Test: Environment - 4 - UPSC MCQ

• Predation and parasitism are two types of negative biotic interactions between the organisms living in the Earth.

  • Parasitism is an interaction between a parasite and a host in which the former obtains benefits at the cost of later. A parasite does not cause the death of the host. Whereas Predation is an association between two species, where one species (predator) kills to feed on the prey. Hence, statement 1 is not correct.

  • In Parasitism the weak feed on the strong while in predation it is strong that feeds on the weak. Hence, statement 2 is correct.

  • For example, Glochidium larva attaches to the fins of a fish is an example of parasitism and Birds feeding on fish is an example of predation.

• Option 1 is correct: Change of process is one of the source correction methods used in the abatement of air pollution. Changing or modifying the process of production can help in lowering atmospheric pollutants. For example, coal is washed before pulverizing it to reduce fly ash emissions.

• Option 2 is not correct and option 3 is correct: Existing equipment can be modified to reduce/control undesirable emissions.

  • If open-hearth furnaces are replaced with controlled basic oxygen/electric furnaces then the emission of carbon monoxide, smoke and fumes can be reduced.

  • In petroleum refineries, loss of hydrocarbon vapours from storage tanks (due to evaporation or temperature change) can be reduced by designing storage tanks with floating roof covers.

• Ecological succession is the process that describes how the structure of a biological community (that is, an interacting group of various species in a desert, forest, grassland, marine environment, and so on) changes over time.

  There are two types of succession:

  • Primary Succession: Succession that begins in new habitats or lifeless areas that are uninfluenced by pre-existing communities.

  • Secondary Succession: Succession that follows the disruption of a pre-existing community that existed in the same ecosystem.

• The species that invade a bare area are called pioneer species.

• Primary succession on rocks:

  • These are usually lichens which are able to secrete acids to dissolve rock, helping in weathering and soil formation.

  • These later pave the way for some very small plants like bryophytes, which are able to take hold in the small amount of soil. They are, with time, succeeded by higher plants, and after several more stages, ultimately a stable climax forest community is formed.

  • The climax community remains stable as long as the environment remains unchanged. With time the xerophytic habitat gets converted into a mesophytic one.

• Primary succession in water:

  • The pioneers are the small phytoplankton. Hence option 1 is correct.

  • Phytoplanktons are gradually replaced with time by rooted-submerged plants,rooted-floating angiosperms followed by free-floating plants, then reed-swamp, marsh-meadow, scrub and finally the trees. Hence, options 2, 3 and 4 are not correct.

  • The climax again would be a forest. With time the water body is converted into land.

• Organisms living in this earth are interlinked to each other in one way or other. The interaction between the organisms is fundamental for the survival and functioning of the ecosystem as a whole.

• Antibiosis is a negative interaction in which an organism produces harmful secretions. In this type of relationship, none of the population is benefited. Hence, option (d) is correct.

• For example, some species of blue-green algae that grows in ponds produce toxic substances that kilt fishes as well. In marine waters, the population of some microbes popularly known as red tide cause the destruction of fish and other animals.

• Intraspecific competition is the competition between organisms of the same species.

• Predation is an association between two species, where one species kills to feed on the other.

• Exploitation is the relationship in which one organism is benefited by direct utilization of another.

• Grasslands are found on every continent except Antarctica. These terrestrial ecosystems occupy roughly 19 percent of the earth's surface. They are characterised by treeless herbaceous plants dominated by a wide variety of grass

• Features of Grasslands:

  • The grasslands are found where rainfall is about 25-75 cm per year, not enough to support a forest, but more than that of a true desert. Typical grasslands are vegetation formations that are generally found in temperate climates.

  • Grasslands are dominated by grasses. Large shrubs or trees are not found. Hence, statement 2 is not correct.

  • Grasslands have a rich variety of animals. Hence, statement 1 is correct.

  • The soil is always exposed, sometimes rocky but more often sandy with fixed or mobile dunes. Forage is available only during the brief wet season. Boreal forest soils are characterized by thin podzols. Hence, statement 3 is not correct.

  • Grasslands have been the home for grazing animals for millions of years.

