE HS ENVS study materials
WBCHSE HS ENVS study resources

WBCHSE HS ENVS practice questions

One question at a time. Build your WBCHSE HS ENVS understanding.

First 50 of 200 questions. Each one lists the choices, the correct answer, and an explanation. The checker at the top of this page saves progress in this browser when it is available.

Continue in the practice tool above to load more questions, 50 at a time.

Question 1Fundamentals of Environment and Ecology

In the WBCHSE environmental studies syllabus, the biosphere is best described as which of the following?

  1. The gaseous envelope lying above the tropopause
  2. Only the layer of soil that supports rooted plants
  3. The zone of life where the atmosphere, hydrosphere and lithosphere interact Correct answer.
  4. The complete body of water covering the Earth's surface

Explanation

The biosphere is the global zone in which living organisms exist, formed where the atmosphere, hydrosphere and lithosphere overlap and interact. It is not restricted to soil, water or upper air alone, but includes all these compartments together with their living inhabitants.

Question 2Fundamentals of Environment and Ecology

Which pair of organisms correctly illustrates a symbiotic relationship in which both partners benefit?

  1. Nepenthes capturing insects in its pitcher
  2. Lichen formed by an alga and a fungus Correct answer.
  3. Cuscuta growing on a host shrub
  4. Tapeworm living in the intestine of a mammal

Explanation

In a lichen the algal partner photosynthesises and supplies carbohydrates while the fungus provides shelter, anchorage and minerals, so both partners gain; this is mutualism. The other examples involve one partner gaining at the expense of another or a predatory habit.

Question 3Fundamentals of Environment and Ecology

A food chain in a grassland begins with grass and passes through grasshopper, frog and snake. At which trophic level does the frog feed?

  1. Second trophic level
  2. Third trophic level Correct answer.
  3. Fourth trophic level
  4. First trophic level

Explanation

Producers such as grass occupy the first trophic level, primary consumers the second, and secondary consumers the third. The frog eats the grasshopper, a primary consumer, so the frog is a secondary consumer and therefore occupies the third trophic level.

Question 4Fundamentals of Environment and Ecology

Which of the following is an abiotic component of an ecosystem?

  1. Humus content of the topsoil Correct answer.
  2. Bacteria decomposing leaf litter
  3. Fungi growing on dead wood
  4. Earthworms burrowing in the soil

Explanation

Abiotic components are the non-living physical and chemical factors of an ecosystem, and humus is dead organic matter mixed into soil, classified among these non-living factors. Bacteria, fungi and earthworms are living organisms and therefore belong to the biotic component.

Question 5Fundamentals of Environment and Ecology

In the context of environmental studies, 'ecological pyramid' refers to which of the following?

  1. A map showing the annual rainfall received by a region
  2. A chart of the population growth of a single species over time
  3. A graphical representation of trophic levels showing numbers, biomass or energy Correct answer.
  4. A list of the species recorded in a protected forest area

Explanation

An ecological pyramid is a diagram in which successive trophic levels are represented by bars, the length of each bar indicating numbers, biomass or energy. Species lists, rainfall maps and single-species growth curves describe different features and are not ecological pyramids.

Question 6Fundamentals of Environment and Ecology

Which of the following is a renewable natural resource?

  1. Natural gas trapped in sedimentary rock
  2. Petroleum of the Bombay High field
  3. Groundwater recharged by monsoon rain Correct answer.
  4. Coal seams of the Damodar valley

Explanation

Renewable resources are replenished by natural processes within a humanly useful timescale, and groundwater is recharged by rainfall and seepage. Coal, petroleum and natural gas are fossil fuels formed over millions of years and are therefore non-renewable.

Question 7Fundamentals of Environment and Ecology

Which gas is chiefly responsible for the natural greenhouse effect that keeps the Earth's mean temperature above freezing?

  1. Argon
  2. Oxygen
  3. Water vapour Correct answer.
  4. Nitrogen

Explanation

Water vapour is the most abundant greenhouse gas in the atmosphere and absorbs and re-emits infrared radiation, contributing the largest share of the natural greenhouse effect. Nitrogen, oxygen and argon are essentially transparent to infrared radiation and play no significant greenhouse role.

