UPSC CDS-1

31. Which one of the following substances do silver articles react with, t

Which one of the following substances do silver articles react with, that makes the silver articles black ?

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Sulphur
Oxygen
Carbon dioxide
Phosphorus
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Silver articles become black due to their reaction with sulphur compounds present in the atmosphere, such as hydrogen sulphide (H₂S). This reaction forms a layer of black silver sulphide (Ag₂S) on the surface of the silver.
– The tarnishing of silver is primarily caused by the reaction with sulphur compounds, not oxygen or carbon dioxide under normal atmospheric conditions.
– The reaction is typically represented as: 2Ag(s) + H₂S(g) → Ag₂S(s) + H₂(g).
– While silver does react with oxygen at high temperatures, the common tarnishing phenomenon is due to sulfurization.
– Phosphorus is a reactive non-metal but does not cause silver tarnishing in this manner.

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32. When we heat lead nitrate [Pb(NO₃)₂] in a boiling tube, we observe the

When we heat lead nitrate [Pb(NO₃)₂] in a boiling tube, we observe the emission of brown fumes. Which one of the following is the brown gas ?

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NO
N₂O₂
NO₃
NO₂
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When lead nitrate [Pb(NO₃)₂] is heated, it undergoes thermal decomposition, producing lead(II) oxide (PbO), oxygen gas (O₂), and nitrogen dioxide gas (NO₂). The brown fumes observed are due to nitrogen dioxide (NO₂).
– The balanced chemical equation for the decomposition of lead nitrate is: 2Pb(NO₃)₂(s) → 2PbO(s) + 4NO₂(g) + O₂(g).
– Nitrogen dioxide (NO₂) is a toxic, reddish-brown gas.
– Nitrogen monoxide (NO) is a colourless gas.
– N₂O₂ is a dimer of NO, and while related to nitrogen oxides, it is not the species responsible for the prominent brown fumes in this decomposition.
– NO₃ is a highly reactive radical and not the stable product gas observed as brown fumes.

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33. Growing of two or more crops simultaneously on the same field in a def

Growing of two or more crops simultaneously on the same field in a definite pattern is known as

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mixed cropping
inter cropping
mixed farming
hybrid farming
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Growing two or more crops simultaneously on the same field in a definite pattern is specifically known as inter cropping.
– Inter cropping involves planting crops in specific arrangements, such as alternating rows of different crops. This pattern helps in efficient resource utilization and can offer benefits like pest and disease control, as well as soil improvement.
– Mixed cropping involves growing multiple crops simultaneously but without a definite pattern, typically by mixing the seeds before sowing.
– Mixed farming is a broader term that involves both crop cultivation and livestock rearing on the same farm.
– Hybrid farming usually refers to agricultural practices that utilize hybrid seeds or potentially a combination of conventional and modern farming techniques.

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34. Osmosis is the process of movement of water molecules from its

Osmosis is the process of movement of water molecules from its

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higher concentration to its lower concentration through a cell wall.
lower concentration to its higher concentration through a fully permeable membrane.
higher concentration to its lower concentration through a fully permeable membrane.
higher concentration to its lower concentration through a semi-permeable membrane.
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Osmosis is defined as the net movement of solvent molecules (typically water) from a region of higher solvent concentration (or higher water potential) to a region of lower solvent concentration (or lower water potential) through a selectively permeable or semi-permeable membrane.
– The key components of osmosis are the movement of *solvent* (water), the direction from *higher to lower* water concentration/potential, and the presence of a *semi-permeable membrane*.
– A semi-permeable membrane allows solvent molecules to pass through but restricts the passage of solute molecules.
– A fully permeable membrane allows both solute and solvent to pass freely, so osmosis as defined does not occur across such a membrane; diffusion would happen.
– The cell wall of plant cells is generally fully permeable, not semi-permeable. The cell membrane is the semi-permeable barrier.

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35. Which cell organelles have their own DNA and Ribosomes ?

Which cell organelles have their own DNA and Ribosomes ?

