Test: Science and Technology - 3 - UPSC MCQ

• Statement 1 is correct: The cells having nuclear material without nuclear membrane are termed prokaryotic cells. The organisms with these kinds of cells are called prokaryotes. Examples are bacteria and blue green algae. The nucleus of the bacterial cell is not well-organised like the cells of multicellular organisms.

• Statement 2 is incorrect: Eukaryotes, can be unicellular or multicellular and include animals, plants, fungi and protists. The cells having well-organised nucleus with a nuclear membrane are designated as eukaryotic cells.

• Similarities between Prokaryotic and Eukaryotic cells – Although prokaryotic and eukaryotic cells have many differences, they share some common features, including the following:

  • DNA: Genetic coding that determines all the characteristics of living things.

  • Cell (or plasma) membrane: Outer layer that separates the cell from the surrounding environment and acts as a selective barrier for incoming and outgoing materials.

  • Cytoplasm: Jelly-like fluid within a cell that is composed primarily of water, salts and proteins.

  • Ribosomes: Organelles that make proteins.

• Statements 1 and 2 are correct: Hepatitis C and Chicken Pox are caused by viruses.

• Statement 3 is correct: Common cold is mostly caused by a number of different types of viruses. More than 200 different types of viruses are known to cause the common cold, with most common being the rhinovirus causing approximately 30%-40% of all adult colds. Other commonly implicated viruses include coronavirus (COVID-19), adenovirus, respiratory syncytial virus, and parainfluenza virus.

• Statement 4 is incorrect: Malaria is caused by Protozoa and not by virus.

Noise pollution refers to the presence of excessive noise in the surroundings. Noise pollution may cause many health-related problems such as:

• Hypertension (high blood pressure). Hence, statement 1 is correct.

• Hearing disability - A person who is exposed to a loud sound continuously may get temporary or even permanent impairment of hearing. Hence, statement 2 is correct.

• Sleeping disorders. Hence statement 3 is correct.

• Anxiety. Hence, statement 4 is correct.

• Statement 1 is correct: Plants do not grow well when the soil is either too acidic or too basic.

  • If the soil is basic, organic matter (compost) is added to it. Organic matter releases acids which neutralises the basic nature of the soil.

  • Excessive use of chemical fertilisers makes the soil acidic. When the soil is too acidic, it is treated with bases like quick lime (calcium oxide) or slaked lime (calcium hydroxide).

• Statement 2 is correct: Indigestion is caused by release of too much of acid by our stomach. Milk of Magnesia, which contains magnesium hydroxide, helps in relieving indigestion by neutralising the effect of excessive acid.

• Statement 1 is correct: Transgenic animals are those animals that have had their DNA manipulated to possess and express an extra (foreign) gene. Transgenic rats, rabbits, pigs, sheep, cows and fish have been produced, although over 95 per cent of all existing transgenic animals are mice.

• Statement 2 is incorrect: The trade of Transgenic animals across international borders is not referred to as Biopiracy. Biopiracy is the term used to refer to the use of bio-resources by multinational companies and other organisations without proper authorisation from the countries and people concerned without compensatory payment. For instance, some companies in the United States tried to patent a variety of Basmati rice, whose knowledge has been traditionally present in the rice communities of India since historical times.

• Statement 3 is correct: Transgenic animals can be used for testing for vaccine safety as well as chemical safety.

  • Vaccine safety: Transgenic mice are being developed for use in testing the safety of vaccines before they are used on humans. Transgenic mice are being used to test the safety of the polio vaccine. If successful and found to be reliable, they could replace the use of monkeys to test the safety of batches of the vaccine.

  • Chemical safety testing: This is known as toxicity/safety testing. The procedure is the same as that used for testing toxicity of drugs. Transgenic animals are made that carry genes which make them more sensitive to toxic substances than non-transgenic animals. They are then exposed to the toxic substances and the effects studied. Toxicity testing in such animals will allow us to obtain results in less time.

