UGC NET Paper 2: Environmental Science 21st Dec 2018 (Previous Year Paper)

Explanation:

• Natural systems are regularly interacting and interdependent components of air, water, land and biological resources.
• Sun is our life source which makes it possible for life to exist on Earth.
• The United Nations (UN) defines sustainability simply as “meeting the needs of the present without compromising the ability of future generations to meet their own needs.”
• This sun as a resource will never run out.
• It is free, sustainable, and completely inexhaustible.
• We will have a steady, limitless supply of sunlight for another 5 billion years.
• We cannot maintain our Earth's ecosystems or continue to function as we do if more sustainable choices are not made.
• If harmful processes are maintained with no change, it is likely that we will run out of fossil fuels, huge numbers of animal species will become extinct, and the atmosphere will be irreparably damaged.
• Natural ecosystems, whose components are the results of natural selection, are sustainable;
• Solar radiation is the fundamental energy driving our climate system, and nearly all climatic and biological processes on Earth are dependent on solar input.
• Energy from the sun is essential for many processes on Earth including warming of the surface, evaporation, photosynthesis, and atmospheric circulation.

​Both Assertion and Reason statements are correct and R is the correct explanation of A. 

Hence, option 1 is the correct answer.

Explanation:

• The “alpine timberline” is a transition zone alternating between trees, shrubs, and grasslands along the altitude gradient.
• It is at the forefront of the struggle for survival, and is an ecotone that marks the transition between forest and alpine shrub or meadow along altitude gradients.
• It represents the highest altitude at which shoots of woody plants can grow and ripen under the air temperatures which prevail at the height of tree canopies.
• Within this zone, the timberline migrates upwards or downwards as a result of long-term changes in environmental conditions, including changes in temperature, precipitation, the occurrence of strong winds, the availability of carbon, and the amount of damage due to frost.
• These are characterized by lower annual temperatures and insufficient precipitation, resulting in which the trees experiencing a cold climate and physiological drought that hamper their growth.
• Additionally, the alpine timberline fluctuates with variations in multiple factors, such as dominant tree species, topography, and climatic conditions.
• The dynamics in different regions currently present distinct characteristics. For eg. In the alpine region of the Himalayas, the timberline shifted 10 m year⁻¹ from the 1970s to 2006. Near the Yamunotri watershed, the alpine timberline moved to a higher altitude at an average rate of 4 m year⁻¹ during the past 20 years.
• It is critical for maintaining alpine biodiversity and functioning montane ecosystems—is the long-term result of natural environmental conditions and is extremely sensitive to global change.
• Temperature and moisture are the major limiting factors.
• The gradual decrease in temperature with elevation in montane systems greatly influences vegetation metabolic processes and alpine timberline formation. Therefore, the temperature is generally regarded as the primary driver of the alpine timberline. On a global scale, the alpine timberline possessed a trend consistent with the global ground isotherm (6.7 ± 0.8 °C). However, changing temperatures in different regions create an asynchronism between the dynamics of alpine timberline and global warming
• Additionally, rainfall is also an important factor regulating alpine timberlines in some regions and can improve growing conditions. In short, water and heat conditions are the key drivers affecting alpine timberlines; however, the dynamic mechanisms involved remain undetermined as yet.

A and R are correct and R is the correct explanation of A.

Hence, option 1 is the correct answer.

The correct answer is 60.0 L mol-1 cm-1.

Key PointsGiven:

Path length, l = 5.0 cm

Slope = 300.0 L mol^-1

Using the formula:

Slope = Molar absorptivity (E) x Path length

300 = E × 5

E = $300\over5$ = 60

Therefore, the correct answer is 60.0 L mol-1 cm-1.

The correct option is '3) (A) is true, but (R) is false.'

Key Points

• Assertion (A): The acid rain lowers the fertility of soil.
• This statement is true.
• Soil Fertility Impact: Acid rain, which contains sulfuric and nitric acids, can lower the pH of the soil, making it more acidic. This negatively impacts soil fertility by leaching important nutrients such as calcium, magnesium, and potassium from the soil.
• Impact on Microorganisms: Acidic soil conditions can also hurt beneficial soil microorganisms, which play a crucial role in nutrient cycling and maintaining soil health.
• Reason (R): Hydrogen ions exchange the nutrient anions.
• This statement is false.
• Ion Exchange Mechanism: The process that typically occurs in the soil due to acid rain involves hydrogen ions (H⁺) replacing essential nutrient cations (positively charged ions) like calcium (Ca²⁺), magnesium (Mg²⁺), and potassium (K⁺) rather than anions (negatively charged ions). This process is called cation exchange.
• Cation vs. Anion Exchange: The exchange of hydrogen ions with nutrient cations leads to the leaching of these essential nutrients from the soil and reduces soil fertility. While anion exchange also occurs, it is less relevant to the specific impact of acid rain on soil fertility.
• Evaluation of the Relationship Between A and R:
• While the assertion (A) is true that acid rain lowers the fertility of soil, the reason (R) provided is incorrect.
• Reason (R) incorrectly states that hydrogen ions exchange with nutrient anions, whereas the actual process involves the exchange of hydrogen ions with nutrient cations.
• Therefore, (A) is true, but (R) is false and does not provide the correct explanation for (A).

Additional Information

• Soil Acidification: The process of soil acidification can be detrimental to plant growth and soil structure.
• Environmental Concerns: The decline in soil fertility caused by acid rain can lead to reduced agricultural productivity and forest degradation.
• Preventive Measures: Liming of soil is a common practice to neutralize acidity and restore soil health.

The correct answer is X-ray fluorescence spectrometry.

Key Points

Spectrophotometry:

• Spectrophotometry is a standard and inexpensive technique to measure light absorption or the number of chemicals in a solution.
• It uses a light beam which passes through the sample, and each compound in the solution absorbs or transmits light over a certain wavelength.
• Spectrophotometry is used for the quantitative determination of a great variety of substances in solution.
• These range from water and wastewater analysis to pharmaceutical quality control and food analysis.
• Applications: Quantifying concentrations of compounds, determining the structure of a compound, finding functional groups in chemicals, determining the molecular weight of compounds, determining the composition of materials etc.

Flame Photometry

• Flame photometry is defined as the measurement of the intensity of the light emitted when any alkali or earth metal is introduced into the flame.
• Because of the emission of radiation, it is also known as flame emission spectroscopy.
• Based on the element in the sample, it produces emission spectra and different colours to the flame.
• The principle of the flame photometer is based on the measurement of the emitted light intensity when a metal is introduced into the flame.
• The wavelength of the colour gives information about the element and the colour of the flame gives information about the amount of the element present in the sample.
• Applications: A flame photometer can be used to determine the concentration of certain metal ions like sodium, potassium, lithium, calcium and caesium etc.

Atomic Absorption Spectroscopy

• Atomic absorption spectroscopy (AAS), is a technique for measuring the concentrations of metallic elements in different materials.
• As an analytical technique, it uses electromagnetic wavelengths, coming from a light source.
• Distinct elements will absorb these wavelengths differently.
• It uses the principle that atoms (and ions) can absorb light at a specific, unique wavelength.
• When this specific wavelength of light is provided, the energy (light) is absorbed by the atom.
• Applications: Atomic absorption spectroscopy is utilized across many industries and is instrumental in the detection of metals within a sample. As such, this process is commonly utilized in pharmacology, archaeology, manufacturing, mining, and forensics.

X-ray fluorescence spectrometry

• XRF (X-ray fluorescence) is a non-destructive analytical technique used to determine the elemental composition of materials.
• XRF analyzers determine the chemistry of a sample by measuring the fluorescent (or secondary) X-ray emitted from a sample when it is excited by a primary X-ray source.
• Each element in a sample produces a set of characteristic fluorescent X-rays (fingerprints) unique for that specific element, which is why XRF spectroscopy is an excellent technology for qualitative and quantitative analysis of material composition.
• Applications: XRF can be used for a variety of analytical procedures, including geology, soil surveys, and field analysis. Due to the versatility of XRF, it can be used to examine everything from sewage sludge, car exhausts, river water, etc.

Therefore, the correct answer is ​X-ray fluorescence spectrometry.

