Test: Science and Technology- 3 - UPSC MCQ

• Growth regulators are chemical substances, other than naturally produced hormones, which promote, inhibit or modify growth and development in plants. The naturally produced growth hormones are broadly grouped under five major classes. They are Auxin, Ethylene, Cytokinins, Gibberellins and Abscissic acid.
• Auxin: Auxin is a growth promoter, generally produced by the growing apex of stem and root of the plants. It helps in the elongation of shoot and root tips behind apical meristem. The naturally produced auxins is Indole-3-Acetic Acid (IAA).
  • Functions of Auxin:
    • It promotes cell elongation. Hence pair 1 is correctly matched.
    • It suppresses the growth of lateral bud. If the tip of a plant is removed, the lateral branches begin to grow; In most of the plants apical bud suppresses the development of lateral buds. This is called apical dominance.
    • It delays fall of leaves. (leaf abscission)
• Gibberellin: Gibberellin or Gibberellic Acid (GA) was initially isolated from a fungus Gibberella fujikuroi. In plants, it is produced in embryos, roots, and young leaves and it enhances growth.
  • Functions of Gibberellins
    • It helps in elongation of stems in genetically dwarf plants. By using gibberellin the height of the dwarf plants can be increased.
    • It breaks dormancy of seeds and buds. Hence pair 2 is not correctly matched.
    • It induces parthenocarpy. (Formation of seedless fruits without fertilization) or provides stimulus received by pollination.
• Cytokinins: They were extracted from coconut milk. Cytokinins are synthesized in root apex, endosperm of seeds, and young fruits where cell division takes place continuously.
  • Functions of Cytokinins
    • They stimulate cell division, cell enlargement and cell differentiation.
    • They prevent aging of plant parts. Hence pair 3 is correctly matched.
    • They inhibit apical dominance and help in growth of lateral buds into branches.
• Ethylene: Ethylene is a gaseous hormone. It is found in ripening fruits, young flowers and young leaves.
  • Functions of Ethylene
    • It induces ripening of fruits.
    • It promotes senescence and abscission of leaf, and flowers. Hence pair 4 is correctly matched.
    • In cells it only increases the width not the length.
• Abscissic acid: Abscissic acid also known as Dormin is a naturally occurring growth inhibitor found in wide variety of plants. It is synthesised in leaves.
  • Functions of Abscissic acid:
    • It induces dormancy of buds and seeds as opposed to Gibberellin, which breaks dormancy.
    • It promotes the senescence of leaf, i.e., fall of leaves happen due to abscissic acid.
    • It inhibits seed germination and development.
    • It causes closing of Stomata.

• Conductors, semiconductors, and insulators are classified on the basis of conductivity/resistivity.
• Conductors possess very low resistivity (or high conductivity).
• Semiconductors have resistivity or conductivity intermediate to conductors and insulators.
• Insulators have high resistivity (or low conductivity).
  • Thus resistivity of semiconductors is more than conductors but less than insulators. Hence statement 1 is not correct.
• Semiconductors can be :
  • Elemental semiconductors: Silicon(Si) and Germanium(Ge)
  • Compound semiconductors: Examples are:
    • Inorganic: CdS, GaAs, CdSe, InP, etc.
    • Organic: anthracene, doped pthalocyanines, etc.
    • Organic polymers: polypyrrole, polyaniline, polythiophene, etc.
• Most of the currently available semiconductor devices are based on elemental semiconductors Si or Ge and compound inorganic semiconductors. Hence statement 2 is correct.