• A forest ecosystem is composed of trees, shrubs or any other woody vegetation with closed canopy cover. These are usually found in regions where there is plenty of rainfall.

• Tropical Forests:

  • In Tropical forests, there is no winter, and there are only two seasons (rainy and dry). The length of daylight is 12 hours and varies little.

  • In Tropical Forests one square kilometre may contain as many as 100 different tree species. Trees are 25-35 m tall, with shallow roots, mostly evergreen, with large dark green leaves. Plants such as orchids, bromeliads, vines, ferns, mosses, and palms are present in tropical forests.

  • Tropical forests have the largest variety of life forms in all of nature, with thousands of different species of mammals, birds, reptiles, amphibians and insects. Many of the animals in these forests are highly adaptive to their diverse environment having developed camouflage and strong defences. Hence option (a) is the correct answer.

• Temperate forests:

  • Temperate forests have a wide range of temperatures that correlate with the distinctive seasons. Temperatures range from hot in the summer, with highs of 30^OC, to extremely cold in the winter, with lows of -30^OC.

  • Temperate forests receive abundant amounts of precipitation, usually between 20 and 60 inches of precipitation annually. This precipitation is in the form of rain and now.

  • They are characterized with a variety of deciduous trees. Decreasing temperatures and shortened daylight hours in fall mean decreased photosynthesis for plant.

• Taiga Forests:

  • The taiga is sometimes called the boreal forest or the coniferous forest. It is the largest of all the land biomes.

  • The taiga is the driest and coldest of the three.

  • This forest is covered with evergreen, or coniferous, trees.

  • The taiga has the coldest weather of the forest biomes. Winters can get as cold as -50^OC. Winter can last for six months with the temperature averaging below freezing. Summers are warmer, but very short.

  • The precipitation is only slightly more than the desert or the tundra. Average precipitation is between 12 and 30 inches per year. It falls as rain in the summer and snow in the winter.

  • The layer of good soil is thin because the leaves don’t fall from the trees, like in the temperate forest.

• The large population of bacteria decomposes organic matter present in water. They consume oxygen dissolved in water. The amount of oxygen that water can hold in the solution is limited. Even a moderate amount of organic matter when decomposes in water can deplete the water of its dissolved oxygen. The concentration of dissolved oxygen in water is very important for aquatic life. If the concentration of dissolved oxygen in water is below 6 ppm, the growth of fish gets inhibited. If too much organic matter is added to water, all the available oxygen is used up.

• Thus, the amount of oxygen required by bacteria to break down the organic matter present in a certain volume of a sample of water is called Biochemical Oxygen Demand (BOD). The amount of BOD in the water is a measure of the amount of organic material in the water, in terms of how much oxygen will be required to break it down biologically. Clean water would have a BOD value of less than 5 ppm whereas highly polluted water could have a BOD value of 17 ppm or more. Hence statement 1 is correct and statement 2 is not correct.

• Organism: An organism is a fundamental functional unit in ecology because it interacts directly with the environment as well as with other organisms, e.g., a rabbit

• Population: It refers to the organisms of the same species that are in proximity to one another, e.g., a group of rabbits. Hence, statement 2 is not correct.

• Community: It includes all the populations occupying a given area. The size of a community depends on our scale of reference. The community and the non-living environment together are referred to as an ecological system or ecosystem, e.g., a pond with fish and plants. Hence, statement 1 is not correct.

• Biome: It refers to a large regional or subcontinental ecosystem characterized by similarity in vegetation and climate. It is made of many similar ecosystems. An ecosystem is much smaller than a biome. For example, a grassland biome implies many ecosystems that are similar because grasses are, their principal plants and grazers are their predominant animals. Hence, statement 3 is correct.

• The ecological pyramids are of three categories:

  • Pyramid of numbers,

  • Pyramid of biomass, and

  • Pyramid of energy or productivity

• Pyramid of Numbers:

  • This deals with the relationship between the numbers of primary producers and consumers of different levels. It is a graphic representation of the total number of individuals of different species, belonging to each trophic level in an ecosystem.