The correct answer is (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i).

Key PointsSoil profile: 

• A soil profile is a vertical cross-section that can be viewed by excavating a rectangular pit or sampling the soil layer by layer.
• A soil profile is divided into layers called horizons.
• The main soil horizons are O, A, B and C.

Therefore, the correct answer is (a) - (ii), (b) - (iii), (c) - (iv), (d) - (I).

Additional Information

The correct answer is CO2.

Key Points

• While pure, neutral water would have a pH of 7, CO2 in the air dissolves in water to form carbonic acid, giving it a slightly acidic pH of 5.6.
• Acid rain occurs when nitrogen and sulfur oxides present in exhaust gases from burning fossil fuels dissolve in the water to form stronger sulfuric, sulfurous, and nitric acids.
• These acids in rain can lower the pH to 3 or lower, about 400 times stronger acid than the pH of 5.6.

Therefore, the correct answer is CO2.

The correct answer is N2 and O2.

Key Points

• The atmosphere contains many gases, most in small amounts, including some pollutants and greenhouse gases.
• The most abundant gas in the atmosphere is nitrogen, with oxygen second and argon, an inert gas the third most abundant gas in the atmosphere.
• The atmosphere is composed of a mix of several different gases in differing amounts.
• The permanent gases whose percentages do not change from day to day are nitrogen, oxygen and argon.
• Nitrogen accounts for 78% of the atmosphere, oxygen 21% and argon 0.9%.
• Gases like carbon dioxide, nitrous oxides, methane, and ozone are trace gases that account for about a tenth of 1% of the atmosphere.
• Water vapour is unique in that its concentration varies from 0-4% of the atmosphere depending on where you are and what time of the day it is.

Therefore, the correct answer is N2 and O2.

The correct answer is N2O.

Key Points

• Nitrous oxide (N₂O), also called laughing gas, is often used by dentists as an anaesthetic.
• The important source of N₂O is found in the natural and agricultural cycling of the nitrogen that is necessary for the maintenance of living matter.
• N₂O is particularly important because it is an unreactive gas which is not water-soluble and does not absorb visible radiation i.e., does not undergo photodissociation in the troposphere.
• The atmospheric lifetime of N₂O is estimated to be about 150 years.
• Its primary destruction path is its transportation to the stratosphere where it absorbs UV radiation to form N₂ and an oxygen atom (O).
• A minor destruction pathway (about 3.5a %) is the reaction with O(1D) to form two NO molecules.
• N₂O thus acts as a carrier of reactive nitrogen to the stratosphere.
• It is one of the many forms of nitrogen that participate in the biogeochemical cycle of nitrogen.

Therefore, the correct answer is N2O.

Additional Information

• Reactive nitrogen species formed in the troposphere, such as NO or nitrogen dioxide (NO₂), have very short atmospheric lifetimes.
• Nitric oxide (NO) results from the combination of O₂ and N₂ in lightning strikes. It is a radical and so is very reactive in the atmosphere.
• Nitrogen dioxide (NO₂) is a brown gas, the responsible colour of photochemical smog. This is produced by the combustion of fossil fuels and biomass as well as by the oxidative decomposition of ammonia in the atmosphere. It is a radical and so is reactive in the atmosphere.
• Dinitrogen tetraoxide (N₂O₄) has a very weak N-N bond and is in equilibrium with NO₂. It is a diamagnetic substance. It reacts with water to form nitrous and nitric acids and it oxidizes many metals.

The correct answer is Chaparral forest.

Key PointsChaparral forest:

• Chaparral is a type of woodland characterized by a combination of dry soil, warm weather, and short, hardy shrubs.
• The chaparral biome is dominated by short woody plants, rather than grasses (as in the grassland biome) or tall trees (as in forest biomes).
• Chaparral occurs in the Mediterranean area.
• The climate over there is hot with dry summers and wet winters.
• The rainfall in this area is about 60 to 80 cm.
• It has evergreen vegetation.
• It has summer-drought-tolerant plants and drought-adapted animals.

Therefore, the correct answer is chaparral forest.

Additional InformationTropical forest:

• Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may also be referred to as lowland equatorial evergreen rainforests.

Temperate forest:

• A temperate forest is a forest found between the tropical and boreal regions, located in the temperate zone.
• It is the second largest biome on our planet, covering 25% of the world's forest area, only behind the boreal forest, which covers about 33%.

Deciduous forest:

• Deciduous forest is vegetation composed primarily of broad-leaved trees that shed all their leaves during one season.

Correct Answer: Option 1) Both (A) and (R) are correct and (R) is the correct explanation of (A).

Key Points

• Assertion (A): Edges in landscapes generally have more generalist species is true because:
• Edges or ecotones are transitional zones where two different ecosystems meet, such as a forest and grassland.
• These areas often support a mix of species from both ecosystems, as well as species that specifically thrive in edge conditions.
• Generalist species, which are highly adaptable and can thrive in a variety of conditions, often populate edges due to the varied resources and habitats available.
• Reason (R): Edges have unique habitats is true because:
• Edges create distinct microenvironments where conditions differ from those in the interior of the adjacent ecosystems.
• These conditions can include variations in light, moisture, temperature, and nutrient availability.
• Such unique habitats can support a diverse array of organisms, including generalist species that can adapt to multiple environments.
• Reason (R) explains why Assertion (A) is correct:
• The presence of generalist species at edges is due to the unique conditions and resources. These characteristics make edges favorable environments for generalist species, which can utilize the varied conditions effectively.
• Thus, the unique habitats created by edges (Reason R) are indeed the reason why edges host more generalist species (Assertion A).

Additional Information

• Ecotones:
• Ecotones are transition zones between two biomes or different ecosystems. They are characterized by greater species diversity due to the overlap of species from both adjacent ecosystems and some unique species adapted to the edge conditions.
• Edge Effect:
• The edge effect refers to the phenomenon where there is greater variety and density of plant and animal species in the transitional zones or edges between ecosystems compared to the interior areas.
• Generalist Species:
• Generalist species can thrive in a wide variety of environmental conditions and can make use of a variety of different resources. They are often more adaptable to changes in the environment compared to specialist species that have more specific habitat or resource requirements.

The correct answer is It will accelerate global warming.

Key Points

• Arctic ice reflects light from the Sun.
• The frozen sea of our world has acted as a massive parasol that helps keep the planet cool and its climate stable.
• If ice is replaced by forest which is green and dark, the reflectivity will reduce.
• Though trees will absorb more CO₂, lower reflectivity will amplify global warming.

Therefore, the correct answer is it will accelerate global warming.

The correct answer is Stealing food from another predator's catch.

Key Points

Kleptoparasitism:

• Kleptoparasitism is a form of feeding in which one animal deliberately takes food from another.
• The strategy is evolutionarily stable when stealing is less costly than direct feeding, which can mean when food is scarce or when victims are abundant.
• Many kleptoparasites are arthropods, especially bees and wasps, including some true flies, dung beetles, bugs, and spiders.
• Cuckoo bees are specialized kleptoparasites which lay their eggs either on the pollen masses made by other bees or on the insect hosts of parasitoid wasps.
• This may be intraspecific, involving stealing from members of the same species, or interspecific, from members of other species.

Therefore, the correct answer is stealing food from another predator's catch.

The correct answer is 2) Only (i), (ii), (iii).

Key PointsUnderstanding the statements in relation to Lacustrine Zone

• Broad Deep Lake-like Basin
• The lacustrine zone in a reservoir typically describes the part that resembles a deep lake, characterized by a broad and deep basin.
• This area is generally found near the dam where water is the deepest. Hence statement (i) is correct.
• Autochthonous Nature
• Autochthonous refers to materials such as organic matter that originate within the lake itself rather than being transported from outside.
• The lacustrine zone, being deep and inactive, often supports autochthonous production due to the presence of internally generated nutrients. Hence statement (ii) is correct.
• P > R (Production greater than Respiration)
• P > R indicates that the primary production (P) of organic material via photosynthesis exceeds respiration (R).
• This condition can occur in the lacustrine zone where nutrient inputs can lead to high productivity. Hence statement (iii) is correct.
• Turbid Water
• Turbid water usually contains high levels of suspended particles, making it less clear.
• The lacustrine zone in a reservoir typically has clearer, less turbid water compared to other zones such as the riverine zone. Hence statement (iv) is incorrect.

