UPSC CDS-1 Archives

11. Which one of the following is applicable to collision-coalescence proc

Which one of the following is applicable to collision-coalescence process of precipitation?

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Clouds which do not extend beyond the freezing level

Clouds which extend beyond the freezing level

All types of clouds

Cirrocumulus cloud

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UPSC CDS-1 – 2018

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The collision-coalescence process is a mechanism of rain formation that is most effective in warm clouds, i.e., clouds where the temperature is above freezing (0°C) throughout. In these clouds, larger cloud droplets fall and collide with smaller droplets, merging with them (coalescing). As they collect more droplets, they grow larger until they become heavy enough to fall as raindrops. This process does not require ice crystals.

The collision-coalescence process is the primary mechanism for precipitation in warm clouds (not extending beyond the freezing level).

Clouds that extend beyond the freezing level often involve the ice crystal process (Bergeron-Findeisen process), where supercooled water droplets evaporate and deposit water vapor onto ice crystals, which then grow and fall as snow or melt into rain. Cirrocumulus clouds are high-altitude ice clouds.

12. Which of the following causes adiabatic temperature changes in

Which of the following causes adiabatic temperature changes in atmosphere?

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Deflection and advection

Latent heat of condensation

Expansion and compression of the air

Partial absorption of solar radiation by the atmosphere

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Adiabatic temperature changes occur when the temperature of an air parcel changes due to expansion or compression without any heat exchange with its surroundings. When air rises, it expands due to lower atmospheric pressure, and this expansion causes it to cool (adiabatic cooling). When air sinks, it is compressed by higher pressure, and this compression causes it to warm (adiabatic warming).

Adiabatic processes involve temperature changes caused by work done during expansion or compression of air, not by heat transfer.

Deflection and advection involve horizontal air movement. Latent heat exchange (like condensation or evaporation) involves the release or absorption of heat, making the process non-adiabatic. Absorption of solar radiation is a form of heat transfer.

13. A protein is synthesized in the endoplasmic reticulum bound ribosomes

A protein is synthesized in the endoplasmic reticulum bound ribosomes and it targets to the inner thylakoid space of chloroplast. How many double-layered membrane layers it has to pass to reach its destination?

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The protein is synthesized in endoplasmic reticulum-bound ribosomes, meaning it enters the ER lumen or membrane. To reach the inner thylakoid space of a chloroplast, it must move from the ER system to the chloroplast. Assuming a pathway where the protein is released from the ER lumen into the cytoplasm (e.g., via retrotranslocation, crossing the ER membrane) and then imported into the chloroplast, the path would involve crossing the following membrane layers:
1. Crossing the ER membrane to exit the lumen into the cytoplasm (1 layer).
2. Crossing the outer chloroplast membrane (1 layer).
3. Crossing the inner chloroplast membrane (1 layer).
4. Crossing the thylakoid membrane to enter the inner thylakoid space (1 layer).
Total membrane layers crossed = 1 + 1 + 1 + 1 = 4.

Reaching the inner thylakoid space from the cytoplasm requires crossing the chloroplast outer membrane, inner membrane, and thylakoid membrane (3 layers). Starting from the ER lumen adds the step of exiting the ER, which requires crossing the ER membrane.

The standard pathway for most chloroplast proteins is synthesis on free ribosomes in the cytoplasm followed by post-translational import. The mention of synthesis on ER-bound ribosomes implies a non-standard or specific targeting route, or potentially release from the ER system into the cytoplasm before import. Chloroplasts have a double membrane envelope (outer and inner membranes) and an internal thylakoid membrane system.

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14. Lysosome is formed from which of the following cell organelles?

Lysosome is formed from which of the following cell organelles?

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Nucleus

Endoplasmic reticulum

Golgi bodies

Ribosomes

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Lysosomes are membrane-bound organelles containing digestive enzymes. They are formed from the Golgi apparatus (also known as Golgi complex or Golgi bodies). Proteins and lipids synthesized in the endoplasmic reticulum are transported to the Golgi apparatus for further processing and packaging. Lysosomes bud off from the trans face of the Golgi apparatus.

