Test: Science and Technology -1 - UPSC MCQ

‘Diazotrophs’ are bacteria and archaea (single celled organisms) that fix atmospheric nitrogen gas into a more usable form such as ‘ammonia’. A diazotroph is a microorganism that is able to grow without external sources of fixed nitrogen. Diazotrophs can be divided into two types: Free living diazotrophs - Cyanobacteria - generate oxygen as a by-product of photosynthesis, yet some are able to fix nitrogen as well. Eg. - Anabaena cylindrica andNostoc commune. Marine cyanobacteria, such as Trichodesmium and Cyanothece, are major contributors to oceanic nitrogen fixation. Anaerobes - Example - Clostridium. Other examples include Sulphate-reducing bacteria found in ocean sediments (e.g. Desulfovibrio), and some Archean methanogens, like Methanococcus, fix nitrogen in muds, animal intestines and anoxic soils. Symbiotic diazotrophs - Rhizobia—these are the species that associate with legumes, Frankias—much less is known about these 'actinorhizal' nitrogen fixers. The bacteria also infect the roots leading to the formation of nodules. Association with animals - Shipworms may be the only species that derive significant benefit from their gut symbionts. In terms of generating nitrogen available to all organisms, the symbiotic associations greatly exceed the free-living species with the exception of cyanobacteria.

Both statements 1 and 2 are correct: Viruses are microscopic organisms. They reproduce only inside the cells of the host organism, which may be a bacterium, a plant or an animal. While not inside an infected cell or in the process of infecting a cell, viruses exist in the form of independent particles, or ‘virions’, consisting of:

(i) the genetic material, long molecules of DNA or RNA;

(ii) a protein coat, which surrounds and protects the genetic material.

(iii) an outside envelope of lipids. KB) In evolution, viruses are an important means of horizontal gene transfer, which increases genetic diversity in a way analogous to sexual reproduction.

Viruses are considered by some to be a life form, because they carry genetic material, reproduce, and evolve through natural selection, but lack key characteristics (such as cell structure) that are generally considered necessary to count as life. Because they possess some but not all such qualities, viruses have been described as "organisms at the edge of life", and as replicators.

Manure is an organic material that is used to fertilize land, usually consisting of the feces and urine of domestic livestock, with or without accompanying litter such as straw, hay, or bedding. Farm animals void most of the nitrogen, phosphorus, and potassium that is present in the food they eat, and this constitutes an enormous fertility resource. In some countries, human excrement is also used. Livestock manure is less rich in nitrogen, phosphorus, and potash than synthetic fertilizers and hence must be applied in much greater quantities than the latter.

Advantages of Manure: The organic manure is considered better than fertilisers. This is because:

● It enhances the water holding capacity of the soil.

● It makes the soil porous due to which exchange of gases becomes easy.

● It increases the number of friendly microbes.

● It improves the texture of the soil.

Option (d) is the incorrect statement. Synthetic fertilizers provide specific nutrients to plants in a specified quantity, manure on the other hand provides all nutrients in varying proportions.

Option (b) is the correct answer.

Microbes are also used for commercial and industrial production of certain chemicals like organic acids, alcohols and enzymes.

Examples of acid producers are

Pair 1 is incorrectly matched. Aspergillus niger (a fungus) of citric acid, Acetobacter aceti (a bacterium) of acetic acid;

Pair 3 is incorrectly matched. Clostridium butylicum (a bacterium) of butyric acid and

Pair 4 is incorrectly matched. Lactobacillus (a bacterium) of lactic acid,

Pair 2 is correctly matched.

Yeast (Saccharomyces cerevisiae) is used for commercial production of ethanol.

Pasteurization is a process in which water and certain packaged and non-packaged foods (such as milk and fruit juice) are treated with mild heat, usually to less than 100 °C (212 °F), to eliminate pathogens and extend shelf life. The process is intended to destroy or deactivate organisms and enzymes that contribute to spoilage or risk of disease.

