General Science Mixed Quiz: Set 70

The correct answer is B, chitin. The wall of a fungal cell is built of chitin, a nitrogen-containing polysaccharide that is also found in the exoskeleton of insects, and it is one of the main reasons fungi were taken out of the plant kingdom and given a kingdom of their own. A is wrong because cellulose is the wall material of plant cells and of some algae, and fungi have very little of it. C is wrong because peptidoglycan, also called murein, is the wall material of bacteria, that is of the kingdom Monera, and it is the target of antibiotics such as penicillin. D is wrong because lignin is not a wall-forming polysaccharide at all but the substance that stiffens the woody tissue of higher plants.

The correct answer is C, Thiourea (accelerator). Accelerators speed up the vulcanisation of rubber; they are not a part of paint.

An oil paint is made of a pigment that gives colour and covering power, a vehicle or drying oil such as linseed oil that binds the film, a thinner that makes it easy to spread, a drier that speeds up hardening, fillers or extenders that add body, and an anti-skinning agent that stops a skin forming in the tin. Titanium dioxide is the most widely used white pigment, turpentine is the classic thinner, and polyhydroxy phenols are used as anti-skinning agents. Thiourea and similar compounds belong to rubber technology, where accelerators shorten the time sulphur takes to cross-link rubber.

A is wrong: turpentine oil is a standard thinner in paint.

B is wrong: polyhydroxy phenols are used in paint as anti-skinning agents.

D is wrong: titanium dioxide is the main white pigment in paints.

Exam tip: paint = pigment + vehicle (linseed oil) + thinner (turpentine) + drier + filler + anti-skinning agent.

The correct answer is B, water. In this cell hydrogen is fed to the anode and oxidised, oxygen is fed to the cathode and reduced, and the two combine to give water, so the cell produces electricity for as long as the gases are supplied and leaves no polluting exhaust. Cells of this kind gave both power and drinking water on the Apollo spacecraft and are now used in buses, trains and backup power units. A is wrong because no carbon enters the reaction; carbon dioxide would appear only if a hydrocarbon or an alcohol were the fuel. C is wrong because hydrogen peroxide is not the product of the overall cell reaction, although peroxide species can form as unwanted intermediates at a poor catalyst. D is wrong because ammonia contains nitrogen, which is not a reactant here, though ammonia is studied separately as a possible carrier of hydrogen fuel.

The correct answer is B, Fallopian tube. In human beings the sperm meets and fuses with the egg inside the fallopian tube, also called the oviduct.

The ovary releases one egg in a month, and the funnel shaped mouth of the fallopian tube collects it. Sperms swim up from the vagina through the cervix and the uterus into the tube, and fusion usually happens in its wider upper part. The fertilised egg, now a zygote, begins to divide as the tube's lining pushes it along, and reaches the uterus in a few days as a ball of cells that implants in the thick uterine wall and grows there with the help of the placenta.

Option A is wrong because the uterus is where the embryo implants and develops, after fertilisation. Option C is wrong because the ovary only makes and releases the egg. Option D is wrong because the vagina is the passage the sperms enter through.

Exam tip: egg made in the ovary, fertilised in the fallopian tube, developed in the uterus.

The correct answer is B, castor. The eri silkworm, Samia ricini, feeds on castor leaves, and its silk is called ahimsa silk because the moth is allowed to emerge before the cocoon is used, leaving a broken fibre that is spun like cotton instead of being reeled. Option A is wrong because mulberry is the food of Bombyx mori, and growing mulberry for it is called moriculture. Option C is wrong because Arjun, along with Asan, is the host of the tropical tasar silkworm. Option D is wrong because Som, with Soalu, is the host of the muga silkworm of Assam. The examiner's favourite trick here is to offer two tree names from the tasar and muga groups beside castor. Castor is Ricinus communis, grown widely in Assam and the North-East, which is why eri rearing is concentrated there alongside muga.

The correct answer is C, Hepatitis B. The hepatitis B vaccine was the first vaccine made by recombinant DNA technology. Scientists cut out the gene for the surface protein of the hepatitis B virus and put it into yeast cells; the yeast then made that protein in large amounts, and the purified protein is injected as the vaccine. Because only one viral protein is used and no whole virus is involved, the vaccine cannot cause the disease, which is what makes recombinant vaccines safe. It was licensed in the mid 1980s and in India it is part of the pentavalent shot given to infants. A is wrong because the polio vaccine is either the killed virus of Salk or the weakened live virus of Sabin. B is wrong because no vaccine against AIDS has been licensed so far. D is wrong because the smallpox vaccine used the live vaccinia virus, and the disease was declared eradicated in 1980. Exam tip: hepatitis B, first recombinant vaccine, made in yeast from the surface antigen gene.