• TB is caused by bacteria (Mycobacterium tuberculosis) and it most often affects the lungs. TB is spread through the air when people with lung TB cough, sneeze or spit. A person needs to inhale only a few germs to become infected. Every year, 10 million people fall ill with tuberculosis (TB). Despite being a preventable and curable disease, 1.5 million people die from TB each year – making it the world’s top infectious killer. Hence statement 1 is correct. Hence statement 1 is correct. 
• XDR-TB, an abbreviation for extensively drug-resistant tuberculosis (TB), is a form of TB which is resistant to at least four of the core anti-TB drugs. XDR-TB involves resistance to the two most powerful anti-TB drugs, isoniazid and rifampicin, also known as multidrug-resistance (MDR-TB), in addition to resistance to any of the fluoroquinolones (such as levofloxacin or moxifloxacin) and to at least one of the three injectable second-line drugs (amikacin, capreomycin or kanamycin). Hence statement 2 is not correct.
• MDR-TB and XDR-TB both take substantially longer to treat than ordinary (drug-susceptible) TB, and require the use of second-line anti-TB drugs, which are more expensive and have more side-effects than the first-line drugs used for drug-susceptible TB.
• Under Universal Immunization Programme, immunization of children starts as soon as child is born. Vaccination against childhood tuberculosis (BCG), polio (OPV) and maternally transmitted Hepatitis B (Hep B vaccine) are given to a child immediately after birth. After this, specific vaccines are given at recommended ages and routes as outlined in National Immunization Schedule. Hence statement 3 is correct.

• Branching descent and natural selection are the two key concepts of the Darwinian Theory of Biological Evolution.
• In his 'The Origin of Species', Darwin used the idea of branching descent to describe the process of descent with modification and how it results in the origin of new species (different species share common ancestral species).
• The essence of Darwinian theory about evolution is natural selection. The rate of appearance of new forms is linked to the life cycle or the life span. Microbes that divide fast have the ability to multiply and become millions of individuals within hours. A colony of bacteria (say A) growing on a given medium has built-in variation in terms of the ability to utilize a feed component. A change in the medium composition would bring out only that part of the population (say B) that can survive under the new conditions. In due course of time, this variant population outgrows the others and appears as a new species. This would happen within days. For the same thing to happen in a fish or fowl would take millions of years as life spans of these animals are in years. Here we say that the fitness of B is better than that of A under the new conditions. Nature selects for fitness.
• One must remember that the so-called fitness is based on characteristics which are inherited. Hence, there must be a genetic basis for getting selected and to evolve. Another way of saying the same thing is that some organisms are better adapted to survive in an otherwise hostile environment. Adaptive ability is inherited. It has a genetic basis. Fitness is the end result of the ability to adapt and get selected by nature.

• Cryogenic engines are highly efficient propulsion systems used in the upper stages of rockets. They offer a higher specific impulse, which measures the efficiency or thrust of an engine, resulting in an increased payload capacity. A Cryogenic rocket stage is more efficient and provides more thrust for every kilogram of propellant it burns compared to solid and earth-storable liquid propellant rocket stages. Hence statement 1 is correct.
• The main components of a cryogenic rocket engine include an igniter, combustion chamber (thrust chamber), fuel cryo pumps, fuel injector, oxidiser cryo pumps, gas turbine, cryo valves, regulators, fuel tanks, and a rocket engine nozzle.
• Cryogenic engine makes use of Liquid Oxygen (LOX) and Liquid Hydrogen (LH₂) as propellants which liquefy at -183 deg C and -253 deg C respectively. LOX and LH₂ are stored in their respective tanks. Typically, these engines use a combination of liquid oxygen (LOX) as the oxidizer and liquid hydrogen (LH₂) as the fuel. The use of cryogenic fuels allows for high performance and efficiency in rocket engines. Hence statement 2 is correct. • For the Chandrayaan-3 mission, the CE-20 cryogenic engine was used. The CE-20 was India’s first cryogenic engine with a gas-generator cycle and the largest cryogenic engine to be made by ISRO.  It took its first flight in June 2017.

• Satellites in geostationary orbit (GEO) circle Earth above the equator from west to east following Earth’s rotation – taking 23 hours 56 minutes and 4 seconds – by travelling at exactly the same rate as Earth. This makes satellites in GEO appear to be ‘stationary’ over a fixed position. Hence statement I is correct and statement II is not correct.
• In order to perfectly match Earth’s rotation, the speed of GEO satellites should be about 3 km per second at an altitude of 35 786 km. This is much farther from Earth’s surface compared to many satellites.
• GEO is used by satellites that need to stay constantly above one particular place over Earth, such as telecommunication satellites. This way, an antenna on Earth can be fixed to always stay pointed towards that satellite without moving. It can also be used by weather monitoring satellites, because they can continually observe specific areas to see how weather trends emerge there