Question 8Fundamentals of Environment and Ecology

Two populations of the same species live in adjoining habitats separated by a broad river that they cannot cross. Over a long period this separation is most likely to produce which outcome?

  1. The two populations accumulate different variations and may diverge Correct answer.
  2. The two populations immediately merge into a single larger gene pool
  3. The two populations lose the ability to reproduce altogether
  4. The two populations interbreed freely and remain genetically identical

Explanation

Geographic isolation stops gene flow between the two populations, so mutations and natural selection act on each separately and they may gradually diverge. This is the classic route to speciation, and interbreeding between them becomes progressively less likely.

Question 9Fundamentals of Environment and Ecology

In an ecosystem, energy transfer from one trophic level to the next is inefficient mainly because which of the following occurs?

  1. Decomposers return energy directly to the producers
  2. Producers absorb almost all the solar energy that falls on them
  3. Consumers convert all ingested food into new body tissue
  4. Much energy is lost as heat through respiration at each level Correct answer.

Explanation

At each trophic level organisms use a large part of the energy they obtain for respiration, releasing it as heat, and some remains in uneaten or undigested matter. Only about ten per cent is passed on, which is why food chains rarely have more than four or five links.

Question 10Fundamentals of Environment and Ecology

A pond ecosystem is found to have a pyramid of numbers that is inverted. Which situation best explains this?

  1. A forest supports fewer deer than the tigers that hunt them
  2. Phytoplankton in a lake support fewer zooplankton than themselves
  3. A field of grass supports a smaller number of grazing cattle
  4. A single large banyan tree supports a very large number of insects Correct answer.

Explanation

An inverted pyramid of numbers arises when one large producer individual supports many small consumers, as when a single tree feeds numerous insects. The counts of organisms then increase at higher trophic levels even though energy flow still decreases.

Question 11Fundamentals of Environment and Ecology

Which sequence correctly represents the process of succession on bare rock in a humid region?

  1. Mosses, lichens, shrubs, trees
  2. Trees, shrubs, mosses, lichens
  3. Lichens, mosses, herbs and shrubs, trees Correct answer.
  4. Shrubs, lichens, trees, mosses

Explanation

On bare rock, crustose lichens are the pioneer community; they weather the rock and add organic matter, allowing mosses to follow, then herbs and shrubs, and finally a tree-dominated climax. Each stage modifies the habitat so that the next can establish.

Question 12Fundamentals of Environment and Ecology

Which of the following best describes the role of decomposers in nutrient cycling?

  1. They fix atmospheric nitrogen into nitrate within root nodules
  2. They absorb sunlight and convert it into chemical energy
  3. They break down dead organic matter and release inorganic nutrients Correct answer.
  4. They transfer nutrients directly from one consumer to another

Explanation

Decomposers such as bacteria and fungi mineralise dead organic matter, releasing nutrients like nitrogen, phosphorus and carbon back into the soil and water in inorganic forms. This makes the nutrients available again to producers and closes the biogeochemical cycle.

Question 13Fundamentals of Environment and Ecology

In the nitrogen cycle, which process converts ammonia in the soil into nitrite and then nitrate?

  1. Nitrification Correct answer.
  2. Denitrification
  3. Nitrogen fixation
  4. Ammonification

Explanation

Nitrification is the two-step oxidation of ammonia to nitrite by Nitrosomonas-type bacteria and then to nitrate by Nitrobacter-type bacteria. The nitrate formed is the form most readily absorbed by plant roots.

Question 14Fundamentals of Environment and Ecology

A farmer notices that repeated heavy irrigation in a semi-arid region has left a white crust on the soil surface and reduced crop yield. Which process most probably explains this?

  1. Leaching of nutrients into deep groundwater
  2. Accumulation of soluble salts through evaporation of irrigation water Correct answer.
  3. Waterlogging that increases soil aeration
  4. Rapid decomposition of soil humus by earthworms

Explanation

In semi-arid regions, irrigation water containing dissolved salts evaporates from the surface and leaves the salts behind, gradually building up a saline crust. High soil salinity raises osmotic stress on roots and lowers yields, a process called salinisation.