The correct answer is A, Mycoplasma. Mycoplasmas are the smallest living cells known, they lack a cell wall altogether, and because of that they can change shape and are not affected by antibiotics that act on the wall; they cause diseases in plants and animals and are placed in the kingdom Monera. B is wrong because Escherichia coli is a normal rod-shaped bacterium with a well-developed peptidoglycan wall and is much larger than a mycoplasma. C is wrong because yeast is a unicellular fungus with a chitin wall and a true nucleus, so it is both walled and eukaryotic. D is wrong because Chlorella is a green alga, a walled eukaryotic cell with chloroplasts, used as a food supplement and in studies of photosynthesis. Candidates should also note that a mycoplasma is often called the smallest known organism capable of independent life, which is why it is the standard answer to questions on the smallest living cell.

The correct answer is B, Papaver Somniferum. Opium is the dried latex of the opium poppy, whose botanical name is Papaver somniferum; the second word means sleep bringing. The milky latex is collected by making shallow cuts in the unripe capsule, and from it come the medicines morphine and codeine, used to control pain and cough. India grows the crop only under licence from the Narcotics Commissioner at Gwalior in Madhya Pradesh, and the licensed districts lie in Madhya Pradesh, Rajasthan and Uttar Pradesh, which is why state papers ask this question. Option A is wrong because Emblica officinalis is amla, the Indian gooseberry, rich in vitamin C. Option C is wrong because Rauvolfia serpentina is sarpagandha, the source of reserpine used for high blood pressure. Option D is wrong because Cinchona species yield quinine, the old treatment for malaria. Exam tip: opium Papaver somniferum, amla Emblica officinalis, quinine from Cinchona.

The correct answer is C, Apis dorsata, the rock bee, the largest of the Indian honey bees, which builds a single huge comb on cliffs and tall buildings and yields the most honey per colony, yet is fierce and cannot be kept in hives. Option A is wrong because Apis florea, the little bee, is the smallest and gives the least honey. Option B is wrong because Apis cerana indica, the Indian hive bee, is the species traditionally kept in Indian hives, so it is domesticated. Option D is wrong because Apis mellifera, the Italian or European bee, is the species most used in commercial apiaries for its gentleness and high yield in managed hives. Note the contrast the question rests on: highest yield in the wild against the best bee to manage.

The correct answer is B, Galileo Galilei. Galileo was the first to argue that, with air resistance removed, every body falls with the same acceleration regardless of its mass. He reached this by rolling balls down inclined planes and timing them, and the idea is linked in popular accounts with his experiment from the Leaning Tower of Pisa. This overturned the older belief of Aristotle that heavier bodies fall faster. The acceleration he described is g, about 9.8 metres per second squared near the earth. A is wrong because Einstein built on this in the general theory of relativity through the equivalence principle, long afterwards. C is wrong because Edison was an inventor of the electric lamp and phonograph and did no work on falling bodies. D is wrong because Newton, born the year Galileo died, later explained why this happens through his law of gravitation. Exam tip: remember the order - Galileo found that all bodies fall alike, Newton explained the cause.

The correct answer is B. Mosses and liverworts grow on damp soil, rocks and tree trunks, that is on land, but they have no vascular tissue and their male gametes must swim through a film of water to reach the female gamete, so reproduction fails without water; living on land and breeding in water is exactly the position of amphibians among animals. A is wrong because bryophytes are not aquatic plants; the truly aquatic members of the plant kingdom are the algae. C is wrong because tolerance of salt and fresh water describes certain fishes and some algae, not the bryophytes. D is wrong because a seasonal change of form is common to many plants and has nothing to do with the name amphibians of the plant kingdom.

The correct answer is C, Thallophyta. Litmus is a purple dye taken from lichens, and in the classification used in school science lichens are placed in Thallophyta, the group of simple plants whose body is an undifferentiated thallus with no true root, stem or leaf. Algae and fungi belong to the same group, and a lichen is in fact a partnership of an alga and a fungus living together. Litmus is a natural indicator: it stays purple in a neutral solution, turns red in acid and blue in base, and is used both as a solution and as litmus paper. Option A is wrong because gymnosperms are well developed plants with naked seeds, such as pine and cycas. Option B is wrong because pteridophytes, the ferns, are the first plants with vascular tissue. Option D is wrong because bryophytes such as moss and Marchantia are called the amphibians of the plant kingdom. Exam tip: litmus is red in acid, blue in base and purple when neutral.

The correct answer is B, unfertilised eggs. The queen can lay both fertilised and unfertilised eggs; the unfertilised ones develop into haploid males called drones, a form of parthenogenesis, while fertilised eggs give rise to diploid females. Option A is wrong because fertilised eggs become workers or queens, not drones. Option C is wrong because although a laying worker can sometimes produce drones in a queenless colony, that is an exception and not the normal origin of drones, so it cannot be stated for all cases. Option D is wrong because royal jelly fed throughout the larval period produces a queen, not a drone; caste among the females is decided by diet, while the drone's sex is decided by the egg being unfertilised. Drones do no work in the hive, gather no food and have no sting; after the nuptial flight they are driven out of the colony, so their number falls sharply in a lean season.