Statement 1 is correct. Milk is heated to about 700C for 15 to 30 seconds and then suddenly chilled and stored. By doing so, it prevents the growth of microbes.

Statement 2 is correct. Pasteurised milk can be consumed without boiling as it is free from harmful microbes. KB) The process was named after the French scientist Louis Pasteur, whose research in the 1880s demonstrated that thermal processing would inactivate unwanted microorganisms in wine.

Spoilage enzymes are also inactivated during pasteurization. Today, pasteurization is used widely in the dairy industry and other food processing industries to achieve food preservation and food safety.

Statement 1 is correct.

● Nitrogen is a vital macronutrient for most plants.

● Nitrogen is an inert gas which is necessary for life.

● It is the most abundant element in the atmosphere.

● A little over 78% of dry air on Earth is nitrogen.

● Atmospheric nitrogen, or dinitrogen, is unreactive and cannot be utilized by plants directly. Statement 2 is correct.

● Nitrogen is being changed into forms that are harmful, and the natural nitrogen cycle is being disturbed.

● Nitrogen compounds running off from farmland have led to water pollution problems around the world, while nitrogen emissions from industry, agriculture and vehicles make a big contribution to air pollution.

Statement 3 is also correct.

● Nitrogen can be a pollutant when it escapes into the environment and react with other organic compounds.

● It is either released into the atmosphere, gets dissolved in water sources such as rivers, lakes or groundwater, or remains in the soil. It can even be a factor in the greenhouse effect.

Option (c) is the correct answer.

Pair 1 is correctly matched. Lichens are organisms which is a symbiotic relationship between two separate organisms, which is an algae, and a fungus. The fungus provides shelter, water and minerals to the algae and, in return, the algae prepares and provides food to the fungus.

Pair 2 is incorrectly matched. Cuscuta (Amarbel) is a plant that does not have chlorophyll. It takes readymade food from the plant on which it climbs. The plant on which it climbs is called the host. Since it deprives the host of valuable nutrients, Cuscuta is called a parasite.

Pair 4 is not correctly matched. Rhizobium is a bacterium that can take atmospheric nitrogen and convert it into a usable form. But Rhizobium cannot make its own food. So it often lives in the roots of gram, peas, moong, beans and other legumes and provides them with nitrogen. In return, the plants provide food and shelter to the bacteria. They, thus, it has a symbiotic relationship with plants and not animals.

● It is a 2.7-meter infrared telescope sitting inside a Boeing 747SP aeroplane, flying at an altitude of 38,000-45,000 feet above the surface.

● It is globally unique and, with the start of regular operations in 2014.

○ It has been successfully used for scientific research during a total of approximately 800 flights.

● It was designed to observe cosmic objects in far-infrared wavelengths.

○ This allows researchers to watch star formation by looking through huge, cold clouds of gas

○ The project has generated 309 scientific studies.

○ In 2020, SOFIA discovered water molecules (H2O) on the sun-facing side of the Moon.

○ In 2019, SOFIA also discovered helium hydride — the first molecule formed in the Universe almost 14 billion years ago.

○ SOFIA also identified atmospheric circulation patterns in Jupiter.

○ It also mapped the magnetic field within G47, one of the Milky Way’s spiral arms.

Statement 1 is correct. Our mouth has the salivary glands which secrete saliva. Saliva contains the enzyme amylase, also called ptyalin, which is capable of breaking down starch into simpler sugars.

Statement 2 is correct. The inner lining of the stomach secretes mucus, hydrochloric acid and digestive juices. The mucous protects the lining of the stomach. The acid kills many bacteria that enters along with the food and makes the medium in the stomach acidic and helps the digestive juices to act. The digestive juices break down the proteins into simpler substances. Digestive juices are also known as ‘gastric juices’. These include ‘pepsin’ and ‘renin’. Pepsin converts proteins into simpler, more easily absorbed substances. Renin aids in the digestion of milk proteins.

