Oceans

Answer: (b) 2 and 3 only

The Deep Ocean Mission belongs to the Ministry of Earth Sciences, not the Ports ministry. Samudrayaan is its manned-submersible project, and the submersible Matsya-6000 carries three people.

• ✗ 1. The Deep Ocean Mission was launched on 7 September 2021 by the Ministry of Earth Sciences (MoES), not the Ministry of Ports, Shipping and Waterways.
• ✓ 2. Matsya-6000 is a self-propelled manned submersible designed to carry three people to depths of up to 6,000 metres.
• ✓ 3. Samudrayaan was launched under the umbrella of the Deep Ocean Mission as its first component, deep-sea exploration with a manned submersible.

Remember · Deep Ocean Mission: Ministry of Earth Sciences, launched 2021. Samudrayaan = manned submersible project; Matsya-6000 carries 3 people to 6,000 m (built by NIOT).

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Answer: (a) Both Statement I and Statement II are correct and Statement II explains Statement I

In the northern winter, land loses heat fast while the oceans, helped by warm currents such as the Gulf Stream and North Atlantic Drift, stay relatively warm. A given temperature is therefore found farther north over the sea and farther south over land, so the isotherms bend poleward over oceans and equatorward over continents; the warmer ocean air is the reason.

• ✓ Statement-I January isotherms swing north over the North Atlantic and south over Europe and especially the Siberian plain.
• ✓ Statement-II Oceans cool slowly and warm currents add heat, so in January the air over them is warmer than over the cold northern landmasses; this contrast is what bends the isotherms, so II explains I.

Remember · January (NH winter): isotherms bend poleward over oceans, equatorward over land; July reverses it. Deviation is sharper in the Northern Hemisphere because it has more land.

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Answer: (b) II only

The oceans, through photosynthesis by plankton and some bacteria, generate about half or more of the oxygen on Earth, so rain forests do not out-produce them: NOAA notes that one marine bacterium alone makes more oxygen than all tropical rainforests combined. Water can hold only a small amount of dissolved oxygen compared with air, so surface water never has several times more oxygen than the atmosphere.

• ✗ I Roughly half of Earth's oxygen production comes from the ocean (IUCN says more than half), and NOAA notes that the marine bacterium Prochlorococcus alone produces up to 20% of the biosphere's oxygen, a higher share than all the tropical rainforests combined.
• ✓ II NOAA says roughly half of the oxygen production on Earth comes from the ocean, mostly from oceanic plankton: drifting plants, algae and some bacteria that can photosynthesize.
• ✗ III NCERT notes that the amount of dissolved oxygen is fairly low compared with the amount of oxygen in air, which is why aquatic organisms breathe much faster than land ones. Water is therefore poorer in oxygen than air, not richer.

Remember · The ocean makes about half or more of Earth's oxygen (mostly phytoplankton); water holds far less oxygen than air.

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Answer: (a) 1 only

In the northern winter the oceans stay warmer than the land, so January isotherms bulge north over the oceans and dip south over the continents. Statement 2 fails because the Gulf Stream and North Atlantic Drift are warm currents that make the North Atlantic warmer, not colder.

• ✓ 1. In January the isotherms swing northward over the oceans and southward over the land masses, most clearly over the North Atlantic and Europe.
• ✗ 2. The Gulf Stream and North Atlantic Drift are warm currents. They make the North Atlantic warmer, which is why the isotherms bend north there.

Remember · January isotherms: bend poleward over oceans, equatorward over continents. Gulf Stream and North Atlantic Drift are warm currents.

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Answer: (c) Both 1 and 2

Both statements are correct. The Red Sea lies in an arid region: no river drains into it and rainfall is scant. With very high evaporation and little fresh water coming in, it is one of the saltiest seas.

• ✓ 1. The Red Sea region is arid with little precipitation. The UN Regular Process assessment calls it an arid area with high evaporation, and NOAA explains its high salinity by very high evaporation and little fresh-water inflow.
• ✓ 2. No river brings water into the Red Sea; the UN assessment marks it as a sea with 'no rivers'. With so little fresh water, evaporation keeps the sea very salty; NCERT gives its salinity as high as 41 parts per thousand.

Remember · Red Sea: arid, no rivers, scant rain, very high evaporation and very high salinity (about 41 parts per thousand).

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Answer: (a) Restoration of damaged coral reefs

Biorock technology is used to restore damaged coral reefs. A low-voltage electric current is passed through seawater between a submerged metal frame and an anode, so that minerals in the water deposit as limestone on the frame, and corals attached to it grow quickly.

• ✓ (a) With an anode and a cathode in sea water and a current between them, calcium and carbonate ions combine and stick to the cathode structure as calcium carbonate; corals adhere to it and grow fast. The UN has cited biorock artificial reefs as successful in certain areas.
• ✗ (b) Biorock is not a plant-residue building material; it is limestone grown from seawater minerals on an electrified frame.
• ✗ (c) Nothing in Biorock concerns locating or extracting shale gas.
• ✗ (d) Biorock has no link to salt licks for forest animals; it is an undersea technology.

