Q. Which of the following adds/add nitrogen to the soil?

  1. Excretion of urea by animals
  2. Burning of coal by man
  3. Death of vegetation

Select the correct answer using the codes given below:

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (c) 1 and 3 only

  • When coal is burnt, nitrogen helps to form oxides which may be released as flue gases and thereby pollute the atmosphere.
    • It does not add nitrogen to the soil unless the oxides so created enter into the nitrogen cycle.
    • Then, what remains after burning coal is Fly Ash.
    • Fly Ash is devoid of nitrogen content.
  • Nitrogenous Waste products of Living organisms such as urea and uric acid and dead remains of organisms are converted back to inorganic ammonia by the bacteria.

Q. Improper handling and storage of cereal grains and oilseeds result in the production of toxins known as aflatoxins which are not generally destroyed by normal cooking process. Aflatoxins are produced by

(a) Bacteria

(b) Protozoa

(c) Moulds

(d) Viruses

Answer: (c) Moulds

  • Aflatoxins are various poisonous carcinogens and mutagens that are produced by certain molds, particularly Aspergillus species.
  • Aflatoxins are a family of toxins produced by certain fungi that are found on agricultural crops such as maize (corn), peanuts, cottonseed, and tree nuts.
  • The main fungi that produce aflatoxins are Aspergillus flavus and Aspergillus parasiticus, which are abundant in warm and humid regions of the world.
  • Aflatoxin-producing fungi can contaminate crops in the field, at harvest, and during storage.
  • The fungi grow in soil, decaying vegetation and various staple foodstuffs and commodities such as hay, sweetcorn, wheat, millet, sorghum, cassava, rice, chili peppers, cottonseed, peanuts, tree nuts, sesame seeds, sunflower seeds, and various spices. In short, the relevant fungi grow on almost any crop or food.
    • When such contaminated food is processed or consumed, the aflatoxins enter the general food supply. They have been found in both pet and human foods, as well as in feedstocks for agricultural animals. Animals fed contaminated food can pass aflatoxin transformation products into eggs, milk products, and meat.
      • For example, contaminated poultry feed is the suspected source of aflatoxin-contaminated chicken meat and eggs in Pakistan.
  • Children are particularly affected by aflatoxin exposure, which is associated with stunted growth, delayed development, liver damage, and liver cancer.
    • Adults have a higher tolerance to exposure, but are also at risk. No animal species is immune.
  • Aflatoxin poisoning most commonly results from ingestion, but the most toxic aflatoxin compound, B1, can permeate through the skin.
  • Prevention:
    • A primary means of limiting risk from aflatoxins in the food supply is food hygiene in the commercial commodity supply chain, such as rejecting moldy grain for use in food processing plants and testing of batches of ingredients for aflatoxin levels before adding them to the mix.
    • Regulatory agencies such as the FDA set limits on acceptable levels.
    • Grain drying itself, which is necessary for viable combine harvesting in many regions, lays the fundamentals for this effort by preventing stored grain from being too damp in the first place.
  • A mold is one of the structures that certain fungi can form. The dust-like, colored appearance of molds is due to the formation of spores containing fungal secondary metabolites. The spores are the dispersal units of the fungi.
  • Not all fungi form molds. Some fungi form mushrooms; others grow as single cells and are called microfungi (for example yeasts).
  • A large and taxonomically diverse number of fungal species form molds. The growth of hyphae results in discoloration and a fuzzy appearance, especially on food.
  • Molds cause biodegradation of natural materials, which can be unwanted when it becomes food spoilage or damage to property. They also play important roles in biotechnology and food science in the production of various pigments, foods, beverages, antibiotics, pharmaceuticals and enzymes.
  • Some diseases of animals and humans can be caused by certain molds: disease may result from allergic sensitivity to mold spores, from growth of pathogenic molds within the body, or from the effects of ingested or inhaled toxic compounds (mycotoxins) produced by molds.