• Other benefits of the Transgenic animals:

  • Normal physiology and development: Transgenic animals can be specifically designed to allow the study of how genes are regulated, and how they affect the normal functions of the body and its development, e.g., study of complex factors involved in growth such as insulin-like growth factor. By introducing genes from other species that alter the formation of this factor and studying the biological effects that result, information is obtained about the biological role of the factor in the body.

  • Study of disease: Many transgenic animals are designed to increase our understanding of how genes contribute to the development of disease. These are specially made to serve as models for human diseases so that investigation of new treatments for diseases is made possible. Today transgenic models exist for many human diseases such as cancer, cystic fibrosis, rheumatoid arthritis and Alzheimer’s.

  • Biological products: Medicines required to treat certain human diseases can contain biological products, but such products are often expensive to make. Transgenic animals that produce useful biological products can be created by the introduction of the portion of DNA (or genes) which codes for a particular product such as human protein (α-1-antitrypsin) used to treat emphysema. Similar attempts are being made for treatment of phenylketonuria (PKU) and cystic fibrosis. In 1997, the first transgenic cow, Rosie, produced human protein-enriched milk (2.4 grams per litre). The milk contained the human alpha-lactalbumin and was nutritionally a more balanced product for human babies than natural cow-milk.

- Statement 1: Correct. The Old Pension Scheme (OPS) provided a pension calculated as 50% of the last drawn salary of government employees. It was a defined benefit scheme where the pension amount was predetermined based on the employee's last salary.

- Statement 2: Incorrect. The OPS was specifically for government employees, not all citizens or NRIs. It was not open to the entire public.

Thus, the correct answer is C: 1 only.

• Statement 1 is correct: E-cigarettes are battery-powered devices that heat a solution of nicotine and different flavours to create aerosol, which is then inhaled. These devices belong to a category of vapour-based nicotine products called ENDS.

• Statement 2 is correct: The Parliament passed the Prohibition of Electronic Cigarettes (Production, Manufacture, Import, Export, Transport, Sale, Distribution, Storage, and Advertisement) Bill, 2019, which makes production, manufacture, import, export, transport, sale, distribution or advertisements of e-cigarettes a cognizable offence.

• Harmful effects of the use of e-cigarettes: In May 2019, the Indian Council of Medical Research (ICMR) released a white paper stating that the uses of ENDS, or e-cigarettes. It stated the “documented adverse effects” which include DNA damage; carcinogenesis (initiation of cancer formation); cellular, molecular and immunological toxicity; respiratory, cardiovascular and neurological disorders. It also impacts foetal development and pregnancy. Accordingly ICMR recommended a “complete prohibition” of these products.

• Statement 1 is correct: Space-based internet can provide low cost internet to everywhere on Earth, even to remote areas, or places with difficult terrain, where it is difficult to set up cables or mobile towers. Signals from satellites in space can overcome this obstacle easily.

• Statement 2 is correct: It can increase light pollution on Earth as light reflected from these man-made satellites can interfere with and be mistaken for light coming from other heavenly bodies.

• Statement 3 is correct: Satellites used in space based internet are placed in the low Earth orbit (LEO), around 200-2000 km from the Earth’s surface. Low and medium earth orbits lie at considerably lower altitudes than the geostationary orbit. This reduces the latency or the time lag of the internet signals.

• The key difference in the newly envisaged space-based internet services and the older ones:

  • While most of the existing systems use satellites in geostationary orbit, the new space-based internet services will be provided from constellations of satellites placed in low-earth or medium-earth orbits.

• Advantage: Low and medium earth orbits lie at considerably lower altitudes than the geostationary orbit. This reduces the latency or the time lag of the internet signals. Latency refers to the time lag between a user seeking data, and the server sending that data. While the older systems have a time latency of about 600 ms, the new systems will have latency of about 20-30 ms, which is close to what is provided by the traditional internet systems at present on the earth.

