UGC NET Paper 2: Environmental Science 25th June 2019 Shift 1 (Previous Year Paper)

The correct answer is Absorbing water and minerals.

Key Points

• Mycorrhizae are a symbiotic association between plant roots and fungi.
• Their major role is to enhance nutrient and water uptake by the host plant by exploiting a larger volume of soil than roots alone can do.
• Mycorrhizae come in many forms, dependent upon both host plant and fungal taxonomy.
• The ability of mycorrhizae to improve host plant nutrient and water acquisition and to help in the defence of root pathogens and root grazing can alter the host plant's performance.
• Mycorrhizae are being used in agriculture, forestry, and restoration to improve yield and overcome some of the pollutants associated with plantings on disturbed sites.
• The ability of mycorrhizal fungi to accumulate heavy metals and radionuclides makes them possible candidates for the restoration and remediation of polluted environments.

Therefore, the correct answer is Absorbing water and minerals.

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

Key Points

• India exhibits a tropical climate. In the continental part of the country, the pH of rainwater is alkaline above 5.6.
• The alkalinity of continental mass is aided because of the two measure factors i.e., soil erosion and anthropogenic activities.
• The agricultural sector has an immense use of alkaline fertilizers to replenish and supplement the soil.
• Because of erosion, the soil dust particles get suspended in the atmosphere and contribute to the alkaline nature of rainwater.
• Suspended soil particles are scavenged with rainwater during the below cloud scavenging process.
• Therefore, enhancing the pH of rainwater.

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

Additional Information

• In contrast to this, over oceans, the rainwater is acidic.
• The presence of high NSS-SO₂ and low NSS-Ca concentrations are observed.
• This causes insufficient buffering, which aids the acidity of the rainfall.

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

Key Points

• Water in a reservoir is not polluted if the BOD level is less than 5 mgL-1.
• High BOD indicates active microbial growth.
• BOD is the measure of how much oxygen bacteria need to break down organic matter in a specific volume of water.
• A low BOD indicates clean water, whereas a high BOD suggests dirty water.
• When there is a significant amount of organic matter in the water from sewage or other discharges, microorganisms use dissolved oxygen (DO).

Therefore, assertion (A) is false but reason (R) is true.

The correct answer is Polycyclic Aromatic Hydrocarbons.

Key Points

• Polycyclic aromatic hydrocarbons (PAHs) are organic compounds with multiple aromatic rings.
• PAHs are common atmospheric pollutants that have been linked to cancer, teratogenicity, and genotoxicity.
• PAHs are produced by incomplete combustion or pyrolysis of carbon and hydrogen-containing materials such as coal, oil, wood, and petroleum products.
• Volatile organic compounds have a high vapour pressure but a low water solubility.
• Many VOCs are man-made chemicals used in the production of paints, pharmaceuticals, and refrigerants.
• Some PAHs are semi-volatile but most of them stick to the solid particles and get deposited on organic particulate matter.

Therefore, the correct answer is Polycyclic Aromatic Hydrocarbons.

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

Key Points

Composition of soil air:

• The soil air contains many gases, of which nitrogen, oxygen, carbon dioxide, and water vapour are the most important.
• Soil air constantly moves from the soil pores into the atmosphere and from the atmosphere into the pore space.
• Soil air and atmospheric air differ in their compositions.
• Soil air contains a much greater proportion of carbon dioxide and a lesser amount of oxygen than atmospheric air.
• Soil air contains a far great amount of water vapour than atmospheric air.

 

 

 

• Burning fossil fuels in automobiles and industries release carbon dioxide, a greenhouse gas, into the atmosphere.
• Soil carbon sequestration is a process in which CO₂ is removed from the atmosphere and stored in the soil carbon pool.
• This process is primarily mediated by plants through photosynthesis, with carbon stored in the form of SOC.

Therefore, assertion (A) is true, but reason (R) is false.

The correct answer is CFC-11.

Key Points

• The ozone-depleting potential (ODP) is a measure of how much damage a chemical can cause to the ozone layer compared with a similar mass of trichlorofluoromethane (CFC-11).
• In other words, ozone-depleting potential is measured relative to CFC-11 and it represents the amount of ozone destroyed by the emission of vapour over its entire atmospheric lifetime relative to that caused by the emission of the same mass of CFC-11.
• CFC-11, with an ozone-depleting potential of 1.0, is used as the base figure for measuring ozone-depleting potential.
• The higher the number, the more damage a chemical can cause to the ozone layer.
• Bromotrifluoromethane (halon‑1301) has an ozone-depleting potential of 10.0.
• Carbon dioxide (CO₂), a naturally occurring greenhouse gas, has an ozone-depleting potential of 0.

Therefore, the correct answer is CFC-11.

The correct answer is 20 and 30 respectively.

Key Points National Ambient Air Quality Standards (NAAQS):

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is 20 and 30 respectively.

The correct answer is Lead.

Key Points

• Ink samples are notorious for containing Lead and Cadmium contents.
• The highest level of Lead is observed in black colour according to numerous studies.
• Lead causes toxicity in living cells by following ionic and oxidative stress mechanisms.
• Cadmium is very toxic and once it is absorbed by humans, it remains in the body for life.
• In the liver, it can cause hepatotoxicity and it can also accumulate in the tissues of the kidneys causing nephrotoxicity.

Therefore, the toxic metals present in the colour printing inks of magazine pages are both Lead and Cadmium.

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

Key Points

• The most common and practical method of removing colloidal particles is by chemical coagulation.
• This is a process of destabilizing colloids, aggregating them and binding them for ease of sedimentation.
• Colloids artificially produced by coagulants, usually the hydroxides of iron and aluminium (mostly lyophobic in nature), are mainly positively charged ions.
• The colloids most commonly found in natural waters are negatively charged.
• Hence a cation is required to neutralize the charge.
• A trivalent cation is the most efficient cation.
• Therefore, the hydroxides of Aluminium (III) or Iron (III) are used.

​Therefore, both assertion (A) and reason (R) are true and reason (R) is the correct explanation of assertion (A).

The correct answer is Gasification.

Key Points

• In gasification conversion, heat is used to break down lignocellulosic feedstocks like wood and forest products into synthesis gas, chiefly carbon monoxide and hydrogen.
• A gasifying agent (air, oxygen, or steam) is then used to partially oxidise or reform the feedstock, producing synthesis gas (syngas).
• The different types of feedstocks, their moisture content, the kind of gasifier being used, the gasification agent, and the temperature and pressure inside the gasifier will all have an impact on the composition of syngas.

Therefore, the correct answer is gasification.

Explanation:

The electrostatic precipitator is one of the most widely used collection devices for particulates. An electrostatic precipitator (ESP) is a particulate collection device that removes particles from a flowing gaseous stream (such as air) using the force of an induced electrostatic charge.