  • In a forest or lake ecosystem, the pyramid is always in an upright position. However, the pyramid of Numbers in a parasitic food chain is inverted. For example, a single tree supports many fruit-eating birds. These birds support more numbers of parasites like lice. These parasites support a large variety of other parasites like bacteria and fungi. Hence option 1 is correct.

• Pyramid of Biomass:

  • In this approach individuals in each trophic level are weighed instead of being counted. This gives us a pyramid of biomass, i.e., the total dry weight of all organisms at each trophic level at a particular time.

  • Pyramid of biomass is usually determined by collecting all organisms occupying each trophic level separately and measuring their dry weight.

  • In many ecosystems, such as in forests and grasslands, the biomass of producers is much greater than that of the herbivores, which in turn outweigh the carnivores and so on. Thus, we experience a gradual decline in the biomass of organisms at each hierarchic trophic level. These pyramids are in an upright position. Hence option 2 is not correct.

  • However, in a pond ecosystem, producers are small organisms, so their biomass is also less. But the primary and secondary consumers are bigger, so their biomass is more. Therefore, the value of biomass shows a gradual increase, making it an inverted pyramid. Hence option 3 is correct.

• Pyramid of Energy: An energy pyramid, reflects the laws of thermodynamics, with conversion of solar energy to chemical energy and heat energy at each trophic level and with loss of energy being depicted at each transfer to another trophic level. Hence the pyramid is always upward, with a large energy base at the bottom.

• Wetland types found in coastal watersheds include salt marshes, bottomland hardwood swamps, fresh marshes, mangrove swamps, etc.

• Flood Protection: Coastal wetlands protect upland areas, including valuable residential and commercial property, from flooding due to sea-level rise and storms. Hence option 4 is correct.

• Coastal wetlands provide habitat for many federally threatened and endangered species, They act as a habitat for migratory birds and animals. Hence option 1 is correct.

• Coastal Wetlands can improve water quality by removing pollutants from surface waters. Three pollutant removal processes provided by wetlands are particularly important: sediment trapping, nutrient removal, and chemical detoxification. Hence option 3 is correct.

• Recharges a drinking water source, such as a wellhead or source protection area. Reduces levels of contaminants in surface waters that recharge underlying or adjacent groundwaters such as wells. Hence option 4 is correct.

• Enhances or protects water quality through chemical action, by the removal of nutrients, by the retention or removal of sediments or organic matter, or by moderating the adverse water quality effects of soil erosion or stormwater runoff.

• Photochemical smog is a mixture of pollutants that are formed when nitrogen oxides and volatile organic compounds (VOCs) react to sunlight, creating a brown haze above cities. It occurs in warm, dry, and sunny climates. The main components of the photochemical smog result from the action of sunlight on unsaturated hydrocarbons and nitrogen oxides produced by automobiles and factories. Photochemical smog has a high concentration of oxidizing agents and is, therefore, called oxidizing smog.

• Formation of Photochemical Smog:

  • When fossil fuels are burnt, a variety of pollutants are emitted into the earth’s troposphere including hydrocarbons (unburnt fuels) and nitric oxide (NO). When these pollutants build up to sufficiently high levels, a chain reaction occurs from their interaction with sunlight in which NO is converted into nitrogen dioxide (NO₂).

  • This NO₂ in turn absorbs energy from sunlight and breaks it up into nitric oxide and free oxygen atoms.

    • NO₂(g) → NO(g) + O(g)

  • Oxygen atoms are very reactive and combine with the O2 in the air to produce ozone.

    • O(g) + O₂ (g) → O₃ (g)

  • The ozone formed in the above reaction reacts rapidly with the NO to regenerate NO2. NO₂ is a brown gas and at sufficiently high levels can contribute to haze.

    • NO(g) + O (g)→NO (g) + O (g)

  • Ozone is a toxic gas and both NO2 and O3 are strong oxidizing agents and can react with the unburnt hydrocarbons in the polluted air to produce chemicals such as formaldehyde, acrolein, and peroxyacetyl nitrate (PAN).