• Statement 1 is not correct: The transfer of heat by radiation does not require any medium. It can take place whether a medium is present or not. When we come out in the sun, we feel warm. How does the heat from the sun reach us? It cannot reach us by conduction or convection as there is no medium such as air in most parts of the space between the earth and the sun. From the sun the heat comes to us by another process known as radiation.
• Statement 2 is correct: Since the primary source of infrared radiation is heat or thermal radiation, any object which has a temperature radiates in the infrared. Even objects that we think of as being very cold, such as an ice cube, emit infrared. When an object is not quite hot enough to radiate visible light, it will emit most of its energy in the infrared. For example, hot charcoal may not give off light but it does emit infrared radiation which we feel as heat. The warmer the object, the more infrared radiation it emits.

• A hypersonic missile is a weapon system which flies at least at the speed of Mach 5 i.e. five times the speed of sound and is manoeuvrable. Hence statement 1 is not correct.
• The manoeuvrability of the hypersonic missile is what sets it apart from a ballistic missile as the latter follows a set course or a ballistic trajectory. Hypersonic missiles mostly are cruise missiles that do not follow a ballistic trajectory and can be manoeuvred to the intended target. Hence statement 2 is not correct.
• The two types of hypersonic weapons systems are Hypersonic Glide Vehicles (HGV) and Hypersonic Cruise Missiles. The HGV is launched from a rocket before gliding to the intended target while the hypersonic cruise missile is powered by air-breathing high-speed engines or ‘scramjets’ after acquiring their target.
• Conventional hypersonic weapons use only kinetic energy i.e. energy derived from motion, to destroy unhardened targets or even underground facilities. Hence statement 3 is correct.
• India is also developing an indigenous, dual-capable (conventional as well as nuclear) hypersonic cruise missile as part of its Hypersonic Technology Demonstrator Vehicle programme and has successfully tested a Mach 6 scramjet

• Blood cells are the cells which are produced during hematopoiesis and found mainly in the blood. Blood is composed of the blood cells which accounts for 45% of the blood tissue by volume, with the remaining 55% of the volume composed of plasma, the liquid portion of the blood.
• There are three types of blood cells. They are:
  • Red blood cells (Erythrocytes). Hence, option 4 is not correct.
  • White blood cells (Leukocytes)
  • Platelets (Thrombocytes)
• What are White Blood Cells?
  • White blood cells account for only about 1% of our blood, but their impact is big.
    • White blood cells are also called leukocytes. They protect us against illness and disease.
    • White blood cells are made in the bone marrow.
    • They are stored in our blood and lymph tissues.
    • Because some white blood cells have a short life of 1 to 3 days, your bone marrow is always making them.
• What are the types of WBC?
  • Monocytes. They have a longer lifespan than many white blood cells and help to break down bacteria.
  • Lymphocytes. They create antibodies to fight against bacteria, viruses, and other potentially harmful invaders. Hence, option 2 is correct.
  • Neutrophils. They kill and digest bacteria and fungi. They are the most numerous type of white blood cell and your first line of defense when infection strikes.  Hence, option 1 is correct.
  • Basophils. These small cells seem to sound an alarm when infectious agents invade your blood. They secrete chemicals such as histamine, a marker of allergic disease, that help control the body's immune response. Hence, option 3 is correct.
  • Eosinophils. They attack and kill parasites and cancer cells, and help with allergic responses

• Immunity refers to the state of being insusceptible to a particular disease. It is a condition that permits either natural or acquired resistance to disease.
• It can be classified as:
  • Active immunity - It results when exposure to a disease organism triggers the immune system to produce antibodies to that disease. Exposure to the disease organism can occur through infection with the actual disease (resulting in natural immunity), or introduction of a killed or weakened form of the disease organism through vaccination (vaccine-induced immunity). Either way, if an immune person comes into contact with that disease in the future, their immune system will recognize it and immediately produce the antibodies needed to fight it. Active immunity is long-lasting, and sometimes life-long.
  • Passive immunity
    • It is provided when a person is given antibodies to a disease rather than producing them through his or her immune system. Hence statement 1 is correct.
    • A newborn baby acquires passive immunity from its mother through the placenta. A person can also get passive immunity through antibody-containing blood products such as immune globulin, which may be given when immediate protection from a specific disease is needed.
    • It can develop naturally when a mother's antibodies are transferred to a fetus or infant. It can also occur artificially when antibodies are transferred, often through a blood or plasma transfusion. Hence statement 2 is correct.
    • This is the major advantage of passive immunity; protection is immediate, whereas active immunity takes time (usually several weeks) to develop. Hence statement 3 is correct.
    • However, passive immunity lasts only for a few weeks or months. Only active immunity is long-lasting. Hence statement 4 is correct.

