Environment and Ecology: UPSC Previous Year Questions (Prelims)

Explanation

Option 2 is correct: Common mynas are native to South Asia, with their breeding range extending from Afghanistan through India and Sri Lanka to Bangladesh. They have been introduced to many tropical regions worldwide, except South America. While generally resident in India, occasional east-west movements occur. The Common Myna is an omnivorous, opportunistic feeder, often foraging on insects disturbed by grazing cattle. It thrives in urban environments and is known for its strong territorial instincts, often found in open woodlands.

Option 1 is incorrect: Painted storks forage in flocks in shallow waters along rivers or lakes. A wading bird that lives in the wet-lands of tropical Asia. They feed on fish, frogs, and insects in shallow water. It has distinctive pink tertial feathers Option 3 is incorrect: The habitat of Black-necked Crane is in the high altitude wetlands and grasslands of the Tibetan plateau, Sichuan (China), and eastern Ladakh (India). They are not opportunistic feeders.

Explanation

Decomposers are organisms that primarily feed on dead organisms or the waste from living organisms. Some organisms perform a similar function as decomposers, and are some-times called detritivores. The difference lies in the way decomposers and detritivores break down organic material. Detritivores must digest organic material within their bodies in order to break it down and gain nutrients from it. Decomposers do not need to digest organic material internally in order to break it down. Fungi and Bacteria are examples of decomposers. Scavengers are the one among the first to arrive at a dead organism’s remains. It includes jack-als, wolves, raccoons, and opossums.

Explanation

Ecological succession is the process by which the structure of a biological community evolves over time. In grasslands, the dominance of grasses over trees is maintained due to specific environmental factors.

Option (c) is correct: Grasslands are found in regions with seasonal rainfall or semi-arid conditions where water availability is limited. Grasses are more drought-resistant than trees and can survive with less water. Grasslands are often subject to frequent fires which prevent the establishment of trees. Grasses can quickly regenerate after a fire while trees are more vulnerable and less likely to survive. Thus these factors together maintain the dominance of grasses and prevent the succession to a forest ecosystem.

Option (a), (b) and (d) are incorrect:

Insects and fungi play roles in ecosystems but they are not the primary factors preventing trees from replacing grasses in grasslands. Insects and fungi can affect plant health but they do not determine the overall structure of grassland ecosystems. Limited Sunlight and Paucity of Nutrients are not the primary limiting factor for tree growth. In fact grasses are highly efficient at utilizing available nutrients and sunlight which allows them to dominate these ecosystems.

Explanation

Productivity is the rate of biomass production. It is measured in mass per unit volume per unit time. The quantity of biomass or organic matter created by plants during photosynthesis per unit area during a certain time is referred to as primary production. Gross primary productivity of an ecosystem is the rate of production of organic matter during photosynthesis. A considerable amount of GPP is utilized by plants in respiration.

Option (c) is correct: The correct sequence of ecosystems in decreasing order of productivity is Mangroves > Grasslands > Lakes > Oceans Mangroves have the highest productivity due to abundant nutrients, tidal action, and high photosynthetic rates making them crucial breeding grounds for marine life (NPP: ~2000 gC/m²/year). Grasslands follow, as they receive ample sunlight but have moderate water availability, supporting rapid grass growth (NPP: ~600-1500 gC/m²/year). Lakes are less productive than grasslands because nutrient availability varies with depth and type (eutrophic lakes are more productive than oligotrophic ones) (NPP: ~300-1000 gC/m²/year). Oceans have the lowest productivity, as vast open waters are nutrient-poor, and deep layers receive minimal sunlight, though coastal areas and coral reefs are exceptions (NPP: ~50-200 gC/m²/year).

Explanation

Food Chain is the successive transfer of nutrients and energy from one creature to another. A food chain shows a straightforward relationship and only one component of the food or energy flow. E.g. Grasses Grasshopper Frog Snake Hawk/Eagle.