• Effects of Photochemical Smog: The common components of photochemical smog are ozone, nitric oxide, acrolein, formaldehyde, and peroxyacetyl nitrate (PAN). Photochemical smog causes serious health problems. Both ozone and PAN act as powerful eye irritants. Ozone and nitric oxide irritate the nose and throat and their high concentration causes headache, chest pain, dryness of the throat, cough and difficulty in breathing. Hence option (d) is the correct answer.

• Ozone in the stratosphere is a product of UV radiations acting on dioxygen (O2) molecules. The UV radiations split apart molecular oxygen into free oxygen (O) atoms. Ozone is thermodynamically unstable and decomposes to molecular oxygen. Thus, a dynamic equilibrium exists between the production and decomposition of ozone molecules.

• In recent years, there have been reports of the depletion of this protective ozone layer because of the presence of certain chemicals in the stratosphere. The main reason for ozone layer depletion is the release of chlorofluorocarbon compounds (CFCs), also known as freons. These compounds are nonreactive, nonflammable, nontoxic organic molecules and therefore used in refrigerators, air conditioners, in the production of plastic foam, and by the electronic industry for cleaning computer parts, etc. Once CFCs are released into the atmosphere, they mix with the normal atmospheric gases and eventually reach the stratosphere. In the stratosphere, they get broken down by powerful UV radiations, releasing chlorine-free radicals. The chlorine radicals then react with stratospheric ozone to form chlorine monoxide radicals and molecular oxygen. The reaction of chlorine monoxide radical with atomic oxygen produces more chlorine radicals. The chlorine radicals are continuously regenerated and cause the breakdown of ozone. Thus, CFCs are transporting agents for continuously generating chlorine radicals into the stratosphere and damaging the ozone layer. Hence statements 1 and 3 are correct.

• In winter, a special type of cloud called polar stratospheric cloud is formed over Antarctica. These polar stratospheric clouds provide a surface on which chlorine nitrate formed gets hydrolyzed to form hypochlorous acid. It also reacts with hydrogen chloride produced as per reaction (v) to give molecular chlorine. When sunlight returns to Antarctica in the spring, the sun’s warmth breaks up the clouds, and HOCl and Cl₂ are photolyzed by sunlight. The chlorine radicals thus formed, initiate the chain reaction for ozone depletion as described earlier. Hence statement 2 is correct.

• The greenhouse effect is a natural process that warms the Earth’s surface. When the Sun’s energy reaches the Earth’s atmosphere, some of it is reflected back to space and the rest is absorbed and re-radiated by greenhouse gases. Earth is surrounded by a blanket of air called the atmosphere. Greenhouse gas molecules in the atmosphere trap heat as they are transparent to sunlight but not to heat radiation. If the amount of carbon dioxide crosses the delicate proportion of 0.03 percent, the natural greenhouse balance may get disturbed. Carbon dioxide is a major contributor to global warming.

• Besides carbon dioxide, other greenhouse gases are methane, water vapor, nitrous oxide, and ozone. Methane is produced naturally when vegetation is burnt, digested, or rotted in the absence of oxygen. Large amounts of methane are released in paddy fields, coal mines, rotting garbage dumps, and by fossil fuels. Chlorofluorocarbons (CFCs) are man-made industrial chemicals used in air conditioning etc. CFCs are also damaging the ozone layer. Nitrous oxide occurs naturally in the environment. In recent years, their quantities have increased significantly due to the use of chemical fertilizers and the burning of fossil fuels.

Hence option (d) is the correct answer.

• Carbon oxides, or oxocarbons, are a class of organic compounds containing only carbon and oxygen. The most basic oxocarbons are carbon monoxide and carbon dioxide.

• Carbon monoxide: Carbon monoxide (CO) is a colorless and odorless gas, highly poisonous to living beings because of its ability to block the delivery of oxygen to organs and tissues. It is produced as a result of the incomplete combustion of carbon. CO is poisonous as it binds to hemoglobin to form carboxyhemoglobin, which is about 300 times more stable than the oxygen-hemoglobin complex. In blood, when the concentration of carboxyhemoglobin reaches about 3–4 percent, the oxygen-carrying capacity of blood is greatly reduced. This oxygen deficiency results in headaches, weak eyesight, nervousness, and cardiovascular disorder. In pregnant women who have the habit of smoking the increased CO level in blood may induce premature birth, spontaneous abortions, and deformed babies. Hence statement 1 is correct.