ESP can be operated at high temperatures and pressures, and its power requirement is low. An electrostatic precipitator is a type of filter (dry scrubber) that uses static electricity to remove soot and ash from exhaust fumes before they exit the smokestacks. 

∴ An electrostatic precipitator is a device to control particulate emissions only.

The correct answer is Magnetic field separation.

Key Points

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is magnetic field separation.

Explanation

• The symbol within the pictogram shows an ‘o’ represents oxygen and the flame represents the hazardous products.
• The flame-over-circle pictogram is only used for hazardous products that are oxidizing solids, liquids, or gases.
• Oxidizing solids, liquids, or gases readily release oxygen or another oxidizing substance such as bromine, chlorine, or fluorine.
• Therefore, these products pose a severe fire hazard.

The hazards are categorized into 3 classes:

• Oxidizing gases- Category 1
• Oxidizing liquids- Category 1, category 2, and category 3
• Oxidizing solids- Category 1, category 2, and category 3.

​Hence, option 1 is the correct answer.

The correct answer is (b) and (c) only.

Key Points

• Prime Minister Narendra Modi was conferred with the Champion of Earth award by UNEP in 2018.
• The award was given for his work in championing the International Solar Alliance along with French President Emmanuel Macron and also Prime Minister Narendra Modi’s commitment towards eliminating single-use plastic items in India by 2022.

Therefore, the correct answer is (b) and (c) only.

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

Key Points

• Wind speed is one of the key factors for generating power from windmills.
• A wind turbine's installed capacity or rated power corresponds to an electrical power output of a speed between 12 and 16 m/s, with optimal wind conditions.
• For safety reasons, the plant does not produce greater power at high wind conditions than those for which it is designed.
• During storms, the plant is switched off.
• The maximum power output cannot be increased by having a more wind speed than the optimal wind speed.
• A windmill's power output is therefore at its highest for the ideal wind speed.
• The mechanical loading of the components of a wind turbine, like the blades or the shaft, originates from the aerodynamic force on the rotor blades.
• Turbulence, therefore, causes variations in mechanical loading.
• In other words, it causes fatigue loading.

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

The correct answer is ∼ 117 dB.

Key Points

Given:

​The sound pressure level of 1 aeroplane (SPL_i) = 110 dB

Number of aeroplanes (n) = 5

​Using the formula:

​$SPL = 10\log(\sum_{i=1}^{n}10{SPL_i\over10})$

$SPL = 10\log(10^{{110}\over10}+10^{{110}\over10}+10^{{110}\over10}+10^{{110}\over10}+10^{{110}\over10})$

$SPL = 10\log(5\times10^{11})$

$SPL= 10(\log5+10log10^{11})$

$SPL= 10(0.698+10\times11)$

$SPL= 10\times0.698+110$

SPL = 116.98

SPL = ~ 117 dB

Shortcut Method

Using the formula:

​$L_{eq} = L_i+10log(n)$

Where,

L_eq = total sound level

L_i = sound produced by the source

n = number of sources

Therefore,

$L_{eq} = 110+10log(5)$

L_eq = 110 + 10 x 0.698

Leq = 110 + 6.9

Leq = 116.9

Leq = ~ 117 dB

Therefore, the correct answer is ~ 117 dB.

The correct answer is 24124 µg/m3.

Key Points

Given:

• Emission rate of pollutants = 500 x 10⁸ µg/s
• Effective stack height = 200 m
• Average wind speed at the effective height of the stack = 5 m/s
• Horizontal dispersion coefficient = 400 m
• Vertical dispersion coefficient = 200 m

​The formula used:

​

Where, C (x,y) = Concentration at the ground level at the point (x,y), µg/m³

x = distance directly downwind, m

y = horizontal plume from the centerline, m

Q = emission rate of pollutants, µg/s

H = effective stack height, m

uH = average windspeed at the effective height of the stack, m/s

σ_y = horizontal dispersion coefficient (standard deviation), m

σ_z = vertical dispersion coefficient (standard deviation), m 

Since we have to find the downwind ground-level concentration of pollutant, therefore we will use the following formula:

$C(2,0) = {500\times10^8\over 3.14\times5\times400\times200} \exp ({-200^2\over2\times200^2})$

$C(2,0) = {500\times10^8\over 3.14\times5\times400\times200} \exp ({-40000\over2\times40000})$

$C(2,0) = {100\times10^4\over 3.14\times8} \exp (-0.5)$

$C(2,0) = {100\times0.606\over 3.14\times8}$

C(2,0) = 24124 µg/m3

Explanation:

Levels of the Organization are natural systems in the environment that are arranged in a hierarchical order by part-whole relationships among various levels.

Organism - An individual living being that has the ability to act or function independently. Eg. Plant, Animal, etc.

Population -  It is the group of organisms usually of the same species, occupying a defined area during a specific time. Eg. Shrubs, trees, etc.

Community -  It is a group of populations of two or more species occupying the same geographic area at the same time. Eg, a forest community includes trees, animals, etc.

Ecosystem - It is a structural and functional unit of the biosphere consisting of a community of living beings and the physical environment, both interacting and exchanging materials between them.

Landscape - This is the spatially heterogeneous geographic area characterized by diverse interacting patches or ecosystems. Eg. Grasslands, lakes, etc.

Biome - It is a biogeographical unit consisting of a biological community that has formed in response to the physical environment in which they are found and a shared regional climate. Eg. Deserts, Tropical rainforests, etc.

Ecosphere - It is the planetary closed ecological system in which various forms of energy and matter interact on a continual basis. The Atmosphere, hydrosphere, lithosphere, and biosphere are its major components.

Organism> Population> Community> Ecosystem> Landscape> Biome> Ecosphere.

Hence, option 2 is the correct answer.

The correct answer is 'Species'

Key Points

• Species:
• A species is the largest unit within which gene flow is possible.
• Members of the same species can interbreed and produce fertile offspring.
• Species are typically reproductively isolated from other species, meaning there is no gene flow between different species.
• Gene flow within a species helps to maintain genetic diversity and allows for adaptation and evolution.

Additional Information

• Population:
• A population is a group of individuals of the same species living in a specific area.
• While gene flow can occur within a population, it is a smaller unit compared to the species as a whole.
• Gene flow between different populations of the same species helps maintain the species' genetic diversity.
• Genus:
• A genus comprises multiple species that are closely related.
• Gene flow between different species within a genus is generally not possible due to reproductive barriers.
• Family:
• A family includes several genera that share certain similarities.
• Gene flow between different genera within a family is generally not possible due to reproductive barriers at both species and genus levels.