Question 15Fundamentals of Environment and Ecology

Which of the following is the most direct cause of the greenhouse effect intensifying due to human activity?

  1. Increased emission of carbon dioxide from burning fossil fuels Correct answer.
  2. Formation of argon during volcanic eruptions
  3. Release of oxygen from photosynthesis in forests
  4. Increased emission of nitrogen from legume cultivation

Explanation

Burning coal, oil and gas releases carbon dioxide that absorbs outgoing infrared radiation, strengthening the greenhouse effect. Nitrogen and oxygen are not greenhouse gases, and argon is chemically inert in this context.

Question 16Fundamentals of Environment and Ecology

Which of the following correctly distinguishes a habitat from a niche?

  1. Habitat is the physical place where an organism lives, while niche is its functional role Correct answer.
  2. Habitat is the functional role of a species, while niche is its address
  3. Habitat and niche are identical concepts used interchangeably
  4. Habitat refers only to aquatic environments, while niche refers only to terrestrial ones

Explanation

The habitat is the physical location or set of conditions in which an organism lives, whereas the niche is its functional role, including its resource use, tolerance limits and interactions with other species. Two species may share a habitat but occupy different niches.

Question 17Fundamentals of Environment and Ecology

In a lake, phytoplankton, zooplankton, small fish and large fish form a food chain. If a pollutant that biomagnifies enters the water, which group is expected to show the highest concentration per unit body mass?

  1. Small fish
  2. Zooplankton
  3. Phytoplankton
  4. Large fish Correct answer.

Explanation

Biomagnification is the progressive increase in the concentration of a persistent substance along a food chain. Because each predator consumes many prey and retains the pollutant, the highest trophic level, here the large fish, accumulates the greatest concentration per unit mass.

Question 18Fundamentals of Environment and Ecology

Which of the following best explains why the pyramid of energy is always upright in an ecosystem?

  1. Energy is lost as heat at each transfer, so higher levels hold less Correct answer.
  2. Numbers of organisms always decrease towards higher trophic levels
  3. Biomass always increases towards higher trophic levels
  4. Energy is created anew at each trophic level

Explanation

The second law of thermodynamics ensures that energy transfer is never completely efficient; a large fraction is dissipated as heat during respiration at each level. Consequently each successive trophic level contains less energy than the one below, so the energy pyramid can never be inverted.

Question 19Fundamentals of Environment and Ecology

Which statement about the carbon cycle is correct?

  1. Combustion of fossil fuels returns stored carbon to the atmosphere Correct answer.
  2. Respiration removes carbon dioxide from the atmosphere
  3. Decomposition permanently locks carbon in the lithosphere
  4. Photosynthesis releases carbon dioxide into the atmosphere

Explanation

Fossil fuels store carbon that was removed from the atmosphere long ago; burning them oxidises this carbon to carbon dioxide and returns it to the atmosphere. Photosynthesis removes carbon dioxide, while respiration and decomposition release it.

Question 20Fundamentals of Environment and Ecology

In a population that is growing exponentially, the rate of increase is proportional to which quantity?

  1. The carrying capacity of the habitat
  2. The square of the environmental resistance
  3. The number of deaths only
  4. The current population size Correct answer.

Explanation

Exponential growth follows dN/dt = rN, so the rate of change is directly proportional to the present population size N. As N grows, the absolute number of new individuals added per unit time grows with it, provided resources remain unlimited.

Question 21Fundamentals of Environment and Ecology

Which of the following best describes the concept of an ecological footprint?

  1. The area of productive land and water needed to support a population's consumption and waste Correct answer.
  2. The total area of forest reserved for a national park
  3. The number of species recorded in a given habitat
  4. The distance an animal travels during seasonal migration

Explanation

The ecological footprint measures the biologically productive area required to supply the resources a population consumes and to absorb the wastes it generates. Comparing it with available biocapacity indicates whether a population is living within its means.