Bio-piracy 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.

Statement 1 is correct: A pseudopod or pseudopodia is a temporary arm-like projection of a eukaryotic cell membrane. Pseudopods are used for motility and ingestion. They are often found in amoebas. It keeps on changing its shape. The projections of varying lengths protrude out of the body. These are called pseudopodia (pseudo: false; podia: feet).

Statement 2 is correct: A white blood cell (WBC) in human blood is another example of a single cell which can change its shape.

Statement 1 is incorrect. Bacteria can fix atmospheric nitrogen while free-living in the soil (examples Azospirillum and Azotobacter), thus enriching the nitrogen content of the soil. Fungi are also known to form symbiotic associations with plants (mycorrhiza). Many members of the genus Glomus form mycorrhiza. The fungal symbiont in these associations 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. 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 bio fertilizer. Blue green algae also add organic matter to the soil and increase its fertility.

The United Nations General Assembly during its 74th Plenary Meeting proclaimed 2019 as the International Year of the Periodic Table of Chemical Elements. UNESCO has launched the International Year of The Periodic Table.

Statement 1 is incorrect. The Periodic Table, also known as the periodic table of elements is a tabular display of the chemical elements, which are arranged by atomic number, electron configuration, and recurring chemical properties. The structure of the table shows periodic trends. The seven rows of the table, called periods, generally have metals on the left and nonmetals on the right. The columns, called groups, contain elements with similar chemical behaviours.

Statement 2 is correct. 1869 is considered as the year of discovery of the Periodic System by the Russian scientist, Dmitri Mendeleev.

Every day we are exposed to a large number of infectious agents. However, the body is able to protect itself from the majority of such agents.

This overall ability of the host to fight the disease-causing organisms, conferred by the immune system is called immunity. Immunity is of two types:

(i) Innate immunity and

(ii) Acquired immunity Innate immunity is non-specific type of defence, that is present at the time of birth. This is accomplished by providing different types of barriers to the entry of the foreign agents into our body. Innate immunity consists of four types of barriers.

These are —

(i) Physical barriers: Skin on our body is the main barrier which prevents entry of the microorganisms. Mucus coating of the epithelium lining the respiratory, gastrointestinal and urogenital tracts also help in trapping microbes entering our body.

(ii) Physiological barriers : Acid in the stomach, saliva in the mouth, tears from eyes–all prevent microbial growth.

(iii) Cellular barriers: Certain types of leukocytes (WBC) of our body like polymorpho-nuclear leukocytes (PMNL-neutrophils) and monocytes and natural killer (type of lymphocytes) in the blood as well as macrophages in tissues can phagocytose and destroy microbes.

(iv) Cytokine barriers: Virus-infected cells secrete proteins called interferons which protect non-infected cells from further viral infection.

Statement 1 is correct- B. thuringiensis forms protein crystals during a particular phase of their growth. These crystals contain a toxic insecticidal protein.

Statement 2 is correct- Bt toxin protein exist as inactive protoxins but once an insect ingest the inactive toxin, it is converted into an active form of toxin due to the alkaline pH of the gut which solubilise the crystals.

The activated toxin binds to the surface of midgut epithelial cells and create pores that cause cell swelling and lysis and eventually cause death of the insect. Bt toxin is produced by a bacterium called Bacillus thuringiensis. Bt toxin gene has been cloned from the bacteria and been expressed in plants to provide resistance to insects without the need for insecticides.

Fertilization of Gametes (egg) results in the formation of Zygote which begins to develop into an Embryo. The zygote divides repeatedly to give rise to a ball of cells. The cells then begin to form groups that develop into different tissues and organs of the body. This developing structure is termed an embryo. The embryo gets embedded in the wall of the uterus for further development.