Important Points

• Species represent a fundamental unit of biological classification in which organisms are capable of exchanging genes through reproduction.
• Understanding the concept of species and gene flow is essential for the study of evolution, ecology, and conservation biology.

The correct answer is (a), (b) and (c) only.

Key Points

• The wind rose is a vector diagram or a graphical chart, presented in a circular format, that illustrates wind direction and speed, measured at weather stations.
• It shows the possibility of every direction of the wind and its strength.
• The length of each bar shows the frequency of this direction.
• Each concentric circle represents a different frequency, rising from zero at the centre to increasing frequencies at the outside circles.
• The longest bar means the most frequent direction.
• It also shows the percentage (%) of time during which the wind blows in one direction or another.
• The colours mean wind speed.
• The longest colour is the most frequent.

Therefore, the correct answer is (a), (b) and (c) only.

The correct answer is the Water content of the leaf.

Key Points

• The reflectance characteristics of vegetation depend on the properties of leaves, including the orientation and the structure of the leaf canopy.
• The amount of radiation reflected for a particular wavelength depends on leaf pigmentation, thickness, composition (cell structure) and the amount of water in the leaf tissue.
• In the SWIR range, reflectance is mainly determined by the free water in the leaf tissue; more free water results in less reflectance.
• Wavelengths around 1.45 μm and 1.95 μm are, therefore, called water absorption bands.
• The plant may change colour when its leaves dry out, for instance, at the harvest time for a crop (e.g. yellow).
• At this stage, there is no photosynthesis, which causes reflectance in the red portion of the spectrum to become higher.
• Also, the leaves will dry out, resulting in a higher reflectance of SWIR radiation, whereas reflectance in the NIR range may decrease.

Therefore, the spectral response pattern of leaves in healthy vegetation in the SWIR region of EMR is primarily a function of the water content of the leaf.

 Additional Information

• In the visible portion of the spectrum, the reflection of the blue and red components of incident light is comparatively low because these portions are absorbed by the plant (mainly by chlorophyll) for photosynthesis; the vegetation reflects relatively more green light.
• The reflectance in the NIR range is highest, but the amount depends on leaf development and cell structure.

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

Key Points

• Temperature is also a crucial factor influencing the rate of biogas production.
• During winters in cold areas, the production of biogas decreases considerably due to low temperatures that inhibit methanogenesis.
• The optimum temperature for methanogenesis to occur is between 35°C to 42°C which falls under the mesophilic temperature range.
• Since during the winters, the temperature drops very significantly, even reaching below 0°C in some places, therefore, the production of biogas gets reduced during the winter period.

Therefore, both assertion (A) and reason (R) are true and reason (R) correctly explains assertion (A).

The correct answer is 41.

Key Points

• The electromagnetic radiation emitted by the sun covers an extensive range of wavelengths, from radiowaves through the infrared, visible and ultraviolet to X-rays and gamma rays.
• However, 99% of the energy of solar radiation is contained in the wavelength band from 0.15 to 4 μm, comprising the near ultraviolet, visible and near-infrared regions of the solar spectrum, with a maximum wavelength at about 0.5 μm.
• About 41% of the solar radiation received at the earth’s surface on clear days is visible radiation within the spectral range of 0.4 to 0.7 μm.
• In comparison, 51% is infrared radiation in the spectral region 0.7 to 4 μm.
• The total radiation emitted by the sun in unit time remains practically constant.

Therefore, visible radiation accounts for 41% of the total solar radiation incident on top of the atmosphere.

The correct answer is Eudrilus eugeniae.

Key Points

• Epigeic earthworms are found in environments with a lot of organic debris.
• They eat excrement, rotting plant roots, and leaf litter while living at or close to the soil's surface.
• These earthworms don't dig long-term tunnels.
• Typically, epigeic species have dark skin tones (pigmentation).
• Epigeic species often have short (1–18 cm) lengths.

Examples of Epigeic earthworms:

• Dendrobaena veneta
• Dendrobaena hortensis
• Dendrobaena octaedra
• Eisenia fetida
• Eisenia andrei
• Dendrodrilus rubidus
• Eiseniella tetraedra
• Eudrilus eugeniae
• Allolobophoridella eiseni

Therefore, the correct answer is Eudrilus eugeniae.

Additional Information

• Earthworms naturally turn garbage with rigid structures into compost through vermicomposting.
• Compost created through this environmentally friendly procedure is traditionally and frequently used as a natural fertiliser to promote plant development.

The correct answer is >13.0 μm.

Key Points

Greenhouse gases are those radiatively active gases that absorb radiations of wavelengths longer than 4 μm.

 

 

 

 

 

Therefore, CO2 has a very strong absorption band in >13.0 μm wavelength region.

The correct answer is (a), (b) and (c).

Key Points

Ground truth data collection 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 in order to generate their spectral signatures so as to model the spectral behaviour of specific Earth surface features.
• To assess the accuracy of thematic maps generated and information derived from images and validate them.

Therefore, the correct answer is (a), (b), and (c).

The correct answer is 4.25 mgL-1.

Key Points Given:

Organic Carbon = 2.5 mgL-1

​Since, 

OM = 1.72 x OC

OM = Organic matter

OC = Organic Carbon

Therefore, OM = 1.72 x 2.5 mgL-1

 Therefore, OM = 4.25 mgL-1

The correct answer is Increases biodiversity.

Key Points

• The “intermediate disturbance hypothesis” predicts that maximum levels of biodiversity should be observed under some intermediate disturbance frequency because few species are able to tolerate very intense disturbance regimes, and few are able to compete successfully in habitats that experience little or no disturbance.
• Diversity is low at first because only the fastest reproducers or species that happen to be located in close proximity can colonize in the short time available.
• If the frequency of disturbance is too high, then the community will consist only of the few early colonizers.
• With lower disturbance frequencies, the species number will increase with new arrivals until, at some intermediate frequency, maximum biodiversity is attained.
• If the disturbance frequency is too low, then species numbers are reduced by competition for resources and/or by interference.
• This unimodal relationship between species richness and disturbance has become an ecological paradigm.

Therefore, moderate disturbance in an ecosystem leads to an increase in biodiversity.

The correct answer is Reduction in nutrient cycling.

Key Points

• The majority of heterotrophic organisms that decompose decaying organic materials or detritus are bacteria and fungi.
• They secrete various enzymes from their bodies into the decomposing plant and animal wastes, breaking them down into more easily digested materials like minerals that are added to the soil.
• These elements improve the soil and aid in the development of the farmers.
• Waste and dead bodies would accumulate in the absence of decomposers.
• There wouldn't be a replenishment of nutrients.
• The nutrient cycle would not be complete in the absence of these decomposers.

Therefore, the correct answer is the reduction in nutrient cycling.

