UPSC NDA-2

31. Girth of stem of a plant increases due to division of cells in

Girth of stem of a plant increases due to division of cells in

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apical meristem only.
lateral meristem only.
apical and intercalary meristem.
both apical and lateral meristem.
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Increase in the girth or diameter of a plant stem or root is called secondary growth. This growth is primarily due to the activity and division of lateral meristems, namely the vascular cambium and the cork cambium.
Apical meristems are located at shoot and root tips and are responsible for primary growth (increase in length). Intercalary meristems are found at the base of nodes and leaves, also contributing to primary growth in certain plants (like grasses). Lateral meristems (vascular and cork cambium) are responsible for secondary growth (increase in thickness).
The vascular cambium produces secondary xylem (wood) and secondary phloem, adding to the stem’s diameter. The cork cambium produces periderm, including cork, which replaces the epidermis as the protective outer layer.

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32. Which one of the following tissues is known as basic packing tissue an

Which one of the following tissues is known as basic packing tissue and found in xylem and phloem ?

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Collenchyma
Parenchyma
Sclerenchyma
Vessels
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Parenchyma tissue is composed of living cells that are typically isodiametric (roughly equal in diameter). These cells form the bulk of ground tissues in plants (cortex, pith) and are also present in xylem and phloem rays and parenchyma. Due to their widespread occurrence and roles in storage, secretion, and basic metabolic functions, they are often referred to as basic packing tissue.
Parenchyma cells are thin-walled and versatile. They are found throughout the plant body and participate in various functions like photosynthesis, storage, and secretion.
Collenchyma is a living support tissue providing mechanical support to growing stems and petioles. Sclerenchyma provides rigid support and strength to mature plant parts using thick, lignified walls (fibers and sclereids). Vessels are conducting elements in xylem responsible for water transport.

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33. How are evergreen plants with woody stems having naked seed classified

How are evergreen plants with woody stems having naked seed classified ?

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Angiosperms
Monocotyledons
Pteridophytes
Gymnosperms
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Gymnosperms are a group of seed-bearing plants that produce “naked” seeds, meaning their seeds are not enclosed within an ovary or fruit. Many gymnosperms, such as conifers, are evergreen trees or shrubs with woody stems.
The defining characteristic of gymnosperms is the presence of naked seeds. They are vascular plants and include forms like conifers, cycads, ginkgo, and gnetophytes.
Angiosperms (flowering plants) have seeds enclosed within a fruit. Pteridophytes (ferns and horsetails) are vascular plants but do not produce seeds; they reproduce via spores. Monocotyledons are a subgroup of Angiosperms.

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34. Which one of the following statements about the process of photosynthe

Which one of the following statements about the process of photosynthesis is correct ?

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Chemical energy is converted into light energy.
Carbon dioxide is oxidised to form carbohydrate.
Water molecule splits into hydrogen and oxygen.
Light energy is directly used to split water.
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During the light-dependent reactions of photosynthesis, water molecules are split (photolysis) using light energy absorbed by chlorophyll. This process yields oxygen, electrons, and protons (hydrogen ions). Oxygen is released as a byproduct.
Photosynthesis involves two main stages: light-dependent reactions and light-independent reactions (Calvin cycle). The splitting of water occurs in the light-dependent reactions and is crucial for providing electrons and protons for subsequent steps and releasing oxygen.
The overall equation for photosynthesis is $6CO_2 + 6H_2O \rightarrow C_6H_{12}O_6 + 6O_2$. Carbon dioxide is reduced to carbohydrate, not oxidized. Light energy is converted into chemical energy stored in glucose and other organic molecules.

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35. Shoots of plant show upward movement and it can be designated to be

Shoots of plant show upward movement and it can be designated to be

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Negatively phototropic
Positively chemotropic
Positively hydrotropic
Negatively geotropic
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The upward movement of plant shoots is a response to gravity. Since gravity pulls downwards, movement upwards is against the direction of gravity. This response to gravity is called gravitropism (or geotropism).
Plant shoots typically exhibit negative gravitropism (growing away from gravity) and positive phototropism (growing towards light). The question asks about the upward movement, which is primarily defined relative to the gravitational pull.
Positive gravitropism is seen in roots, which grow downwards into the soil. Phototropism is the growth of a plant in response to a light stimulus. Chemotropism is movement in response to chemicals, and hydrotropism is movement in response to water.

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36. Which one of the following methods can be used to separate anthracene

Which one of the following methods can be used to separate anthracene from a mixture of salt and anthracene ?