All organisms are made of small microscopic units called cells. A cell is the smallest structural and functional unit of an organism. Each cell of an organism performs certain functions such as nutrition, transport, excretion and reproduction. To perform these functions, the cell needs energy. The food has stored energy, which is released during respiration. Therefore, all living organisms respire to get energy from food. During breathing, we breathe in air.

The air we breathe in is transported to all parts of the body and ultimately to each cell. In the cells, oxygen in the air helps in the breakdown of food. Statement 1 is incorrect. The process of breakdown of food in the cell with the release of energy is called cellular respiration. Cellular respiration takes place in the cells of all organisms. Statements 2 and 3 are correct. In the cell, the food (glucose) is broken down into carbon dioxide and water using oxygen.

When breakdown of glucose occurs with the use of oxygen it is called aerobic respiration. Food can also be broken down, without using oxygen. This is called anaerobic respiration. Breakdown of food releases energy.

Biocontrol refers to the use of biological methods for controlling plant diseases and pests. In agriculture, there is a method of controlling pests that relies on natural predation rather than introduced chemicals. A key belief of the organic farmer is that biodiversity furthers health. The more variety a landscape has, the more sustainable it is. The organic farmer, therefore, works to create a system where the insects that are sometimes called pests are not eradicated, but instead are kept at manageable levels by a complex system of checks and balances within a living and vibrant ecosystem. The use of biocontrol measures will greatly reduce our dependence on toxic chemicals and pesticides. An important part of the biological farming approach is to become familiar with the various life forms that inhabit the field, predators as well as pests, and also their life cycles, patterns of feeding and the habitats that they prefer. This will help develop appropriate means of biocontrol.

Some examples of biocontrol are -

Statement 1 is correct. An example of microbial biocontrol agents that can be introduced in order to control butterfly caterpillars is the bacteria Bacillus thuringiensis (often written as Bt). These are available in sachets as dried spores which are mixed with water and sprayed onto vulnerable plants such as brassicas and fruit trees, where these are eaten by the insect larvae.

Statement 2 is incorrect. A biological control being developed for use in the treatment of plant disease is the fungus Trichoderma. Trichoderma species are free-living fungi that are very common in the root ecosystems. They are effective biocontrol agents of several plant pathogens.

Statement 3 is also incorrect. Baculoviruses are pathogens that attack insects and other arthropods. The majority of baculoviruses used as biological control agents are in the genus Nucleopolyhedrovirus. These viruses are excellent candidates for species-specific, narrow spectrum insecticidal applications. They have been shown to have no negative impacts on plants, mammals, birds, fish or even on non-target insects

Statement 1 is correct: Endocrine glands release hormones into the bloodstream to reach a particular body part called target site. The target site responds to the hormone. There are many endocrine glands or ductless glands in the body.

Statement 2 is correct: The changes which occur at adolescence are controlled by hormones. Hormones are chemical substances. These are secretions from endocrine glands, or endocrine system.

The male hormone or testosterone begins to be released by the testes at the onset of puberty. The production of these hormones is under the control of another hormone secreted from an endocrine gland called the pituitary gland.

Blood, fluid that transports oxygen and nutrients to the cells and carries away carbon dioxide and other waste products. Technically, blood is a transport liquid pumped by the heart (or an equivalent structure) to all parts of the body, after which it is returned to the heart to repeat the process. Blood is both a tissue and a fluid. It is a tissue because it is a collection of similar specialized cells that serve particular functions. These cells are suspended in a liquid matrix (plasma), which makes the blood a fluid. If blood flow ceases, death will occur within minutes because of the effects of an unfavourable environment on highly susceptible cells. So, all three statements are the functions of blood.

Statement 1 is correct. Kalamsat V-2 is a student satellite which is the first to use the Fourth stage (PS4) of PSLV as an orbital platform. It was taken into orbit by PSLV-C44.

Statement 2 is incorrect. Kalamsat V-2 was developed by Students of Space Kidz India which is a chennai based Private organisation.