The correct answer is - Extrusive igneous

Note: UGC NET answer key mentions the correct answer as option 1 - Intrusive igneous, but the correct answer should be Extrusive igneous, as the word "Lava" has been used here. 

• Lava is molten rock that has erupted onto the Earth's surface.
• Magma is molten rock located beneath the Earth's surface.

Key Points

• Extrusive Igneous Rock
• Forms when lava cools and crystallizes on the Earth's surface.
• Cools rapidly due to exposure to air or water, leading to fine-grained or glassy textures.
• Examples include basalt, pumice, and obsidian.

Additional Information

• Intrusive Igneous Rock
• Forms when magma cools and crystallizes below the Earth's surface.
• Cools slowly, allowing large crystals to form.
• Examples include granite and diorite.
• Metamorphic Rock
• Forms from existing rocks that are transformed by heat, pressure, or chemically active fluids.
• Does not involve the cooling of lava or magma.
• Examples include marble and schist.
• Sedimentary Rock
• Forms from the accumulation and compaction of sediment or from the precipitation of minerals from water.
• Does not involve the cooling of lava.
• Examples include sandstone and limestone.

The correct answer is Pyranometer.

Key Points

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is Pyranometer.

The correct answer is Epigeic.

Key Points

• The most common type of earthworm used in vermicomposting is the epigeic earthworm, which can withstand a wide range of environmental conditions (such as temperature and moisture) and consume enormous volumes of organic waste per day.
• These earthworm species are typically found in topsoil, which contains a variety of microorganisms and organic debris.
• They make good candidates for vermicomposting because of their short lifespans, rapid rate of reproduction, and ease of handling.
• 80-90% of the earthworms commercially raised for vermicomposting come from two epigeic species: Eisenia fetida (redworm) and Eisenia andrei.
• These typical composting species are categorised as nonburrowing varieties of earthworms since they do not dig deeply into the soil.
• They can thrive on mounds of manure or rotting organic matter.
• Due to their quicker activity in converting organic wastes into vermicompost, nonburrowing earthworm varieties are more commonly used in vermicomposting than burrowing types.
• They reside at or near the soil's surface and feed on human waste, decaying plant roots, and leaf litter.

Therefore, the correct answer is epigeic.

The correct answer is Tamil Nadu.

Key Points

• Tamil Nadu is the first state in India to make rainwater harvesting compulsory.
• In India, rainfall is the primary source of freshwater.
• India receives an average of 1,170 millimetres (46 in) of rain per year.

Therefore, the correct answer is Tamil Nadu.

Additional Information

 Some traditional water harvesting techniques:

• ​Kuls: Jammu, Himachal Pradesh.
• Tanka: Rajasthan.
• Virdas: Gujarat.
• Bamboo drip irrigation: Northeast.
• Tanks: Karnataka.
• Zing: Ladakh.
• Stepwell: Rajasthan and Gujarat.
• Baoris / bers: Rajasthan.
• Apatani: Arunachal Pradesh.
• Pyne-ahar: Bihar.

The correct answer is Solid Waste Management Rules, 2016.

Key Points

• The new Solid Waste Management Rules (SWM), 2016, were recently announced by the Union Ministry of Environment, Forests, and Climate Change (MoEF&CC).
• The Municipal Solid Wastes (Management and Handling) Rules, 2000, which had been in effect for the previous 16 years, were replaced by these.
• The rules are now applicable beyond municipal areas and will extend to urban agglomerations, census towns, notified industrial townships, areas under the control of Indian Railways, airports, airbases, port and harbour, defence establishments, special economic zones, State and Central government organizations, places of pilgrims, religious & historical importance.
• The source segregation of waste has been mandated to channel the waste to wealth by recovery, reuse and recycling.

Therefore, the correct answer is Solid Waste Management Rules, 2016.

The correct answer is Chemical composition and atomic constitution.

Key Points

• The hardness of a mineral can be described as its resistance to external deformation processes such as scratching, abrasion, rubbing, or indentation.
• The hardness of a mineral depends on its chemical composition and atomic constitution.
• In general, a qualitative attribute is determined in relative terms when a mineral's hardness is measured using standard methods.
• It is a fairly constant and diagnostic property of minerals.

Therefore, the correct answer is chemical composition and atomic constitution.

Additional Information

• The Mohs’ scale of hardness comprises ten minerals arranged in order of ascending hardness; the softest is assigned a value of 1 and the hardest a value of 10.

The correct answer is Tropical deciduous.

Key Points

• Forest types in India are:

 

 

 

 

 

 

 

 

 

 

 

Therefore, tropical deciduous forests have the highest percentage of forests in India.

The correct answer is 66.7%.

Calculation:

Given:

Saturation vapour pressure = 900 mbar

Actual vapour pressure = 600 mbar

Since, 

$Relative \ Humidity (RH) = {Actual\ Vapour \ Pressure \over Saturation \ Vapour \ Presure}\times100$

$RH = {600\over 900}\times100$

RH = 66.7%

Therefore, the correct answer is 66.7%.

The correct answer is (a), (b), (c), and (d).

Key Points

The restored ecosystem should have the following attributes:

• Similar diversity and community structure in comparison with reference sites.
• Presence of indigenous species.
• The presence of functional groups is necessary for long-term stability.
• The capacity of the physical environment to sustain reproducing populations.
• Normal functioning.
• Integration with the landscape.
• Elimination of potential threats.
• Resilience to natural disturbances.
• Self-sustainability.

Therefore, the correct answer is (a), (b), (c), and (d).

The correct answer is (d), (a), (b) and (c).

Key Points

• The primary productivity of different biomes:

 

 

 

 

 

 

Therefore, the correct increasing order of primary productivity of different biomes is Temperate grasslands < Savannah < Boreal forests < Temperate forests.

The correct answer is ultraviolet < infrared < visible.

Key Points

• For the solar spectrum, the area under the curve between 0.38 and 0.78 μm (the wavelengths visible to the human eye) is 47% of the total area.
• That is, 47% of the solar energy striking the outside of our atmosphere is in the visible portion of the spectrum.
• The ultraviolet range contains 7% of the energy.
• The infrared wavelengths deliver the remaining 46%.
• The total area under the solar spectrum curve is called the solar constant, and it is estimated to be 1,372 W/m².

 

 

 

 

 

 

 

 

 

 

                Figure: Solar spectrum graph.

Therefore, the correct answer is ultraviolet < infrared < visible.

The correct answer is Black carbon.

Key PointsPrimary air pollutants:

• Primary air pollutants are those that are produced and released directly from specific sources.
• Examples: Particulate matter (including black carbon), carbon monoxide, nitrogen oxide, and sulfur oxide.

