UPSC CDS-2

21. In which one among the following mediums would the speed of sound be m

In which one among the following mediums would the speed of sound be maximum ?

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Distilled water
Sea water
Drinking water
Methanol
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UPSC CDS-2 – 2024
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The speed of sound depends on the properties of the medium through which it travels, specifically its density and compressibility (bulk modulus). Sound travels fastest in solids, then liquids, and slowest in gases. Among the given liquids, sea water has dissolved salts, which makes it slightly denser and less compressible than distilled or drinking water. Methanol is less dense than water. Generally, sound travels faster in denser and less compressible liquids. Therefore, the speed of sound is highest in sea water among the given options.
– Speed of sound increases with the stiffness (bulk modulus) of the medium and decreases with density, though the effect of stiffness is usually more significant in liquids and solids.
– Dissolved salts in sea water increase its density and bulk modulus compared to fresh water.
Typical speed of sound in air at 20°C is about 343 m/s. In fresh water at 20°C, it’s about 1482 m/s. In sea water at 20°C and typical salinity, it’s about 1522 m/s. In methanol at 20°C, it’s about 1100 m/s. This confirms that sound travels faster in sea water than the other liquid options provided.

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22. Which one among the following is not a part of vascular bundle in pl

Which one among the following is not a part of vascular bundle in plants ?

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Phloem
Xylem
Cambium
Endodermis
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UPSC CDS-2 – 2024
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A vascular bundle in plants is the primary conducting strand, composed mainly of xylem and phloem, which transport water, minerals, and sugars. In dicotyledonous plants and gymnosperms, cambium is also present between xylem and phloem, facilitating secondary growth. The endodermis, however, is a layer of ground tissue that surrounds the vascular cylinder (stele), particularly prominent in roots and some stems, and is not considered part of the vascular bundle itself.
– Vascular bundles contain xylem (water transport) and phloem (sugar transport).
– Cambium is involved in secondary growth and is part of the vascular bundle structure in plants with secondary growth.
– The endodermis functions as a selective barrier controlling the movement of substances into the vascular cylinder via the Casparian strip.
Vascular bundles can be arranged differently in different plant organs and species (e.g., scattered in monocot stems, in a ring in dicot stems, forming a central cylinder in roots). The endodermis plays a crucial role in filtering substances absorbed by the root before they enter the xylem.

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23. Halophytes are the plants that grow on which one, among the following

Halophytes are the plants that grow on which one, among the following categories of soil ?

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Acidic soil
Saline soil
Black soil
Sandy soil
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UPSC CDS-2 – 2024
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Halophytes are a category of plants that have adapted to survive and grow in soils with high salt concentrations. This environment is typically toxic to most conventional plants.
– Halophytes possess specific physiological adaptations (like salt excretion, succulence, or accumulating salts in specific tissues) to tolerate saline conditions.
– Saline soils are characterized by excessive amounts of soluble salts, mainly sodium chloride, sodium sulfate, magnesium chloride, and magnesium sulfate.
Examples of halophytes include mangroves, saltmarsh grasses, glassworts, and some species found in arid or semi-arid regions. Different halophyte species employ various mechanisms to cope with salinity stress, such as excluding salt uptake, excreting excess salt through salt glands, or diluting salt concentration by increasing water storage (succulence).

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24. Which one among the following is not a feature of Xerophytes ?

Which one among the following is not a feature of Xerophytes ?

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Smaller leaves
Large number of stomata
Waxy cuticle
Stomata in pits
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Xerophytes are plants adapted to arid conditions and have features that reduce water loss. A large number of stomata would lead to high transpiration and water loss, which is contrary to the adaptations of xerophytes.
Xerophytic adaptations aim at reducing water loss (e.g., reduced leaf surface area, thick cuticle, sunken stomata) or storing water.
Typical xerophytic features include smaller leaves (or modified into spines), thick waxy cuticles, sunken stomata or stomata located in pits, presence of trichomes (hairs) to trap moisture, and often succulent tissues for water storage. They tend to have fewer stomata per unit area or stomata that are effectively protected from dry air.