Q. Which of the following diseases can be transmitted from one person to another through tattooing?

  1. Chikungunya
  2. Hepatitis B

Select the correct answer using the codes given below:

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (b) 2 and 3 only

  • Chikungunya is a mosquito-borne viral disease caused by the chikungunya virus (CHIKV), an RNA virus in the alphavirus genus of the family Togaviridae.
  • It was first recognized in 1952 during an outbreak in southern Tanzania. 
  • Symptoms: Chikungunya causes fever and severe joint pain, which is often debilitating and varies in duration.
    • Dengue and Zika have similar symptoms to chikungunya, making chikungunya easy to misdiagnose.
  • Transmission: Chikungunya is transmitted to humans by the bites of infected female mosquitoes. 
    • Most commonly, the mosquitoes involved are Aedes aegypti and Aedes albopictus
      • These two species can also transmit other mosquito-borne viruses, including dengue.
        • They bite throughout daylight hours, although there may be peaks of activity in the early morning and late afternoon. 
  • Prevalence: According to WHO, It is prevalent in Africa, Asia, and the Americas; but sporadic outbreaks have been reported in other regions.
  • Treatment Options: Presently, there is no cure for chikungunya, with symptomatic relief being the primary approach.
    • Treatment involves the use of analgesics, antipyretics, rest, and adequate fluid intake.
    • There is currently no approved vaccine or specific treatment for chikungunya virus infections.
  • Hepatitis is inflammation of the liver.
  • Inflammation is swelling that happens when tissues of the body are injured or infected.
  • It can damage your liver. This swelling and damage can affect how well your liver functions.
  • Hepatitis can be an acute (short-term) infection or a chronic (long-term) infection. 
  • What causes hepatitis? There are different types of hepatitis, with different causes:
    • Viral hepatitis is the most common type. It is caused by one of several viruses — hepatitis viruses A, B, C, D, and E.
    • Alcoholic hepatitis is caused by heavy alcohol use.
    • Toxic hepatitis can be caused by certain poisons, chemicals, medicines, or supplements.
    • Autoimmune hepatitis is a chronic type in which your body’s immune system attacks your liver. The cause is not known, but genetics and your environment may play a role.
  • How is viral hepatitis spread?
    • Hepatitis A and hepatitis E usually spread through contact with food or water that is contaminated with an infected person’s stool. You can also get hepatitis E by eating undercooked food.
    • Hepatitis B, hepatitis C, and hepatitis D spread through contact with the blood of someone who has the disease. 
    • Hepatitis B and D may also spread through contact with other body fluids. This can happen in many ways, such as sharing drug needles or having unprotected sex.
  • Treatment:
    • Hepatitis A and E are self-limiting diseases (i.e. go away on their own) and require no specific antiviral medications.
    • For Hepatitis B and C, effective medications are available.
  • HIV stands for Human Immunodeficiency Virus, which is a virus that attacks the immune system in the human body.
  • It primarily targets and damages CD4 immune cells, which are essential for the body’s ability to fight infections and diseases.
    • Over time, HIV weakens the immune system, leaving the body vulnerable to opportunistic infections and cancers.
  • Transmission:
    • HIV is primarily spread through the exchange of certain bodily fluids such as blood, semen, vaginal fluids, and breast milk.
  • Severity:
    • If left untreated, the virus destroys a person’s immune system and they are said to be in the Acquired Immunodeficiency Syndrome stage (AIDS) where they get several opportunistic infections that may result in death.
  • Cure:
    • Although there are no cures for the infection at present, the disease can be managed using antiretroviral therapy.
      • These medicines suppress the replication of the virus within the body, allowing the number of CD4 immune cells to bounce back.

Q. Consider the following organisms:

  1. Agaricus
  2. Nostoc
  3. Spirogyra

Which of the above is/are used as biofertilizer/biofertilizers?