Secondary air pollutants:

• Secondary air pollutants are those that are produced in the lower atmosphere as a result of chemical interactions.
• Examples: Ozone and secondary organic aerosol (haze).
• Because secondary pollutants synthesise in a variety of ways and the creation is poorly understood, they are more difficult to manage.
• They naturally occur in the atmosphere and result in issues like photochemical haze.

Therefore, the correct answer is black carbon.

Additional Information

• Soot, often known as black carbon, is a fine particle air pollutant (PM_2.5) that causes climate change.
• The incomplete combustion of fossil fuels, wood, and other fuels results in the formation of black carbon.
• The carbon in the fuel would completely burn away to produce carbon dioxide (CO₂), but combustion is never complete and other byproducts such as carbon monoxide, volatile organic compounds, organic carbon, and black carbon particles are also created.
• Soot is a term used frequently to describe the complicated mixture of particulate debris produced by incomplete combustion.

The correct answer is CARTOSAT-2.

Key Points​​

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is CARTOSAT-2.

The correct answer is 5 × 1019.

Key Points

Given:

​Confinement time = 2 seconds

According to Lawson's criteria, for Deuterium (H²) and Tritium (H³), the reaction requirement is given as follows:

nτ > 10²⁰ m^-3s

where, n = ion density and

τ = confinement time

Therefore, nτ > 1020 m-3s

n = $10\times10^{19} \over 2$   

n = 5 x 10¹⁹

Therefore, the correct answer is 5 x 1019.

The correct answer is the Cetane number.

Key Points

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is the cetane number.

Explanation

• Magma is a mixture of liquid rock, crystals, and gas.
• It is characterized by a wide range of chemical compositions, with high temperatures, and properties of the liquid.
• This magma may erupt to the surface or it gets crystallizes before it reaches the surface.
• Processes that operate during transportation toward the surface or during storage in the crust can alter the chemical composition of the magma. These processes are referred to as magmatic differentiation.
• Each mineral begins to crystalline at a different temperature, and if these minerals are somehow removed from the liquid, the liquid composition will change. The process is called magmatic differentiation by fractional crystallization.
• Mafic minerals like olivine and pyroxene crystalline first. These minerals have high oxide content with SiO₂ of about 45-55%.

Hence, option 1 is the correct answer.

The correct answer is Biosafety.

Key Points

• The Cartagena Protocol on Biosafety to the Convention on Biological Diversity is an international agreement which aims to ensure the safe handling, transport and use of living-modified organisms (LMOs) resulting from modern biotechnology that may have adverse effects on biological diversity, also taking into account risks to human health.
• It was adopted on 29 January 2000 as a supplementary agreement to the Convention on Biological Diversity and entered into force on 11 September 2003.
• It establishes an advance informed agreement (AIA) procedure for ensuring that countries are provided with the information necessary to make informed decisions before agreeing to the import of such organisms into their territory.
• The Protocol contains a reference to a precautionary approach and reaffirms the precaution language in Principle 15 of the Rio Declaration on Environment and Development.
• The Protocol also establishes a Biosafety Clearing-House to facilitate the exchange of information on living modified organisms and assist countries in implementing the Protocol.

Therefore, the correct answer is biosafety.

The correct answer is Gram Sabha.

Key Points

• According to the Forest Rights Act of 2006, the transit permit regime concerning the transportation of minor forest produce shall be modified and given by the Committee constituted under clause (e) of sub-rule (1) of rule 4 or the person authorized by the Gram Sabha.

Therefore, the correct answer is Gram Sabha.

Additional Information

• The Forest Rights Act, which was enacted in 2006, recognises the rights of tribal communities that live in the forest as well as other traditional forest dwellers to the forest resources that were essential to their ability to provide for a variety of needs, including subsistence, habitation, and other sociocultural requirements.
• It acknowledges and grants the occupation of forest land to other traditional forest dwellers (OTFD) and forest-dwelling scheduled tribes (FDST), who have lived there for many generations.
• The procedure for assessing the kind and scope of Individual Forest Rights (IFR), Community Forest Rights (CFR), or both that may be granted to FDST and OTFD must be started by the Gram Sabha.

The correct answer is: 2) (b), (c) and (d) only

Key Points

 

• Randomly coiled (a):
• This statement is incorrect.
• Fulvic acids are not characterized primarily by random coiling. Instead, they are known for their smaller molecular size and chemical complexity. Random coiling is more commonly associated with larger humic substances, not fulvic acids.
• More polar (b):
• This statement is correct.
• Fulvic acid molecules are indeed more polar due to their higher oxygen content compared to humic acids. This increased polarity makes them more soluble in water across a range of pH values.
• Highly charged (c):
• This statement is correct.
• Fulvic acids carry a high number of charge sites, attributed to their many functional groups such as carboxyl and hydroxyl groups. This high level of charge contributes to their reactivity and ability to chelate nutrients.
• Smaller molecules than humic acid molecules (d):
• This statement is correct.
• Fulvic acid molecules are indeed smaller in size when compared to humic acids. This smaller size makes them more mobile and bioavailable in soil and aquatic environments.

Additional Information

• Fulvic Acids:
• Fulvic acids are one of the fractions of humus, the organic component of soil, resulting from the decomposition of organic matter by soil microorganisms.
• They are globally significant in the environment for their ability to chelate minerals and enhance nutrient absorption by plants.
• Properties of Fulvic Acids:
• The higher oxygen content in fulvic acids accounts for their higher polarity, which aids their solubility and helps them remain dissolved in water across a wide pH range.
• The smaller molecular size and high number of functional groups contribute to their chemical reactivity, making them more effective in nutrient cycling and remediation processes.

The correct answer is (a), (b) and (c).

Key Points

• Forest fire represents a significant threat to ecological and social systems, causing escalating social, eco-environmental and fiscal costs along with the changing climate.
• It is a result of complex human-environment interactions involving fuel, climate and fire-weather conditions, and topography.
• The different factors that affect the occurrence of forest fires are:
• Fuel type attributes (proportion of pine, fir, broadleaf, and others in each subcompartment; dominant species age).
• Local topography (elevation, slope and aspect)
• Weather on the ignition day (daily precipitation, daily average temperature and daily average relative humidity).
• Human activity (population density, distance to nearest road, distance to nearest settlement).
• Wildfires are dependent on the amount of fine fuel available for either ignition or propagation.

Therefore, the correct answer is (a), (b) and (c).

The correct answer is Taiga.

Key Points

• The taiga covers 17 million square kilometres (6.6 million square miles), or 11.5% of the land surface of the planet, making it the biggest terrestrial biome in the world.
• The tropical rainforest biome is the area that covers about 12 million square kilometres of the Earth.
• The desert biome covers about 9 million square kilometres.
• The grassland biome covers about 12 million square kilometres

Therefore, the correct answer is taiga.