• Disadvantages:

  • More number of satellites needed: Since, lower the altitude of satellite, lower is the area on Earth it can cover, the number of satellites needed in the low and medium earth orbits are higher. Another reason contributing to increase in the number of satellites needed for the new space-based internet systems is that the time for which a particular satellite will remain at a location is much less, thus making it necessary that there are a greater number of satellites in the orbits to provide uninterrupted internet services.

  • Problem of Space debris: Such higher number of satellites in Earth’s orbit can greatly contribute of space debris problem.

  • Light Pollution: Light pollution is excessive, misdirected, or obtrusive artificial (usually outdoor) light. Light reflected from these satellites can be confused for light coming from the heavenly bodies by the astronomers. An American company, Space-x has been aiming to put close to 42,000 satellites in low-earth orbit as part of its Starlink project. The Starlink project aims to provide global space internet by 2021. Other companies also aim to provide space-based internet services.

• Statement 1 is correct: Typhoid fever is a systemic infection caused by Salmonella Typhi, a bacterium, usually through ingestion of contaminated food or water. Typhoid fever is an acute illness characterized by prolonged fever, headache, nausea, loss of appetite, and constipation or sometimes diarrhoea.

• Statement 2 is correct: Typhoid can be prevented by using vaccination. There are three typhoid vaccines that are currently recommended by World Health Organization (WHO) for control of endemic and epidemic typhoid fever:

  • an injectable typhoid conjugate vaccine (TCV- licensed for children from 6 months of age and adults up to 45 years of age;

  • an injectable unconjugated polysaccharide vaccine for persons aged two years and above; and

  • an oral live attenuated Ty21a vaccine in capsule formulation for those over six years of age.

• About TCV:

  • Among the available typhoid vaccines, TCV is preferred at all ages for routine programmatic use in view of its improved immunological properties, suitability for use in younger children and expected longer duration of protection. Typbar TCV, short for typhoid conjugate vaccine was recently approved by the WHO against typhoid fever. It is the only vaccine deemed safe enough for use in infants starting at 6 months of age.

  • This vaccine is the first conjugate vaccine — a vaccine in which a weak antigen (of the typhoid germ) is attached to a strong antigen (from the tetanus germ) to elicit antibody responses — against a bacterial disease (typhoid) that “affects up to 20 million people annually”.

• Pair 1 is correctly matched: Coke is used in the manufacture of steel. Coke is a tough, porous and black substance. It is an almost pure form of carbon. It is also used in the extraction of many metals.

• Pair 2 is correctly matched: Earlier, coal tar was used for metalling the roads, however these days, bitumen, a petroleum product, is used for road surfacing.

• Pair 3 is correctly matched: PET (polyethylene terephthalate) is a polyester that is used for making bottles, utensils, films, wires and many other useful products.

• What are Polyesters?

  • Polyester is a synthetic fibre. Fabric made from this fibre does not get wrinkled easily. It remains crisp and is easy to wash. So, it is quite suitable for making dress material. Terylene is a popular polyester. It can be drawn into very fine fibres that can be woven like any other yarn. PET is also a popular polyester. Polyester is made up of the repeating units of a chemical called an ester. Esters are the chemicals which give fruits their smell. Fabrics sold by names like polycot, polywool, terrycot, etc. are made by mixing two types of fibres. Polycot is a mixture of polyester and cotton. Polywool is a mixture of polyester and wool.

• Statement 1 is correct: The microorganisms like aerobic and anaerobic bacteria are used in sewage treatment plants. They breakdown the organic matter, thereby reducing the organic content of the sewage along with the Biological Oxygen Demand of the treated sewage water. The treated sewage water then becomes fit to be released to the natural water bodies. Cleaning of environment - In nature, microorganisms decompose dead organic waste of plants and animals converting them into simple substances. These substances are again used by other plants and animals. Thus, microorganisms can be used to degrade the harmful and smelly substances and thereby clean up the environment.

• Statement 2 is correct: Many medicines are sourced from microorganisms such as bacteria and fungi.