Question 22Fundamentals of Environment and Ecology

Two species of barnacle occupy the same rocky shore, but one is confined to the upper zone while the other occupies the lower zone. When the upper-zone species is removed, the lower-zone species spreads upwards. Which conclusion is best supported?

  1. The two species occupy identical niches in the absence of competition
  2. The fundamental niche of the lower-zone species includes the upper zone Correct answer.
  3. The realised niche of each species is narrower than its fundamental niche
  4. The upper-zone species has no effect on the other species

Explanation

The spread of the lower-zone species into the upper zone once its competitor is removed shows that its fundamental niche extends there and that competition had restricted it to a narrower realised niche. The experiment demonstrates competitive exclusion operating in the field.

Question 23Fundamentals of Environment and Ecology

In a grassland food web, a drought sharply reduces the grass. Which of the following secondary effects is most consistent with ecological principles?

  1. The population of grasshoppers feeding on grass will decline Correct answer.
  2. The number of decomposers will immediately become zero
  3. The population of grasshoppers will increase because of reduced competition
  4. The carnivores will switch to eating grass directly

Explanation

A fall in the producer level reduces the food available to primary consumers, so the grasshopper population dependent on grass is expected to decline. This illustrates bottom-up control, in which the abundance of higher trophic levels is limited by resources at the base.

Question 24Fundamentals of Environment and Ecology

A lake receives heavy nutrient-rich runoff, and subsequent algal blooms are followed by a crash in dissolved oxygen. Which sequence best explains the oxygen depletion?

  1. Algae photosynthesise more and raise oxygen levels permanently
  2. Algal cells store oxygen internally and prevent its release
  3. Dead algae are decomposed by bacteria that consume dissolved oxygen Correct answer.
  4. Nutrients chemically combine with oxygen and remove it from water

Explanation

Nutrient enrichment causes eutrophication; the bloom dies, and aerobic bacteria decompose the dead algal biomass, consuming dissolved oxygen. The resulting hypoxia can kill fish and other aerobic organisms, showing why nutrient loading is a serious water-pollution problem.

Question 25Natural Resources and Their Conservation

In the classification of natural resources, which pair consists only of renewable resources?

  1. Petroleum and peat
  2. Copper ore and limestone
  3. Solar energy and wind Correct answer.
  4. Coal and natural gas

Explanation

Renewable resources are those replenished by natural processes within a humanly useful timescale, such as solar radiation and wind, which are continuously available. Coal, petroleum, peat and mineral ores form over geological time and are therefore non-renewable.

Question 26Natural Resources and Their Conservation

Which soil conservation measure involves ploughing along the contour of a slope rather than up and down it?

  1. Strip cropping
  2. Shelter-belt planting
  3. Terracing
  4. Contour ploughing Correct answer.

Explanation

Contour ploughing follows the level lines of a slope so that each furrow traps water and slows downslope flow, reducing sheet erosion. Terracing cuts stepped platforms, strip cropping alternates crop bands, and shelter belts are rows of trees.

Question 27Natural Resources and Their Conservation

The chief cause of the greenhouse effect linked to deforestation is best described as:

  1. Increase in soil nitrogen fixation after clearing
  2. Increased emission of chlorofluorocarbons from cleared land
  3. Rise in oxygen concentration of the atmosphere
  4. Reduction in the carbon dioxide absorbed by vegetation Correct answer.

Explanation

Growing vegetation absorbs atmospheric carbon dioxide during photosynthesis and stores carbon in biomass. When forests are cleared, this sink is lost and the stored carbon is released, raising the atmospheric concentration of carbon dioxide, a major greenhouse gas.

Question 28Natural Resources and Their Conservation

In a food chain, the total energy available to the next trophic level is roughly one-tenth of that at the previous level. This principle is known as:

  1. Gause's competitive exclusion principle
  2. Liebig's law of the minimum
  3. The ten per cent law of energy flow Correct answer.
  4. The law of limiting factors

Explanation

The ten per cent law states that only about ten per cent of energy at one trophic level is transferred to the next, the rest being lost mainly as heat through respiration. This is why food chains rarely have more than four or five links.