The correct answer is D, Ar and N2. An ordinary filament bulb is filled with a mixture of argon and nitrogen because both are chemically unreactive and will not burn the white-hot tungsten filament. The filament works at about 2,500 degrees Celsius, and in air it would oxidise within seconds. The inert filling also raises the pressure inside the glass, which slows the evaporation of tungsten atoms, so the filament lasts longer and the glass blackens less. Argon is preferred among the noble gases because it is the cheapest, making up nearly one per cent of air. A is wrong because hydrogen is highly inflammable and would be a danger inside a hot bulb. B is wrong for the same reason, as the hydrogen in it makes the mixture unsafe. C is wrong because the oxygen in it would oxidise and break the filament at once. Exam tip: tungsten filament, melting point about 3,400 degrees Celsius, in an argon-nitrogen filling.

The correct answer is B, an alga and a fungus. In a lichen the algal partner, called the phycobiont, photosynthesises and supplies food, while the fungal partner, the mycobiont, gives shelter and absorbs water and minerals; lichens grow on bare rock as pioneers and die in polluted air, so they serve as indicators of air pollution. A is wrong because an association of a fungus with a bacterium is not a lichen and has no such standard name. C is wrong because a fungus living with the root of a higher plant is a mycorrhiza, another famous symbiosis but a different one. D is wrong because the nitrogen-fixing partnership of an alga with a bacterium, as in a rice field, is not a lichen either.

The correct answer is D, Pinctada margaritifera. Pinctada margaritifera is the black lip pearl oyster, a bivalve mollusc of the warm shallow water of the Indo-Pacific, where it fastens itself to coral reefs by strong threads. The dark rim of its shell gives the species its name, and the dark nacre inside yields the grey to black pearls sold as Tahitian pearls. In Indian waters it occurs around the Andaman and Nicobar Islands and in the Gulf of Mannar, while the related Pinctada fucata is the oyster of the old pearl fishery of the Gulf of Mannar. Option A is wrong because Aplysia dactylomela is the spotted sea hare, a sea slug. Option B is wrong because Dentalium neohexagonum is a tusk shell, a burrowing scaphopod. Option C is wrong because the name in option C belongs to a chiton, the flat mollusc with eight plates that clings to rocky shores. Exam tip: Pinctada is the pearl oyster genus, margaritifera the black lip species.

The correct answer is A, Karl von Frisch, who decoded the dance language of bees: a round dance for a source near the hive and a waggle or tail-wagging dance for a distant one, in which the angle of the straight run shows the direction of the food relative to the sun. Options B and D are wrong as the answer to this question although Konrad Lorenz and Nikolaas Tinbergen shared the 1973 Nobel Prize in Physiology or Medicine with von Frisch for work on animal behaviour; Lorenz is remembered for imprinting in birds and Tinbergen for his experiments on instinct. Option C is wrong because Charles Darwin wrote on natural selection and did study comb building, but the dance language was not his discovery.

The correct answer is C, Arthropoda. Arthropoda is the largest phylum of the animal kingdom, holding more described species than all the others together, because it contains the insects along with the crustaceans, spiders, scorpions and centipedes; its members have a chitinous exoskeleton and jointed legs. A is wrong because Chordata, the phylum of animals with a notochord, contains the fishes, amphibians, reptiles, birds and mammals but is far smaller in number of species. B is wrong because Mollusca, with the snails, bivalves, squids and octopuses, is the second largest phylum. D is wrong because Annelida, the segmented worms such as the earthworm and the leech, is smaller still. A useful figure to carry into the hall is that more than two thirds of all described animal species are arthropods, most of them insects, which is why no other phylum can be the answer to this question.

The correct answer is A, Kerria lacca, earlier named Laccifer lacca, a tiny scale insect whose female settles on the twigs of a host tree, sucks its sap and secretes the resin we call lac. Option B is wrong because Bombyx mori is the mulberry silkworm and secretes silk from a modified salivary gland. Option C is wrong because Apis dorsata is the rock bee, which makes honey and beeswax. Option D is wrong because Antheraea proylei is the oak tasar silkworm of the Himalayan belt. A further point often asked is that it is the female lac insect, and not the male, that produces the resin of commerce, and that the scraped lac is refined into seedlac, button lac and shellac. The lac insect belongs to the order Hemiptera, the group of sap-sucking bugs, and the lac of commerce is the hardened secretion that covers the female's body on the twig.

The correct answer is B, genus. In binomial nomenclature the first word of the name is the generic name, the genus to which the organism belongs, and the second is the specific epithet; thus Panthera is the genus that also holds the lion as Panthera leo and the leopard as Panthera pardus, while tigris is the epithet of the tiger. A is wrong because the species is named by the second word, and in any case a species name is meaningful only along with its genus. C is wrong because the family of the cats is Felidae, a rank above the genus and never part of the two-word name. D is wrong because the class here is Mammalia, several ranks higher and also never written in the binomial name.