Statement 1 is correct: A food chain is a linear flow of energy and nutrients from one organism to another. Primary producers primary consumers secondary consumers tertiary consumers. Statements 2 and 3 are incorrect:

Food chains are not limited to a single species or population. They involve multiple species across different trophic levels (e.g., producers, primary consumers, secondary consumers). A food chain represents interactions between different species, not within a single population. A food chain does not illustrate the numbers of organisms eaten by others. It shows the sequence of energy transfer and feeding relationships. The number of organisms at each trophic level is better represented by a food web or ecological pyramid (e.g., pyramid of numbers, pyramid of biomass).

Explanation

An ecological niche refers to both the physical space an organism occupies and its functional role in an ecosystem, including its interactions with other organisms, resource utilization, and contribution to energy flow and nutrient cycling. The concept was introduced by Joseph Grinnell (1917) and further developed by G. Evelyn Hutchinson (1957).

Option (a), (c) and (d) are incorrect:

Ecotone is transition zone between two different ecosystems such as a mangrove forest between land and sea. It does not define the functional role of an organism. Habitat is the physical location where an organism lives (e.g., a pond for a frog) but does not describe its interactions and role in the ecosystem. Home range is the area in which animal regularly moves within for feeding and other activities, but it does not account for ecological interactions.

Explanation

About 71% of the earth’s surface is covered with water. Out of the total water present on the planet earth, the majority is in the form of seas and oceans (more than 97%) and is termed as saline water. While the remaining water is termed as freshwater.

Option (c) is correct: The decreasing order of proportion of freshwater in different forms: Snow caps, icebergs and glaciers groundwater soil moistures freshwater lakes atmosphere rivers. Groundwater makes the largest portion of freshwater after freshwater that exists as ice caps and glaciers.

Explanation

Water Pollution is the contamination of water bodies, usually as a result of human activities. Heavy metal water pollution is the contamination of water with toxic heavy metals, such as lead, mercury, cadmium, arsenic, and chromium etc. Heavy metals can enter the water through natural processes and human activities. Options 1, 3 and 5 are correct: Arsenic, Fluoride, Iron, Uranium, Nitrate, are some major groundwater pollutants in India.

Option 2 is incorrect: Sorbitol is a sugar alcohol found in fruits and plants with diuretic, laxative and cathartic properties. It is not related with drinking water pollution.

Option 4 is incorrect: Formaldehyde is used to preserve fish longer. The use of this chemical is banned in fresh foods by the Food Safety and Standards Authority of India. The International Agency for Research on Cancer (IARC) of WHO classifies formaldehyde as "carcinogenic to humans". Formaldehyde is not established as a drinking water pollutant.

Explanation

E-waste is any electrical or electronic equipment that’s been discarded. Recently, India’s first e-waste clinic was inaugurated in Bhopal. E-waste Sources Constituents PCBs, glass panels, and Computer monitors Lead Resistors & Semiconductors Cadmium Relays and switches, &PCBs Mercury Galvanised steel plates & decorator or hardener Chromium Cabling, Computer & housing Plastics & PVC Electronic equipments & circuit boards Brominated flame-retardants Front panels of CRTs Barium, Phosphorus & Heavy metals Copper wires, PCB tracks Copper Nickel Cadmium batteries Nickel Lithium-ion battery Lithium Motherboards Beryllium Options 1, 2, 3, 5 and 6 are correct: All elements in these options are the harmful constituents that are released into the environment due to improper disposal of e-waste.

Option 4 is incorrect: Heptachlor is a pesticide classified under Persistent Organic Pollutants (POPs) per the Stockholm Convention. It is unrelated to e-waste.

Option 7 is incorrect: Plutonium, while used in some industrial and military applications, is a radioactive material and is not classified as part of e-waste.

Explanation

Normal rain has a pH of about 5.6 when pH falls below this; it is called Acid rain (pH 4.2 to 4.4). Acid rain results when Sulphur Dioxide (SO₂) & Nitrogen Oxides (NOX) react with water, oxygen & other chemicals to form Sulfuric & Nitric acids. NOx + SO₂ + Moisture + other chemicals Acid Rain (HNO₃ + H₂ SO₄) Acid rain harms microorganisms in the soil; inhibits the activity of nitrogen fixation bacteria; soil acidification; ocean acidification; affects the growth of plants; food chain; kills aquatic animals; corrosion of metals and weathering of stone buildings & statues.