  • Such medicines called, antibiotics, kill or stop the growth of the disease-causing microorganisms.

  • These days a number of antibiotics are being produced from bacteria and fungi. Streptomycin, tetracycline and erythromycin are some of the commonly known antibiotics which are made from fungi and bacteria.

  • The antibiotics are manufactured by growing specific microorganisms and are used to cure a variety of diseases.

• Statement 3 is correct: Bacteria can be used for increasing the fertility of soils as some bacteria are able to fix nitrogen from the atmosphere to enrich soil with nitrogen and increase its fertility. These microbes are commonly called biological nitrogen fixers.

• Statement 4 is correct: Vaccination development is one of the most important uses of bacteria. These days vaccines are made on a large scale from microorganisms to protect humans and other animals from several diseases.

  • Several diseases, including cholera, tuberculosis, smallpox and hepatitis can be prevented by vaccination. A vaccine works by training the immune system to recognize and combat pathogens, either viruses or bacteria.

  • To do this, certain molecules from the pathogen must be introduced into the body to trigger an immune response. These molecules are called antigens, and they are present on all viruses and bacteria.

• Other benefits of micro-organisms:

  • Commercial production of alcohol and wines use Yeast. Yeasts are the main fermenter and alcohol producer in the production of wine, beer and other alcohol drinks. The main yeast species used is Saccharomyces cerevisiae. It ferments the sugars, coming from different sources, e.g., grapes for wine, barley for beer, to alcohol and carbon dioxide.

  • Bacteria and yeast are helpful for fermentation of rice idlis and dosa batter.

  • Formation of curd: Curd contains several microorganisms. Of these, the bacterium, Lactobacillus promotes the formation of curd. It multiplies in milk and converts it into curd. Bacteria are also involved in the making of cheese, pickles and many other food items.

• Statement 1 is correct: Manure provides humus to soil while fertilizer does not provide any humus to soil.

• Statement 2 is correct: While fertilizers are man-made inorganic salts, manure is an organic substance.

• Statement 3 is incorrect: Fertilizers are very rich in plant nutrients while manure is relatively less rich.

Only the first statement is correct. The changes that occur at adolescence, such as physical growth, development of secondary sexual characteristics, and changes in mood and behavior, are largely controlled by hormones, including testosterone, estrogen, and progesterone. However, the second statement is incorrect. While the pituitary gland does secrete several important hormones, not all hormones in the body are secreted by the pituitary gland. Other organs and glands in the body also secrete hormones, including the adrenal glands, thyroid gland, pancreas, and ovaries/testes, among others.

• Statement 1 is correct: Cell membrane is present in both the plant and animal cells. The cell membrane, also called as the plasma membrane, encloses the cytoplasm and nucleus of the cell. It is porous and allows the movement of substances or materials both inward and outward. The cell membrane gives shape to the cell.

• Statement 2 is incorrect: Vacuoles are present both in plant and animal cells, though they are bigger in plant cells than in animal cells. A plant cell contains a large, singular vacuole that is used for storage and maintaining the shape of the cell. In contrast, animal cells have many, smaller vacuoles. The vacuoles perform functions such as storage, ingestion, digestion, excretion, and expulsion of excess water.

• Statement 3 is correct: Cell wall is present only in the plant cells, it is not found in animal cells. In plants, in addition to the cell membrane, there is an outer thick layer in cells called cell wall. This additional layer surrounding the cell membrane is required by plants for protection. Plant cells need protection against variations in temperature, high wind speed, atmospheric moisture etc. as they are exposed to these variations because they cannot move.

Adaptations are found in the natural world among animals, which help them in surviving in their habitat.

Some of the adaptations found in the animals are:

• Polar bears have long curved and sharp claws which help them in walking on ice and to catch and hold prey. Presence of white fur reduces their visibility in the snowy background which helps them in catching prey. It also protects them from the extreme cold. Hence, statement 1 is correct.

• Elephants have large ears which help the elephant to keep cool in the hot and humid climate of the rainforest. They also help them to hear even very soft sounds. Hence, statement 2 is correct.