Remember · Biorock (mineral accretion): low-voltage current in seawater grows limestone on metal frames, letting corals attach and recover. Used to restore reefs.

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Answer: (d) 1, 2 and 3

All three statements follow directly from the text of the UN Convention on the Law of the Sea (UNCLOS, 1982): Article 3 fixes the 12-nautical-mile limit of the territorial sea, Article 17 gives every State's ships the right of innocent passage, and Article 57 caps the Exclusive Economic Zone at 200 nautical miles.

• ✓ 1. Article 3 lets a State set its territorial sea up to 12 nautical miles, measured from baselines fixed under the Convention.
• ✓ 2. Article 17 gives ships of all States, coastal or land-locked, the right of innocent passage through the territorial sea.
• ✓ 3. Article 57 says the EEZ cannot go beyond 200 nautical miles from the same baselines used to measure the territorial sea.

Remember · UNCLOS 1982: territorial sea up to 12 nautical miles (Art. 3); innocent passage for all ships (Art. 17); EEZ up to 200 nautical miles from the baselines (Art. 57).

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Answer: (b) 2 and 3

Primary producers make their own food by photosynthesis. In the sea these are the phytoplankton, which include cyanobacteria and diatoms. Copepods are tiny crustaceans and foraminifera are shelled protists; both eat other organisms, so they are consumers.

• ✗ 1. Copepods are small crustaceans; they graze on phytoplankton or live as parasites on fish, so they are consumers, not producers.
• ✓ 2. Cyanobacteria (blue-green algae) are photosynthetic bacteria and form part of the ocean's phytoplankton.
• ✓ 3. Diatoms are single-celled, silica-walled algae that make their own food using sunlight; they are among the most important phytoplankton.
• ✗ 4. Foraminifera are single-celled protists with shells that capture food such as bacteria, diatoms and even copepods; they are consumers, even though some species harbour algae inside.

Remember · Ocean food chains start with phytoplankton (cyanobacteria, diatoms, dinoflagellates, coccolithophores). Zooplankton such as copepods and foraminifera are consumers.

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Answer: (b) 2 and 3 only

Statements 2 and 3 are correct. Seabed exploration rights in international waters come from the International Seabed Authority, not from the Global Ocean Commission, which was only an independent advisory body.

• ✗ 1. The Global Ocean Commission (launched 2013) was an independent international commission working on threats to the high seas; it issues no licences. Exploration areas are allocated by the International Seabed Authority (ISA), set up under UNCLOS.
• ✓ 2. India holds ISA exploration rights over 75,000 sq. km of the Central Indian Ocean Basin for polymetallic nodules, and a later ISA contract for polymetallic sulphides in the Indian Ocean.
• ✓ 3. Polymetallic nodules lying on the deep seafloor, including in the Central Indian Ocean Basin, carry rare earth elements alongside nickel, copper, cobalt and manganese.

Remember · The International Seabed Authority, not the Global Ocean Commission, licenses seabed exploration beyond national jurisdiction; India holds ISA contracts for nodules and sulphides.

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Answer: (c) Both 1 and 2

Both statements are correct: winds push warm surface water to the western side of tropical oceans, while in the temperate zone the westerlies carry warm water to the eastern side, that is, to the west coasts of continents.

• ✓ 1. In the tropics the easterly trade winds push warm water west and hold it there, so the western side of an ocean is warmer than the east. This matches warm currents along the east coasts of continents in tropical latitudes and cool waters off their west coasts.
• ✓ 2. Ocean circulation follows the planet's wind pattern, and in the middle latitudes the surface winds are the westerlies, which carry warm water eastwards, so the eastern side of the ocean is the warm side. NCERT notes that west coasts of continents in middle and higher latitudes are bordered by warm waters, as in north-western Europe.

Remember · Tropics: trade winds pile warm water in the west of the ocean. Temperate zone: westerlies carry warm water to the east, so west coasts of continents there are mild.

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Answer: (b) 2 only

Only statement 2 is correct: ice caps and glaciers hold about 2 per cent of Earth's water, well above the 0.68 per cent held as groundwater, while rivers and lakes together hold only about 0.009 per cent.

• ✗ 1. NCERT's table gives fresh water lakes 0.009 per cent and rivers 0.0001 per cent of all water, far less than groundwater at 0.68 per cent.
• ✓ 2. The same table gives ice caps 2.0 per cent (glaciers are counted with them), which is roughly three times the groundwater share of 0.68 per cent.

Remember · Earth's water: oceans 97.3%, ice caps and glaciers 2.0%, groundwater 0.68%, lakes 0.009%, atmosphere 0.0019%, rivers 0.0001%.

