Daily Quiz: UPSC Prelims Marathon- August 25

Explanation:

Statement 1 is correct: Sunlight: Corals need to grow in shallow water where sunlight can reach them. Corals depend on the zooxanthellae (algae) that grow inside of them for oxygen and other things, and since these algae needs sunlight to survive, corals also need sunlight to survive. Corals rarely develop in water deeper than 165 feet (50 meters).

Statement 2 is correct: Warm water temperature: Reef-building corals require warm water conditions to survive. Different corals living in different regions can withstand various temperature fluctuations. However, corals generally live in water temperatures of 68–90° F or 20–32° C.

Statement 3 is correct: Saltwater: Corals need saltwater to survive and require a certain balance in the ratio of salt to water. This is why corals don’t live in areas where rivers drain fresh water into the ocean (“estuaries”).

Statement 4 is incorrect:  Corals are sensitive to pollution and sediments. Sediment can create cloudy water and be deposited on corals, blocking out the sun and harming the polyps. Wastewater discharged into the ocean near the reef can contain too many nutrients that cause seaweeds to overgrow the reef.

Statement 1 is incorrect: Acid rain results when Sulfur dioxide (SO₂) and nitrogen oxides (NO_X) are emitted into the atmosphere and transported by wind and air currents.  The SO₂ and NO_X react with water, oxygen and other chemicals to form Sulfuric and nitric acids.  These then mix with water and other materials before falling to the ground.

Statement 2 is correct: Dead or dying trees are a common sight in areas affected by acid rain. Acid rain leaches aluminum from the soil.  That aluminum may be harmful to plants as well as animals. Acid rain also removes minerals and nutrients from the soil that trees need to grow.

Statement 3 is correct: The acidic particles corrode metal and cause paint and stone to deteriorate more quickly. They also dirty the surfaces of buildings and other structures such as monuments.

Statement 1 is incorrect: The Dardanelles Strait, a vital transportation bridge between the Black Sea and Mediterranean Sea, is a narrow channel of water that connects the Aegean Sea to the Sea of Marmara.

It separates Asian Turkey from European Turkey (Trace), thus it also separates the two continents

Statement 2 is incorrect: The Bosporus Strait (or Bosphorus) connects the Black Sea to the Sea of Marmara.Bordered on both sides by the massive city of Istanbul, the strait is one of the planet’s most strategic waterways.This body of water serves as a primary highway for the transport of energy to Europe from Russia and western Asia. Crossed by two large suspension bridges, the strait is just over 2 miles across at its widest point; about 32km (20 miles) in length, and a measured 30-120m (100-395ft) deep.

The episodic nature of the Earth’s glacial and interglacial periods within the present Ice Age (the last couple of million years) have been caused primarily by cyclical changes in the Earth’s circumnavigation of the Sun. Variations in the Earth’s eccentricity, axial tilt, and precession comprise the three dominant cycles, collectively known as the Milankovitch Cycles.

The first of the three Milankovitch Cycles is the Earth’s eccentricity. Eccentricity is, simply, the shape of the Earth’s orbit around the Sun. This constantly fluctuating, orbital shape ranges between more and less elliptical (0 to 5% ellipticity) on a cycle of about 100,000 years. These oscillations, from more elliptic to less elliptic, are of prime importance to glaciation in that it alters the distance from the Earth to the Sun, thus changing the distance the Sun’s short wave radiation must travel to reach Earth, subsequently reducing or increasing the amount of radiation received at the Earth’s surface in different seasons.

Axial tilt, the second of the three Milankovitch Cycles, is the inclination of the Earth’s axis in relation to its plane of orbit around the Sun. Oscillations in the degree of Earth’s axial tilt occur on a periodicity of 41,000 years from 21.5 to 24.5 degrees. Today the Earth’s axial tilt is about 23.5 degrees, which largely accounts for our seasons.  Because of the periodic variations of this angle the severity of the Earth’s seasons changes. With less axial tilt the Sun’s solar radiation is more evenly distributed between winter and summer. However, less tilt also increases the difference in radiation receipts between the equatorial and polar regions.