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Distillation
Sublimation
Evaporation
Chromatography
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Anthracene is a polycyclic aromatic hydrocarbon known for its property of sublimation, which is the process of transitioning directly from the solid to the gas phase upon heating, without passing through a liquid phase. Salt (e.g., sodium chloride) is an ionic compound with a very high melting point and does not sublime under normal conditions. Therefore, sublimation is an effective method to separate anthracene from a mixture containing salt. By heating the mixture, anthracene will turn into a gas and can be collected by cooling the vapour, leaving the non-sublimable salt behind.
– Anthracene sublimes easily upon heating.
– Salt does not sublime under typical conditions.
– Sublimation is used to separate a sublimable solid from non-sublimable solids.
Other methods like distillation and evaporation are generally used for separating liquids or separating dissolved solids from solvents. Chromatography is a technique for separating components of a mixture based on different affinities for a stationary and mobile phase, which could be used but is not as direct or efficient as sublimation for this specific type of mixture.

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37. Which one of the following pairs of elements is liquid at room tempera

Which one of the following pairs of elements is liquid at room temperature and at normal pressure ?

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Gallium and Bromine
Mercury and Bromine
Gallium and Mercury
Gallium and Caesium
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At standard room temperature (approximately 25°C) and normal pressure, only two elements are liquids: Mercury (Hg), a metal, and Bromine (Br₂), a non-metal.
– Mercury is the only metallic element that is liquid at room temperature.
– Bromine is the only non-metallic element that is liquid at room temperature.
– Gallium (melting point 29.8 °C) and Caesium (melting point 28.5 °C) melt just above typical room temperature but are usually considered solid at 25°C.
While Gallium and Caesium have very low melting points and can melt in slightly warmer conditions or even in the hand, Mercury and Bromine are consistently liquid under standard room temperature conditions.

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38. What is the colour of the precipitate obtained by passing CO₂ gas thro

What is the colour of the precipitate obtained by passing CO₂ gas through lime water ?

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Green
Blue
White
Brown
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Lime water is an aqueous solution of calcium hydroxide (Ca(OH)₂). When carbon dioxide (CO₂) gas is passed through lime water, it reacts with calcium hydroxide to form calcium carbonate (CaCO₃) and water. Calcium carbonate is insoluble in water and precipitates out as a fine suspension, which appears white.
– Reaction: Ca(OH)₂(aq) + CO₂(g) → CaCO₃(s) + H₂O(l)
– Calcium carbonate (CaCO₃) is the precipitate formed.
– Calcium carbonate is a white solid.
If CO₂ is passed through lime water for a prolonged period, the white precipitate of calcium carbonate dissolves as it reacts further with CO₂ and water to form soluble calcium bicarbonate (Ca(HCO₃)₂): CaCO₃(s) + H₂O(l) + CO₂(g) → Ca(HCO₃)₂(aq).

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39. What is the number of water molecules present in a Ferrous Sulphate cr

What is the number of water molecules present in a Ferrous Sulphate crystal ?

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1
3
5
7
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Ferrous Sulphate commonly exists as a hydrated salt known as green vitriol. The chemical formula for this hydrated form is FeSO₄·7H₂O. This indicates that each formula unit of ferrous sulphate is associated with 7 molecules of water of crystallization.
– Ferrous Sulphate forms hydrated crystals.
– The most common hydrate is the heptahydrate (FeSO₄·7H₂O).
Other less common hydrates of ferrous sulphate also exist, such as the monohydrate (FeSO₄·H₂O) and tetrahydrate (FeSO₄·4H₂O). However, unless otherwise specified, ferrous sulphate crystals usually refer to the heptahydrate.

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40. Which one of the following compounds is used in ‘black and white’ phot

Which one of the following compounds is used in ‘black and white’ photography ?

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AgF
AgBr
AgCl
Ag₂SO₄
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Silver halides are widely used in ‘black and white’ photography due to their sensitivity to light. When light strikes a silver halide crystal, it initiates a chemical change that can later be developed into a visible image. Silver bromide (AgBr) is the most common silver halide used in photographic films, although silver chloride (AgCl) and silver iodide (AgI) are also used, particularly in photographic papers. Among the options provided, AgBr is a standard compound used in black and white photography.
– Silver halides are photosensitive compounds.
– AgBr is widely used in photographic films.
The photographic process involves exposing the silver halide crystals on film or paper to light, creating a latent image. This image is then developed using chemical solutions which convert the exposed silver halide into metallic silver (appearing black). Unexposed silver halide is removed during fixing.

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