Additional Information

• Characteristics of Lacustrine Zones
• Lacustrine zones are key areas in large artificial reservoirs where water resides for long periods, allowing sedimentation to occur.
• The water in these zones is generally more stable and clearer due to reduced sediment inflow and higher settling rates of suspended particles.
• Comparison with Riverine and Transitional Zones
• Unlike the riverine (inflow) and transitional (middle) zones of a reservoir, the lacustrine zone is characterized by its depth and clearer water.
• The riverine zone is more turbulent with high levels of suspended sediments and nutrients, leading to turbid conditions.

The correct answer is 120 ± 4.706 gC/m2/year.

Key PointsGiven:

Number of assessment years = 4

Mean = 120 gC/m2/year

Standard deviation = 4 gC/m2/year

t = 2.353

Using the formula:  

Confidence interval = $\bar{x}\ ± t× {SD\over\sqrt n}$

Where, 

x̄ = Mean,

SD = Standard deviation

t = z score

n = number of observationsHence, Confidence interval = $120\ ± 2.353× {4\over\sqrt 4}$

   = 120 ± 2.353 × 2

   = 120 ± 4.706 

Therefore, the correct answer is 120 ± 4.706 gC/m2/year.

The correct answer is (a) - (ii), (b) - (iv), (c) - (iii), (d) - (i).

Key Points

Therefore, the correct answer is (a) - (ii), (b) - (iv), (c) - (iii), (d) - (i).

Additional Information

Sulphur dioxide:

• Sulfur dioxide affects the respiratory system, particularly lung function, and can irritate the eyes.
• Sulfur dioxide irritates the respiratory tract and increases the risk of tract infections.
• It causes coughing, and mucus secretion and aggravates conditions such as asthma and chronic bronchitis.

Ozone:

• Depending on the level of exposure, ozone can cause coughing and sore or scratchy throat, make it more difficult to breathe deeply and vigorously and cause pain when taking a deep breath.
• It can inflame and damage the airways, make the lungs more susceptible to infection, and aggravate lung diseases such as asthma, emphysema, and chronic bronchitis.
• Increase the frequency of asthma attacks.

Carbon monoxide:

• Breathing air with a high concentration of CO reduces the amount of oxygen that can be transported in the bloodstream to critical organs like the heart and brain.
• At very high levels, which are possible indoors or in other enclosed environments, CO can cause dizziness, confusion, unconsciousness and death.

Lead:

• Lead is known to cause a range of health effects, from behavioural problems and learning disabilities to seizures and death.
• Children six years old and under are most at risk from exposure to lead-based paint because they crawl on the floor and they put their hands and other items which can have lead-based paint dust on them into their mouths.
• Because their bodies are still growing, children tend to absorb more lead than adults.

The correct answer is Both (A) and (R) are correct and (R) is the correct explanation of (A).

Key Point

• CFCs reach the stratosphere because the Earth's atmosphere is always in motion and mixes the chemicals added to it.
• CFC molecules are indeed several times heavier than air.
• Gases such as CFCs that do not dissolve in water and that are relatively unreactive in the lower atmosphere are mixed relatively quickly and therefore reach the stratosphere regardless of their weight.

Thus the assertion is true.

• Because CFCs are extremely unreactive in the troposphere, they eventually migrate up to the stratosphere, where they are bombarded with UV radiation and slowly degrade (photodissociate) to release free chlorine.
• The chlorine efficiently reacts with and destroys O₃.

Thus the reason is also true and it correctly explains the assertion.

Therefore, the correct answer is both (A) and (R) are correct and (R) is the correct explanation of (A).

The correct answer is (A) is true, but (R) is false.

Key Points

• Water temperature is a physical property expressing how hot or cold water is.
• Temperature is an important factor to consider when assessing water quality.
• In addition to its effects, temperature influences several other parameters and can alter the physical and chemical properties of water.
• Considered alone, the water temperature can affect the metabolic rates and biological activity of aquatic organisms.
• There is a direct relationship between metabolic rates and water temperature.
• Temperature fluctuations can also affect the behaviour choices of aquatic organisms, such as moving to warmer or cooler water after feeding, predator-prey responses and resting or migrating routines

Thus the assertion is true.

• When water temperatures increase, it causes the gas and water molecules to gain more energy which in turn breaks the weak molecular interactions between water and oxygen molecules, causing the oxygen to escape.
• Thus a condition of hypoxia is developed in water bodies due to an increase in temperature which severely affects aquatic life.

Thus the reason is false.

Therefore, the correct answer is (A) is true, but (R) is false.

The correct answer is O3.

Key Points

Primary air pollutants:

• Primary pollutants are those pollutants which are formed and emitted directly from particular sources.
• Examples are particulates, carbon monoxide, nitrogen oxide, and sulfur oxide.

Secondary air pollutants: 

• These pollutants form in the atmosphere.
• They are not emitted directly from a source (like vehicles or power plants).
• Instead, they form as a result of the pollutants emitted from these sources reacting with molecules in the atmosphere to form a new pollutant.
• Examples are ozone and secondary organic aerosol (haze).

Secondary pollutants are harder to control because they have different ways of synthesizing and the formation is not well understood.

They form naturally in the environment and cause problems like photochemical smog.

Ground-level ozone is a colourless and highly irritating gas that forms just above the earth's surface.

It is called a secondary pollutant because it is produced when two primary pollutants react in sunlight and stagnant air.

Therefore, the correct answer is O₃.

Additional Information 

CO₂, SO₂ and NOx are examples of primary air pollutants in the troposphere which are emitted usually from the process of combustion.

The correct answer is Sunlight.

Key PointsClassical smog:

• Classical smog is formed when there is a high concentration of sulphur dioxide and particulate matter produced due to the combustion of fuels.
• It occurs in cold and humid climates.
• It is also known as London smog or Sulphurous smog and causes the dark brownish colour of the atmosphere.
• The necessary ingredients and the conditions for the development of classical smog are as follows:

1. Primary pollutants- sulfur dioxide and soot particles
2. Secondary pollutants - H₂SO₄, sulfate aerosols, etc
3. Radiation temperature inversion
4. High relative humidity and usually foggy
5. Low temperature (< 35°F)

Therefore, the correct answer is sunlight.

Additional Information

• Sunlight is the necessary precursor for photochemical smog.

The correct answer is Only (i), (ii) and (iii).

Key Points

• At a given temperature, pH indicates the intensity of the acidic (pH < 7) or basic characteristic (pH > 7) of the system, and is controlled by dissolved chemical compounds and biochemical processes.
• In unpolluted surface waters, pH is principally controlled by the balance between carbon dioxide, carbonate, and bicarbonate known as the carbonate system.
• The chemical species in this carbonate system include carbon dioxide (CO₂(g), carbonic acid (H₂CO₃), bicarbonate (HCO₃), carbonate (CO₃), and hydrogen ion (H⁺).
• The relative proportion of these chemical species determines the acidity and alkalinity of the water, thus controlling the overall pH of natural waters.

 Therefore, the correct answer is Only (i), (ii) and (iii).

The correct answer is The concentration of CO2 and the year of measurement.

Key Points

• The Keeling Curve is a graph that shows the ongoing change in the concentration of carbon dioxide in Earth’s atmosphere.
• It is a graph that represents the concentration of carbon dioxide (CO₂) in Earth’s atmosphere since 1958.
• The Keeling Curve is named after its creator, Dr Charles David Keeling.

The correct answer is the concentration of CO2 and the year of measurement.

The correct answer is (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i).

Key Points

Therefore, the correct answer is (a) - (ii), (b) - (iii), (c) - (iv), (d) - (i).

Additional InformationDifferent types of mass movements:

Falls:

• Instantaneous fall of weathered rock materials including large blocks from steep hillslopes or earthen materials from steep or cliffed valleysides of streams under the influence of gravity is called fall.
• The size of rock fragments depends on the size and pattern of rock joints.
• The velocity of fall is the greatest of all other types of mass movement.
• Based on materials, fall is subdivided into rock fall, debris fall and earthfall.