The process of developing transgenic crops is an elaborate one as inserting transgenic genes into plants to elicit a sustained, protective response is a mix of both science and chance.

• There is an array of crops — brinjal, tomato, maize, chickpea — in various stages of trials that employ transgenic technology. However, cotton remains the only transgenic crop that is being commercially cultivated in India. Hence statement 1 is correct.
• India’s biotech regulator Genetic Engineering Appraisal Committee (GEAC) gave approval to conduct BRL-1 trial for resistance against Pink Bollworm. The genetically modified cotton expresses Cry2Ai gene for resistance against Pink Bollworm. Hence statement 2 is correct

• Galvanisation or galvanization is the process of applying a protective zinc coating to iron or steel, to prevent rusting. The most common method is hot dip galvanizing, in which steel sections are submerged in a bath of molten zinc. Hence statement 2 is correct.
• The primary purpose of galvanizing is to provide protection against corrosion for metal surfaces, particularly steel. Hence statement 1 is correct.
• This process offers several advantages :
  • Corrosion Resistance: The zinc coating acts as a sacrificial anode, meaning that it corrodes preferentially to the underlying steel or iron. This sacrificial corrosion helps protect the base metal from rust and corrosion.
  • Durable Coating: Zinc is a highly durable and long-lasting metal, providing a protective layer that withstands environmental exposure, including moisture, humidity, and various atmospheric conditions.
  • Extended Lifespan: Galvanizing significantly extends the lifespan of steel or iron structures and components. The corrosion resistance provided by the zinc coating helps prevent the gradual deterioration of the underlying metal.
  • Low Maintenance: Galvanized surfaces require minimal maintenance. The protective zinc layer continues to provide corrosion resistance even if it becomes scratched or damaged, reducing the need for frequent reapplication of coatings.
  • Cost-Effective: While there is an initial cost associated with the galvanizing process, the long-term cost-effectiveness is high due to the extended lifespan of the galvanized metal and the reduced need for maintenance.
  • Cathodic Protection: The zinc coating acts as a cathode in the electrochemical corrosion process. This cathodic protection helps prevent the corrosion of the underlying steel, which serves as the anode.
  • Uniform Coating: Galvanizing provides a uniform and complete coating on all surfaces, including intricate shapes and hard-to-reach areas. This ensures comprehensive corrosion protection for the entire metal structure.
  • Environmentally Friendly: Zinc is a natural element and is recyclable. The galvanizing process generates minimal waste, and the zinc coating can be recycled at the end of its useful life.
• Common applications of galvanizing include the protection of structural steel in buildings, bridges, fences, guardrails, and various industrial equipment. Galvanized coatings are also used in the production of pipes, electrical conduits, and automotive components, among other applications.

• Electric eels generate electric shocks through specialized chemical reactions in cells called electrolytes. These cells are unique to electric fish, such as electric eels, and allow them to produce electric discharges for various purposes, including hunting, navigation, communication, and self-defense.
• Electric eels have thousands of electrolytes stacked in series, forming electric organs along the length of their bodies. These electrolytes are specialized cells that function as biological batteries.
• When the electric eel wants to generate an electric shock, its nervous system sends a signal to the electrolytes, triggering an action potential
• The action potential opens ion channels in the electrocyte cell membranes. This allows the movement of ions, particularly sodium and potassium ions, across the cell membrane.
• The controlled movement of ions creates a voltage potential across the electrocyte cell membrane. This is similar to the process that occurs in nerve cells but is highly specialized in electric fish for generating electric discharges. • The electrolytes are stacked in a series arrangement. This stacking increases the voltage potential, allowing electric eels to generate electric shocks of considerable strength.
• The electrolytes are activated sequentially along the length of the electric organ, creating a wave of electric discharges. This sequential activation contributes to the production of a continuous electric shock.
• Electric eels can modulate the frequency, duration, and intensity of their electric discharges. They can produce both low-voltage pulses for navigation and higher-voltage shocks for hunting and self-defense.
• Hence option (b) is the correct answer