• To prevent themselves freezing to death, penguins huddle together in tightly-packed groups to conserve heat and shelter themselves from the intense winds of the Antarctica. Penguins on the outskirts regularly muscle their way inside the huddle. Hence, statement 3 is correct.

• As there is competition for food in rainforests, some animals are adapted to get food which is not easily reachable. A striking example is that of the bird Toucan, which possesses a long, large beak. This helps a toucan to reach the fruits on branches which are otherwise too weak to support its weight. Hence, statement 4 is correct.

Other adaptations found in the animals:

Polar bears:

• They also have a layer of fat under their skin. They are so well-insulated that they have to move slowly and rest often to avoid getting overheated. Physical activities on warm days necessitate cooling. So, the polar bear goes for swimming.

• They have a strong sense of smell so that they can catch their prey for food.

Penguins:

• They also have a thick skin and a lot of fat to protect them from cold. Like polar bears, penguins are also good swimmers. Their bodies are streamlined and their feet have webs, making them good swimmers.

• Pair 1 is correctly matched: Mushroom is a Saprotroph, which means it takes its nutrition from dead and decaying organic matter. It falls under the category of fungus.

• Pair 2 is incorrectly matched: Insectivorous plants are partial heterotrophs whereas other plants are autotrophs. Insectivores plants are not the examples of parasitic nutrition in plants. Parasitic plants cannot photosynthesise and hence, are depended on other living organisms for their nutrition. Insectivorous plants can photosynthesise but lack only in nitrogen. So,to fulfil this requirement, they consume the digestive nutrients in the insects.

• Pair 3 is correctly matched: Plants as well as Algae are called autotrophs. Algae contains chlorophyll can also prepare its own food by photosynthesis. The mode of nutrition in which organisms make food themselves from simple substances is called autotrophic nutrition. Most of the plants are autotrophs. All animals are categorised as heterotrophs since they depend on plants and other animals for food. Only a few plants are parasitic or saprotrophic or partial heterotrophic. Such plants derive nutrition from other organisms. Insectivorous plants are partial heterotrophs.

• Saprotrophic nutrition: Saprotrophs are the organisms that obtain their nutrition from dead and decaying organic matter. Saprotrophs secrete digestive juices onto dead and decaying matter to dissolve it and then absorb nutrients from it. Fungi are the example of organisms that have saprotrophic nutrition.

• Insectivorous plants: Insectivorous plants are such kind of plants which can trap insects and digest them. Such plants may be green or of some other colour. They have a pitcher-like or jug-like structure which is the modified part of leaf. The apex of the leaf forms a lid which can open and close the mouth of the pitcher. Inside the pitcher there are hair which are directed downwards. When an insect lands in the pitcher, the lid closes and the trapped insect gets entangled into the hair. The lid closes and the insect is trapped. The insect is digested by the digestive juices secreted in the pitcher and its nutrients are absorbed.

• It must be noted that insectivorous plants can photosynthesis their food as well, however, since they are found in nutrient-deficient soils, they rely on trapping insects for the supply of nutrients like nitrogen.

• Parasitic nutrition in plants: Parasitic plants such as the yellow wiry branched structure twining around the stem and branches of a tree called Cuscuta (Amarbel) does not have chlorophyll. It takes readymade food from the plant on which it is climbing. The plant on which it climbs is called the host. Since it deprives the host of valuable nutrients, Cuscuta is called the parasite.

• Statement 1 is correct: Bile is a complex fluid containing water, electrolytes and organic molecules like bile acids, cholesterol, phospholipids and bilirubin that flows through the biliary tract into the small intestine. Bile contains bile acids, which are critical for digestion and absorption of fats and fat-soluble vitamins in the small intestine.

• Statement 2 is incorrect: Bile is secreted by the liver of most vertebrates, that aids in the digestion of lipids in the small intestine. In humans, it is secreted by the liver, and stored and concentrated in the gallbladder.