Flows:

• The diagonal downslope movement of rock fragments and soils along a sliding plane with enough water is called flow.
• It is further subdivided into solifluction, debris flow, mudflow, earthflow, rock avalanche etc.
• Flow involves downslope rapid movement of rock debris or soils saturated with water-like viscous fluid.

Subsidence:

• Subsidence is the sinking of the earth’s surface in response to geologic or man-induced causes.
• When subsidence occurs in great belts, providing troughs for the accumulation of sediments, the resulting features are termed geosynclines; nonlinear subsidence produces basins and irregular depressions.
• Subsurface solution during cave formation may lead to a series of subsidence features at the ground surface, which, collectively, are termed karst topography.

Lateral movement:

• Lateral movement occurs when earthquake shaking causes a mass of soil to lose cohesion and move relative to the surrounding soil.
• Lateral movement can be entirely horizontal and occur on flat ground, but it is more likely to occur on or around sloping ground, such as adjacent to hillsides and waterways.
• Lateral mass movement includes (a) Block slide, (b) Spread, (c) Cambering, (d) Sackung etc.

The correct answer is Physical Weathering.

Key Points

Therefore, the correct answer is physical weathering.

The correct answer is Pycnocline.

Key Points

Therefore, the correct answer is pycnocline.

The correct answer is Linear.

Key Points

Darcy's law states that the flow rate Q is proportional to the cross-sectional area A times the hydraulic gradient.

$Q = KA ({dh\over dL})$

Where, 

Q = flow rate (m³/day)

K = hydraulic conductivity, or the coefficient of permeability (m/day)

A = cross-sectional area (m²)

$({dh\over dL})$ = the hydraulic gradient

Hence, there is a linear relationship between the flow rate or flow velocity and the hydraulic gradient.

Darcy’s law assumes linearity between flow rate and hydraulic gradient, which is a valid assumption in most, but not all, circumstances.

Therefore, the correct answer is linear.

The correct answer is (i), (ii) and (iii).

Key Points

• Ground truth refers to the data collected on-site, on the surface of the Earth regarding characteristics of the Earth's surface features.
• Ground truth data are complementary to the remote sensing data as it helps to link the image data to the ground reality.
• The process of ground truth data collection involves the collection of information about the area of study from field surveys, analysis of aerial photographs or high spatial resolution data and personal experience.
• It also involves taking the geographic coordinates of the sampling locations and comparing them with the coordinates of the image features to understand and analyse the location errors and their effect on the study and analysis outputs.
• More specifically, ground truthing refers to a process in which a feature on a remote-sensing image is compared to ground reality to verify the image features.
• In cases, where there are maps as the output of remote sensing data interpretation and analysis, it allows help in determining the accuracy of the maps generated by the remote sensing data analysts or image analysis software.
• This minimises errors in the computer-assisted thematic information extraction procedures.

It is carried out typically for the following purposes:

• To calibrate a remote sensor,
• To help in remote sensing data correction,
• To provide reliable data to identify each feature of interest present in the image to aid and guide the process of image interpretation/analysis,
• To locate representative areas of each image feature to generate their spectral signatures to model the spectral behaviour of specific Earth surface features, and
• To assess the accuracy of thematic maps generated and information derived from images and validate them.

Therefore, the correct answer is (i), (ii) and (iii).

The correct answer is 4.0 cm.

Key Points

• Microwave frequencies range between 109 Hz (1 GHz) to 1000 GHz with respective wavelengths of 30 to 0.03 cm.
• Within this spectral domain are many communication systems applications that are important in both the military and civilian sectors.
• Microwave sensors provide information on the atmosphere and surface in the presence of clouds.
• Medium-length (C-band) microwaves penetrate through clouds, dust, smoke, snow, and rain to reveal the Earth's surface.
• The ability of microwaves to pass through clouds enables scientists to monitor conditions underneath a hurricane.
• Microwaves have the lowest energies and allow scientists to pierce dense, interstellar clouds to see the motion of cold gas.

Therefore, the correct answer is 4.0 cm.

The correct answer is P-band.

Key PointsCommonly used frequency bands:

Therefore, the correct answer is P-band.

The correct answer is (i), (ii), (iii) and (iv).

Key Points

• Spatial data quality elements provide information on the fitness for use of a spatial database by describing why, when and how the data are created, and how accurate the data are.
• The data quality parameter provides insight to the user on the dataset fitness-for-use.
• Essentially the data quality of a particular dataset is described by the data quality elements and sub-elements.
• The elements include an overview describing the purpose and usage, as well as specific quality elements reporting on the lineage, positional accuracy, attribute accuracy, temporal accuracy, logical consistency and completeness.
• Depending on these elements the user takes decisions on whether data is relevant to their application.

Therefore, the correct answer is (i), (ii), (iii) and (iv).

The correct answer is (i), (ii), and (iii).

Key Points

• Range resolution is the ability of a radar to distinguish between two or more targets that are very close to each other.
• The degree of range resolution depends on the width of the transmitted pulse. the type and size of the target.
• Radar resolution is defined as the minimum separation between two objects of equal reflectivity that will enable them to appear individually in a processed radar image.
• Radar systems are generally used to distinguish point targets; the impulse response defines their ability to do so.

The formula for determining the ground-range resolution is:

$R_{gr} = {cτ\over 2\cos\ β}$

Where τ is the pulse compression, c is the speed of light, and β angle of depression which is also denoted by θ_d.

Thus range resolution in radar is a function of pulse compression, speed of light, and angle of depression.

Therefore, the correct answer is (i), (ii), and (iii).

The correct answer is Both (A) and (R) are correct, but (R) is not the correct explanation of (A).

Key Points

• The volume of carbon dioxide in the atmospheric column becomes uniform at altitude because the sources and sinks for CO₂ are generally at ground level and, as it rises, CO₂ becomes well-mixed into the atmosphere.
• At ground level, CO₂ levels will be heavily influenced by local and seasonal sources such as forests, grasslands, and human activity.
• That is, if you have a city or industrial area, CO₂ emissions will be high due to the burning of fossil fuels.
• In the case of nature, forests and grasslands will absorb CO₂ during the local spring and summer when they grow and emit CO2 in fall and winter as they decompose.

Thus the assertion is true.

• Carbon dioxide once added to the atmosphere hangs around, for a long time: between 300 to 1,000 years.
• Thus, as humans change the atmosphere by emitting carbon dioxide, those changes will endure on the timescale of many human lives.

Thus the reason is also true but it does not explain the assertion.

Therefore, the correct answer is both (A) and (R) are correct, but (R) is not the correct explanation of (A).

The correct answer is Compensation depth.

Key Points

Therefore, the correct answer is Compensation depth.

The correct answer is Microorganisms.

Key Points

• Saprophytes are living organisms that survive and feed on the remains of other species that have died or decayed.
• They are regarded as particularly essential in the field of soil biology.
• These microorganisms break down complex organic materials into simpler chemicals, which are then utilised by plants for a variety of metabolic functions.
• They feed on the nonliving organic matter known as detritus at a microscopic level.
• They are mainly dominated by fungi and bacteria.

Therefore, the correct answer is microorganisms.

The correct answer is Tundra vegetation.

Key Points

Tundra:

• The tundra is the coldest of all the biomes with an annual average temperature of less than 5°C, and precipitation (mostly in the form of snow) of less than 100 mm per year.
• The weather conditions in the tundra are so harsh that only a handful of plants and animals can even survive there.
• Due to extremely cold temperatures, the layer just below the surface remains permanently frozen.
• This frozen layer of ground is called permafrost.

Desert:

• Deserts cover about one-fifth of the Earth's surface and occur where rainfall is less than 50 cm/year.
• Temperatures exhibit daily extremes because the atmosphere contains little humidity to block the Sun's rays.
• Desert surfaces receive a little more than twice the solar radiation received by humid regions and lose almost twice as much heat at night.
• Mean annual temperatures range from 20-25° C.
• The extreme maximum ranges from 43.5-49° C. Minimum temperatures sometimes drop to -18° C.