• ISRO initiated a project called Project NETRA, which is an early warning system in space to detect debris and other hazards to Indian satellites.
• Under NETRA the ISRO plans to put up many observational facilities: connected radars, telescopes; data processing units and a control centre. They can, among others, spot, track and catalogue objects as small as 10 cm, up to a range of 3,400 km and equal to a space orbit of around 2,000 km.
• Project NETRA consists of high-precision, long-range telescope in Leh and a radar in the North East. Along with them, the Multi-Object Tracking Radar (MOTR)  at the Satish Dhawan Space Centre in Sriharikota, and the telescopes at Ponmudi and Mount Abu.
• Hence option (c) is the correct answer.

• Transformers facilitate the long-distance transmission of electrical power by adjusting the voltage of the electrical current. This process is crucial for ensuring efficient and economical power transmission.
• Transformers have coils of wire, and when electricity flows through one coil, it creates a changing magnetic field.
• Transformers can either increase (step up) or decrease (step down) the voltage. For long-distance transmission, they often use step-up transformers to increase the voltage. 
• Higher voltage means lower current and lower current reduces energy loss during transmission. This makes it more efficient and cheaper to send electricity over long power lines. Thus it facilitates the long-distance transmission of electrical power 
• Power plants generate electricity at a lower voltage. Transformers increase the voltage for efficient long distance travel over transmission lines. 
• Closer to homes, other transformers decrease the voltage for safe use in households.
• Hence option (a) is the correct answer

• In evolutionary biology, adaptive radiation is a process in which organisms diversify rapidly from an ancestral species into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, or opens new environmental niches. Starting with a recent single ancestor, this process results in the speciation and phenotypic adaptation of an array of species exhibiting different morphological and physiological traits. Example - Darwin Finch & Australian marsupials. Hence option (a) is the correct answer.
• In evolutionary biology, convergent evolution is the process whereby organisms not closely related (not monophyletic), independently evolve similar traits as a result of having to adapt to similar environments or ecological niches. It is the opposite of divergent evolution, where related species evolve different traits.
• Secondary succession is one of the two types of ecological succession of plant life. secondary succession is a process started by an event (e.g. forest fire, harvesting, hurricane, etc.) that reduces an already established ecosystem (e.g. a forest or a wheat field) to a smaller population of species, and as such secondary succession occurs on preexisting soil whereas primary succession usually occurs in a place lacking soil.
• Sequential evolution involves relatively minor changes in the gene pool of a particular population from one generation to the next. No new species result from such change, but the descendant population is not genetically identical to the preceding population. Such evolution of gene pools from one generation to the next is called sequential evolution.

• A cell consists of three parts: the cell membrane, the nucleus, and, between the two, the cytoplasm. Within the cytoplasm lie intricate arrangements of fine fibers and hundreds or even thousands of miniscule but distinct structures called organelles.
• Cell membrane: Every cell in the body is enclosed by a cell (Plasma) membrane. The cell membrane separates the material outside the cell, extracellular, from the material inside the cell, intracellular. It maintains the integrity of a cell and controls passage of materials (ions and molecules) into and out of the cell. Hence pair 2 is correctly matched.
• Nucleus and Nucleolus: The nucleus, formed by a nuclear membrane around a fluid nucleoplasm, is the control center of the cell. Threads of chromatin in the nucleus contain deoxyribonucleic acid (DNA), the genetic material of the cell. The nucleolus is a dense region of ribonucleic acid (RNA) in the nucleus and is the site of ribosome formation.
• Cytoplasm: The cytoplasm is the gel-like fluid inside the cell. It is the medium for chemical reaction. It provides a platform upon which other organelles can operate within the cell. All of the functions for cell expansion, growth and replication are carried out in the cytoplasm of a cell.
• Cytoplasmic organelles are "little organs" that are suspended in the cytoplasm of the cell. Each type of organelle has a definite structure and a specific role in the function of the cell. Examples of cytoplasmic organelles are mitochondrion, ribosomes, endoplasmic reticulum, golgi apparatus, and lysosomes.
  • The Endoplasmic reticulum (ER) and Golgi body are single membrane bound structures. The membrane has the same structure (lipid-protein) as the plasma membrane but ribosomes do not have membranes. Ribosomes are involved in synthesis of proteins in the cell, Golgi bodies in secreting and the ER in transporting and storing the products. These three organelles operate together.
  • Ribosomes are present either as free particles in cytoplasm or attached to ER. Also found stored in nucleolus inside the nucleus. 80S types found in eukaryotes and 70S in prokaryotes (S- svedberg unit of measuring ribosomes). Ribosomes are sites in a cell lin which protein synthesis takes place. Hence pair 1 is correctly matched.
  • The Golgi apparatus, or Golgi complex, functions as a factory in which proteins received from the ER are further processed and sorted for transport to their eventual destinations: lysosomes, the plasma membrane, or secretion. In addition, as noted earlier, glycolipids and sphingomyelin are synthesized within the Golgi. Hence pair 3 is correctly matched.
  • Lysosomes are present in almost all animal cells and some non-green plant cells. They perform intracellular digestion. Lysosomes are called 'suicidal bags' as enzymes contained in them can digest the cell's own material when damaged or dead. Hence pair 4 is correctly matched.