• Statement 3 is correct: The food coming from the stomach is acidic and has to be made alkaline for the pancreatic enzyme to act. Bile accomplishes this. Bile salts break- down larger globules of fats into smaller globules increasing the efficiency of enzyme action. The liver is an organ only found in vertebrates which detoxifies various metabolites, synthesizes proteins and produces biochemicals necessary for digestion. In humans, it is located in the right upper quadrant of the abdomen, below the diaphragm. Its other roles in metabolism include the regulation of glycogen storage, decomposition of red blood cells and the production of hormones. In vertebrates, the gallbladder is a small hollow organ where bile is stored and concentrated before it is released into the small intestine. In humans, the pear-shaped gallbladder lies beneath the liver, although the structure and position of the gallbladder can vary significantly among animal species. It receives and stores bile produced by the liver, via the common hepatic duct and releases it via the common bile duct into the duodenum, where the bile helps in the digestion of fats.

Biotechnology can be used to introduce genetic modification in the plants/ crops to the effect that:

• The nutritional value of food can be increased, e.g., golden rice, i.e., Vitamin ‘A’ enriched rice. Hence, statement 1 is correct.

• The efficiency of mineral usage by plants can be increased (this prevents early exhaustion of fertility of soil). Hence, statement 2 is correct.

• The post-harvest losses can be reduced. Hence, statement 3 is correct.

• They become more tolerant to abiotic stresses (cold, drought, salt, heat). Hence, statement 4 is correct.

• Their reliance on chemical pesticides (pest-resistant crops) gets reduced.

• Statement 1 is correct: Polymerase Chain Reaction (PCR) can be used for early diagnosis of presence of an infection as it works by amplifying the small amounts of DNA of the pathogen. Very low concentration of a bacteria or virus (at a time when the symptoms of the disease are not yet visible) can be detected by amplification of their nucleic acid by PCR.

  • PCR is now routinely used to detect HIV in suspected AIDS patients.

  • It is being used to detect mutations in genes in suspected cancer patients too.

  • It is a powerful technique to identify many other genetic disorders.

• Statement 2 is correct: Enzyme Linked Immuno-sorbent Assay (ELISA) test is based on the principle of antigen-antibody interaction. Infection by pathogen can be detected by the presence of antigens (proteins, glycoproteins, etc.) or by detecting the antibodies synthesised against the pathogen. For effective treatment of a disease, early diagnosis and understanding its pathophysiology is very important. Using conventional methods of diagnosis (serum and urine analysis, etc.) early detection is not possible.

  • Presence of a pathogen (bacteria, viruses, etc.) is normally suspected only when the pathogen has produced a disease symptom. By this time the concentration of pathogen is already very high in the body.

  • Recombinant DNA technology, Polymerase Chain Reaction (PCR) and Enzyme Linked Immuno-sorbent Assay (ELISA) are some of the techniques that serve the purpose of early diagnosis.

• Freezing of water to ice is a reversible change. Conversion of milk to curd is an irreversible change. Melting of chocolate is a reversible change. Conversion of raw eggs to boiled eggs is an irreversible change.

• There are two types of changes:

  • Reversible changes: Where a change is made physically and can be undone or reversed.

  • Irreversible changes: Where the change is made chemically and can't be reversed into its original states.

• Statement 1 is incorrect: Methanogens are microbes that produce methane by growing anaerobically ( not aerobically) on cellulosic material. In addition to methane, some amounts of Carbon dioxide and Hydrogen gas are also produced. One such microbe is Methanobacterium. Methanogens belong to the domain archaea, which is distinct from bacteria. Both bacteria and Archaea are prokaryotic organisms.

• Statement 2 is correct: Biogas is a mixture of gases predominantly containing methane. It is produced by the microbial activity and may be used as fuel.