Taiga:

• Mean annual temperatures in the taiga range from a few degrees Celsius above freezing to −10 °C (14 °F) or more.
• Areas with a mean annual temperature below freezing are susceptible to the formation of permafrost soils.
• Areas of the taiga located in the centre of continents generally receive 30 to 50 cm (12 to 20 inches) of annual precipitation.

Shrubland:

• The average annual rainfall in the shrublands is between 200 to 1,000 millimetres.
• The summers are hot and dry, while the winters are cool and moist.
• The average annual temperature is 17° C and can reach up to 37.7° C in the summer and stays around 10° C during the winter.

​Therefore, the correct answer is Tundra vegetation.

The correct answer is Both (A) and (R) are correct and (R) is the correct explanation of (A).

Key Points

• Thiamine deficiency is a possible driver of wildlife population decline.
• Thiamine deficiency doesn’t usually kill affected individuals but causes sublethal impacts such as behavioural and reproductive problems.
• In the last few decades, thiamine deficiency has been observed in fish and wildlife in the Great Lakes, Alaska, Sweden, and other areas in North America and Europe.
• Thiamine is an essential vitamin needed for cell function.

Thus the assertion is true.

• Thiamine is an essential micronutrient that plays a crucial role in energy metabolism.
• Thiamine deficiency has been linked to neurological disorders, immunosuppression, and lower reproductive viability.
• These disorders potentially reduce populations of affected species.

Thus the reason is also true and it correctly explains the assertion.

Therefore, the correct answer is both (A) and (R) are correct and (R) is the correct explanation of (A).

The correct answer is the r-selected population.

Key PointsCharaceristics of r and k-selected population.

Therefore, the correct answer is the r-selected population.

The correct answer is the Continuous exchange of organisms.

Key Points Wildlife corridors:

• Wildlife corridors are also known as habitat corridors or green corridors.
• Wildlife corridors are also known as ecoducts and eco-passages.
• These wildlife areas are designed to keep local migratory animal species from the encroaching human populations in areas of high interaction between the two.
• These green corridors are also designed to keep animals out of danger of highways, busy roads, and other areas where their traditional migratory patterns intersect with potentially dangerous manmade places.
• Wildlife corridors allow these animals to pass over or under roads and other manmade obstacles to keep them safe and their territory somewhat intact.
• A wildlife corridor is a way of connecting these fragmented habitats.
• The corridor allows movement between isolated patches of habitat without other disturbances, such as traffic or development.

Therefore, the correct answer is the continuous exchange of organisms.

The correct answer is 560.

Key PointsPermutations: 

A permutation is an arrangement in a definite order of many objects taken some or all at a time.

$L!\over A!\ ×\ G!\ ×\ F!$

​Factorial notation: 

The notion n! represents the product of first n natural numbers.

​For a natural number n

n! = n (n - 1)!

    = n (n - 1) (n - 2)!   [provided (n ≥ 2)]

    = n (n - 1) (n - 2) (n - 3)!   [provided (n ≥ 3)]

Note: 0! = 1

Given:

Tigers = 8

Small wild animals = 3

Small goats = 3

Domestic fowls = 2

$8!\over 3!\ ×\ 3!\ ×\ 2!$

$8\ × \ 7 \ × \ 6 \ × \ 5 \ × \ 4 \ × \ 3 \ × \ 2 \ × \ 1\over3 \ × \ 2 \ × \ 1 \ × \ 3 \ × \ 2 \ × \ 1 \ × \ 2 \ × \ 1$

8 × 7 × 5 × 2 = 560

Therefore, the correct answer is 560.

The correct answer is 1 - 5 kHz.

Key Points

• The human ear reacts to various frequencies in different ways.
• The frequency range between 1 and 5 kHz is the most sensitive.
• Generally, high and low tones are perceived as mid-range sounds.
• The intensity of the sound also affects the hearing curve.
• With the increase in the volume of the signal, the hearing curve reaches an equilibrium value.
• The "normal" hearing frequency range is between 20 Hz and 20,000 Hz.
• This range of hearing is influenced by age, occupation and gender.
• As we age, hearing sensitivity at high frequencies decreases by about 12 kHz.
• Sounds that are above the threshold of hearing are called ultrasound, and those below infrasound.

Therefore, the correct answer is 1 - 5 kHz.

The correct answer is low biomass.

Key Points

• An oligotrophic lake or water body has relatively low productivity due to the low nutrient content in the lake.
• The waters of these lakes are usually quite clear due to the limited growth of algae in the lake.
• The waters of such lakes are of high-drinking quality.
• Such lakes support aquatic species that require well-oxygenated, cold waters such as lake trout.
• Oligotrophic lakes are usually found in the cold regions of the world where the mixing of nutrients is rare and slow due to the low temperatures of the lake waters.
• Lake is divided into different zones that divide the water from top to bottom.
• The zones are the littoral zone, limnetic zone, profundal zone, euphotic zone, and benthic zone.
• The profundal zone is a deep zone of an inland body of freestanding water, such as a lake or pond, located below the range of effective light penetration.
• This is typically below the thermocline, the vertical zone in the water through which temperature drops rapidly.
• Since oligotrophic lakes have clear water, low nutrient content and relatively low productivity, the profundal zones present there have low biomass.

Therefore, the correct answer is low biomass.

The correct answer is High.

Key Points

• Early successional communities are those that establish themselves relatively quickly after disturbance, while late successional communities are those that establish themselves much later.
• Early successional systems tend to have smaller plant biomass, shorter plant longevity, faster rates of soil nutrient consumption, a reduced role for decomposer organisms, more open and rapid biogeochemical cycling, higher rates of net primary productivity, lower stability, and lower diversity than late successional systems.
• Early successional plants tend to have high rates of photosynthesis and respiration, high rates of resource uptake, and high light compensation points.
• Transpiration rates are generally high in early successional plants.

Therefore, the correct answer is high.

The correct answer is 24 mg/L.

Key PointsGiven: 

The flow rate of the tributary, Qw =  4 m3/s

The flow rate of the river, Qs =  8.0 m3/s

The concentration of pollutant X in the tributary, Cw = 12 mg/L

The concentration of pollutant X in the river, Cs = 30 mg/L

Using the formula:

$C_m = {C_sQ_s + C_wQ_w\over Q_s + Q_w}$

Where Cm = concentration of pollutant X downstream after mixing

Cm = ${(30\times 8) + (12\times 4)\over 8 +4}$ = 24 mg/L

Therefore, the correct answer is 24 mg/L.

The correct answer is Two plates move away from one another.

Key Points

• The mid-ocean ridge is the most extensive chain of mountains on Earth, stretching nearly 65,000 kilometres (40,390 miles) and with more than 90% of the mountain range lying underwater, in the deep ocean.
• The massive mid-ocean ridge system is a continuous range of underwater volcanoes that wraps around the globe like seams on a baseball, stretching nearly 65,000 kilometres (40,390 miles).
• The majority of the system is underwater, with an average water depth to the top of the ridge of 2,500 meters (8,200 feet).
• Mid-ocean ridges occur along divergent plate boundaries, where the new ocean floor is created as the Earth’s tectonic plates spread apart.
• A divergent boundary occurs when two tectonic plates move away from each other.
• As the plates separate, the molten rock rises to the seafloor, producing enormous volcanic eruptions of basalt.
• The speed of spreading affects the shape of a ridge – slower spreading rates result in steep, irregular topography while faster-spreading rates produce much wider profiles and more gentle slopes.

Therefore, the correct answer is two plates move away from one another.

Additional InformationA divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, earthquakes are common and magma (molten rock) rises from the Earth’s mantle to the surface, solidifying to create a new oceanic crust. The Mid-Atlantic Ridge is an example of divergent plate boundaries.

When two plates come together, it is known as a convergent boundary. The impact of the colliding plates can cause the edges of one or both plates to buckle up into mountain ranges or one of the plates may bend down into a deep seafloor trench. The Pacific Ring of Fire is an example of a convergent plate boundary.

Two plates sliding past each other form a transform plate boundary. One of the most famous transform plate boundaries occurs at the San Andreas fault zone, which extends underwater.