Lysosomes are part of the endomembrane system and originate from the Golgi apparatus.

The enzymes found in lysosomes are synthesized in the endoplasmic reticulum, transported to the Golgi, and then packaged into vesicles that mature into lysosomes. The primary function of lysosomes is intracellular digestion.

15. Which one of the following pairs about organ/part that helps in locomo

Which one of the following pairs about organ/part that helps in locomotion is not correctly matched?

Euglena : Flagellum

Paramecium : Cilia

Nereis : Pseudopodia

Starfish : Tubefeet

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The question asks which pair about an organ/part that helps in locomotion is *not* correctly matched.
A) Euglena: Flagellum – Correct. Euglena is a motile protozoan that uses a whip-like structure called a flagellum for propulsion.
B) Paramecium: Cilia – Correct. Paramecium is a motile protozoan covered in numerous short, hair-like structures called cilia, which it uses for movement and feeding.
C) Nereis: Pseudopodia – Incorrect. Nereis is a genus of marine polychaete worms. Polychaetes like Nereis use lateral, fleshy appendages called parapodia (often bearing bristles called chaetae) for locomotion (crawling, swimming) and respiration. Pseudopodia are temporary cytoplasmic extensions used for locomotion and feeding by some protozoans (like Amoeba) and certain cells in multicellular organisms. Nereis does not use pseudopodia for locomotion.
D) Starfish: Tubefeet – Correct. Starfish (sea stars) are echinoderms that use their tube feet, which are part of the water vascular system, for locomotion, grasping, and feeding.

Different organisms have evolved diverse structures for locomotion depending on their environment and body plan.

Pseudopodia (“false feet”) are characteristic of amoeboid movement. Flagella and cilia are whip-like or hair-like structures used by many protists and some animal cells. Parapodia are characteristic appendages of polychaete worms. Tube feet are unique to echinoderms.

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16. In which one of the following types of connective tissues in animals d

In which one of the following types of connective tissues in animals does fat get stored?

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Adipocyte

Chondrocyte

Osteocyte

Reticulocyte

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Connective tissue is a type of animal tissue that supports, connects, or separates different types of tissues and organs in the body. Different types of connective tissue include adipose tissue, cartilage, bone, blood, etc. Fat storage is primarily a function of adipose tissue. The main cells that make up adipose tissue and are specialized for storing fat are called adipocytes. Therefore, fat gets stored in adipocytes, which are found in adipose tissue.

Adipose tissue is a specialized connective tissue that serves as the body’s main energy reserve by storing fat in the form of triglycerides.

Chondrocytes are cells found in cartilage. Osteocytes are cells found in bone tissue. Reticulocytes are immature red blood cells found in the bone marrow and peripheral blood. Only adipocytes are primarily involved in fat storage.

17. Which one of the following is a true fish as per the biological system

Which one of the following is a true fish as per the biological system of classification?

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Silverfish

Jellyfish

Cuttlefish

Flying fish

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The question asks which option represents a ‘true fish’ according to biological classification. True fishes belong to the superclass Pisces (or equivalent phylogenetic groups like Osteichthyes and Chondrichthyes). Let’s examine the options:
A) Silverfish: This is an insect (Zygentoma order), not a fish.
B) Jellyfish: This is a marine invertebrate belonging to the phylum Cnidaria, not a fish.
C) Cuttlefish: This is a marine mollusc belonging to the class Cephalopoda, not a fish.
D) Flying fish: This is a type of marine ray-finned bony fish belonging to the family Exocoetidae. It is a true fish.

In everyday language, ‘fish’ is often used loosely, but in biology, a ‘true fish’ refers to aquatic vertebrates with gills that lack limbs with digits, typically belonging to the superclass Pisces.

Many animals with “fish” in their common name are not true fish (e.g., starfish, crayfish, shellfish). True fish include cartilaginous fish (sharks, rays) and bony fish (most common fish).