Statement 3 is correct. The Kalamsat V-2 will serve as Communication satellite for ham radio transmission used by amateurs for non-commercial activities. KB) Polar Satellite Launch Vehicle (PSLV) is the third generation launch vehicle of India. It is the first Indian launch vehicle to be equipped with liquid stages. After its first successful launch in October 1994, PSLV emerged as the reliable and versatile workhorse launch vehicle of India with 39 consecutively successful missions by June 2017.

During 1994-2017 period, the vehicle has launched 48 Indian satellites and 209 satellites for customers from abroad. Besides, the vehicle successfully launched two spacecraft – Chandrayaan-1 in 2008 and Mars Orbiter Spacecraft in 2013 – that later traveled to the Moon and Mars respectively

Option (b) is the correct answer. Blood vessels: There are different types of blood vessels in the body. You know that during inhalation a fresh supply of oxygen fills the lungs. Oxygen has to be transported to the rest of the body. Also, the blood picks up the waste materials including carbon dioxide from the cells. This blood has to go back to the heart for transport to the lungs for removal of carbon dioxide. So, two types of blood vessels, arteries and veins are present in the body.

Pair 2 is incorrectly matched. Arteries carry oxygen-rich blood from the heart to all parts of the body. Since the blood flow is rapid and at a high pressure, the arteries have thick elastic walls.

Pair 1 is incorrectly matched. Veins are the vessels which carry carbon dioxide-rich blood from all parts of the body back to the heart. The veins have thin walls. There are valves present in veins which allow blood to flow only towards the heart.

All statements are correct. With rapid increase in human population, conventional agricultural may not be able to meet the demand of food. One of the alternate sources of proteins for animal and human nutrition is Single Cell Protein (SCP).

Single - cell protein (SCP) refers to edible unicellular microorganisms. The biomass or protein extract from pure or mixed cultures of algae, yeasts, fungi or bacteria may be used as an ingredient or a substitute for protein-rich foods, and is suitable for human consumption or as animal feeds. It has a very high rate of biomass production and growth. Incidentally, industrial agriculture marked by a high-water footprint, high land use, biodiversity destruction, general environmental degradation and contributes to climate change by emission of a third of all greenhouse gases. Production of SCP does not necessarily exhibit any of these serious drawbacks

Statement 1 is correct. Vitamins are organic substances made by plants and animals that are essential for the human body to grow and function properly. They help us in protecting our body against diseases. They also help in keeping our eyes (Vitamin A), bones (Vitamin D), teeth and gums (Vitamin C) healthy.

Statement 2 is incorrect. Vitamins are both water and fat soluble. Vitamins A, D, E, K are fat-soluble. These can dissolve in fats and oils. They are absorbed along with fats in the diet and can be stored in the body's fatty tissue. Vitamin C and members of the vitamin B complex are water-soluble. They can dissolve in water. Water-soluble vitamins are carried to the body's tissue but are not stored in the body.

The heart is an organ which beats continuously to act as a pump for the transport of blood, which carries other substances with it.

Statement 1 is correct. Heart is divided into 4 chambers, two upper and two lower.

Statement 2 is incorrect. The two upper chambers are called the atria (singular: atrium) and the two lower chambers are called the ventricles. The partition between the chambers helps to avoid mixing up of blood rich in oxygen with the blood rich in carbon dioxide.

Statement 3 is incorrect. The walls of the chambers of the heart are made up of muscles. These muscles contract and relax rhythmically. This rhythmic contraction followed by its relaxation constitutes a heartbeat. While the pulse is due to the blood flowing in the arteries. The number of beats per minute is called the pulse rate. A resting person, usually has a pulse rate between 72 and 80 beats per minute.

Statement 1 is correct. DNA fingerprinting involves identifying differences in some specific regions in DNA sequence called as repetitive DNA, because in these sequences, a small stretch of DNA is repeated many times. These repetitive DNA are separated from bulk genomic DNA as different peaks during density gradient centrifugation. The bulk DNA forms a major peak and the other small peaks are referred to as satellite DNA.

