UPSC Geoscientist Archives

31. Natural population change is calculated by

Natural population change is calculated by

adding the death rate and the birthrate

subtracting the death rate from the birthrate

multiplying the death rate with the birthrate

dividing the death rate by the birthrate

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Natural population change is the difference between the number of live births and the number of deaths occurring in a given population over a specific period. It is typically calculated per 1,000 people.

The formula for calculating natural population change is Birth Rate minus Death Rate. A positive result indicates natural increase, while a negative result indicates natural decrease.

Total population change also includes migration (net migration = immigration – emigration), which is added to the natural population change to get the overall population change.

32. Which of the following are called ‘benthos’?

Which of the following are called ‘benthos’?

Microscopic plants which float on the ocean water

Animals which swim in the water

Plants and animals which live on the ocean floor

Plants and animals which float on the ocean water

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Benthos (or benthic organisms) are the organisms that live on, in, or near the bottom of a body of water, such as an ocean, lake, or river. This category includes a wide range of organisms, from plants like seagrasses to animals like worms, clams, starfish, crustaceans, and even some fish that live on the bottom.

– Benthos are bottom-dwelling aquatic organisms.
– They live on the substrate of the water body.

Aquatic organisms are typically classified based on their habitat and movement within the water column:
– Plankton: Organisms (plants and animals) that float or drift in the water.
– Nekton: Organisms that can actively swim and move independently of water currents.
– Benthos: Organisms that live attached to, or on or in, the bottom substrate.

33. Which one of the following is correct?

Which one of the following is correct?

In humid tropical region, humus content is high in soil

Glacial till exhibits deep horizon

Humus accumulates in cold climate

In equatorial climates, humus content is high in soil

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– A) In humid tropical regions, high temperatures and high rainfall lead to rapid decomposition of organic matter by microbes, resulting in low humus content in the soil. (Incorrect)
– B) Glacial till is unconsolidated glacial sediment and serves as a parent material for soil development. While soils *can* develop on till, the till itself doesn’t “exhibit deep horizons”; soil horizons (A, B, C) develop *within* the soil profile over time through pedogenic processes. Glacial action often mixes material rather than creating distinct deep horizons in the till layer itself. (Incorrect)
– C) In cold climates, low temperatures significantly slow down the rate of decomposition of organic matter by microorganisms. This leads to the accumulation of undecomposed or partially decomposed organic matter, forming a thicker layer of humus (or organic horizons like O horizon) on or in the soil. (Correct)
– D) Equatorial climates are humid tropical regions with rapid decomposition, leading to low humus content. (Incorrect, same reason as A).

– Decomposition rate of organic matter is highly dependent on temperature and moisture.
– Cold climates slow down decomposition, promoting humus accumulation.
– Warm, humid climates accelerate decomposition, limiting humus accumulation.

Humus is stable, dark organic matter that remains after the decomposition of plant and animal residues. It is crucial for soil structure, water retention, and nutrient availability. Soils in environments like tundra or boreal forests often have significant organic horizons due to slow decomposition rates.

34. Which one of the following deserts is not located around 20°-30° latit

Which one of the following deserts is not located around 20°-30° latitude North or South of the Equator?

Atacama

Kalahari

Great Victoria

Gobi

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Most of the world’s major deserts are located in the subtropical high-pressure belts, which are found approximately between 20° and 30° latitude North and South of the equator. These areas experience sinking air, leading to dry conditions.
– Atacama Desert (South America): Located around 24° S. (Fits the pattern)
– Kalahari Desert (Southern Africa): Located around 20-30° S. (Fits the pattern)
– Great Victoria Desert (Australia): Located around 28° S. (Fits the pattern)
– Gobi Desert (Central Asia): Located primarily between 40° and 50° N latitude. It is a cold winter desert, formed due to rain shadow effect (blocked by the Himalayas) and continentality (far from oceans). This location is outside the 20°-30° range.

– Subtropical deserts are commonly found in the 20°-30° latitude bands due to atmospheric circulation patterns (Hadley Cell).
– Other desert types exist due to rain shadow effect, continentality, or polar conditions.

The Atacama is one of the driest non-polar deserts in the world. The Gobi Desert experiences large seasonal temperature swings due to its continental location. Deserts cover about one-third of the Earth’s land surface.

35. The process through which groundwater is brought up to the surface is

The process through which groundwater is brought up to the surface is called

eluviation

illuviation

capillary action

desilication

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Capillary action is the phenomenon where a liquid moves up through a narrow space against the force of gravity. In the context of soil, this occurs because water molecules are attracted to soil particles (adhesion) and to each other (cohesion). These forces, combined with surface tension, draw water upwards through the pore spaces in the soil from the water table below, bringing groundwater closer to or onto the surface (known as capillary rise).

– Capillary action allows water to move upwards in narrow tubes or porous materials.
– It is a key mechanism for the upward movement of groundwater in soil.
– Adhesion, cohesion, and surface tension are the forces involved.

Eluviation and illuviation are processes related to the movement and accumulation of soil materials within different soil horizons, primarily driven by percolating water moving downwards. Desilication is a weathering process that removes silica from minerals, common in tropical climates but not the process that brings groundwater to the surface.

36. Which of the following are called ‘terrestrial planets’?

Which of the following are called ‘terrestrial planets’?

Earth, Mars, Jupiter, Mercury

Jupiter, Mercury, Saturn, Earth

Earth, Mercury, Mars, Venus

Mercury, Mars, Earth, Saturn

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Terrestrial planets are the inner, rocky planets of our solar system. They are characterized by having solid surfaces. In our solar system, the terrestrial planets are, in order from the Sun: Mercury, Venus, Earth, and Mars. The outer planets (Jupiter, Saturn, Uranus, Neptune) are gas giants or ice giants, primarily composed of gases and liquids, and are also known as Jovian planets.