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

Key Points

• Soil texture is a summation of proportions of sand, silt and clay content.
• It is a very stable characteristic that influences soil biophysical properties.
• Soil texture is interrelated with soil fertility and quality in the long term.
• The soil texture is associated with soil porosity, which in turn regulates the water holding capacity, gaseous diffusion and water movement that determines the soil health.
• It is the soil texture and mineralogy that affect most aspects of soil biogeochemistry and are reflected in strong correlations with soil organic matter (OM), nitrogen (N) mineralization, and moisture.

Hence, assertion (A) is false.

• The humus fraction (humic substances) of the soil organic matter gives the soil many important characteristics.
• This fraction is colloidal (very small particles that will stay suspended when dispersed in water) and is capable of absorbing a tremendous amount of water.
• A unit weight of a humus fraction can hold up to 20 times its weight in water.

Hence, reason (R) is true.

 Therefore, (A) is false, but (R) is true.

Explanation:

Given data

White balls = 3

Black balls = 2

To find

Two balls of different colors i.e. a white and a black ball.

Solution

Probability of finding two different color balls = (3C1 + 2C1)/ 5C2

(3C1 + 2C1)/ 5C2 =   

 

                             = 6/10

                             = 3/5

Hence, option 2 is the correct answer.

Explanation

Chi-square test

• A chi-square (χ²) statistic is a measure of the difference between the observed and expected frequencies of the outcomes of a set of events or variables.
• Chi-square is useful for analyzing such differences in categorical variables, especially those nominal in nature.
• χ2 depends on the size of the difference between actual and observed values, the degrees of freedom, and the sample size.
• χ2 can be used to test whether two variables are related or independent from one another.
• It can also be used to test the goodness-of-fit between an observed distribution and a theoretical distribution of frequencies.

X_c² = Σ $\frac{(O_i - E_i)^2}{E_i}$

Where,

c = Degree of Freedom

O = observed Value

E = Expected Value

Hence, option 1 is the correct answer.

Additional Information

• Normal distribution or Gaussian distribution is a type of continuous probability distribution for a real-valued random variable.
• Student's t-distribution (or simply the t-distribution) is any member of a family of continuous probability distributions that arise when estimating the mean of a normally distributed population in situations where the sample size is small and the population's standard deviation is unknown.
• Poisson distribution is a discrete probability distribution that expresses the probability of a given number of events occurring in a fixed interval of time or space if these events occur with a known constant mean rate and independently of the time since the last event.

The correct answer is 9.

Key Points

Given:

​Velocity (u) increased by a factor of 1.5

Magnetic field (B) increased by a factor of 2

Using the formula:

​$P = {1\over4}σ u^2B^2Ad$

​ Where,

P = Maximum power produced

u = Fluid velocity

B = Magnetic flux density

σ = Electrical conductivity of the conducting fluid

A = Plate area

d = distance between the plates

Since, new B' = 2 times of B and u' = 1.5 times of u

Keeping all other quantities the same, therefore the increased power produced is:

P' = (1.5)² x (2)²

P' = 9 times

Therefore, the correct answer is 9.

The correct answer is ∼ 6.7 mg/L.

Key Points

Given:

BOD of wastewater stream = 20.0 mg/L

BOD of river = 5.0 mg/L

Rate of flow of wastewater stream = 1.0 m³/s

Rate of flow of the river = 8.0 m3/s

Using the formula:

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

​Where,

​C_m = Concentration downstream of the junction

Q_m = Mixture's flow is the sum of the two-stream flows (Q_s + Q_w)

Q_s = Rate of flow of the main river/stream

C_s = Pollutant concentration of the mainstream/river

Q_w = Rate of flow of wastewater stream

C_w = Pollutant concentration of the wastewater stream

​Therefore, the BOD downstream from the point of discharge is given as:

​$C_m = {(20\times1)+(5\times8)\over 1 +8}$

C_m = 6.66 = ~6.7 mg/L

Therefore, the correct answer is ~6.7 mg/L.

The correct answer is ∼ 41.2 years.

Key Points

Given:

​Initial population = 350 million

Population growth rate = 2% = 0.02

Carrying capacity = 1.4 billion

First, we calculate the growth rate constant (r) using the formula:

​$r = {R_o\over 1-{N_0\over k}}$

$r = {0.02\over 1-{0.35\times10^9\over 1.4\times10^9}}$

r = 0.026

​Now, to calculate the time (t), we'll use the following formula:

$t = {1\over r}\ln[{k\over N_0} {-1}]$

$t = {1\over0.026}\ln[{1.4\times10^9\over 0.35\times10^9} {-1}]$

$t = {1\over0.026}\ln[{4-1}]$

$t = {1\over0.026}\ln[{3}]$

$t = {1\over0.026}\times1.09$

t = 38.46 x 1.09

t = 41.91

t = ∼ 41.2 

Therefore, the correct answer is ∼ 41.2 years.

Explanation:

• The face a slope presents to the sun – north or south – plays a role in the local climate created on it.
• This "microclimate" helps determine the types of plants that colonize the slope and influences which animals are drawn to the area seeking their preferred foods and suitable shelter.
• The basic difference between north- and south-facing slopes – the relative amount and intensity of sunlight they receive – leads to profound ecological differences, similar (but reversed) in the Northern and Southern Hemisphere.

Amount of Sunlight

• In the Northern Hemisphere, north-facing slopes in latitudes from about 30 to 55 degrees receive less direct sunlight than south-facing slopes.
• The lack of direct sunlight throughout the day, whether in winter or summer, results in north-facing slopes being cooler than south-facing slopes.
• During winter months, portions of north-facing slopes may remain shaded throughout the day due to the low angle of the sun.
• This causes snow on north-facing slopes to melt slower than on south-facing ones. The scenario is just the opposite for slopes in the Southern Hemisphere, where north-facing slopes receive more sunlight and are consequently warmer.
• Near the equator, north- and south-facing slopes receive roughly the same amount of sunlight because the sun is almost directly overhead.
• At the poles, north and south slopes tend to be either shrouded in darkness all winter long, or bathed in sunlight all summer long, with only slight variation between the slopes in spring and fall.

Depth of Soil

• Depth of soil on a slope, whether it faces north or south, depends on the steepness of the slope. The steeper the incline, the higher the rate of soil erosion from rain runoff. Soils on steep slopes are primarily made up of rock fragments because pieces of lightweight organic matter, such as leaves, wash away before they can decompose into soil. Slopes that have a gentle incline tend to accumulate a deeper layer of soil. In the Northern Hemisphere, soil on south-facing slopes dries out faster and is warmer than soil on north-facing slopes due to longer exposure to sunlight – the opposite applies in the Southern Hemisphere.