The correct answer is Brazil.

Key Points

• Tropical forests presently cover about 1.84 billion hectares or about 12% of Earth's land surface (3.6% of Earth's surface).
• The world's largest rainforest is the Amazon rainforest.
• Brazil has the largest extent of rainforest cover, including nearly two-thirds of the Amazon.
• Rainforests also exist outside the tropics, including in temperate North America, South America, Australia, and Russia.
• An estimated 50% of terrestrial biodiversity is found in rainforests
• Rainforests are thought to store at least 250 billion tons of carbon
• Deforestation and degradation of tropical forests account for roughly 10% of global greenhouse emissions from human activities.

Therefore, the correct answer is Brazil.

The correct answer is NO₃-.

Key Points

• Nitrogen is important for all plants to live, and it comes in many forms.
• Nitrate (NO₃^-) is the form of nitrogen most used by plants for growth and development.
• Nitrate is the form that can most easily be lost to groundwater.
• Nitrate ions do not bind to the soil solids because they carry negative charges, but exist dissolved in the soil water, or precipitated as soluble salts under dry conditions.
• The nitrate form of nitrogen is so soluble that it leaches easily when excess water percolates through the soil.
• Nitrate moves freely toward plant roots as they absorb water.
• Once inside the plant, NO3- is reduced to an NH₂ form and is assimilated to produce more complex compounds.

Therefore, the correct answer is NO3-.

Explanation:

Given Data

Height = 200 m

Temperature on ground = 35⁰C

Environmental Lapse rate = 4.0⁰C per km

Environmental lapse rate = 4.0⁰C per km

Environmental lapse rate = 4.0⁰C per 1000m

Environmental lapse rate = 0.4⁰C per 100m

Change in temperature at 200 m = 0.4⁰C  + 0.4⁰C = 0.80C

Therefore,

The temperature at the top of the layer = 35⁰C + 0.8⁰C = 35.8⁰C.

Hence, option 1 is the correct answer.

Explanation:

Given data

Pressure = 6.0 mb

Temperature = 27⁰C

Formula to be used

Density, D = $\frac{Pressure \ in \ Pascal}{(Temperature \ in\ Kelvin\ \times \ Gas \ constant)}$

Calculation:

D = $\frac{6\ \times 100}{(27 \ +\ 273)\ \times 461.5}$(6*100/ ((27+273)*461.5))

D = 0.00433 kg/m³

Therefore, density of Vapour pressure = 4.33 x 10^-3 kg/m³

Hence, option 1 is the correct answer.

Assertion (A): Stratosphere is a strongly layered structure.

This statement is true. The stratosphere does have temperature layers, where the temperature increases with altitude. This creates some level of stratification. However, the layers are not as distinct as in some other parts of the atmosphere, and there is still some mixing between them.

Reason (R): Stratosphere is neutrally stable.

This statement is false. The stratosphere is stably stratified, meaning that air parcels tend to stay put and resist vertical movement. This stability is mainly due to the increasing temperature with altitude, which inhibits rising air from cooling and becoming denser (so it doesn't sink back down).

Therefore:

Assertion (A) is  true,

Reason (R) is false.

The reason given does not explain the assertion properly.

The correct explanation for the layered structure of the stratosphere is the temperature inversion, not neutral stability

The correct answer is China.

Key Points

• The ecological footprint is the only metric that measures how much nature we have and how much nature we use.
• The ecological footprint adds up all the productive areas for which a population, a person or a product competes.
• It measures the ecological assets that a given population or product requires to produce the natural resources it consumes (including plant-based food and fibre products, livestock and fish products, timber and other forest products, and space for urban infrastructure) and to absorb its waste, especially carbon emissions.
• China's physical quantity of ecological footprint in 2018 was 4.03 gha.
• China had the largest total ecological footprint of any country because of its huge population.

Therefore, the correct answer is China.

The correct answer is t calculated value < 2.306, thus emissions do not differ significantly.

Key PointsGiven:

Mean 1, x̄₁  = 6.4 kg

Mean 2, x̄₂ = 5 kg

Standard deviation, σ = 4

n₁ = n₂ = 5

Using the formula:

$t = {\bar{x}_1 - \bar{x}_2\over \sigma }× \sqrt{n_1n_2\over n_1 +n_2}$

$t = {6.4 - 5\over 4 }× \sqrt{5×5\over 5 +5}$

$t = {1.4 \over4}× \sqrt{25\over 10}$

t = 0.35 × 1.58 = 0.553

t_cal = 0.553

Therefore, the correct answer is that t calculated value is < 2.306, thus emissions do not differ significantly.

The correct answer is Both (A) and (B) are true.

Key Points

• The word phytophagous is an adjective that means plant-eating, and it’s typically used to describe arthropods that feed on the tissues of living plants, but not those that consume pollen or nectar.
• Phytophagous insects are generally considered to be those that feed on green plants.
• They include species that attack roots, stems, leaves, flowers, and fruits, either as larvae or as adults or in both stages.
• Examples: Orthoptera, Lepidoptera, Coleoptera, Heteroptera, Hymenoptera, and Diptera

Thus A is true.

• Sarcophagus organisms are those that live and feed on dead and decaying organisms.
• They are considered extremely important in soil biology.
• They break down the complex organic matter into simpler substances that are taken up by the plants for various metabolic activities.

Thus B is also true.

Therefore, the correct answer is both (A) and (B) are true.

The correct answer is Microscale turbulence.

Key Points

Thermals:

• The thermal motion refers to the random motions of molecules, atoms, electrons or other subatomic particles.
• The thermal motion of particles rises with the temperature of those particles and is governed by the laws of thermodynamics.
• A thermal column (or thermal) is a rising mass of buoyant air, a convective current in the atmosphere, that transfers heat energy vertically.
• Thermals are created by the uneven heating of the Earth's surface from solar radiation and are an example of convection, specifically atmospheric convection.

Deep convection:

• Deep convection, as used in meteorology, refers to the rapid ascent of air parcels in the Earth’s troposphere driven by the buoyancy generated by phase change in water.
• Deep convection undergirds some of the Earth’s most important and violent weather phenomena and is responsible for many aspects of the observed distribution of energy, momentum, and constituents (particularly water) in the Earth’s atmosphere.
• Deep convection refers to the thermally driven turbulent mixing that moves air parcels from the lower to the upper atmosphere.
• In the tropics, this generally involves the vertical ascent of warm moist air and, ultimately, precipitation.

Molecular conduction and diffusion:

• Conduction is the transfer of heat through a solid, liquid or gas by direct contact.
• During conduction, heat is transferred through the vibration of molecules in a substance.
• As something gets warmer, it begins to increase the vibration and movement of the molecules that it consists of.
• During the day, sunlight heats the ground, which in turn heats the air directly above it via conduction.
• At night, the ground cools and the heat flows from the warmer air directly above to the cooler ground via conduction.
• Diffusion is a consequence of concentration gradients.
• The process of mixing fluid properties by molecular and turbulent motions.
• Diffusion by turbulence is much more rapid than diffusion by molecular motions.

Microscale turbulence:

• Turbulence is the effect of groups of eddies of different sizes.
• Turbulence from wind-generated eddies is called mechanical turbulence.
• Atmospheric turbulence is small-scale, irregular air motions characterized by winds that vary in speed and direction.
• Turbulence is important because it mixes and churns the atmosphere and causes water vapour, smoke, and other substances, as well as energy, to become distributed both vertically and horizontally.
• From the top of the molecular layer or microlayer to the top of the boundary layer, molecular conduction is negligible while turbulent convection takes over, moving the warm air upward to distribute sensible heat throughout the boundary layer.
• This causes the transport of latent heat and sensible heat from the surface layer in a vertical direction towards the upper atmosphere.

​Therefore, the correct answer is microscale turbulence.

The correct answer is 40 km/hr.