Statement 2 is incorrect. 99.9 percent of base sequence among humans is the same. It is these differences in sequence of DNA which makes every individual unique in their phenotypic appearance. If one aims to find out genetic differences between two individuals or among individuals of a population, sequencing the DNA every time would be a daunting and expensive task. Imagine trying to compare two sets of 3 × 106 base pairs. DNA fingerprinting is a very quick way to compare the DNA sequences of any two individuals.

Hence, statement 1 is incorrect.

● Atlas will facilitate the development of better drugs and more accurate predictions of unintended toxicity.

● It will also aid regenerative medicine — the process of replacing, engineering or regenerating human cells, tissues or organs to establish normal function. Hence, statement 2 is correct.

IndiGen Project

● This programme, an initiative of the Council of Scientific and Industrial Research’s (CSIR), is about undertaking whole genome sequencing of thousands of individuals representing diverse ethnic groups from India.

● It is an independent project of CSIR. Hence, statement 3 is incorrect.

All three are asexual mode of reproduction in plants. Budding in Yeast, Fragmentation in Algae, Spore formation in Moss and Ferns results in reproduction. Budding, in biology, a form of asexual reproduction in which a new individual develops from some generative anatomical point of the parent organism. In some species buds may be produced from almost any point of the body, but in many cases, budding is restricted to specialized areas.

The initial protuberance of proliferating cytoplasm or cells, the bud, eventually develops into an organism duplicating the parent. The new individual may separate to exist independently, or the buds may remain attached, forming aggregates or colonies. Fragmentation in multicellular organisms is a form of asexual reproduction in which an organism is split into fragments. Each of these fragments develop into matured fully grown individuals that are identical to their parents.

Fragmentation, also known as splitting, as a method of reproduction is seen in many organisms such as filamentous cyanobacteria, molds, lichens, many plants, and animals such as sponges, acoel flatworms, some annelid worms and sea stars. Spore formation is a method of asexual reproduction which is found in non-flowering plants such as fungi (Rhizopus) and bacteria. In this method of reproduction, the parent plant produces hundreds of tiny spores which can grow into new plants.

Statement 1 is correct. Transfer of pollen from the Anther to the Stigma of a flower is called pollination.

Statement 2 is incorrect. When the pollen of a flower lands on the stigma of a flower of a different plant of the same kind, it is called cross-pollination KB) Reproductive Part of a Plant Flowers are the reproductive parts of a plant. Male and female gametes are produced in the flower.

The flower consists of four main parts-

• Sepals: They are the green leaf-like structures which protect the flower in the bud stage.

• Petals: They are the coloured structures. They are the most beautiful part of the flower that attracts the birds and insects for pollination Stamens: They are the male reproductive parts. Stamens consist of two parts – anther and filament. Anther is a swollen part of the stamen. The filament is a long, slender stalk which attaches the stamen to the flower. Pollen grains are formed inside the anther which produces the male gametes.

• Pistil or Carpel: It is the female reproductive part of the flower. It consists of three parts – stigma, style and ovary. The stigma is at the top of the pistil. It receives the pollen grains during pollination. The style is a long, tube-like structure which passes the pollen grains to the ovary. The ovary is the swollen part present at the basal part of the pistil. The ovary consists of the ovule which bears the female gamete. Uni-sexual and Bisexual Flowers Flowers can be of two types depending upon whether both the sexual parts – male and female are present in the same flower or different flower.

• Bisexual flowers: Flowers which contain both the stamens and the pistil are known as bisexual flowers. For example- Rose, Hibiscus, Gulmohar, Mustard etc.

• Uni-sexual flowers: The flowers which contain either the stamens or the pistil are known as unisexual flowers. For example- Maize, Papaya, Cucumber etc.