The third and final of the Milankovitch Cycles is Earth’s precession. Precession is the Earth’s slow wobble as it spins on axis. This wobbling of the Earth on its axis can be likened to a top running down, and beginning to wobble back and forth on its axis. The precession of Earth wobbles from pointing at Polaris (North Star) to pointing at the star Vega. When this shift to the axis pointing at Vega occurs, Vega would then be considered the North Star. This top-like wobble, or precession, has a periodicity of 23,000 years.Due to this wobble a climatically significant alteration must take place. When the axis is tilted towards Vega the positions of the Northern Hemisphere winter and summer solstices will coincide with the aphelion and perihelion, respectively. This means that the Northern Hemisphere will experience winter when the Earth is furthest from the Sun and summer when the Earth is closest to the Sun. This coincidence will result in greater seasonal contrasts. At present, the Earth is at perihelion very close to the winter solstice.

Statement 1 is incorrect: The census was conducted by the Asian Nature Conservation Foundation (ANCF) at the Indian Institute of Science (Bengaluru), several NGOs and independent conservationists aided the Project Elephant Directorate and forest departments of 23 states.

Statement 2 is correct: It was first-ever synchronised all-India Elephant Population census that covered 1.10 lakh square kilometres and spanned four regions of the country.

Statement 3 is incorrect: Karnataka has the highest number of elephants (6,049), followed by Assam (5,719) and Kerala (3,054).

Statement 4 is correct: The population estimation of Asian elephants in 2017 census is lower than from the last census estimate in 2012 (between 29,391 and 30,711).

All statements are correct

Black Carbon (BC) has recently emerged as a major contributor to global climate change, possibly second only to CO₂ as the main driver of change. BC particles strongly absorb sunlight and give soot its black color. BC is produced both naturally and by human activities as a result of the incomplete combustion of fossil fuels, biofuels, and biomass. Primary sources include emissions from diesel engines, cook stoves, wood burning and forest fires. Reducing CO₂ emissions is essential to avert the worst impacts of future climate change, but CO₂ has such a long atmospheric lifetime that it will take several decades for CO₂ concentrations to begin to stabilize after emissions reductions begin. In contrast, BC remains in the atmosphere for only a few weeks, so cutting its emissions would immediately reduce the rate of warming, particularly in the rapidly changing Arctic. Moreover, reduced exposure to BC provides public health co-benefits, especially in developing countries. Technologies that can reduce global BC emissions are available today.

BC warms the climate in two ways. When suspended in air, BC absorbs sunlight and generates heat in the atmosphere, which warms the air and can affect regional cloud formation and precipitation patterns. When deposited on snow and ice, it absorbs sunlight, again generating heat, which warms both the air above and the snow and ice below, thus accelerating melting. Because BC remains in the atmosphere for only one to four weeks, its climate effects are strongly regional. Its short lifetime also means that its climate effects would dissipate quickly if black carbon emissions were reduced, thus benefiting most directly the countries or communities that invest in policies to reduce BC emissions.

The Ganga basin outspreads in India, Tibet (China), Nepal and Bangladesh over an area of 10,86,000 Sq.km.
In India, it covers states of Uttar Pradesh, Madhya Pradesh, Rajasthan, Bihar, West Bengal, Uttarakhand, Jharkhand, Haryana, Chhattisgarh, Himachal Pradesh and Union Territory of Delhi draining an area of 8,61,452 Sq.km which is nearly 26% of the total geographical area of the country.

The Indus basin extends over China (Tibet), India, Afghanistan and Pakistan draining an area of 11,65,500 Sq.km. In India, the basin spreads over states of Jammu & Kashmir, Himachal Pradesh, Punjab, Rajasthan, Haryana and Union Territory of Chandigarh having an area of 3,21,289 Sq.km which is nearly 9.8% of the total geographical area

The Godavari basin extends over states of Maharashtra, Andhra Pradesh, Chhattisgarh and Odisha in addition to smaller parts in Madhya Pradesh, Karnataka and Union territory of Puducherry having a total area of 3,12,812 Sq.km with a maximum length and width of about 995 km and 583 km and accounts for nearly 9.5% of the total geographical area of the country.

The Brahmaputra basin spreads over countries of Tibet (China), Bhutan, India and Bangladesh having a total area of 5,80,000 Sq.km. In India, it spreads over states of Arunachal Pradesh, Assam, West Bengal, Meghalaya, Nagaland and Sikkim and and extends over an area of 1,94,413 Sq.km which is nearly 5.9 % of the total geographical area of the country.