40 Important EVS Questions.
10 Units. Explained.

Correct: B. It integrates natural sciences with policy, technology and social dimensions

Environmental Sciences combines ecology, chemistry, geology, engineering, public policy and human behaviour to study linked environmental problems. An interdisciplinary question may require more than one of these perspectives.

Common trap: Do not treat Environmental Sciences and ecology as identical.

Correct: C. Photosynthesis

Photosynthetic organisms incorporate CO₂ into organic matter using light energy. Respiration, combustion and many decomposition processes generally return CO₂ to the atmosphere.

Common trap: Do not confuse carbon fixation with carbon release.

Correct: B. 20 kJ

Producers → primary consumers: 2,000 × 0.10 = 200 kJ. Primary → secondary consumers: 200 × 0.10 = 20 kJ. The 10% rule is an approximate teaching model, not a fixed value for every ecosystem.

Common trap: Count the number of trophic transfers before calculating.

Correct: B. Resilience

Resilience is the capacity to recover after disturbance. Resistance refers to remaining relatively unchanged when a disturbance occurs. Wetlands may display both properties in different circumstances.

Common trap: Recovery after change = resilience; little change during disturbance = resistance.

Correct: B. 5

Using pH = −log₁₀(aH⁺), pH = −log₁₀(10⁻⁵) = 5. In introductory calculations, concentration is often used as an approximation for activity in dilute solutions.

Common trap: The negative sign in the pH equation is essential.

Correct: C. 2 meq/L

For alkalinity reported as CaCO₃, 1 meq/L corresponds to 50 mg/L as CaCO₃. Therefore, 100 ÷ 50 = 2 meq/L. This conversion is frequently useful in aqueous chemistry calculations.

Common trap: Do not use the molecular mass 100 g/mol as the equivalent weight; it is 50 g/equiv.

Correct: C. SO₂ and NOₓ can produce acids in the atmosphere

Sulfur dioxide and nitrogen oxides can be oxidised and converted into sulfuric and nitric acids in the atmosphere. Natural rain is already weakly acidic because dissolved CO₂ forms carbonic acid; acid rain typically refers to rain below that natural background.

Common trap: Avoid assuming neutral pH 7 for unpolluted rain.

Correct: B. Loss of electrons

Oxidation is loss of electrons and is generally accompanied by an increase in oxidation number. Reduction is gain of electrons. In environmental chemistry, these ideas help explain transformations of metals and contaminants.

Common trap: Remember OIL RIG: Oxidation Is Loss, Reduction Is Gain.

Correct: C. K/2

For dN/dt = rN(1−N/K), growth is maximum at N = K/2 when r and carrying capacity K are constant. Near carrying capacity, net population growth approaches zero.

Common trap: Differentiate maximum absolute growth from maximum per-capita growth.

Correct: B. 800

NPP = GPP − autotrophic respiration = 1,200 − 400 = 800 g C m⁻² yr⁻¹. The result represents the carbon fixed by producers after their own respiratory losses.

Common trap: Do not add respiration to GPP; subtract it.

Correct: B. Mutualistic association

Lichens are composite symbiotic associations. The photosynthetic partner supplies organic carbon, while the fungal partner provides structural support and influences water and mineral relations. The interaction is often introduced as mutualism, though its ecology can be more complex.

Common trap: Avoid confusing a symbiotic association with predation.

Correct: B. Persistent lipophilic pollutants

Persistent, bioaccumulative chemicals such as some organochlorine compounds may rise in concentration at successive trophic levels. Persistence and biological accumulation are key features behind biomagnification.

Common trap: Bioaccumulation occurs within organisms; biomagnification describes increasing concentration along trophic levels.

Correct: B. 1 m³/day

Q = K × i × A = 2 × 0.05 × 10 = 1 m³/day. This simplified application assumes Darcy-flow conditions and compatible units.

Common trap: Check units: (m/day) × (dimensionless) × (m²) = m³/day.

Correct: C. 25%

Porosity = pore volume / total bulk volume × 100 = 25/100 × 100 = 25%. Porosity is not the same as hydraulic conductivity or permeability.

Common trap: Use bulk volume as denominator, not the volume of solid grains.

Correct: B. Cooling and solidification of molten material

Igneous rocks form when magma or lava cools and solidifies. Sedimentary rocks commonly develop through deposition and lithification, while metamorphic rocks are transformed by heat and pressure without complete melting.

Common trap: Keep formation mechanisms of three major rock groups distinct.

Correct: C. 0.50

NDVI = (NIR − Red)/(NIR + Red) = (0.60 − 0.20)/(0.60 + 0.20) = 0.40/0.80 = 0.50. NDVI is a vegetation index, not a direct measure of biomass in every setting.

Common trap: The denominator is the sum of bands, not the red band alone.

Correct: C. 8

Available wind power P = ½ρAv³. Doubling v multiplies power by 2³ = 8. Actual delivered electricity is lower because the turbine and generator are not perfectly efficient.

Common trap: Wind energy scales with the cube of speed, not the square.

Correct: C. 12.5%

Incident solar power = 1,000 × 1.6 = 1,600 W. Module efficiency = 200/1,600 × 100 = 12.5% under the stated conditions.

Common trap: Use incident power on the entire module area as denominator.

Correct: C. 6 kWh

Energy = power × time = 2 kW × 3 h = 6 kWh. A kilowatt is a unit of power; a kilowatt-hour is a unit of energy.

Common trap: Do not treat kW and kWh as interchangeable units.

Correct: C. 59.3%

The theoretical Betz limit is 16/27 ≈ 59.3% under ideal assumptions. Real turbines operate below this ideal value because of mechanical, aerodynamic and electrical losses.