(a) 1 and 2
(b) 2 only
(c) 2 and 3
(d) 3 only

Answer: (b) 2 only

  • Biofertilizers are substance that contains microbes, which helps in promoting the growth of plants and trees by increasing the supply of essential nutrients to the plants.
  • It comprises living organisms which include mycorrhizal fungi, blue-green algae, and bacteria.
    • Mycorrhizal fungi preferentially withdraw minerals from organic matter for the plant whereas cyanobacteria are characterized by the property of nitrogen fixation.
  • Benefits of biofertilizers
    • Biofertilizers fix atmospheric nitrogen in the soil and root nodules of legume crops and make it available to the plant.
    • They solubilise the insoluble forms of phosphates like tricalcium, iron and aluminium phosphates into available forms.
    • They scavenge phosphate from soil layers.
    • They produce hormones and anti metabolites which promote root growth.
    • They decompose organic matter and help in mineralization in soil.
    • When applied to seed or soil, biofertilizers increase the availability of nutrients and improve the yield by 10 to 25% without adversely affecting the soil and environment.
  • Types of biofertilizers
    • Based on type of microorganism, the bio-fertilizer can also be classified as follows:
      • Bacterial Biofertilizers: e.g. Rhizobium, Azospirilium, Azotobacter, Phosphobacteria.
      • Fungal Biofertilizers: e.g. Mycorhiza
      • Algal Biofertilizers: e.g. Blue Green Algae (BGA) and Azolla.
      • Actinimycetes Biofertilizer: e.g. Frankia.
    • Bio-fertilizer are mostly cultured and multiplied it the laboratory. However, blue green algae and azolla can be mass-multiplied in the field.
  • Characteristics Features of common Biofertilizers
    • Rhizobium: Rhizobium is relatively more effective and widely used biofertilizer. Rhizobium, in association wit legumes, fixes atmospheric N. The legumes and their symbiotic association with the rhizobium bacterium result in the formation of root nodules that fix atmospheric N. Successful nodulation of leguminous crop by rhizobium largely depends on the availability of a compatible stain for a particular legume. Rhizobium population in the soil is dependent on the presence of legumes crops in field. In the absence of legumes the population of rhizobium in the soil diminishes.
    • Azospirillum: Azospirillum is known to have a close associative symbiosis with the higher plant system. These bacteria have association with cereals like; sorghum, maize, pearl millet, finger millet, foxtail millet and other minor millets and also fodder grasses.
    • Azotobacter:  It is a common soil bacterium. Azotobacter chroococcum is present widely in Indian soil. Soil organic matter is the important factor that decides the growth of this bacteria.
    • Blue Green Algae (BGA): Blue green algae are referred to as rice organisms because of their abundance in the rice field. Many species belonging to the genera, Tolypothrix, Nostic, Schizothrix, Calothrix, Anoboenosois and Plectonema are abundant in tropical conditions. Most of the nitrogen fixation BGA are filamenters, consisting of chain of vegetative cell including specialized cells called heterocyst which function as a micronodule for synthesis and N fixing machinery.
  • Nostoc is a genus of blue-green algae or cyanobacteria. They are prokaryotic and perform photosynthesis.
  • They are found mainly in freshwater as free-living colonies or attached to rocks or at the bottom of lakes. They are also found on tree trunks. They are also found as an algal component of lichens in certain bryophytes (Anthoceros).
  • They are capable of nitrogen-fixing and perform photosynthesis. They are also present as an endosymbiont to fungus.
  • Agaricus is a genus of mushroom-forming fungi containing both edible and poisonous species, with over 400 members worldwide and possibly again as many disputed or newly-discovered species.
  • The genus includes the common (“button”) mushroom (Agaricus bisporus) and the field mushroom (A. campestris), the dominant cultivated mushrooms of the West.
  • Spirogyra are free-floating green algae present in freshwater habitats such as ponds, lakes, etc. Spirogyra are commonly known as “water silk or pond silk”.
  • They have a filamentous and unbranched vegetative structure. There are around 400 species of Spirogyra found. The genus Spirogyra is named after the unique spiral chloroplast present in the cells of algae.
  • Spirogyra are photosynthetic and contribute substantially to the total carbon dioxide fixation carried out. They increase the level of oxygen in their habitat. Many aquatic organisms feed on them.

Q. Which of the following statements is/are correct

  1. Viruses lack enzymes necessary for the generation of energy.
  2. Viruses can be cultured in any synthetic medium.
  3. Viruses are transmitted from one organism to another by biological vectors only.

Select the correct answer using the codes given below.