• Carbon dioxide: Carbon dioxide (CO₂) is released into the atmosphere by respiration, burning of fossil fuels for energy, and by decomposition of limestone during the manufacture of cement. It is also emitted during volcanic eruptions. Normally it forms about 0.03 percent by volume of the atmosphere. Hence statement 2 is not correct.

• With the increased use of fossil fuels, a large amount of carbon dioxide gets released into the atmosphere. Green plants require CO₂ for photosynthesis and they, in turn, emit oxygen, thus maintaining the delicate balance. Deforestation and the burning of fossil fuels increase the CO₂ level and disturb the balance in the atmosphere. The increased amount of CO₂ in the air is mainly responsible for global warming.

• Intraspecific interaction in population ecology involves members of the same species interacting with each other.

  Various types include:

  • Colonization:

    • Colonization is the occupation of habitat or territory by a biological community or of an ecological niche by a single population of a species. Colonial life is exhibited by animals demonstrate shades of mutualism and commensalism.

    • Colonisation results in collective efforts in gathering food and a greater chance of fertilization during the reproductive phase. Hence option 2 is correct.

  • Aggregation:

    • It refers to concentrations of animals in large numbers larger than found in a normal distribution. Aggregation is advantageous due to its group survival value.

    • Social life exhibited by tent caterpillars is an example of temporary aggregation. Hence option 1 is correct.

  • Social Organization:

    • Termites, ants, bees etc., are highly evolved insects that show division of labour among the individuals in a population is an important mechanism to regulate population density for certain animals.

• Proto-cooperation is an interaction between organisms of different species (interspecies) in which both organisms benefit, but neither is dependent on the relationship. Hence option 3 is not correct.

• Symbiosis is an ecological relationship between two species (interspecies) that live in close proximity to each other. Hence option 4 is not correct.

• There are lot of factors responsible for the depletion of resources:

  • Overuse or irrational use: Due to unprecedented increase in human population and the industrial advancement, various natural resources are overused or overexploited.

  • Non-equitable distribution of resources: Since natural resources are not distributed equitably across the planet, it led to exploitation of resources at places concentrated with one particular resource, for example coal reserves in Jharkhand and Odisha, petroleum in middle-east countries.

  • Technological and industrial development: Due ever expanding technology and industrial revolution, the need of various resources such as coal, minerals etc have increased rapidly which led to increased mining and faster depletion of resources.

  • Overpopulation: The population explosion has put a severe strain on the natural resources. Both renewable and non-renewable resources are under pressure. In order to satisfy the ever-increasing demands for food, water, clothing and shelter, man has exploited natural resources to such an extent that it has caused ecological imbalance in nature.

Hence option (a) is the correct answer.

• Decomposition is the first stage in the recycling of nutrients that have been used by an organism (plant or animal) to build its body. It is the process whereby the dead tissues break down and are converted into simpler organic forms.

• The rate of decomposition is regulated by climatic factors like temperature and soil moisture as well as by the chemical quality of detritus. These factors limit the rate of decomposition through their regulatory effect on the activities of soil microbes.

• Temperature and Soil moisture: Organic waste matter decomposes rapidly at high temperatures and moist conditions of humid tropical regions. Within a few weeks or months, complete decomposition occurs. However, low temperature sharply reduces the decomposition rate even if the moisture content of the soil is high. Hence option 1 is correct and option 2 is not correct.

• Chemical quality of the Detritus: The chemical quality of detritus is determined by the relative proportions of water-soluble substances like sugars, polyphenols, lignin and nitrogen. Within the same climatic conditions, the decomposition rate is high when detritus is rich in nitrogen and has low amounts of lignin. High quantities of lignin and chitin lower the rate of decomposition. Hence, option 3 is correct.