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Golgi body and Endoplasmic Reticulum
Mitochondria and Plastids
Lysosome and Golgi body
Vacuole and Plastids
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Mitochondria and plastids (like chloroplasts) are unique among eukaryotic cell organelles in possessing their own genetic material (DNA) and ribosomes.
– Both mitochondria and plastids are believed to have originated through endosymbiosis, a process where prokaryotic cells were engulfed by early eukaryotic cells.
– This evolutionary history explains why they retain their own DNA (circular, similar to bacterial DNA) and ribosomes (70S type, similar to bacterial ribosomes), separate from the nuclear DNA and cytoplasmic ribosomes (80S type) of the host cell.
– Other organelles like the Golgi body, Endoplasmic Reticulum, Lysosomes, and Vacuoles are part of the endomembrane system and are dependent on the nucleus for genetic information and protein synthesis. They do not have their own DNA or ribosomes.

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36. A student was doing an experiment on increasing the cell division amon

A student was doing an experiment on increasing the cell division among plants. She asked her supervisor to suggest the specific plant hormone for the same. Had you been her supervisor, which plant hormone would you suggest ?

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Abscisic acid
Gibberellins
Cytokinin
Auxin
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The plant hormone to suggest for increasing cell division among plants would be Cytokinin.
Cytokinins are a class of plant hormones that promote cell division (cytokinesis) in plant roots and shoots. They are involved in cell growth, differentiation, and delay of senescence.
Auxins primarily promote cell elongation, although they interact with cytokinins in regulating cell division and differentiation. Gibberellins promote stem elongation and germination. Abscisic acid is primarily involved in inhibiting growth and promoting dormancy and stress responses.

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37. A child receives a tall beautiful plant as a birthday gift from his fa

A child receives a tall beautiful plant as a birthday gift from his father with a quiz. The father asked her how she would verify whether this tall plant was the progeny of both the tall parents or one tall and one short parent plant. She could verify this through

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cross-pollination
self-pollination
tissue culture
negative propagation
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She could verify this through cross-pollination.
To determine the genotype of a plant showing a dominant phenotype (tall), the standard method is a test cross. A test cross involves cross-pollinating the plant with a homozygous recessive plant (short). If the progeny includes any short plants, the tall parent must be heterozygous (Tt). If all progeny are tall, the tall parent is likely homozygous dominant (TT). This method allows differentiation between potential parental genotypes (Tall x Tall vs. Tall x Short leading to different progeny genotypes).
Self-pollination could also provide clues (a heterozygous plant would produce some recessive offspring upon selfing), but a test cross is more definitive for confirming homozygosity vs. heterozygosity. Tissue culture is a propagation technique, and ‘negative propagation’ is not a standard biological term in this context.

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38. Cell wall is not present in cells of

Cell wall is not present in cells of

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Bacteria
Plants
Fungi
Humans
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Cell wall is not present in cells of Humans.
Animal cells, including human cells, are characterized by the absence of a cell wall. They are surrounded only by a cell membrane.
Bacteria have cell walls typically made of peptidoglycan. Plant cells have cell walls primarily made of cellulose. Fungal cells have cell walls primarily made of chitin.

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39. The Kaleshwaram Lift Irrigation System, which was in the news recently

The Kaleshwaram Lift Irrigation System, which was in the news recently, is constructed in

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Kerala
Gujarat
Telangana
Maharashtra
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The Kaleshwaram Lift Irrigation System is constructed in Telangana.
The Kaleshwaram Lift Irrigation System is a multi-purpose irrigation project on the Godavari River in Kaleshwaram, Telangana, India. It is one of the world’s largest multi-stage lift irrigation projects, designed to provide water for irrigation, drinking, and industrial purposes.
The project involves numerous barrages, pump houses, and canals to lift water from the Godavari River to higher elevations across the state.

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40. In the year 2020 which one of the following tiger reserves of India wa

In the year 2020 which one of the following tiger reserves of India was declared by UNESCO as a Biosphere Reserve?

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Panna Tiger Reserve
Namdapha Tiger Reserve
Dudhwa Tiger Reserve
Pench Tiger Reserve
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In 2020, Panna Tiger Reserve of India was declared by UNESCO as a Biosphere Reserve.
Panna Tiger Reserve in Madhya Pradesh was included in UNESCO’s World Network of Biosphere Reserves in November 2020. It is the 12th biosphere reserve from India to be added to this network.
The recognition highlights the reserve’s significance for biodiversity conservation and sustainable development efforts. Other Biosphere Reserves in India include Nilgiri, Nanda Devi, Sundarbans, Great Nicobar, etc.

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