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (a) 1 only

  • A virus is a small collection of genetic code (either DNA or RNA) surrounded by a protein coat.
  • They lack metabolic machinery of their own to generate energy or synthesize proteins. They can reproduce only within a living cell – hence they are obligate intracellular parasites. They take over the functions of the host cell hence causing infection.
  • Viruses are inactive outside the host (crystallized form) and active inside. This puts them in the unique criteria of living as well as the non-living entity or ‘not truly living’.
    • Unlike bacteria and other microorganisms which can be grown in artificial media, viruses cannot be grown on artificial medium but must be grown in living cells. Viruses cannot be grown on an ordinary culture medium because they are not actually living organisms. Viruses can be cultivated within suitable hosts, such as a living cell.
  • A virus is an acellular organism which are 10 to 100 times smaller than bacteria, about 20-300 nm in size.
  • Structure of a Virus
    • The core of the virus is made up of nucleic acids, which then make up the genetic information in the form of RNA or DNA. The protein layer that surrounds and protects the nucleic acids is called the capsid. Sometimes the capsid is surrounded by an additional spikey coat called the envelope.
    • Viruses are capable of latching onto host cells and getting inside them. When a single virus is in its complete form and has reached full infectivity outside of the cell, it is known as a virion.
  • Spread:
    • The virus enters hosts through horizontal or vertical transmission, mostly horizontal. Examples of horizontal transmission include the following:
      • Direct contact transmissionThis refers to transmission via physical contact between an infected and uninfected subject through kissing, biting, or sexual intercourse, for example.
      • Indirect transmissionHere, the virus is transmitted via contact with contaminated objects or materials such as medical equipment or shared eating utensils.
      • Common vehicle transmission:This transmission mode refers to when individuals pick up the virus from food and water supplies that are contaminated with feces. This often causes epidemic disease.
      • Airborne transmission refers to the respiratory infection that occurs when the virus is inhaled.
    • Once a virus has accessed its host, it recognizes and binds to a specific receptor on the surface of a target cell. One well-studied example is the interaction that occurs between the CCR5 receptor on human T lymphocytes and the gp41 protein present on the surface of the human immunodeficiency virus (HIV).
  • Life cycle of a virus
    • Once a virus has infected a host cell, it can replicate within that cell thousands of times. Rather than dividing and reproducing in the way that cells do, viruses go through a process called the lytic cycle.
    • First, the virus replicates its DNA and protein coats, which are then assembled into new virus particles. This causes the host cell to burst or “lyse,” which is why the cycle is so-called. The new virus particles that are released once the cell has burst then infect surrounding host cells.
    • The process can take as little as twelve hours, as is the case with the norovirus, or as long as several days, as is the case with the Ebola virus.
    • Some complex viruses called phages bind their DNA to that of their host cell or deposit small pieces of their DNA in the cytoplasm. When the cell then divides, the viral DNA is copied into the daughter cells. This cycle, which is called the lysogenic cycle, is less common than the lytic cycle.

Q. Consider the following minerals:

  1. Calcium
  2. Iron
  3. Sodium

Which of the minerals given above is/are required by human body for the contraction of muscles?

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

  • Minerals are inorganic elements present in soil and water, which are absorbed by plants or consumed by animals.
    • While you’re likely familiar with calcium, sodium, and potassium, there is a range of other minerals, including trace minerals (e.g. copper, iodine, and zinc) needed in very small amounts.
  • The minerals are utilized by the body’s organ systems for growth, development, movement, energy production, utilization and maintenance of internal homeostasis. Essential minerals are divided into two main groups based on the concentration required for normal body function: macrominerals and trace minerals.
    • A balanced diet provides all the essential minerals needed to maintain good health. In case of dietary inadequacy to meet mineral requirements, supplements may also be taken.
  • The 13 essential minerals:
    • Calcium: Calcium is the most common and abundant mineral in the body. Calcium builds strong bones and teeth and helps in muscle contraction, blood clotting, nerve transmission, cell signaling and regulation of metabolism. The deficiency of calcium makes bone fragile and easy to fracture. Milk and dairy products, cashew, dates, broccoli, parsley and greens are good sources of dietary calcium.
    • Sodium: Sodium helps in muscle contraction, conducts nerve impulses and controls the fluid balance in the body. The primary source of dietary sodium is table salt. However, salt should be taken in moderation.
    • Potassium: Potassium plays a crucial role in maintaining fluid balance, muscle contraction and nerve impulse conduction. It supports brain health and reduces the risk of stroke. Low potassium causes irregular heartbeats, edema (swelling), brain damage, etc. Bananas, sweet potatoes, avocados, beets and dates are rich sources of potassium.
    • Chloride: Chloride in association with sodium maintains the normal fluid balance in the body. It is used in the formation of hydrochloric acid (stomach acid) for digestion and to sustain electrical neutrality in the body. Table salt, tomatoes, celery and lettuce are rich sources of chloride.
    • Magnesium: Magnesium acts as a cofactor in several enzymatic reactions and is required for the synthesis of deoxyribonucleic acid (DNA) and an antioxidant, glutathione. Green leafy vegetables, legumes, nuts, seeds and whole grains replenish dietary magnesium.
    • Phosphorous: Phosphorus helps build and repair bones and teeth, helps nerves function and makes muscles contract. Phosphorus deficiency leads to bone diseases and growth restriction in children. Meats, poultry, beans, nuts, seeds and dairy products are rich sources of phosphorus.
    • Iodine: It is the mineral used to produce thyroid hormones. It is necessary for the body’s metabolism and physical and mental development. Phosphorus deficiency leads to impaired growth in children and metabolic disorders such as goiter and mental problems and affects menstrual health and pregnancy-related issues. Iodized table salt is the main source and is easily available.
    • Iron: It is used in hemoglobin formation, which carries oxygen in the blood. Iron deficiency can lead to cellular hypoxia (decreased oxygen) and cell death. Green leafy vegetables and meats such as beef, chicken and pork are rich sources of iron.
      • Iron is present in the muscle in the form of myoglobin.
        • Myoglobin has the capacity to store oxygen.
        • This oxygen is used for muscle contraction and for other immediate needs of the muscle.
    • Zinc: This mineral aids in cell division, immunity and wound healing. Low zinc levels impair the immune system. Oysters, red meat, poultry, beans, nuts and whole grains provide major quantities of zinc.
    • Copper: Copper helps in energy production and facilitates iron uptake from the gut. Chocolate, liver, shellfish and wheat bran cereals are rich sources.
    • Manganese: Manganese plays an important role in protein, carbohydrate and cholesterol breakdown and cell division. Along with vitamin K, it helps in blood clotting. Whole grains, nuts, soybeans and rice are rich in manganese.
    • Sulfur: Sulfur has antibacterial properties and helps fight acne-causing bacteria in the skin. It also repairs DNA damage. Seafood and legumes, especially soybeans, black beans and kidney beans are rich sources of sulfur.
    • Selenium: Selenium helps prevent oxidative damage to the cells. It is also very important for the metabolism of the thyroid hormone. Brazil nuts, seafood and organ meats are good sources of selenium.