Effect of Rainfall

• The amount of rain that falls on a slope and is taken up by existing vegetation is determined by how steep the slope is, rather than whether it faces north or south. Rain runs more quickly off steeper slopes and does not have time to be taken up by plants. Rain falling on less steep inclines stays in the soil longer and is utilized by plants and trees, generally resulting in larger plants and/or colonization of plants with higher hydration needs.
• Vegetation on south-facing slopes in the Northern Hemisphere, for example, has less time to take up water because of the drying effect of the sun.

Effect on Plant Communities

• Given the effects of varying solar insolation, plant communities can vary widely between north- and south-facing slopes.
• In the Northern Hemisphere, warmer south-facing slopes green up sooner in spring, stay greener longer in the fall and tend to be drier than north-facing slopes.
• Plants that tolerate these hot, dry conditions – which, depending on the region, may be oaks, pines or drought-tolerant shrubs and grasses –grow well on southern slopes in their native range.
• A few feet away, a cooler, moister north-facing slope with a gradual incline may be dotted with closed mixed-hardwood or conifer forest and shade-tolerant wildflowers. Trees capture indirect sunlight better than low-growing grasses.

​Hence, option 1 is the correct answer.

The correct answer is Bioprecipitation.

Key Points

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Therefore, the correct answer is bioprecipitation.

The correct answer is Sikkim.

Key Points 

• Sikkim made the official decision to switch to organic farming in 2003.
• Sikkim saw a radical metamorphosis in the years that followed, moving from utilising chemicals and pesticides to outright banning them.
• Prime Minister Narendra Modi designated Sikkim as India's first entirely organic state in January 2016.

Therefore, the correct answer is Sikkim.

Additional Information

• The "Sikkim Organic Mission" was established by the State Government in 2010.
• Sikkim's pursuit of the 100% organic label is being accelerated by the Sikkim Organic Mission.
• The Mission assisted by giving out seeds and fertiliser and teaching farmers how to use organic practices.
• Over 66,000 farming households in the state have benefited from the switch to an organic state, which has also promoted sustainable living and rural development.

The correct answer is Sulphate aerosols.

Key Points

• Global cooling is the anticipated cooling of the Earth as a result of orbital forcing or the cooling effects of aerosols.
• When there is an increase in the albedo, the planet cools.
• Sulphate aerosols and white smoke cause an increase in albedo, thereby causing global cooling.

Therefore, the correct answer is sulphate aerosols.

Additional Information

• Black carbon results from the incomplete combustion of biomass and fossil fuels.
• Nitrous oxide and HCFCs are greenhouse gases and result in global warming.

Explanation:

• Dam is essentially an artificial wall constructed across a river which converts a running water ecosystem into a lake type ecosystem.

• With a height of 260.5 m (855 ft) Tehri Dam is the tallest dam in India and 12th tallest dam in the world.

• With a total planned installed capacity of 2400 MW, it is the biggest Hydroelectric power plant in India.

• It is a multi-purpose rock and earth-fill embankment dam on the Bhagirathi River in New Tehri, Tehri Garhwal district in Uttarakhand, India.

• The Tehri Dam has been the object of protests by environmental organizations and local people of the region.

• It spurred concerns about the environmental consequences of locating such a large dam in the fragile ecosystem of the Himalayan foothills and the dam's geological stability.

• The Tehri dam is in the Central Himalayan Seismic Gap, a major geologic fault zone.

• Dam proponents claim that the complex is designed to withstand an earthquake of 8.4 magnitude, but some seismologists say that earthquakes with a magnitude of 8.5 or more could occur in this region.

Probable impacts identified are

• Likely change in the (i) water chemistry, especially with respect to dissolved oxygen and (ii) turbidity of water.
• Likely impact on biodiversity, i.e., flora and fauna of the area.
• Likely obstruction of movements of migrating fish species during breeding season.
• Rivers carry a lot of sediment, which on construction of a dam, will be locked up behind the dam wall.
• Likely impact of water accumulation on the upstream side of the dam, which causes inundation of land including forest-land.
• Since 109 villages (full or partial) and Tehri town (full) were affected and the residents were to vacate their ancestral homes and agricultural fields, a scheme was prepared, to resettle these people, with the idea to improve their living standard, keeping their social bonds intact.
• Likely problem of water-logging and salinity of the land in the command area.

​Hence, option 4 is the correct answer.

Explanation:

• Sustainable development is a process that aims for human well-being and economic development, while ensuring that ecological systems are in balance.
• It is commonly described as finding a balance between ecology, the economy, and society –three interdependent areas in a complex system.
• Yet it is important to remember that neither society nor the economy would exist without diverse ecology.
• The key to sustainable development is achieving a balance between the exploitation of natural resources for socio-economic development, and conserving ecosystem services that are critical to everyone’s well-being and livelihoods.
• Ecosystem services are the benefits people get from nature. Tangible benefits include supplies of food and fresh water, flood mitigation, and improvements to water quality.
• Sustainable development highlights the importance of poverty reduction, and calls for policy implementation that leads to the socioeconomic development of impoverished people.
• Socio-economic development by considering different sustainable livelihoods, multidimensional poverty, living standards, and social development measures.
• Social sustainability is a process for creating sustainable successful places that promote well-being, by understanding what people need from the places they live and work.
• Therefore, Sustainable development presupposes the maintenance of ecosystem integrity, improvement in economic and social conditions of people, and perpetual availability of ecosystem services.

Hence, option 1 is the correct answer.

The correct answer is A - IV, B - I, C - II, D - III.

Key Points

 

 

 

 

Additional Information

• PAHs and HPLC:
• Polycyclic Aromatic Hydrocarbons (PAHs) are a class of organic pollutants with fused aromatic rings.
• They are commonly found in fossil fuels and are generated during the incomplete combustion of organic matter.
• High Performance Liquid Chromatography (HPLC) is an analytical technique used to separate, identify, and quantify each component in a mixture. It is effective for analyzing PAHs due to its high resolution and sensitivity.
• Heavy metals and AAS:
• Heavy metals such as lead, mercury, cadmium, and arsenic are toxic pollutants that accumulate in biological organisms, posing significant health risks.
• Atomic Absorption Spectroscopy (AAS) is widely used for detecting and measuring the concentration of heavy metals in environmental samples. It works by atomizing the sample and measuring the absorbed radiation at specific wavelengths corresponding to the metals of interest.
• Sulphate ions and UV-Vis spectrophotometer:
• Sulphate ions (SO₄²⁻) are commonly found in natural waters and can contribute to water pollution from industrial discharge.
• UV-Visible spectrophotometry is a method used to analyze the concentration of sulphate ions in a solution. The instrument measures the absorbance of light by the sample at specific wavelengths, which correlates to the concentration of sulphate ions.
• Nucleotides and Electrophoresis:
• Nucleotides are the building blocks of nucleic acids like DNA and RNA and are crucial for genetic analysis.
• Electrophoresis is a laboratory technique used to separate molecules based on their size and charge. It is particularly useful in the analysis of nucleotides by applying an electric field to a gel matrix, allowing smaller and more charged molecules to move faster through the gel.