18. Statement I : Bioaccumulation is a process of progressive accumulation

Statement I :
Bioaccumulation is a process of progressive accumulation of heavy metals and pesticides in an organism.
Statement II :
Large fishes of the pond are found to have higher concentration of pesticides than planktons of the same pond.

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Option text is missing in the image.

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Statement I is true. Bioaccumulation is defined as the gradual accumulation of substances, such as pesticides, or other chemicals in an organism. This happens when the rate of intake of the substance exceeds the organism’s ability to remove it through metabolism or excretion. Statement II is also true. This phenomenon, where concentrations of substances like pesticides increase at successively higher levels in a food chain, is called biomagnification. Large fish are typically at higher trophic levels than plankton, and thus accumulate higher concentrations of persistent chemicals that are bioaccumulated by organisms at lower levels and passed up the chain. However, Statement II describes the *result* of bioaccumulation and biomagnification across a food chain, it does not explain the *process* of bioaccumulation (accumulation within a single organism) defined in Statement I. Therefore, Statement II is not the correct explanation for Statement I.

Bioaccumulation is the accumulation within one organism. Biomagnification is the increase in concentration of a substance as it moves up the food chain.

Persistent organic pollutants (POPs) and heavy metals are common substances that undergo bioaccumulation and biomagnification, posing risks to organisms at higher trophic levels, including humans who consume contaminated fish or meat.

19. Statement I : A person may suffer from tuberculosis if she/he frequent

Statement I :
A person may suffer from tuberculosis if she/he frequently visits crowded place.
Statement II :
Bacteria of tuberculosis spread through droplets by sneezing or coughing.

Option text is missing in the image.

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Statement I is true. Tuberculosis (TB) is a contagious disease that spreads through the air. Spending time in crowded places increases the likelihood of being exposed to airborne pathogens from infected individuals. Statement II is also true. The bacteria that cause TB, *Mycobacterium tuberculosis*, are primarily transmitted from person to person through tiny droplets released into the air when a person with active pulmonary TB coughs, sneezes, speaks, or sings. Statement II provides the mechanism (airborne droplet spread) that explains why being in crowded places (where people are in close proximity and may be infectious) increases the risk of contracting TB, as stated in Statement I. Therefore, Statement II is the correct explanation for Statement I.

Tuberculosis is an airborne infectious disease. Transmission occurs through inhaling infectious droplets.

Factors that increase the risk of TB infection and disease include close contact with an infectious person, crowded living conditions, poor ventilation, malnutrition, and weakened immune systems (e.g., due to HIV, diabetes).

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20. Statement I : Tides are the rise and fall of sea levels caused by the

Statement I :
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the Moon and the Sun and the rotation of the Earth.
Statement II :
The Earth rotates from west to east.

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Statement I is true. Tides are indeed caused by the gravitational pull of the Moon and the Sun on Earth’s oceans, combined with the centrifugal force resulting from the Earth-Moon system’s orbit and the Earth’s rotation. Statement II is also true. The Earth rotates on its axis from west to east. However, while Earth’s rotation is an essential component of the tidal mechanism (as it brings different parts of the globe under the influence of the tidal bulges and causes the cyclical rise and fall), the *direction* of rotation (west to east) does not specifically explain *why* the gravitational forces of the Moon and Sun cause bulges or how the combination of forces results in tides. It explains *how* the tidal phenomenon moves across the Earth, but not the fundamental cause described in Statement I. Therefore, Statement II is not the correct explanation for Statement I.

Tides are a result of differential gravitational forces acting on the Earth and the inertia of the water. The rotation of the Earth causes locations to pass through the tidal bulges.

The Moon’s gravitational pull is the primary driver of tides due to its closer proximity. The Sun also influences tides, leading to spring tides (when Moon, Sun, Earth align) and neap tides (when Moon, Sun, Earth are at a right angle). Earth’s rotation relative to the tidal bulges creates the cyclical pattern of high and low tides experienced at a specific location.