Key PointsGiven: 

Speed 1 of predator = 60 km/hr

Speed 2 of predator = 30 km/hr

Using the formula:

Average speed = $Total\ Distance \over Total\ Time$

Suppose, 

D = Distance from the hideout

D = Distance to the hideout

Total Distance = D + D = 2D

Time which is taken to hunt the prey (T₁) = $Distance\ from\ the\ hideout\over Speed\ to\ hunt\ the\ prey$

$T_1 = {D\over60}$

Time which is taken to drag the prey to the hideout (T₂) = $Distance\ to\ the\ hideout\over Speed\ to\ drag\ the\ prey\ to\ hideout$

$T_2= {D\over30}$

Total time taken = T₁ + T₂

T1 + T2 = ${D\over 60} + {D\over30}$

T1 + T2 = $D + 2D \over 60$ = $3D\over60$ = $D\over 20$

Average speed = $Total\ Distance \over Total\ Time$

Average speed = $2D\times 20\over D$

Average speed = 40 km/hr

Therefore, the correct answer is 40 km/hr.

The correct answer is Nitrogen dioxide.

Key Points

• Chemiluminescence (CL) is defined as the production of electromagnetic radiation (ultraviolet, visible or infrared) observed when a chemical reaction yields an electronically excited intermediate or product, which either luminesces (direct CL) or donates its energy to another molecule responsible for the emission (indirect or sensitized CL).
• In the chemiluminescence method of NOx monitoring, some of the chemical reaction products developed remain in an excited state and radiate light when the excitation is discharged.
• This is particularly so at low pressures when the collision frequency is low; the excitation is discharged as light radiation.
• The extra energy bound to the excited molecule can discharge through impact or molecular dissociation.

The chemiluminescence reaction between nitrogen monoxide and ozone is formulated as:

• NO + O₃ → NO₂* + O₂
• NO₂* → NO₂ + hν

NO₂ refers to the excited nitrogen oxide molecule.

These molecules can decay by emission of light of wavelengths longer than 600 nm.

Therefore, the correct answer is Nitrogen dioxide.

The correct answer is H2O.

Key Points

Water vapour (H₂O), carbon dioxide (CO₂), sulphur (either as sulphur dioxide (SO₂) or hydrogen sulphide (H₂S), nitrogen, argon, helium, neon, methane, carbon monoxide, and hydrogen are the constituents of volcanic gases.

The proportion of different gases in volcanic eruption are:

• Water vapour — 50 - 90%
• Carbon dioxide — 1 - 40%
• Sulphur dioxide — 1 - 25%
• Hydrogen sulfide — 1 - 10%
• Hydrogen chloride — 1 - 10%
• Other gases found in lower amounts include carbon disulfide, carbonyl sulfide, and hydrogen fluoride.

Therefore, the major component of volcanic gas emissions is H₂O.

The correct answer is Qinghai-Tibet Plateau.

Key Points

• The Tibetan Plateau, also known as the Qinghai–Tibet Plateau or the Qing–Zang Plateau or as the Himalayan Plateau in India, is a vast elevated plateau located at the intersection of Central, South and East Asia covering most of the Tibet Autonomous Region, most of Qinghai, the western half of Sichuan, Southern Gansu provinces in Western China, southern Xinjiang, Bhutan, the Indian regions of Ladakh and Lahaul and Spiti (Himachal Pradesh) as well as Gilgit-Baltistan in Pakistan, northwestern Nepal, eastern Tajikistan and southern Kyrgyzstan.
• It stretches approximately 1,000 kilometres (620 mi) north to south and 2,500 kilometres (1,600 mi) east to west.
• The Qinghai–Tibetan Plateau (QTP) is called the Third Pole because it is Earth's largest reservoir of ice after the Arctic and Antarctica.
• It feeds more than 2.5 billion people in downstream regions.

Therefore, the correct answer is Qinghai-Tibet Plateau.

The correct answer is the C4 plant.

Key Points

C4 plant:

• C₄ plants are plants which cycle carbon dioxide to 4-carbon sugar compounds to enter the C₃ or the Calvin cycle.
• The C₄ plants are very productive in climatic conditions that are hot and dry and produce a lot of energy.
• Examples: corn, sorghum, sugarcane, millet, switchgrass etc.

Therefore, the correct answer is sorghum.

Additional Information C3 plant:

• C3 plants are plants in which the initial product of the assimilation of carbon dioxide through photosynthesis is 3-phosphoglycerate, which contains 3 carbon atoms.
• These plants are also known as temperate plants.
• These plants reduce carbon dioxide directly in the chloroplast.
• These plants can be annual perennials.
• They are highly rich in proteins.
• Examples: Wheat, oats, rye, orchardgrass etc.​

CAM plant:

• CAM plants are the plants, which fix carbon dioxide by the CAM pathway or Crassulacean acid metabolism.
• It was first discovered in the plants of the Crassulaceae family.
• They are present in arid environments.
• The CAM pathway is adapted to minimise water loss and photorespiration.
• Examples: Orchids, Cacti, Aloe, Pineapple, Agave, Moringa, Some species of Euphorbia and Bromelioideae, etc.

Perennial plant:

• Any plant that persists for several years, usually with new herbaceous growth from a part that survives from growing season to growing season.
• Trees and shrubs, including all gymnosperms (cone-bearing plants), are perennials, as are some herbaceous (nonwoody) flowering plants and vegetative ground covers.
• Examples: bellflowers, chrysanthemums, columbines, dahlias, larkspurs, hollyhocks, phlox, pinks, poppies, primroses etc.

Explanation:

Given data

Scale height, H = 7 km

Height, z = 21 km

Formula to be used

Pressure change with Height, P = P_oe^(-z/H)

Constant values

P_o = Pressure at sea level = 1.01 x 10⁵ Pa

e^-3 =0.04978 = 0.05

Solution

P = 1.01 x 10⁵ e ^(-21/7)

P = 1.01 x 10⁵ e ^(-3)

P = 1.01 x 10⁵ x 0.05

Therefore, the pressure at the height of 21km is 5.05 x 10³ Pa.

Hence, option 1 is the correct answer.

The correct answer is 50 dB(A).

Key Points

Ambient air quality standard for noise:

Therefore, the correct answer is 50 dB(A).

The correct answer is 0.324.

Key PointsGiven:  

Fractional wind velocity drop = 0.1

Using the formula:

C_p = 4a (1 - a)²

Where,

Cp = Coefficient of performance

a = fractional wind velocity drop

Cp = 4 × 0.1 (1 - 0.1)2

Cp = 0.4 × 0.81 = 0.324

Therefore, the correct answer is 0.324.

The correct answer is Coconut and groundnut shells.

Key Points

Therefore, the correct answer is coconut and groundnut shells.

Additional Information

• Biomass fuels (biofuels) refer to chemical energy stored within plants by photosynthesis.
• Primary biomass storage includes any organic matter available on a renewable basis.
• It comprises biomass stocks and an assorted range of waste and residue materials.
• Biogas is the most promising biofuel. It is more directly accessible, has good storage stability, has better overall energetics, and can be applied more flexibly.
• The energy content of biofuel is the chemical energy contained in a given biofuel, measured per unit mass of that fuel, as specific energy, or per unit of volume of the fuel, as energy density.
• Calorific value is the amount of heat energy present in food or fuel and which is determined by the complete combustion of a specified quantity at constant pressure and in normal conditions.

The correct answer is Graphite.

Key Points

• The moderator is a material intentionally placed in a nuclear reactor core to slow neutrons down from their initial fast speeds.
• Adding a moderator makes it much easier to attain a nuclear chain reaction.
• In common water-cooled nuclear reactors, the moderator is the same thing as the coolant: water.
• When fast neutrons strike the hydrogen atoms in H₂O, they slow down a lot.
• There are other good moderators like deuterium, graphite, beryllium, heavy water, sodium and carbon dioxide.

Therefore, the correct answer is graphite.

Additional Information

• The function of the moderator is to slow down the fast neutrons from energies of few MeV to thermal neutrons of ~0.025 eV.
• These materials should have a low neutron absorption cross-section and can also act as coolants requiring high thermal conductivity and heat capacity to absorb the heat.
• The primary function of a coolant is to transfer heat generated at the nuclear reactor core and thus light water, heavy water, and gas are the main examples.

The correct answer is (i), (ii), and (iii).