– Terrestrial planets are rocky and located closer to the Sun.
– Jovian planets (gas/ice giants) are large, gaseous/liquid, and located farther from the Sun.

Besides their composition and location, terrestrial planets typically have higher densities, slower rotation, solid surfaces, and few or no moons or ring systems compared to Jovian planets. Earth is the largest of the terrestrial planets.

37. Indira Gandhi National Centre for the Arts is located at

Indira Gandhi National Centre for the Arts is located at

Allahabad

New Delhi

Kolkata

Bhopal

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The Indira Gandhi National Centre for the Arts (IGNCA) is a premier autonomous institution under the Union Ministry of Culture in India. Its headquarters are located in New Delhi.

– IGNCA is a national institution for arts and culture in India.
– It is located in the capital city.

IGNCA was established in 1987 as a centre for research, academic pursuit, and dissemination in the field of the arts. It aims to explore the relationship between the arts, humanities, and sciences. It houses significant archives and libraries related to Indian art and culture.

38. You are located at 40° N latitude and 90° W longitude. You travel due

You are located at 40° N latitude and 90° W longitude. You travel due North 40°, then due East 60°. What are your new coordinates?

30° N and 80° E

80° S and 30° E

80° N and 30° W

80° N and 30° E

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Starting coordinates: (40° N, 90° W).
1. Travel due North 40°: Moving north increases latitude. Starting at 40° N and moving 40° further north results in a new latitude of 40° N + 40° = 80° N. The longitude remains unchanged. Intermediate coordinates: (80° N, 90° W).
2. Travel due East 60°: Moving east changes longitude. Starting at 90° W and moving 60° east means reducing the westward longitude value towards the Prime Meridian (0°). The new longitude is 90° W – 60° = 30° W. The latitude remains unchanged. Final coordinates: (80° N, 30° W).

– Movement purely north or south changes only latitude.
– Movement purely east or west changes only longitude (assuming travel along a latitude line, though the question specifies ‘due East’ implying change in longitude).
– Longitudes West of the Prime Meridian are typically negative or marked ‘W’. Moving East from West longitudes reduces the westward value.

Latitude lines are parallel to the equator, ranging from 0° at the equator to 90° N or S at the poles. Longitude lines run from the North Pole to the South Pole, ranging from 0° at the Prime Meridian to 180° E or W. 180° longitude is roughly the International Date Line.

39. A species that is not isoelectronic with $^{35}_{17}$Cl$^-$ is

A species that is not isoelectronic with $^{35}_{17}$Cl$^-$ is

$^{31}_{15}$P$^{3-}$

$^{32}_{16}$S$^{2-}$

$^{40}_{18}$Ar$^{2+}$

$^{39}_{19}$K$^+$

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Isoelectronic species are atoms or ions that have the same number of electrons. First, determine the number of electrons in $^{35}_{17}$Cl$^-$:
– Atomic number (Z) = 17 (number of protons)
– Charge = -1
– Number of electrons = Protons – Charge = 17 – (-1) = 18 electrons.
Now check the electron count for each option:
– A) $^{31}_{15}$P$^{3-}$: Z=15. Electrons = 15 – (-3) = 18 electrons. (Isoelectronic)
– B) $^{32}_{16}$S$^{2-}$: Z=16. Electrons = 16 – (-2) = 18 electrons. (Isoelectronic)
– C) $^{40}_{18}$Ar$^{2+}$: Z=18. Electrons = 18 – (+2) = 16 electrons. (Not isoelectronic)
– D) $^{39}_{19}$K$^+$: Z=19. Electrons = 19 – (+1) = 18 electrons. (Isoelectronic)
The species that is not isoelectronic with Cl$^-$ is $^{40}_{18}$Ar$^{2+}$ with 16 electrons.

– Isoelectronic species have the same electron configuration.
– The number of electrons in an ion is calculated by subtracting the charge from the number of protons (atomic number).

Noble gases, like Argon (Ar), are often found as isoelectronic species with neighboring elements when they form ions, as they achieve a stable electron configuration. For instance, Cl$^-$ and K$^+$ are isoelectronic with neutral Argon (Ar), which has 18 electrons (Z=18). The mass number (superscript, e.g., 35) indicates the total number of protons and neutrons and is not relevant for determining the number of electrons.

40. Which one of the following gases is the lightest?

Which one of the following gases is the lightest?

Hydrogen

Helium

Oxygen

Nitrogen

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The lightness of a gas is determined by its molecular or atomic mass (for noble gases). Lighter gases have lower molecular/atomic masses and, at the same temperature and pressure, lower densities. Comparing the molar masses:
– Hydrogen (H₂): approx. 2.016 g/mol
– Helium (He): approx. 4.003 g/mol
– Oxygen (O₂): approx. 32.00 g/mol
– Nitrogen (N₂): approx. 28.01 g/mol
Hydrogen (H₂) has the lowest molar mass among the given options, making it the lightest gas.

– Gas density is directly proportional to its molar mass at constant temperature and pressure (Ideal Gas Law).
– Comparing molar masses allows identification of the lightest gas.

Hydrogen is the most abundant chemical substance in the universe. It is a highly flammable diatomic gas (H₂) under standard conditions. Helium is the second lightest element and is a noble gas, existing as a single atom (He). Oxygen and Nitrogen are the main components of Earth’s atmosphere, existing as diatomic molecules (O₂ and N₂).