• Statement 3 is correct: Methonogens like Methanobacterium are present in the rumen of (a part of stomach) of cattle. A lot of cellulosic material present in the food of cattle is also present in the rumen. In rumen, these microbes help in the breakdown of cellulose and play an important role in the nutrition of cattle. Thus, the excreta of cattle (dung) is rich in these microbes. Dung can be used for generation of biogas, commonly called gobar gas. These Methanogens are also found in the anaerobic sludge during sewage treatment.

• Statement 1 is correct: Fungi are known to form symbiotic associations with plants (mycorrhiza) where the fungi absorbs phosphorus from soil and passes it to the plant. Plants having such associations show other benefits also, such as resistance to root-borne pathogens, tolerance to salinity and drought, and an overall increase in plant growth and development.

• Statement 2 is correct: In addition to nitrogen-fixing bacteria like Rhizobium that live in the plant roots, there are some free-living bacteria in the soil like Azospirillum and Azotobacter that fix atmospheric nitrogen in the soil. These bacteria fix atmospheric nitrogen into organic forms, which is used by the plant as nutrient.

  • Biofertilisers are organisms that enrich the nutrient quality of the soil. The main sources of biofertilisers are bacteria, fungi and cyanobacteria.

  • Cyanobacteria are autotrophic microbes widely distributed in aquatic and terrestrial environments many of which can fix atmospheric nitrogen, e.g. Anabaena, Nostoc, Oscillatoria, etc. In paddy fields, cyanobacteria serve as an important biofertiliser. Blue green algae also add organic matter to the soil and increase its fertility.

  • Currently, in our country, a number of biofertilisers are available commercially in the market and farmers use these regularly in their fields to replenish soil nutrients and to reduce dependence on chemical fertilisers.

• Unique Identification Authority of India (UIDAI) The UIDAI is a statutory authority established on 12th July 2016 by the Government of India under the jurisdiction of the Ministry of Electronics and Information Technology, following the provisions of the Aadhaar Act 2016. Hence, statement 2 is not correct.

• The UIDAI was initially set up by the Government of India in January 2009, as an attached office under the aegis of the Planning Commission. Hence, statement 1 is not correct.

• The UIDAI is mandated to assign a 12-digit unique identification (UID) number (Aadhaar) to all the residents of India. The overall Aadhaar saturation level in the country has crossed 93%, and in the case of the adult population it is nearly 100%.

Plants rely on their roots for uptake of water and minerals like nitrogen, phosphorus, potassium, sulphur, etc. Water and minerals are transported to the leaves by the vessels which run like pipes throughout the root, the stem, the branches and the leaves. They form a continuous path or passage for the nutrients to reach the leaf. They are called vessels. Plants also take carbon dioxide from the atmosphere through the stomata present in their leaves.

• Plants synthesis carbohydrates and other components of food such as proteins and fats. Carbohydrates are made of carbon, hydrogen and oxygen through the process of photosynthesis where carbon dioxide reacts with water in the presence of energy absorbed from sunlight by the plants. Carbon dioxide is taken by plants in the gaseous form from the atmosphere, while water is taken up by the roots from the soil.

• Carbohydrates are made of carbon, hydrogen and oxygen. These are used to synthesise other components of food such as proteins and fats. But proteins are nitrogenous substances which contain nitrogen. Though nitrogen is present in abundance in gaseous form in the air, plants cannot absorb nitrogen in this form.

• Soil has certain bacteria that convert gaseous nitrogen into a usable form and release it into the soil. These are absorbed by the plants along with water. Also, farmers add fertilisers rich in nitrogen to the soil. In this way the plants fulfil their requirements of nitrogen along with the other constituents. Plants can then synthesise proteins and vitamins.

• "Autosomal" genetic disorder means that the gene in question is located on one of the numbered, or non-sex, chromosomes.

• Statement 1 is correct: Sickle cell Anaemia is an autosomal genetic disorder. Sickle-cell anaemia - This is an autosome linked recessive trait that can be transmitted from parents to the offspring when both the partners are carrier for the gene (or heterozygous).