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Answer: (b) 2 only

Statement 2 is right and statement 1 is wrong. OMT (the average temperature of the ocean from the surface down to the 26°C isotherm) in the south-western Indian Ocean during January–March helps predict whether the coming monsoon rainfall will be above or below average, but the 26°C isotherm there lies at about 59 m, not 129 m.

• ✗ 1. OMT is the mean temperature of the layer from the surface down to the 26°C isotherm, which is the first half of the statement. But the January–March climatic mean depth of that isotherm in the south-western Indian Ocean is about 59 m, not 129 m.
• ✓ 2. The January–March south-western Indian Ocean OMT is a better qualitative predictor of Indian summer monsoon rainfall than sea surface temperature; it correctly signals above-average or below-average rain about 80% of the time, against 60% for SST.

Remember · OMT = mean temperature from the surface to the 26°C isotherm; south-western Indian Ocean OMT in January–March forecasts monsoon rain (isotherm depth about 59 m there).

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Answer: (a) They are considered harmful to marine ecosystems.

Microbeads are tiny plastic beads put into cleansers and toothpastes as exfoliants; they slip through water filters, end up in oceans and lakes, and threaten aquatic life.

• ✓ (a) Microbeads are a type of microplastic. They pass easily through water treatment systems into the sea, where marine animals can swallow them and toxins can collect on them, so they are a threat to marine ecosystems.
• ✗ (b) Microbeads are rinsed off the skin and the worry about them is environmental pollution; skin cancer in children is not the reason for the concern.
• ✗ (c) Plastic beads are not taken up into crop plants through their roots; this is not the reason for concern.
• ✗ (d) Microbeads are used in personal care products, not as food additives or adulterants.

Remember · Microbeads are tiny plastic exfoliant beads in cosmetics and toothpaste that escape water treatment and pollute oceans, harming aquatic life.

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Answer: (d) 1, 2 and 3

All three statements are taken as correct. NCERT places coral reefs in the tropical oceans; half of all reef area is in just five countries, and Australia, Indonesia and the Philippines alone hold about 42% of it; and reefs host 32 of the 34 recognised animal phyla (UN).

• ✓ 1. NCERT describes atolls as low islands of coral reefs found in the tropical oceans, so most reefs lie in tropical waters.
• ✓ 2. Half of the world's reef surface lies in only five countries: Australia, Indonesia, the Philippines, France and Papua New Guinea. The GCRMN ranking gives Australia 16.88%, Indonesia 15.26% and the Philippines 9.74% of reef surface, a cumulative 41.88% for the three, which is more than one-third.
• ✓ 3. The UN's World Ocean Assessment says reefs host 32 of the 34 recognised phyla, nearly all of them. UPSC's official key treats this statement as correct; we could not confirm the comparison with rainforests from an official source, so we do not explain it here.

Remember · Reefs: mostly tropical, concentrated in a few countries (Australia, Indonesia, Philippines hold about 42%), and home to 32 of 34 animal phyla.

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Answer: (c) Chandipur

Chandipur, on the Bay of Bengal coast in Balasore district of Odisha, has a very gently sloping shore: at low tide the sea pulls back up to about 5 km, so visitors can walk on the exposed sea bed, and the water returns with the high tide.

• ✓ (c) Odisha Tourism calls Chandipur a 'hide and seek' beach: at each low tide it recedes up to about 5 km, exposing the sea bed, and the sea comes back at high tide (tides come roughly twice a day).
• ✗ (a) Bhavnagar is a port city on the Gulf of Khambhat in Gujarat; it is not the beach known for this walk-on-the-sea-floor phenomenon.
• ✗ (b) Bheemunipatnam is a coastal town near Visakhapatnam in Andhra Pradesh with an ordinary beach, not a receding one.

Remember · Chandipur (Balasore, Odisha) = the 'vanishing sea' beach: at low tide the sea recedes up to about 5 km and you can walk on the sea bed.

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Answer: (b) 2 only

The Indian Ocean Dipole is a sea-surface temperature difference between the western and the south-eastern tropical Indian Ocean, not the Eastern Pacific, so statement 1 is wrong. A positive or negative IOD can strengthen or weaken the effect of an El Nino on the Indian monsoon, so statement 2 is correct.

• ✗ 1. The IOD is measured as the temperature difference between the tropical western Indian Ocean and the tropical south-eastern Indian Ocean. The Eastern Pacific is the region watched for El Nino and La Nina, which is a different phenomenon.
• ✓ 2. The El Nino-induced circulation over India can be countered or supported by the circulation the IOD sets up, depending on the phase and strength of each. This is why a positive IOD can soften an El Nino's damage to the monsoon.

Remember · IOD = west-minus-east sea-surface temperature contrast inside the Indian Ocean. It can counter or reinforce El Nino's effect on the Indian monsoon.

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