Question 29Natural Resources and Their Conservation

Which of the following is an example of an in-situ method of biodiversity conservation?

  1. A national park protecting a wild habitat Correct answer.
  2. Cryopreservation of gametes in a laboratory
  3. A captive breeding centre for a rare mammal
  4. Seed bank storage of endangered plant varieties

Explanation

In-situ conservation protects species within their natural habitat, and a national park conserves the whole ecosystem in place. Seed banks, captive breeding and cryopreservation are ex-situ methods that remove the organism from its natural setting.

Question 30Natural Resources and Their Conservation

Which of the following is a non-conventional source of energy?

  1. Biogas Correct answer.
  2. Anthracite
  3. Bituminous coal
  4. Lignite

Explanation

Non-conventional energy sources are those not traditionally exploited on a large scale, such as biogas, solar, wind and tidal power. Coal in its various grades is a conventional fossil fuel.

Question 31Natural Resources and Their Conservation

The chief function of a leguminous cover crop such as sunhemp in crop rotation is to:

  1. Kill soil-borne pathogens by releasing antibiotics
  2. Enrich soil nitrogen through symbiotic root nodules Correct answer.
  3. Increase soil bulk density for better anchoring
  4. Raise soil pH by adding calcium carbonate

Explanation

Legumes form root nodules with Rhizobium bacteria that fix atmospheric nitrogen into usable compounds, so ploughing them in adds nitrogen to the soil. They do not act as antibiotics, liming agents or compaction agents.

Question 32Natural Resources and Their Conservation

A farmer on a gentle slope notices rills forming after heavy rain and wants the cheapest immediate check on sheet erosion. Which practice should be recommended first?

  1. Ploughing up and down the slope to speed drainage
  2. Building a concrete check dam in the main channel
  3. Abandoning the field and replanting with forest
  4. Contour bunding with grassed waterways Correct answer.

Explanation

Contour bunding creates small earthen barriers along the contour that intercept runoff and allow infiltration, while grassed waterways safely carry excess water away. It is low cost and directly targets sheet and rill erosion on gentle slopes.

Question 33Natural Resources and Their Conservation

A region receives 120 cm of annual rainfall but loses most of it as surface runoff because of bare, compacted soil. Which combination would most directly improve groundwater recharge there?

  1. Concreting the catchment surface
  2. Contour trenches plus vegetative cover Correct answer.
  3. Deep ploughing plus removal of all vegetation
  4. Construction of a lined canal to the sea

Explanation

Contour trenches trap runoff and hold it long enough to percolate, and vegetation improves infiltration by loosening soil and slowing flow. Together they convert surface runoff into groundwater recharge.

Question 34Natural Resources and Their Conservation

In a biogas plant, the gas is produced by anaerobic digestion of cattle dung. The main combustible component of the gas is:

  1. Carbon dioxide
  2. Methane Correct answer.
  3. Nitrogen
  4. Hydrogen sulphide

Explanation

Biogas typically contains about 50 to 70 per cent methane, which burns to release energy. Carbon dioxide and nitrogen are diluents and hydrogen sulphide is a trace impurity that causes odour and corrosion.

Question 35Natural Resources and Their Conservation

Which statement best explains why shifting cultivation is considered unsustainable when fallow periods are shortened?

  1. Crop yields rise because nutrients accumulate faster
  2. Soil organic matter and nutrients are not replenished before the next cropping cycle Correct answer.
  3. Pests are eliminated by frequent clearing
  4. Rainfall declines permanently once forest is cleared

Explanation

Shifting cultivation relies on a long fallow during which vegetation regrows and restores soil fertility. If the fallow is cut short, nutrients removed by crops are not replaced and soil organic matter declines, so yields fall and land degrades.

Question 36Natural Resources and Their Conservation

Which of the following best illustrates the difference between a renewable and a non-renewable groundwater resource?