• Hydroponics is a method of growing plants without soil, using water enriched with balance mineral nutrients essential for plant growth and yield. The nutrients and PH level are maintained suiting to the selected crop for better growth. With increasing water scarcity due to frequent droughts and declining land availability for farming, government agencies are promoting hydroponic for growing vegetables, fruits and fodder. Hence statement 1 is correct.
• Aquaponics is a sustainable farming method that combines aquaculture (the cultivation of aquatic organisms like fish) with hydroponics (the growing of plants in nutrient-rich water without soil). This combination creates biological processes that occur in both systems to create a closed-loop environment where fish and plants thrive together. Hence statement 2 is correct.
• Unlike hydroponics, in which one needs to add nutrients to the water for the plants to grow,in aquaponics the nutrients come from fish. The fish produce ammonia,which gets converted by two types of bacteria: first to nitrite and then to nitrate that in turn serve as fertilisers for plants. Hence statement 3 is correct.

• Direct seeding is a crop establishment system wherein rice seeds are sown directly into the field, as opposed to the traditional method of growing seedlings in a nursery, then transplanting into flooded fields.
• Direct-seeded rice is seen to be one of the most efficient, sustainable, and economically viable rice production systems used today. Compared to the conventional puddled transplanted rice (PTR) method prevalent in Asia, DSR delivers faster planting and maturing, conserves scarce resources like water and labor, is more conducive to mechanization, and reduces emissions of greenhouse gases that contribute to climate change.
• Advantages of direct seeding
  • No significant reduction of yield under optimal conditions
  • Savings on irrigation water by 12-35% under efficient water management practices
  • Reduces labor and drudgery by eliminating seedling uprooting and transplanting
  • Reduces cultivation time, energy, and cost
  • No plant stress from transplanting
  • Faster maturation of crops
  • Lower GHG emissions
  • Mechanized DSR provides employment opportunities for youth through service provision business model o
  • Increases total income by reducing cost of cultivation
• Current constraints
  • Higher seed rates
  • Seeds exposed to birds and pests
  • Weed management
  • Higher risk of lodging
  • Risk of poor or non-uniform crop establishment
• Hence option (c) is the correct answer.

• Statement 1 is correct and 2 is not correct. Deep Ocean Mission (DOM)
• DOM is implemented by the Ministry Of Earth Sciences (MoES) and was approved in 2021 at a cost of nearly Rs 4,077 crore over a five-year period in a phased manner.
• The mission aims to develop technologies for deep-sea mining and a manned submersible to carry three people to a depth of 6,000 meters in the ocean

All the statements are correct.

• Syngas or synthetic gas, is a mixture of primarily hydrogen and carbon monoxide that often also contains some amount of carbon dioxide and methane and that is highly combustible.
• Syngas is used primarily in the production of hydrocarbon fuels, such as diesel fuel and methanol, and in the production of industrial chemicals, particularly ammonia.