Key Points

• Scoping is a critical step in the preparation of an EIA, as it identifies the issues that are likely to be of most importance during the EIA and eliminates those that are of little concern.
• Scoping is a systematic exercise that establishes the boundaries of EIA and sets the basis of the analyses you will conduct at each stage.
• A quality scoping study reduces the risk of including inappropriate components or excluding components that should be addressed.

It involves: 

• Identifying all relevant issues and factors, including cumulative effects, social impacts, and health risks.
• Facilitating meaningful public engagement and review.
• Determining the appropriate time and space boundaries of the EIA.
• Identifying the important issues to be considered in the EIA, such as setting the baseline and identifying alternatives.

Scoping helps to select what is needed and what is not relevant, and thus it serves as a work plan for the entire EIA process.

The information gathered during the scoping phase is used in the next steps of the EIA.

Therefore, the correct answer is (i), (ii), and (iii).

The correct answer is A plan of action to prevent an emergency and steps to be taken when emergencies occur.

Key Points

• A core part of the impact management step is developing an environmental management plan (EMP), which forms the basis for impact management during project construction and operation, and outlines activities for continuous monitoring.
• It also translates recommended mitigation measures into specific actions that will be carried out by the project proponent.
• The typical elements of EMPs can be summarized as follows: 
• ​Mitigation measures.
• Monitoring.
• Capacity Development.
• Implementation Schedule and Cost Estimates.
• Integration of the EMP with the project.
• ​Another typical component of an EMP is a contingency plan.
• The EIA must include an assessment of possible risks and external contingencies (natural events and disasters) relevant to the proposed project activities, identifying and determining those that pose risks or threats to the health of the population and the structure of ecosystems.
• A contingency plan establishes lines of action to follow, assigns responsibilities, and functions, and establishes quick and effective responses to emergencies.

Therefore, the correct answer is a plan of action to prevent an emergency and steps to be taken when emergencies occur.

The correct answer is: 4) (i), (ii) and (iii).

Key PointsUnderstanding the statements in relation to energy losses in a flat-plate solar collector

• Conduction Losses
• Conduction occurs when heat energy is transferred through a solid material, such as the collector plate or the insulation material.
• This process can lead to energy losses as heat moves from the hotter areas of the collector to the cooler surroundings. Hence, statement (i) is correct.
• Convection Losses
• Convection occurs when heat is transferred by the movement of fluids, such as air or water.
• In a solar collector, convection losses can happen when air or another fluid carries heat away from the surface of the collector. Hence, statement (ii) is correct.
• Radiation Losses
• Radiation involves the transfer of heat energy through electromagnetic waves.
• Any object at a temperature above absolute zero emits radiation, and the collector surface can lose energy by emitting infrared radiation to the surroundings. Hence, statement (iii) is correct.

Additional Information

• Minimizing Energy Losses
• To reduce conduction losses, high-quality insulation materials are used to minimize heat transfer through the solid parts of the collector.
• Reducing convection losses typically involves creating a vacuum or using covers to prevent fluid movement near the collector surface.
• To reduce radiation losses, selective coating materials are used on the collector surface that have low emissivity (low tendency to emit radiation).
• Efficiency Considerations
• The efficiency of a flat-plate solar collector depends on how well it can minimize these energy losses while maximizing the absorption of solar radiation.
• Understanding and managing these three types of energy losses is crucial for designing effective and efficient solar collectors.

The correct answer is 50∶50.

Key Points

• Deuterium–tritium fusion (D+T) is a type of nuclear fusion in which one deuterium nucleus fuses with one tritium nucleus, giving one helium nucleus, one free neutron, and 17.6 MeV of energy.
• It is the most efficient type of fusion for fusion devices.
• The amount of energy obtained is described by the mass-energy relation E = mc².
• 80% of the energy (14.1 MeV) becomes the kinetic energy of the neutron traveling at 1/6 the speed of light.
• Thus an equal amount of deuterium and tritium are required in this fuel for a nuclear fusion reaction to take place i.e D: T = 50:50.

Therefore, the correct answer is 50:50.

The correct answer is Stratospheric ozone.

Key Points

• Radiative forcing is what happens when the amount of energy that enters the earth’s atmosphere is different from the amount of energy that leaves it.
• Energy travels in the form of radiation: solar radiation enters the atmosphere from the sun and infrared radiation exits as heat.
• If more radiation is entering the earth than leaving — as is happening today — then the atmosphere will warm up.
• This is called radiative forcing because the difference in energy can force changes in the earth’s climate.
• Radiative forcing measures how much energy is coming in from the sun, compared to how much is leaving.

​Positive radiative forcing:

• It means the earth receives more incoming energy from sunlight than it radiates to space.
• This net gain of energy will cause warming.
• Examples: CO₂, N₂O, CH₄, Halocarbons, Tropospheric ozone, Black carbon on snow, etc.

Negative radiative forcing:

• It means that the earth loses more energy to space than it receives from the sun, which produces cooling.
• Examples: Stratospheric ozone, Land use, Cloud albedo effect, etc.

Therefore, the correct answer is stratospheric ozone.

The correct answer is ∼ 2.0 eV.

Key PointsGiven: 

The colour in the visible region is blue where the average wavelength is 500 nm.

h = 6.6 × 10^-34 Js

Using the formula:

$E = {hc\over \lambda}$

where, c = speed of light = 3 × 10⁸ m/s

$E = {6.6 × 10^{-34} × 3 × 10^8 \over 500 × 10^{-9}}$

= 0.0396 × 10^-17 J

1 Joule = 6.2 × 10¹⁸ eV

Thus, 0.0396 × 10-17 J = 0.0396 × 10-17 × 6.2 × 1018 = 2.4 = ∼ 2.0 eV

Therefore, the correct answer is ∼ 2.0 eV.

The correct answer is 40.

Key Points

• Tidal energy is a form of power produced by the natural rise and fall of tides caused by the gravitational interaction between the Earth, the sun, and the moon.
• Tidal currents with sufficient energy for harvesting occur when water passes through a constriction, causing the water to move faster.
• Using specially engineered generators in suitable locations, tidal energy can be converted into useful forms of power, including electricity.
• Other forms of energy can also be generated from the ocean, including waves, persistent ocean currents, and the differences in temperature and salinity in seawater.
• Suitable locations for capturing tidal energy include those with large differences in tidal range, which is the difference between high tide and low tides, and where tidal channels and waterways become smaller and tidal currents become stronger.
• There are very few commercial-sized tidal power plants operating in the world.
• The first was located in La Rance, France.
• The largest facility is the Sihwa Lake Tidal Power Station in South Korea.
• In 2018, the number of suitable sites for harnessing tidal power in the world was limited to 40 only.

Therefore, the correct answer is 40.

The correct answer is 100 tonnes.

Key PointsGiven: 

Output power = 500 MW

Efficiency, η = 30%

Sulphur content in coal = 1%

1 tonne of coal produces 8000 kWh of energy

Since, $Input\ power = {Output\ power\over efficiency}$

$Input\ power = {500×10^3\over 0.30}$ = 1666666.6 kW

For every 3 units of energy entering the average thermal power plant, approximately 1 unit is converted to electricity and 2 units are rejected to the environment as waste heat.

First, calculate the heat input to the plant.

1 kW = 1 kJ/sec

1666666.6 kW = 1666666.6 kJ/sec

For 24 hours, 

1666666.6 kJ/sec × 3600 sec/hour × 24 hours

= 14.4 × 10¹⁰ kJ

1 tonne of coal produces 8000 kWh of energy

We have to convert 8000 kWh into kJ by using the formula:

$heat\ input\over kWhr\ electricity$

$8000\ kWhr× {1\ kJ/sec\over 1\ kW} × 3600\ sec/hour$

= 28800000 kJ

For 14.4 × 1010 kJ, we require

$14.4× 10^{10} \ kJ \over 28800000\ kJ/ton$ = 5000 tonnes

The sulphur content of coal is 1%

5000 × 0.01 = 50 tonnes sulphur

The molecular weight of SO₂ (32 + 2 × 16 = 64) is half of which is sulphur.

Thus, 50 tonnes of S corresponds to (50 × 2) 100 tonnes of SO₂.

Therefore, the correct answer is 100 tonnes.