  1. Renewable water is recharged by rainfall at a usable rate; non-renewable water is fossil water recharged over geological time Correct answer.
  2. Renewable water is always fresh; non-renewable water is always saline
  3. Renewable water is surface water; non-renewable water is rainwater
  4. Renewable water is stored in confined aquifers; non-renewable water is in unconfined aquifers

Explanation

The distinction rests on the rate of replenishment: renewable groundwater is refilled by recharge within human timescales, whereas fossil water in deep aquifers accumulated over thousands of years and is effectively mined once extracted.

Question 37Natural Resources and Their Conservation

The chief reason tropical rainforests support very high species diversity despite nutrient-poor soils is that:

  1. Herbivores are scarce, so plants escape damage
  2. Nutrients are held mainly in the living biomass and recycled rapidly Correct answer.
  3. The soils contain large reserves of humus that sustain many species
  4. Low rainfall prevents nutrients from leaching away

Explanation

In tropical rainforests most nutrients are locked in vegetation and litter, and decomposition and uptake are rapid, so the nutrient pool turns over quickly. The soil itself holds little, which is why clearing the forest rapidly depletes fertility.

Question 38Natural Resources and Their Conservation

Which of the following is the most appropriate method of conserving a wild animal species whose habitat has been fragmented into small isolated patches?

  1. Increasing pesticide use around the patches
  2. Establishing wildlife corridors between the patches Correct answer.
  3. Removing all predators from the patches
  4. Converting the patches into plantations

Explanation

Corridors reconnect isolated habitat patches, allowing gene flow, migration and access to resources, which reduces inbreeding and local extinction risk. The other measures either destroy habitat or destabilise the ecosystem.

Question 39Natural Resources and Their Conservation

In a pond ecosystem, if all the herbivorous fish are removed, the most immediate expected effect is:

  1. An increase in dissolved oxygen
  2. Immediate extinction of the predatory fish
  3. A rise in phytoplankton biomass Correct answer.
  4. A fall in phytoplankton biomass

Explanation

Herbivorous fish graze on phytoplankton and keep their population in check. Removing them releases phytoplankton from grazing pressure, so their biomass rises, often causing algal blooms and lowered oxygen at night.

Question 40Natural Resources and Their Conservation

Which of the following practices best exemplifies sustainable use of a forest resource?

  1. Selective felling with replanting of harvested species Correct answer.
  2. Burning undergrowth to clear land for annual crops
  3. Converting forest land to permanent concrete construction
  4. Clear-felling an entire watershed every year

Explanation

Selective felling removes only mature trees of chosen species and replanting restores the stand, so the forest continues to provide timber and ecosystem services. The other practices remove the resource faster than it regenerates.

Question 41Natural Resources and Their Conservation

A coastal village depends on mangrove forests for storm protection. Which argument best supports conserving the mangroves rather than replacing them with shrimp ponds?

  1. Mangroves yield higher immediate cash returns than shrimp
  2. Mangroves cannot regenerate after any disturbance
  3. Shrimp ponds require no freshwater and therefore cannot fail
  4. Mangroves provide storm buffering and nursery habitat whose loss raises long-term vulnerability Correct answer.

Explanation

Mangroves dissipate wave energy and serve as nurseries for fish and crustaceans, giving continuing ecological and economic benefits. Replacing them with ponds yields short-term profit but removes coastal protection and fisheries support, increasing vulnerability.

Question 42Natural Resources and Their Conservation

Which of the following correctly pairs a fossil fuel with its dominant hydrocarbon constituent?

  1. Natural gas - methane Correct answer.
  2. Natural gas - butane
  3. Petroleum - methane
  4. Coal - octane

Explanation

Natural gas is composed predominantly of methane, with smaller amounts of ethane, propane and butane. Petroleum is a mixture of heavier liquid hydrocarbons and coal is a solid, heterogeneous carbonaceous rock.

Question 43Natural Resources and Their Conservation

The chief environmental concern with large dams on rivers is best summarised as:

  1. Complete elimination of all downstream flow in every season
  2. Permanent increase in downstream sediment deposition on floodplains
  3. Loss of all groundwater recharge in the entire basin
  4. Fragmentation of river continuity and displacement of riparian communities Correct answer.