Common trap: The Betz limit is not the overall efficiency of every real wind turbine.

Correct: B. 5 mg/L

Oxygen depletion = initial DO − final DO = 8 − 3 = 5 mg/L. Actual standard BOD₅ analysis can require dilution and seed corrections, so this is a simplified concept exercise.

Common trap: Do not call every oxygen-depletion result a fully corrected laboratory BOD₅ value.

Correct: C. 75%

Removal efficiency = (C_in − C_out)/C_in × 100 = (200 − 50)/200 × 100 = 75%. This concentration-based estimate assumes comparable flows when interpreting mass removal.

Common trap: Always divide by the inlet value.

Correct: C. Suppressed upward mixing and possible pollutant buildup

An inversion means temperature increases with height over a layer, inhibiting vertical convection. Pollutants released below the inversion can be trapped near the surface under suitable meteorological conditions.

Common trap: An inversion is a stability condition, not a pollution-control device.

Correct: B. 3 dB

Difference = 10 log₁₀(I₂/I₁) = 10 log₁₀ 2 ≈ 3.01 dB. A tenfold intensity increase corresponds to 10 dB.

Common trap: For intensity use 10 log, not 20 log (which applies to pressure amplitudes under specified conditions).

Correct: C. Waste prevention or reduction

Preventing waste at source avoids material use, collection and disposal burdens. Reuse and recycling follow in common hierarchy frameworks; disposal is typically the least preferred option.

Common trap: Waste-to-energy is not the same as waste prevention.

Correct: B. Liquid that has percolated through waste and may carry dissolved or suspended contaminants

Rainwater and other liquids passing through refuse can dissolve or carry contaminants, forming leachate. Its management is a major design issue for sanitary landfills.

Common trap: Distinguish leachate (liquid) from landfill gas.

Correct: A. Oxygen-consuming microbial decomposition

Aerobic composting uses oxygen-dependent microbial activity to transform biodegradable organic materials into more stable products. Aeration, moisture and carbon-to-nitrogen balance affect performance.

Common trap: Anaerobic digestion is a different process with different conditions and outputs.

Correct: C. 300 kg

Biodegradable fraction = 500 × 0.60 = 300 kg/day. This calculation does not imply all 300 kg will be recovered or composted; collection and processing losses matter.

Common trap: Convert percentage to decimal before multiplication.

Correct: B. Identify important impacts and define the study’s terms of reference

Scoping identifies the significant environmental issues that need assessment and helps frame study boundaries and terms of reference. Screening, impact prediction, consultation and appraisal serve different functions.

Common trap: Do not confuse screening (whether EIA is required) with scoping (what EIA should study).

Correct: B. Avoiding impacts

Avoidance is preferred because an impact not created does not need repair. Minimisation, restoration and offsets are considered later according to context and applicable requirements.

Common trap: Offsets are not a first-choice substitute for preventing damage.

Correct: B. Environmental management systems

ISO 14001 specifies requirements for an environmental management system that an organisation can use to manage environmental responsibilities. It does not itself impose one universal emission limit for all sectors.

Common trap: A management-system standard is not the same thing as a national emission standard.

Correct: A. Montreal Protocol

The Montreal Protocol controls production and consumption of many ozone-depleting substances. The Paris Agreement concerns climate change; CBD focuses on biodiversity; Ramsar concerns wetlands.

Common trap: Do not confuse stratospheric ozone protection with climate-change treaty goals.

Correct: B. 5

Mean = sum of observations divided by their count = (2+4+6+8)/4 = 20/4 = 5. The mean is sensitive to extreme values, unlike the median in many datasets.

Common trap: Divide by the number of observations, not by the largest observation.

Correct: A. A strong negative linear association

A value close to −1 indicates a strong negative linear association between two measured variables. Correlation alone does not prove that one variable causes the other.

Common trap: Strong correlation does not automatically establish causation.

Correct: B. Reject H₀

Because p < α, reject the null hypothesis under the specified testing assumptions. Statistical significance is not equivalent to practical importance or a 97% probability that the alternative hypothesis is true.

Common trap: A p-value is not the probability that the null hypothesis is true.

Correct: B. 2

Population mean = 12. Squared deviations are (10−12)² = 4 and (14−12)² = 4. Population variance = (4+4)/2 = 4, so population SD = √4 = 2.

Common trap: Population SD divides squared deviations by N; sample SD uses N−1.

Correct: B. A specified time horizon

GWP compares the radiative influence of a unit mass emission against CO₂ over a defined time horizon, commonly 100 years. The selected period matters because gases have different atmospheric lifetimes.

Common trap: A GWP value should not be quoted without its time horizon and assessment context.

Correct: A. Absorption of atmospheric CO₂ and formation of carbonic acid

As seawater absorbs CO₂, carbonate equilibria shift and hydrogen-ion concentration increases, lowering pH. This can affect carbonate availability and calcifying organisms. Ocean acidification does not mean that average seawater has become pH < 7.

Common trap: A falling pH is acidification even when the water remains alkaline.

Correct: B. Stratospheric ozone absorbs harmful UV, while surface ozone can harm health and vegetation

The stratospheric ozone layer helps screen ultraviolet radiation. Near the surface, ozone is a photochemical oxidant that can damage respiratory tissues and vegetation. The molecule is the same; its environmental role depends strongly on location.

Common trap: Location and exposure determine whether ozone is protective or harmful.

Correct: A. Designing products for easy repair, reuse and material recovery

Circular-economy strategies seek to keep products and materials in use and reduce waste through durable design, maintenance, reuse, repair and appropriate recycling. These approaches should still be evaluated for their overall environmental impacts.

Common trap: Recycling alone is not the entire circular economy; product design and reuse matter.