Ecology, Ecosystem and Functions of Ecosystem: UPSC Previous Year Questions (Environment and Ecology)

Explanation

Oxygen production is critical for Earth’s atmosphere, primarily driven by photosynthesis in marine and terrestrial ecosystems.

Statement I is incorrect: Oceans, not rainforests (Amazon, Congo), are the primary oxygen producers. NOAA estimates 50-80% of global oxygen from marine phytoplankton in the photic zone (top 200 meters). NASA cites 50-85%, with Prochlorococcus (a cyanobacterium) contributing 5-20%. Rainforests produce ~28% (National Geographic, WWF), with other terrestrial plants adding ~2%. Oceans’ dominance stems from 71% Earth’s surface and phytoplankton’s rapid turnover (days vs. decades for trees).

Statement II is correct: Marine phytoplankton (diatoms, dinoflagellates) and photosynthetic bacteria (cyanobacteria, e.g., Prochlorococcus) are the main oceanic oxygen producers. NOAA and Smithsonian confirm 50-80% of global oxygen from oceanic photosynthesis, with NASA and WWF estimating 50-85%, including 5-20% from Prochlorococcus. Photosynthesis in the photic zone uses sunlight, CO₂, and nutrients, supporting the marine food web and atmospheric oxygen. The ~50% estimate is conservative but accurate.

Statement III is correct: Well-oxygenated surface water has high dissolved oxygen (DO) (5-10 mg/L, up to 12-15 mg/L in cold, turbulent conditions, per USGS). Atmospheric air contains 21% oxygen (~210,000 ppm, 210 g/L). Surface water’s DO (0.015 g/L) is ~14,000 times less than air, due to low oxygen solubility, confirming it cannot hold "several folds higher" oxygen.

Explanation

Alfalfa, chickpea, and clover are nitrogen-fixing plants. They belong to the leguminous family and form symbiotic associations with Rhizobium bacteria in their root nodules, aiding in nitrogen fixation and enriching soil fertility. Amaranth, purslane (Kulfa), and spinach, are non-legumi-nous plants and lack the ability to fix nitrogen as they do not form symbiotic relationships with nitrogen-fixing bacteria or develop root nodules. This natural ability of legumes like alfalfa, chickpea, and clover to fix nitrogen is extensively utilized in crop rotation practices to replenish soil nutrients and enhance agricultural productivity.

Explanation

Lichens and Mosses do not need soil to grow and survive. Lichens are generally found on rock, tree bark, soil (but can survive without soil as well), houses, tombstones, cars, old farm equipment, etc. Thus, lichen can be found surviving on surfaces without soil. Mosses are non-vascular plants. They do not need soil to survive. They have a rhizoid multi-cell anchoring structure that is used to climb and grip over rocky surfaces. Moss thrives in moist and shady areas. Ferns and Mushrooms generally need soil to grow. Ferns are vascular plants and typically require soil for anchorage and to absorb water and nutrients. While they can grow in places like cracks in rocks, they usually still need some form of substrate (soil or organic material) to thrive. A mushroom is the fleshy, spore-bearing fruiting body of a fungus. They typically require organic matter to decompose as a source of nutrients. Mushrooms are unlikely to grow on a surface without soil unless there is some decaying organic material available.

Explanation

Primary Producers are organisms like plants and algae that produce their own food through photosynthesis or chemo-synthesis. They form the base of the food chain in marine eco-systems. Cyanobacteria and Diatoms are primary producers. Cyanobacteria (also known as blue-green algae) are photosynthetic bacteria that play a significant role in marine ecosystems by converting sunlight into energy and producing oxygen. They are particularly important in nutrient-poor (oligotrophic) oceanic regions. Diatoms are a type of phytoplankton that perform photosynthesis. They are among the most important primary producers in the oceans which contribute significantly to global carbon fixation. They are a key food source for zooplankton and other marine organisms. Copepods and Foraminifera are consumers. Copepods are small crustaceans that are not primary producers. They are zooplankton that feed on phytoplankton (primary producers) and other small organisms. They play a crucial role in marine food webs as a link between primary producers and higher trophic levels. Foraminifera are not primary producers. They are single-celled protists that belong to the zooplankton group. They feed on phytoplankton, detritus, and other small organisms. They are important in marine ecosystems as indicators of environmental conditions.

Explanation

Detritivores also known as detritivores, detritophag-es, detritus feeders, or detritus eaters are heterotrophs that obtain nutrients by consuming detritus (decomposing plant and animal parts as well as feces). By doing so, all these detritivores contribute to decomposition and the nutrient cycles.