Explanation

Dams interrupt the longitudinal continuity of rivers, blocking fish migration and trapping sediment, while submergence displaces people and alters downstream ecology. These are the well-documented social and ecological costs.

Question 44Natural Resources and Their Conservation

Which of the following best describes the role of a decomposer in nutrient cycling?

  1. Fixing atmospheric nitrogen into nitrate in root nodules
  2. Breaking down dead organic matter to release inorganic nutrients Correct answer.
  3. Converting solar energy into chemical energy
  4. Transferring energy directly to top carnivores

Explanation

Decomposers such as bacteria and fungi mineralise dead organic matter, releasing inorganic nutrients like nitrates and phosphates back into the soil for reuse by producers. This closes the nutrient loop in ecosystems.

Question 45Natural Resources and Their Conservation

A city plans to reduce its solid-waste load. Which sequence correctly represents the preferred waste-management hierarchy from most to least desirable?

  1. Prevention, reuse, recycling, safe disposal Correct answer.
  2. Safe disposal, prevention, reuse, recycling
  3. Recycling, landfilling, prevention, reuse
  4. Landfilling, recycling, reuse, prevention

Explanation

The waste hierarchy ranks options by environmental benefit: preventing waste generation is best, followed by reuse, then recycling, with safe disposal such as sanitary landfilling as the last resort.

Question 46Natural Resources and Their Conservation

In a region where groundwater withdrawal exceeds natural recharge, the most likely long-term consequence is:

  1. Permanent improvement in aquifer storage
  2. Spontaneous increase in rainfall recharge
  3. Land subsidence and intrusion of saline water in coastal areas Correct answer.
  4. Rise of the water table and waterlogging

Explanation

When extraction outpaces recharge, aquifer pressure falls, causing compaction and land subsidence; near the coast, the water table drop allows seawater to intrude into the aquifer. Over-abstraction therefore degrades both land and water quality.

Question 47Natural Resources and Their Conservation

Two plots have the same rainfall and slope. Plot A is under continuous cereal cropping with residue removal; Plot B is under agroforestry with mulch return. Which outcome is most defensible?

  1. Plot B will suffer more erosion because trees shade out ground cover
  2. Plot A will have higher soil organic carbon because cereals add more root litter
  3. Both plots will lose soil at identical rates because rainfall and slope are the same
  4. Plot B will have higher infiltration and lower runoff because mulch and tree roots improve structure Correct answer.

Explanation

Mulch protects the surface from raindrop impact and tree roots and organic matter improve aggregate stability and porosity, raising infiltration and cutting runoff. With identical rainfall and slope, land management becomes the decisive variable.

Question 48Natural Resources and Their Conservation

A biodiversity hotspot is defined by which pair of criteria?

  1. Exceptional endemism and severe habitat loss Correct answer.
  2. Large area and low human population
  3. High productivity and low extinction risk
  4. High species richness and low endemism

Explanation

Hotspots are regions with exceptional concentrations of endemic species that have already lost a large proportion of their original habitat. Both high endemism and severe habitat loss must be present.

Question 49Ecosystems, Biodiversity and Wildlife Conservation

In the WBCHSE Environmental Science syllabus, the level of biological organisation that includes a community together with its non-living environment is called a/an:

  1. biome
  2. ecosystem Correct answer.
  3. species
  4. population

Explanation

An ecosystem is the functional unit formed by a biotic community interacting with abiotic factors such as soil, water, light and temperature in a defined area. A population is only one species, and a biome is a very large climatic region, so neither matches the definition given in the stem.

Question 50Ecosystems, Biodiversity and Wildlife Conservation

Which pair correctly matches a trophic level with the type of organism that usually occupies it in a grassland ecosystem?

  1. Primary consumer - grasshopper feeding on grass Correct answer.
  2. Decomposer - hawk catching a snake
  3. Producer - cow grazing on grass
  4. Secondary consumer - grass plant

Explanation

A primary consumer is a herbivore that feeds directly on producers, so a grasshopper eating grass fits the first trophic level of consumers. The other pairs misassign organisms to levels they do not occupy in a grassland food chain.