• Statement 2 is incorrect: Colour blindness is sex-linked genetic disorder. Colour blindness - It is a sex-linked recessive disorder due to defect in either red or green cone of eye resulting in failure to discriminate between red and green colour. This defect is due to mutation in certain genes present in the X chromosome. It occurs in about 8 per cent of males and only about 0.4 per cent of females.

• Statement 3 is correct: Thalassemia is an autosomal genetic disorder. Thalassemia - This is an autosome-linked recessive blood disease transmitted from parents to the offspring when both the partners are unaffected carrier for the gene (or heterozygous).

• Statement 4 is incorrect: Haemophilia is sex-linked genetic disorder. Haemophilia - It is a sex-linked recessive disease, which shows its transmission from unaffected carrier female to some of the male progeny. In this disease, a single protein that is a part of the cascade of proteins involved in the clotting of blood is affected. Due to this, in an affected individual a simple cut will result in non-stop bleeding. The heterozygous female (carrier) for haemophilia may transmit the disease to sons. The possibility of a female becoming a haemophilic is extremely rare because mother of such a female has to be at least carrier and the father should be haemophilic (unviable in the later stage of life).

• Statement 1 is correct: Deoxyribonucleic acid (DNA) and ribonucleic acid (RNA) are the two types of nucleic acids found in living organisms.

• Statement 2 is correct: DNA acts as the genetic material in most of the organisms. RNA acts as a genetic material in some viruses (for example, Tobacco Mosaic viruses, etc.).

• Statement 3 is incorrect: Both DNA and RNA are able to mutate. RNA is unstable and mutate at a faster rate than DNA. Consequently, viruses having RNA genome and having shorter life span mutate and evolve faster.

• Chronologically, the following organisms evolved in the sequence given below:

1) Corals

2) Fishes

3) Birds

4) Flowering plants

• Evolution of life on Earth:

  • Unicellular and multicellular organisms

  • Age of Marine Invertebrates (early shelled organisms, Corals, first land plants, etc.)

  • Fishes (First forests, first amphibians, etc.)

  • Age of Amphibians (First reptiles, sharks, coal forming swamps, etc.)

  • Age of Reptiles (Dinosaurs abundant, early flowering plants, placental mammals, etc.)

  • Age of Mammals (spread of grassy ecosystems, modern humans, extinction of large mammals and birds during Ice age glaciations, glacial outburst floods, etc.)

• Central Pollution Control Board (CPCB): CPCB is a statutory organisation which was constituted in September, 1974 under the Water (Prevention and Control of Pollution) Act, 1974. Hence, statement 1 is not correct. It was also entrusted with the powers and functions under the Air (Prevention and Control of Pollution) Act, 1981. It serves as a field formation and also provides technical services to the Ministry of Environment, Forest and Climate Change of the provisions of the Environment (Protection) Act, 1986.

• Principal Functions of the CPCB: To promote cleanliness of streams and wells in different areas of the States by prevention, control and abatement of water pollution. Hence, statement 2 is correct. To improve the quality of air and to prevent, control or abate air pollution in the country.

• State Pollution Control Board (SPCB): They supplement the CPCB as they are a statutory organization entrusted to implement Environmental Laws and rules within the jurisdiction of a state.

• Pollution control committees (PCC): They perform similar functions to SPCB. The difference between the two is that PCC belongs to Union territories.

• Statement 1 is correct: Bleaching powder is used as a disinfectant and germicide. It liberates Chlorine on exposure to the atmosphere which destroys the germs.

• Statement 2 is incorrect: Bleaching powder is chemically calcium oxychloride (CaOCl2). Bleaching powder is manufactured using Backmann’s plant. Slaked lime and Chlorine are used in this process to produce bleaching Powder. Hence, it is also known as chlorinated lime. Baking soda is the common name of sodium bicarbonate. The chemical formula of baking soda is NaHCO3.

• Statement 3 is incorrect: Bleaching powder is little acidic and also produces oxygen when it is added. Thus, it acts as an oxidizing (not reducing) and a bleaching agent in many chemical industries.