• Soil leaching refers is the movement of nutrient elements from topsoil through the soil profile. Leaching causes significant nutrient losses, particularly in humid regions with high precipitation. Leaching is a natural process caused mainly by precipitation, acidification, and nitrogen saturation. Human activity such as excess watering of the crop in farmland greatly influences some of these factors and the amount of leaching that occurs. Hence statement 2 is correct

• An integrated soil fertility management aims at maximizing the efficiency of the agronomic use of nutrients and improving crop productivity. This can be achieved through a process of Alternate Cropping wherein the plant grown of a farm is changed in 2-3 years, with the use of grain and legumes crops, biological nitrogen is fixed in the soils making it more fertile for the next 2-3 years. Hence statement 1 is correct

• Earthworms (EWs) are a major component of soil fauna communities in most ecosystems and comprise a large proportion of macrofauna biomass. Their activity is beneficial because it can enhance soil nutrient cycling through the rapid incorporation of detritus into mineral soils. In addition to this mixing effect, mucus production associated with water excretion in earthworm guts also enhances the activity of other beneficial soil microorganisms. This is followed by the production of organic matter. They also help to open up the soil by burrowing and make it more receptive to rainfall. Hence statement 3 is correct.

• Lakes and ponds are divided into three different "zones" which are usually determined by depth and distance from the shoreline.

• Littoral Zone: The topmost zone near the shore of a lake or pond is the Littoral zone. This zone is the warmest since it is shallow and can absorb more of the Sun's heat. It sustains a fairly diverse community, which can include several species of algae (like diatoms), rooted and floating aquatic plants, grazing snails, clams, insects, crustaceans fishes, and amphibians. Hence, statement 1 is correct.

• Limnetic Zone: The near-surface open water surrounded by the littoral zone is the limnetic zone. The limnetic zone is well-lighted (like the littoral zone) and is dominated by plankton, both phytoplankton and zooplankton. A variety, of freshwater fish also occupy this zone. Hence, statement 2 is correct.

• Profundal Zone: The deep-water part of the lake or pond is called the profundal zone. This zone is much colder and denser than the other zones. Little light penetrates all the way through the limnetic zone into the profundal zone. The fauna are heterotrophs they eat dead organisms and use oxygen for cellular respiration. Hence, statement 3 is correct.

• Biogas refers to a gas produced by the biological breakdown of organic matter in the absence of oxygen. Hence statement 1 is not correct.

• Biogas is produced by the anaerobic digestion or fermentation of biodegradable materials such as biomass, manure or sewage, municipal waste, green waste and energy crops. This type of biogas comprises methane and carbon dioxiode. The other type is wood gas which is created by gasification of wood or other biomass.

• Biogas is primarily composed of methane gas, carbon dioxide, and trace amounts of nitrogen, hydrogen, and carbon monoxide. Hence statement 2 is correct. Gobar gas is produced from the anaerobic digestion of manure.

• Importance of Biogas:

  • The products of biogas plant, methane gas is used as fuel and liquid humus as natural fertilizer.

  • Biogas can be generated from locally available materials like animal dung, agricultural waste etc.

  • It is a clean fuel.

  • It has high calorific value. Hence statement 3 is not correct.

• Wastes can be classified into various categories like biodegradable and non - biodegradable wastes.

• Wastes that can be degraded or broken down through microbial activities of fungi and bacteria are called biodegradable wastes. Agricultural wastes, faecal remains, dead plants, leather shoes/bags, tin cans falls under this category.

• Wastes which cannot be degraded or broken down through microbial activities are called non-biodegradable wastes. Such wastes include crude petroleum, plastics, styrofoam products, glasses, polymer, synthetic pesticides, radioactive fall out etc.

  • Styrofoam is a pure solid, hard with limited flexibility. It is used for making disposable cutlery, plastic models, CD and DVD cases etc.

Hence option (b) is the correct answer.

• Methane is a gas that is found in small quantities in Earth's atmosphere. Methane is the simplest hydrocarbon, consisting of one carbon atom and four hydrogen atoms. Methane is a powerful greenhouse gas. Methane is flammable and is used as fuel worldwide.

• Although the concentration of methane in Earth's atmosphere is small (around 1.8 parts per million), it is an important greenhouse gas because it is such a potent heat absorber. Methane is produced naturally when vegetation is burnt, digested, or rotted in the absence of oxygen. Other major natural sources of methane include emissions from wetlands and oceans, and from the digestive processes of termites. Sources related to human activities include rice production, landfills, raising cattle and other ruminant animals, and energy generation.