• Statement 1 is not correct: Wolbachia is a genus of bacteria and only lives inside host cells, but not in the environment.
  • Wolbachia was first discovered in the reproductive tissues of mosquitoes Culex pipiens by Hertig and Wolbach in 1924 and the species was later named Wolbachia pipientis.
  • Many mosquitoes, including some of the major disease-transmitting species, carry Wolbachia naturally.
• Statement 2 is correct: How does the Wolbachia Method work?
  • When mosquitoes carry Wolbachia, the bacteria compete with viruses like dengue, Zika, chikungunya and yellow fever.
  • This makes it harder for viruses to reproduce inside the mosquitoes. And the mosquitoes are much less likely to spread viruses from person to person

The Webb Telescope

• About: Launched in 2021 to a point 1 million miles (1.6 million kilometers) away, Webb is the biggest and most powerful astronomical observatory ever sent into space; it sees the universe in the infrared. It is the world’s premier space science observatory. It will solve mysteries in our solar system, look beyond distant worlds around other stars, and probe the mysterious structures and origins of our universe and our place in it. NASA’s $10 billion James Webb Telescope was developed with the assistance of the European Space Agency and the Canadian Space Agency. The telescope launched on an Ariane 5 from Europe’s Spaceport in French Guiana.
• Mission: It will be “a giant leap forward in the quest to understand the Universe and our origins”, as it will examine every phase of cosmic history: from the Big Bang to the formation of galaxies, stars, and planets to the evolution of our own Solar System.

• The direction of conventional current flow in an electrical circuit is considered to be from positive to negative. This convention was established historically before the discovery of the electron, which is a negatively charged particle and is the actual charge carrier in most electric circuits.
• In the early days of electrical theory, scientists were not aware of the existence of electrons or their negative charge. When they observed the flow of electric charge in conductors, they assigned a positive charge to the hypothetical charge carriers.
• Benjamin Franklin introduced the concept of electric charge, suggesting that there were two types of charges: positive and negative. However, he initially assigned a positive charge to the carrier that moved. This convention became widely accepted.
• Later, it was discovered that electrons are the primary charge carriers in conductors, and they have a negative charge. However, by the time this discovery was made, the convention of positive to negative current flow had become firmly established.
• Despite knowing that electrons carry a negative charge, the positive-to-negative convention has been retained for the sake of consistency and convenience. Changing the convention could lead to confusion and make it more challenging to interpret existing circuit diagrams and literature.
• Hence option (a) is the correct answer.

The correct answer is:

2. Both 1 and 2

Explanation:
1. Mitotic cell division indeed occurs in somatic (body) cells, while meiosis occurs in germ cells (reproductive cells).
2. All mitotic progeny are genetically identical to the parent cell, while meiosis results in genetic variation through recombination and independent assortment of chromosomes.

• The maximum density of water at 4 degrees Celsius is a unique and anomalous behavior that arises from the structure of water molecules and the formation of hydrogen bonds. Unlike most substances that contract and become denser as they cool and transition from a liquid to a solid state, water behaves differently.
• Here's why water achieves its maximum density at 4 degrees Celsius
  • Hydrogen Bonding: Water molecules are polar, meaning they have a partial positive charge on the hydrogen atoms and a partial negative charge on the oxygen atom. The oxygen atom is more electronegative, creating a dipole moment. This dipolar nature allows water molecules to form hydrogen bonds with each other.
  • Tetrahedral Arrangement: When water molecules are in the liquid state, they form a loose and constantly changing network of hydrogen bonds. However, as water cools and approaches 4 degrees Celsius, a more ordered and stable arrangement occurs. At 4 degrees Celsius, water molecules tend to form a tetrahedral arrangement due to hydrogen bonding.
  • Open Structure: In the tetrahedral arrangement, water molecules are more spaced out, creating an open structure. This open structure leads to a maximum packing of water molecules, resulting in the highest density.
  • Decrease in Density Below 4 Degrees Celsius: As water continues to cool below 4 degrees Celsius, it undergoes a phase transition from a liquid to a solid (ice). In the process, the hydrogen bonding becomes more ordered, and water molecules form a hexagonal lattice in the ice structure. This hexagonal arrangement is less dense than the open structure at 4 degrees Celsius, causing a decrease in density as water freezes.
  • Specific heat capacity (often shortened to specific heat) refers to a material's property that describes how much heat energy it needs to absorb to raise its temperature by one degree. The concept plays a crucial role in understanding heat transfer and temperature changes in various contexts.
  • The specific heat of water is not maximum at zero degrees Celsius. In fact, it gradually decreases as it approaches 0°C and reaches a minimum around 4°C. It then starts increasing again with rising temperature.
• Hence option (c) is the correct answer.