Explanation:

• Compressibility is the degree to which a soil mass decreases in volume when supporting a load.
• It is lowest in coarse-grained soils where particles are in contact with each other.
• It increases as the proportion of small particles increases and becomes highest in fine-grained soils which contain organic matter.
• Gravels and sands are practically incompressible. If a moist mass of these materials is subjected to compression, there is no significant change in their volume.
• Clays are compressible.
• If a moist mass of clay is subjected to compression, moisture and air may be expelled, resulting in volume reduction which is not immediately recovered when the load is removed.
• Fine-grained soils which contain at least 50 percent of silt and clay may be listed in three classes of compressibility on the basis of their liquid limit. They are as follows:
• Low compressibility - <30
• Medium compressibility- 30-50
• High compressibility- >50​

Hence, option 2 is the correct answer.

Explanation:

Correlation coefficient

r = $\frac{n(\Sigma xy)\ -\ (\Sigma x)(\Sigma y)}{\sqrt{[n\Sigma x^2 - (\Sigma x)^2][n\Sigma y^2\ -\ (\Sigma y)^2]}}$

Where,

n = Sum of values or elements

Σx = Sum of 1st value list

Σy = Sum of 2nd value list

Σxy = Sum of the product of 1st and 2nd values

Σx² = Sum of square of 1st values

Σy³ = Sum of square of 2nd values

Substituting these values in the above formula,

r = (5 (6750) - (150 * 240) )/ ((5 * 4750 - 22500) (5 *12350 - 57600))

r = -2250 / 2277.60

r = -0.987.

Temperature and Humidity are negatively correlated.

Hence, option 1 is the correct answer.

Explanation:

Hence, option 3 is the correct answer.

CONCEPT:

Variance Decomposition in Simple Linear Regression

• In a simple linear regression model Y = a + bX + ∈, the total variance in the dependent variable Y (denoted as S_Y²) can be explained as the sum of:
• Explained variance (due to the regression on X), and
• Unexplained variance or residual/error variance (due to randomness or noise ∈)
• This can be written as:
  

S_Y² = b² × S_X²

only when we assume that the total variance of Y arises from the regression on X and residual variance is not added (as it's already given separately).

• In some contexts, the total variance S_Y² may refer to only the explained component if the residual variance is already excluded or separately measured.
• Given this, if residual variance is already reported, and we are asked to calculate only the variance due to regression (explained part), we use:
  

S_Y² = b² × S_X²

EXPLANATION:

• Given:
• b = 0.2 (regression coefficient)
• S_X² = 250 (variance of X)
• Apply the formula:
  

S_Y² = b² × S_X²

• Substitute the values:
• b² = (0.2)² = 0.04
• S_Y² = 0.04 × 250 = 10
• Residual variance = 5 is given, but it is not added here, as the question is asking only for the variance due to the regression component.

The correct answer is 10

The correct answer is Density and dispersion.

Key Points

A population is a collective group of organisms of the same species occupying a particular space.

The population has the following six characteristics:

1. Population size and density
2. Dispersion
3. Age structure
4. Natality (Birth rate)
5. Mortality (Death rate)
6. Life tables

Therefore, the correct answer is density and dispersion.

Explanation

• In r/K selection theory, selective pressures are hypothesized to drive evolution in one of two generalized directions: r- or K-selection.
• These terms, r and K, are drawn from standard ecological algebra as illustrated in the simplified Verhulst model of population dynamics,

$\frac{dN}{dt} = rN(1 - \frac{N}{K})$

​Where,

N is the population, 

r is the maximum growth rate, 

K is the carrying capacity of the local environment,

dN/dt, the derivative of N with respect to time t, is the rate of change in population with time.

Thus, the equation relates the population density and resource density.

r-selection

• r-selected species are those that emphasize high growth rates, typically exploit less-crowded ecological niches, and produce many offspring, each of which has a relatively low probability of surviving to adulthood.
• In unstable or unpredictable environments, r-selection predominates due to the ability to reproduce rapidly.
• There is little advantage in adaptations that permit successful competition with other organisms, because the environment is likely to change again.
• Among the traits that are thought to characterize r-selection are high fecundity, small body size, early maturity onset, short generation time, and the ability to disperse offspring widely.

k-selection

• By contrast, K-selected species display traits associated with living at densities close to carrying capacity and typically are strong competitors in such crowded niches that invest more heavily in fewer offspring, each of which has a relatively high probability of surviving to adulthood.
• In stable or predictable environments, K-selection predominates as the ability to compete successfully for limited resources is crucial and populations of K-selected organisms typically are very constant in number and close to the maximum that the environment can bear.
• Traits that are thought to be characteristic of K-selection include large body size, long life expectancy, and the production of fewer offspring, which often require extensive parental care until they mature.

Hence, option 2 is the correct answer.

The correct answer is 253.

Key Points

• Environment Protection Act, 1986 is an Act of the Parliament of India.
• It was enacted in May 1986 and came into force on 19 November 1986.
• It has 26 sections and 4 chapters.
• The Act is widely considered to have been a response to the Bhopal gas leak.
• The Environment Protection Act was enacted under Article 253 of the Indian Constitution which provides for the enactment of legislation for giving effect to international agreements.

Therefore, the correct answer is 253.

Additional Information

• Article 48A of the Constitution specifies that the State shall endeavour to protect and improve the environment and safeguard the forests and wildlife of the country.
• Article 51A further provides that every citizen shall protect the environment.

The correct answer is Neutrons first convert fertile material into fissile material and then sustain the fission reaction.

Key Points

• Breeder reactors are designed to generate nuclear fuel at the same time as producing energy for electricity production.
• This is possible because a small number of isotopes will capture neutrons produced in a reactor, starting a reaction that leads to a new, heavy fissile isotope.
• This permits both neutron-induced fission for power generation and neutron capture for fuel generation to occur simultaneously.
• The two main fertile isotopes that are useful for this purpose are uranium-238 which will generate fissile plutonium and thorium-232 which will produce fissile uranium.
• Fast breeder reactors use fast neutrons to sustain the fission reaction as well as breeding.
• The non-fissile isotopes ²³⁸U and ²³²Th are converted to fissile isotopes of ²³⁹Pu and ²³³U, respectively, thus producing fresh fuel during reactor operation.

Therefore, the correct answer is neutrons first convert fertile material into fissile material and then sustain the fission reaction.

Explanation:

Hence, option 2 is the correct answer.