• The reaction of methane and chlorine atoms acts as a primary sink of Cl atoms and is a primary source of hydrochloric acid (HCl) in the stratosphere.

  • CH₄ + Cl → CH₃ + HCl

  • The HCl produced in this reaction leads to catalytic ozone destruction in the stratosphere.

• Biogas is produced after organic materials (plant and animal products) are broken down by bacteria in an oxygen-free environment, a process called anaerobic digestion. Biogas systems use anaerobic digestion to recycle these organic materials, turning them into biogas, which contains both energy (gas), and valuable soil products (liquids and solids). Biogas contains roughly 50-70 percent methane, 30-40 percent carbon dioxide, and trace amounts of other gases.

Hence option (b) is the correct answer.

• Desert locusts are known for causing massive destruction of food crops, greenery, and plants. They reproduce in lakhs and form swarms in search of food. They travel hundreds of miles with their strong wings and legs without taking any break. According to FAO, a one square kilometer swarm of locusts, with about 40 million locusts, can in a day eat as much food as 35,000 people, assuming that each individual consumes 2.3 kg of food per day. Hence only option 2 is not correct

• Praying mantises prey and eat any living organism they can successfully capture and devour. But insects may be herbivores, neutrals and carnivores form the main diet. They eat beetles, weevils, bugs, moths, butterflies, and various insects available in our crops. Thus they act as natural pesticides for controlling the various leaf-eating loopers and semi-loopers, fruit-eating bollworms, leaf folders, and stem borers, bugs including notorious mealybug, weevils like a grey weevil, and beetles like chefer, brown flower beetle, and insect pests like jassids, aphids, hoppers.

• Chalcid Wasps are insects within the superfamily Chalcidoidea, part of the order Hymenoptera. The superfamily contains some 22,500 known species, and an estimated total diversity of more than 500,000 species, meaning the vast majority have yet to be discovered and described. Generally beneficial to humans as a group, chalcidoids help keep various crop pests under control, and many species have been imported as biocontrol agents.

• Soldier beetles are a common outdoor insect that can be abundant in accidental invaders as either larvae or adults. Soldier beetles are nicknamed leatherwings because of their soft, clothlike wing covers, which when brightly colored are reminiscent of uniforms. The soldier beetle life cycle begins as a larva that hatches from an egg in the fall. These larvas are predators and will eat the eggs of many garden pests, as well as damaging larvae and soft insect bodies. They then hibernate in the soil or among fallen leaves until spring.

Hence option (b) is the correct answer

• Sustainable use of resources means that we use the resources in such a way that meets the demands of the present without compromising the ability of future generations to achieve their own requirements.

• The following measures need to be taken to avoid over-exploitation of resources:

  • Cultivation of land taking adequate care of soil fertility.

  • Development of irrigation facilities with proper water management. Use of water-saving devices such as traditional conservation methods and roof-top-water harvesting should be used.

  • Use of bio-fertilisers and bio-pesticides in order to have a biological balance. Hence, option 1 is correct.

  • Judicious use of underground water to avoid steep fall in underground water level.

  • Use of traditional seeds instead of the high yielding hybrid varieties to avoid spread of diseases capable of wiping out the entire crops it happened with the Irish potato crop in 1985 and Bengal rice famines in 1942. Hence, option 2 not is correct.

  • Avoiding the use of non-degradable material like plastic to prevent problems of waste management. Hence, option 3 is correct.

• Homeostasis is the maintenance of stable equilibrium, especially through bodily part functions. For example- Cooling your body through sweating processes. Despite the varying external environmental conditions, organisms try to maintain the constancy of their internal environment that tends to upset their homeostasis. Hence option (b) is the correct answer.

• Regulate some organisms can maintain homeostasis by physiological or sometimes behavioral means which ensures constant body temperature, constant osmotic concentration, etc. for example standing under a shading tree. Mammals and birds are capable of such regulation also known as thermoregulation and osmoregulation. This is the reason for the ‘success’ of mammals to maintain constant body temperature and thrive whether they live in Antarctica or the Sahara Desert. However, Plants do not have a mechanism of Homeostasis.