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25. Which of the following biomolecules does Starch belong to ?

Which of the following biomolecules does Starch belong to ?

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Protein
Carbohydrate
Lipid
Nucleic acid
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UPSC CDS-2 – 2024
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Starch is a polysaccharide, which is a complex carbohydrate made up of many glucose units linked together. It serves as a storage form of glucose in plants.
Biomolecules are molecules produced by living organisms and include carbohydrates, proteins, lipids, and nucleic acids.
Carbohydrates are organic compounds consisting of carbon, hydrogen, and oxygen atoms, usually with a hydrogen-oxygen atom ratio of 2:1. They include simple sugars (monosaccharides), disaccharides, and complex polysaccharides like starch, cellulose, and glycogen.

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26. Which one among the following hormones inhibits the growth activity in

Which one among the following hormones inhibits the growth activity in plants ?

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Auxins
Cytokinins
Abscisic acid
Gibberellins
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UPSC CDS-2 – 2024
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Abscisic acid (ABA) is a plant hormone that acts as an inhibitor of growth and metabolism. It promotes dormancy, stomatal closure during water stress, and leaf senescence.
Plant hormones regulate various aspects of plant growth, development, and responses to environmental stimuli.
Auxins, Cytokinins, and Gibberellins are generally considered growth-promoting hormones, although their effects can vary depending on concentration and plant tissue. Ethylene is another plant hormone, often associated with fruit ripening and senescence, and can also inhibit growth in some contexts.

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27. Xylem in the plants are responsible for the transport of :

Xylem in the plants are responsible for the transport of :

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Water
Water and dissolved minerals
Gases
Food
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UPSC CDS-2 – 2024
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Xylem is the primary water-conducting tissue in vascular plants. It transports water and dissolved inorganic nutrients (minerals) absorbed by the roots upwards to the rest of the plant, especially the leaves.
Xylem and Phloem are the two main transport tissues in plants, forming the vascular system.
Phloem is responsible for the translocation of sugars (food produced during photosynthesis) from the leaves to other parts of the plant. Xylem also provides structural support to the plant body.

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28. Which one among the following is not a micronutrient for plants ?

Which one among the following is not a micronutrient for plants ?

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Iron
Manganese
Magnesium
Chlorine
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UPSC CDS-2 – 2024
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Magnesium is a macronutrient for plants, required in relatively large quantities, whereas Iron, Manganese, and Chlorine are micronutrients, required in smaller quantities.
Plant nutrients are classified into macronutrients and micronutrients based on the amount required by the plant for healthy growth.
Essential macronutrients include Nitrogen, Phosphorus, Potassium, Calcium, Magnesium, and Sulfur. Essential micronutrients include Iron, Manganese, Zinc, Copper, Boron, Molybdenum, and Chlorine.

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29. Which one among the following correctly represents the theme on which

Which one among the following correctly represents the theme on which the interiors of the new Parliament Building is based ?

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Lotus | Banyan
Peacock | Lotus
Peacock | Banyan
Lotus | Peacock
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UPSC CDS-2 – 2023
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The interiors of the new Parliament Building of India are based on national symbols. The Lok Sabha chamber is themed around the Peacock, and the Rajya Sabha chamber is themed around the Lotus.
National symbols like the peacock (national bird) and lotus (national flower) were chosen to represent different parts of the building, reflecting India’s heritage.
The Central Lounge of the new Parliament Building is themed around the Banyan tree, India’s national tree. Therefore, Peacock and Lotus represent the themes of the two main legislative chambers.

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30. The Grand Order of the Chain of the Yellow Star is the highest civilia

The Grand Order of the Chain of the Yellow Star is the highest civilian honour of which among the following countries ?

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Fiji
Papua New Guinea
Egypt
Suriname
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UPSC CDS-2 – 2023
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The Grand Order of the Chain of the Yellow Star is the highest civilian honour awarded by the Republic of Suriname.
National honours are prestigious awards given by countries to recognise significant contributions or achievements.
Suriname is a country in South America. This order is awarded to both citizens and foreign dignitaries.

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