• Neutrons are subatomic particles found in the nucleus of an atom. They have a mass of approximately 1 atomic mass unit (u) or 1.675 x 10^-27 kg.
• Protons are positively charged subatomic particles located in the nucleus of an atom. Like neutrons, they also have a mass of approximately 1 atomic mass unit (u) or 1.675 x 10^-27 kg.
• Electrons are negatively charged subatomic particles found outside the nucleus in electron shells. Electrons have a significantly smaller mass compared to protons and neutrons. The mass of an electron is about 1/1836 times the mass of a proton or neutron. It is approximately 9.109 x 10^-31 kg.
• An alpha particle is a type of nuclear particle consisting of two protons and two neutrons. It is essentially the nucleus of a helium-4 atom. The mass of an alpha particle is approximately 4 atomic mass units (u) or 6.644 x 10^-27 kg. • Thus the electron has the least mass among the particles mentioned.
• Hence option (c) is the correct answer.

• Stripe Rust of wheat o Context: Indian Institute of Wheat and Barley Research, Karnal (Haryana) has appealed to the farmers to remain vigilant against yellow rust. Hence option (b) is the correct answer.
  • Caused by a fungal pathogen, Puccinia striiformis. \
  • It appears in the form of yellow stripes on wheat leaves.
  • Major States affected: Punjab, Himachal Pradesh, Haryana, Jammu & Kashmir, Uttar Pradesh and Uttarakhand.
  • Treatment: Spray Propiconazole Fungicides.

• Sublimation is the process where a substance transitions directly from the solid phase to the gas phase without passing through the liquid phase. Not all materials sublimate readily at standard temperature and pressure, but there are several examples of substances that exhibit sublimation under certain conditions
• Dry Ice (Solid Carbon Dioxide): Dry ice is a common example of a substance that sublimates. It transforms directly from a solid to a gas at temperatures above -78.5 degrees Celsius (-109.3 degrees Fahrenheit) at standard pressure.
• Camphor: Solid camphor can sublimate at room temperature, producing vapors with a distinct, aromatic odor. This property makes camphor useful in mothballs and other applications.
• Naphthalene: Often used as the primary ingredient in mothballs, naphthalene sublimates at room temperature. The vapors help repel insects.
• Iodine: Iodine can sublimate when heated, producing a purple vapor. This property is exploited in laboratory demonstrations.
• Moth Crystals (Para-dichlorobenzene): Similar to naphthalene, para-dichlorobenzene, commonly found in moth crystals, can sublimate at room temperature.
• Anthracene: A crystalline solid that sublimates when heated, anthracene is often used in laboratory settings.
• Benzoic Acid: Solid benzoic acid can undergo sublimation under specific conditions, such as heating.
• Ammonium Chloride: Ammonium chloride sublimates when heated, and this property is utilized in some chemistry experiments.
• Cellulose (C₆H₁₀O₅)n: The main component of plant cell walls, cellulose has a complex structure with strong hydrogen bonds. It decomposes well below its melting point, preventing sublimation altogether. 
• Hence option (b) is the correct answer.

• The effects of forces of the same magnitude on different areas are different. When the person stands on loose sand, the force, that is, the weight of his body is acting on an area equal to the area of his feet. When he lies down, the same force acts on an area equal to the contact area of his whole body, which is larger than the area of his feet. In both cases, the force exerted on the sand is the weight of his body and the force is acting perpendicular to the surface of the sand. The force acting on an object perpendicular to the surface is called thrust. The effect of thrust on sand is larger while standing than while lying. The thrust on the unit area is called pressure.
• Pressure = Thrust/Area
• Thus, higher pressure is exerted by the body on the sand while standing and the person goes down deeper into it as compared to when he is lying down.