• Aquatic animals change the osmotic concentration of the body fluids with that of the ambient water osmotic concentration. The organism also migrates temporarily from one habitat which can be stressful to a more hospitable area and return when a stressful period is over for example- In Keoladeo National Park (Bharatpur) in Rajasthan thousands of migratory birds coming from Siberia during the winter season and other extremely cold northern regions. In bacteria, fungi and lower plants have thick-walled spores that help them to survive unfavorable conditions.

• A mountainous area or an upland region, where water falls from a height. Hence option 1 is correct.

• Temperate climate so that there is continuous flow of water and water does not get frozen due to severe cold.

• Water should be free of silt and impurities. Hence option 2 is correct.

• Flow of streams should be uniform.

• Artificial reservoirs.

• Industrial zones must be located in the close vicinity of the hydro electric project so as to reduce the loss of electricity transmission. Hence option 3 is correct.

• Coral reefs are often called the "rainforests of the sea" for their astounding richness of life. Due to their structural complexity, corals are one of the most productive ecosystems on Earth, providing important services to mankind including fisheries, coastal protection, medicines, recreation, and tourism.

• Corals are tiny animals that live in colonies and derive nourishment and energy from a symbiotic relationship with zooxanthellae algae. Coral reefs are formed over the course of thousands of years as limestone skeletons constructed by corals accumulate and form a structural base for living corals. Scientists estimate reefs provide a home for millions of species - from brightly colored tropical fish to sea cucumbers which produce anti-cancer compounds. The formation of highly consolidated reefs only occurs where the temperature does not fall below 18°C for extended periods of time. The water must also be clear to permit high light penetration. The corals’ requirement for high light also explains why most reef-building species are restricted to the euphotic (light penetration) zone, approximately 70 m. In light of such stringent environmental restrictions, reefs generally are confined to tropical and semitropical waters.

• The diversity of reef corals, i.e., the number of species, decreases in higher latitudes up to about 25° north and south, beyond which reef corals are usually not found. Bermuda, at 32° north latitude, is an exception to this rule because it lies directly in the path of the Gulf Stream’s warming waters.

Hence option (c) is the correct answer.

• Option 1 is correct: A Sanitary landfill is a way of disposing of refuse on land without creating a nuisance to public health. Here the waste is dumped in a site and covered with earth to prevent rodents or insects from entering into it. The waste is then subjected to bacterial decomposition.

• Option 2 is not correct: An increase in the use of pesticides is harmful to the soil and leads to soil pollution. Instead, biological methods of pest control can be used to decrease the need for pesticides.

• Option 3 is correct: Composting waste is an aerobic method of decomposing solid wastes. It involves the decomposition of waste into humus called compost which acts as a good fertilizer for plants. The microorganisms help to stabilize the organic matter. Example Fungi starts working in the first week after dumping the material. Actinomycetes help in the last stages of the breakdown. Bacteria is present all throughout the process. It involves the decomposition of waste into humus called compost which acts as a good fertilizer for plants.

• Standing State: It is the amount of inorganic nutrients found in an ecosystem such as carbon, nitrogen, phosphorus, calcium, etc. Hence, option (c) is the correct answer.

• It represents the part of non-living matter.

• It varies in different kinds of ecosystems and also on a seasonal basis.

• It usually occurs in the growth medium of producers. It determines the productivity of the ecosystem.

• It circulates between living and non-living components of the ecosystem.

• It is being regularly depleted and replenished by the living matters.

• Standing crop is the amount of biomass present in an ecosystem. It represents the entire living matter.

• Pugmark is the term used to refer to the footprint of most animals. These are the marks which are left by different animal species while they are walking, running, or moving from one place to another place. Pugmark of every individual animal species is distinct it is used for identification purposes.

  They are used for:

  • Tracking of animals (especially large cats).

  • To make an accurate identification of the presence of different species

  • Accurate determination of sex

  • Accurate identification of age and physical condition of an animal.

Hence option (d) is the correct answer.