UPSC CDS-2 Archives

11. Symbol of element was introduced by

Symbol of element was introduced by

[amp_mcq option1=”John Dalton” option2=”Antoine Lavoisier” option3=”Jöns Jacob Berzelius” option4=”Robert Boyle” correct=”option3″]

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Jöns Jacob Berzelius, a Swedish chemist, is credited with introducing the modern system of chemical symbols for elements around 1813. He proposed using one or two letters from the Latin name of the element, with the first letter capitalized and the second lowercase (if present). This system is the basis of the symbols used today in the periodic table.

The modern notation of using one or two letters derived from the element’s name as its symbol was proposed by Berzelius.

John Dalton used unique pictorial symbols for elements in his atomic theory. Antoine Lavoisier contributed significantly to the understanding of elements and chemical nomenclature but did not introduce the system of letter symbols. Robert Boyle is known for his definition of an element in “The Sceptical Chymist” and Boyle’s Law related to gases, but not for introducing element symbols.

12. A mixture of sodium chloride (salt) and ammonium chloride can be separ

A mixture of sodium chloride (salt) and ammonium chloride can be separated by

[amp_mcq option1=”sublimation” option2=”filtration” option3=”chromatography” option4=”distillation” correct=”option1″]

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A mixture of sodium chloride (NaCl) and ammonium chloride (NH₄Cl) can be separated by sublimation. Ammonium chloride is a compound that sublimes upon heating, meaning it transitions directly from a solid to a gas without passing through a liquid phase. Sodium chloride, on the other hand, is a stable ionic compound that does not sublime under normal heating conditions; it melts at a high temperature. By heating the mixture, the ammonium chloride vaporizes and can be collected on a cool surface, separating it from the solid sodium chloride residue.

Sublimation is a process used to separate mixtures where one component sublimes and the other does not.

Filtration is used to separate insoluble solids from liquids. Chromatography is used for separating components of a mixture based on their differential partitioning between a stationary and a mobile phase. Distillation is used to separate liquids with different boiling points or to separate liquids from non-volatile solids. None of these methods are suitable for separating solid NaCl from solid NH₄Cl based on their physical properties in this context.

13. Apart from hyper acid secretion, peptic ulcers are also developed due

Apart from hyper acid secretion, peptic ulcers are also developed due to bacterial infection. The causative agent is

[amp_mcq option1=”Helicobacter pylori” option2=”E. coli” option3=”Streptococcus pneumoniae” option4=”Salmonella typhimurium” correct=”option1″]

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The causative agent for peptic ulcers apart from hyper acid secretion is Helicobacter pylori.

For a long time, peptic ulcers (ulcers in the lining of the stomach or duodenum) were primarily attributed to lifestyle factors like stress and diet leading to excessive acid production. However, research by Barry Marshall and Robin Warren in the 1980s revolutionized the understanding of peptic ulcers by demonstrating that the bacterium *Helicobacter pylori* is a major cause. This bacterium can survive in the acidic environment of the stomach and colonize the gastric lining, causing inflammation and making the tissue vulnerable to acid damage, leading to ulcer formation.

The discovery of *H. pylori*’s role in peptic ulcers was initially met with skepticism but was eventually accepted, leading to new treatment regimens involving antibiotics to eradicate the bacterium. Marshall and Warren were awarded the Nobel Prize in Physiology or Medicine in 2005 for this discovery. While *H. pylori* is a primary cause, hyper acid secretion, NSAID use, smoking, and stress can also contribute to ulcer development or exacerbate existing ones.

14. Wings of birds and bats are considered analogous structures because th

Wings of birds and bats are considered analogous structures because they have

[amp_mcq option1=”common origin and common function” option2=”different origin and common function” option3=”common origin and different function” option4=”different origin and different function” correct=”option2″]

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Wings of birds and bats are considered analogous structures because they have different origin and common function.

Analogous structures are features in different species that perform the same function but have evolved independently from different ancestors. This is a result of convergent evolution, where different organisms adapt to similar environments or ecological niches. Bird wings evolved from forelimbs of reptilian ancestors, while bat wings evolved from the forelimbs of mammalian ancestors, and their skeletal structures are fundamentally different, reflecting their distinct evolutionary paths. However, both structures serve the purpose of flight. Homologous structures, in contrast, have a common evolutionary origin but may have different functions (e.g., the forelimbs of humans, bats, whales, and birds all originated from a common tetrapod ancestor but are used for different activities like grasping, flying, swimming).

Studying analogous and homologous structures helps scientists understand evolutionary relationships and the processes of adaptation and diversification. Analogous structures illustrate how natural selection can lead to similar solutions for similar environmental challenges in unrelated organisms.

15. Pearls are harvested from

Pearls are harvested from

[amp_mcq option1=”Prawn” option2=”Pila” option3=”Tuna” option4=”Oyster” correct=”option4″]

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Pearls are harvested from Oysters.

Pearls are natural or cultured gems produced by certain molluscs, most commonly bivalves like oysters (specifically pearl oysters). They form when an irritant, such as a parasite or a piece of shell, enters the mollusc and is covered by layers of nacre (mother-of-pearl) as a defense mechanism. While other molluscs can produce calcareous concretions, true pearls of commercial value are primarily associated with oysters and sometimes mussels. Prawns are crustaceans, Pila is a gastropod snail, and Tuna is a fish; none of these produce pearls.