Option (c) is correct: Earthworms, Millipedes and Woodlice are Detritivores. Detritivores are an important aspect of many ecosystems. They can live on any type of soil with an organic component, including marine ecosystems, where they are termed interchangeably with bottom feeders. Typical detritivorous animals include earth-worm, millipedes, springtails, woodlice, dung flies, slugs, many terrestrial worms, sea stars, sea cucumbers, fiddler crabs, and some sedentary polychaetes such as worms of the family Terebellidae.

Explanation

The phosphorus cycle is unique for not have a significant atmospheric component. Phosphorus is primarily released into the cycle through the weathering of rocks containing phosphate minerals (e.g., apatite). Weathering releases phosphate ions (PO₄³⁻) into soil and water, making it available for uptake by plants and other organisms. Phosphorus is one of the most important nutrients in biological systems since it is a fundamental ingredient of nucleic acids, phospholipids, and several phosphor-ylated compounds.

Explanation

All of the given species can establish a symbiotic relationship with other organisms. Symbiotic Relationship:

A relationship between two (or more) species that may or may not be advantageous to one or both is referred to as symbiotic. Symbiosis typically occurs between different species. Interactions within the same species (intraspecific) are usually not categorized as symbiosis but may involve other forms of cooperation. For eg., Coral has a symbiotic relationship (each gives something to the other and gets something back in return) with ‘zooxanthellae’ microscopic algae which live on coral.

Option 1 is correct: The relationship between cnidarians and dinoflagellate algae is termed "symbiotic" because both the animal host and the algae are benefiting from the association. It is a mutualistic interaction.

Option 2 is correct: Two common mutualistic relationships involving fungi are mycorrhiza (fungi and plant roots) and lichen (fungi and either cyanobacteria or green algae).

Option 3 is correct: Protozoa mostly represent a close mutualistic association between a protozoan and unicellular symbionts such as bacteria, cyanobacteria or/and unicellular algae or protozoans and a multicellular organisms such as ruminants, lower termites, wood-eating cockroaches, plants.

Explanation

Reservoir Volume (Million Cubic km) Percentage of the Total Oceans 1,370 97.25 Ice caps and Glaciers 29 2.05 Groundwater 9.5 0.68 Lakes 0.125 0.01 Soil Moisture 0.065 0.005 Atmosphere 0.013 0.001 Streams and Rivers 0.0017 0.0001 Biosphere 0.0006 0.00004 Water makes up about 71% of the Earth’s surface, while the other 29% consists of continents and islands. Oceans and Seas make up 97% of the Earth’s water and only about 2.5% is in the form of freshwater. 71 % of earth surface constitutes water & only 29 % constitutes a land area of earth. 97 % of water area constitutes Oceans & Seas & 2.5 % as freshwater.

Statement 1 is incorrect: Fresh Water distribution is as given below: Ice Caps and Glaciers > Groundwater >Lakes Ice & Snow > Soil Moisture > Atmosphere > Rivers and Streams.

Statement 2 is correct: While about 69% of earth’s freshwater is in ice caps and glacier, groundwater has about 30% of earth’s freshwater. Kakes, Rivers and swamps etc make up the remaining 1%. While 75 % of freshwater is in glaciers & ice caps, only 7 % of freshwater is groundwater. Saline ground-water 0.93% Saline lakes 0.07% Freshwater 2.5% Surface water and other freshwater 1.3% Atmoshpheric water 0.22% Biological wate 0.22% Rivers 0.46% Swamps and marshes 2.53% Soil moisture 3.52% Ice and snow 73.1% Glaciers and ice caps 68.6% Oceans 96.5% Groundwater 30.1% Lakes 20.1% Surface water and other freshwater Freshwater Total Global water Distribution of Earth’s Water Resources

Explanation

Both warm and mid-latitude deserts have a predomi-nance of xerophytic or drought-resistant plants. This comprises cacti, thorny bushes, wiry grasses with extensive roots, and scattered dwarf acacias.

Option (d) is correct: In order to gather moisture and search for ground water, the majority of desert shrubs have lengthy roots that are widely distributed. These plants typically have a few (or no leaves) tiny, needle-shaped, waxy, leathery leaves or hairy foliage to reduce water loss through transpiration.

Explanation

MSTrIPES stands for Monitoring system for Tigers - Intensive Protection and Ecological Status.M-STrIPES was launched in 2010 by NTCA and WII across Indian tiger reserves. It is a software-based monitoring system, designed to assist wild-life protection. The system consists of two components:

Field based methods for ecological monitoring, law enforcement, recording wildlife offences, and patrolling. A specialised GIS application for reporting, analysis, and data storage. Forest guards are required to use a GPS to track their movements as part of MSTrIPES, in addition to entering their observations on site-specific data sheets.