Pearl cultivation (pearl farming) is a major industry, involving the deliberate insertion of a nucleus or irritant into pearl oysters to stimulate pearl formation. Different types of oysters produce different types of pearls, such as Akoya, South Sea, and Tahitian pearls.

16. All the individuals of a particular organism, such as rose plants, bel

All the individuals of a particular organism, such as rose plants, belong to a taxonomic category called

[amp_mcq option1=”species” option2=”genus” option3=”family” option4=”order” correct=”option1″]

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All the individuals of a particular organism, such as rose plants, belong to a taxonomic category called species.

In biological classification, the species is the fundamental taxonomic rank. A species is typically defined as a group of organisms that can interbreed naturally and produce fertile offspring. All individuals of a specific type of organism, like a particular species of rose plant (e.g., *Rosa gallica*), belong to that single species. A genus is a group of closely related species, a family is a group of related genera, and an order is a group of related families.

The hierarchy of taxonomic ranks typically includes Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species. The scientific name of an organism uses binomial nomenclature, consisting of the genus name and the species name (e.g., *Homo sapiens*).

17. Under the Kingdom Plantae, which of the following individuals are pred

Under the Kingdom Plantae, which of the following individuals are predominantly aquatic?

[amp_mcq option1=”Bryophytes” option2=”Algae” option3=”Pteridophyta” option4=”Gymnosperms” correct=”option2″]

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Algae are predominantly aquatic among the given options.

While taxonomic classifications can vary, in the context of comparing these groups, Algae are overwhelmingly found in aquatic environments (freshwater, marine, brackish). Bryophytes are primarily terrestrial but require moist habitats and water for reproduction. Pteridophyta (ferns) are also mostly terrestrial, although some species are aquatic. Gymnosperms (like conifers) are exclusively terrestrial plants. Therefore, Algae represent the group that is predominantly aquatic.

Algae are a very diverse group of photosynthetic organisms ranging from single-celled microalgae to large multicellular seaweeds. They play crucial roles as primary producers in aquatic ecosystems.

18. If the speed of light in air is represented by c and the speed in a me

If the speed of light in air is represented by c and the speed in a medium is v, then the refractive index of the medium can be calculated using the formula

[amp_mcq option1=”v / c” option2=”c / v” option3=”c / (2. v)” option4=”(c – v) / c” correct=”option2″]

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The refractive index of the medium can be calculated using the formula c / v.

The refractive index (n) of a medium is a dimensionless quantity that describes how fast light travels through the medium. It is defined as the ratio of the speed of light in vacuum (c₀) to the speed of light in the medium (v). Air is often used as an approximation for vacuum, so if the speed of light in air is represented by c and the speed in the medium is v, the refractive index is given by n = c / v.

The refractive index is always greater than or equal to 1 (n ≥ 1), with n=1 for vacuum (or approximately for air). A higher refractive index means light travels slower in the medium and bends more when entering from a medium with a lower refractive index.

19. Which one of the following statements with regard to the ultraviolet l

Which one of the following statements with regard to the ultraviolet light is not correct?

[amp_mcq option1=”It is an electromagnetic wave.” option2=”It can travel through vacuum.” option3=”It is a longitudinal wave.” option4=”Its wavelength is shorter/smaller than that of visible light.” correct=”option3″]

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The statement that ultraviolet light is a longitudinal wave is not correct.

Ultraviolet (UV) light is a form of electromagnetic radiation, just like visible light, radio waves, and X-rays. All electromagnetic waves are transverse waves, meaning their oscillations are perpendicular to the direction of energy transfer (propagation). They can travel through vacuum at the speed of light. Longitudinal waves, such as sound waves, involve oscillations parallel to the direction of propagation and require a medium to travel. UV light has a shorter wavelength than visible light but a longer wavelength than X-rays and gamma rays.

UV radiation is invisible to the human eye but can cause effects like sunburn and skin cancer. It has various applications, including sterilization, medical therapy, and fluorescence. The electromagnetic spectrum is ordered by wavelength and frequency.

20. Which one of the following statements about the properties of neutrons

Which one of the following statements about the properties of neutrons is not correct?

[amp_mcq option1=”Neutron mass is almost equal to proton mass.” option2=”Neutrons possess zero charge.” option3=”Neutrons are located inside the atomic nuclei.” option4=”Neutrons revolve around the atomic nuclei.” correct=”option4″]

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The statement that neutrons revolve around the atomic nuclei is not correct.

Neutrons are fundamental particles found in the nucleus of atoms (with the exception of the most common isotope of hydrogen). They are electrically neutral, possessing zero charge. Their mass is very close to that of a proton, slightly greater but often considered almost equal for simplicity. Protons and neutrons collectively form the atomic nucleus, which is located at the center of the atom. Electrons, which are negatively charged particles, revolve around the atomic nucleus in specific energy levels or orbitals.

The nucleus contains most of the atom’s mass. The number of neutrons in the nucleus determines the isotope of an element. The strong nuclear force binds protons and neutrons together in the nucleus, overcoming the electrostatic repulsion between protons.