Q. Fruits stored in a cold chamber exhibit longer storage life because

(a) exposure to sunlight is prevented

(b) concentration of carbon dioxide in the environment is increased

(c) rate of respiration is decreased

(d) there is an increase in humidity

Answer: (c) rate of respiration is decreased

  • The shelf life of fruits and vegetables can be increased by keeping them in cold storage this results in a slower ripening process and fruits and vegetables remain fresh for a longer duration. 
  • Fruits when stored in a cold chamber exhibit a longer storage life because their rate of respiration is decreased. When fruit respires they release out ethylene which helps in ripening
  • Ethylene is also known as the ‘fruit-ripening hormone‘. Every fruit has a different level of ethylene production.
  • The rate of ethylene production decreases when fruits are kept in cold storage. Thus, the shelf life of fruits increases.

Q. The known forces of nature can be divided into four classes, viz. gravity, electromagnetism, weak nuclear force and strong nuclear force. With reference to them, which one of the following statements is not correct?

(a) Gravity is the strongest of the four

(b) Electromagnetism acts only on particles with an electric charge

(c) Weak nuclear force causes radioactivity

(d) Strong nuclear force holds protons and neutrons inside the nucleus of an atom

Answer: (a) Gravity is the strongest of the four

Universal Forces (The Four Fundamental Forces)
  • The Four Fundamental Forces of Nature are: Gravitational force, Weak Nuclear force, Electromagnetic force and Strong Nuclear force.
    • The weak and strong forces are effective only over a very short range and dominate only at the level of subatomic particles. Gravity and Electromagnetic force have infinite range.
      • Gravitational Force – Weakest force; but has infinite range. (Not part of the standard model)
      • Weak Nuclear Force – Next weakest; but short range.
      • Electromagnetic Force – Stronger, with infinite range.
      • Strong Nuclear Force – Strongest; but short range.
  • Strong Force
    • The strong force is a fundamental force that acts between subatomic particles of matter. The strong force is what binds the quarks together in clusters to form more familiar subatomic particles such as protons and neutrons. The force originates from a property known as the color. This property has no connection with color in the visual world. Particles without color, for example, electrons, do not experience the strong force. But, particles with color such as quarks do experience the strong force.
  • Electromagnetic Force
    • The electromagnetic force, also known as Lorentz’s Force explains how stationary and moving charged particles interact with each other. It is known as an electromagnetic force because of the presence of the formerly distinct electric and magnetic force.
    • The electric force acts between all charged particles whether they are moving or not. While magnetic force only acts between moving charged particles. This means that every charged particle whether moving or not gives off an electric field.
  • Weak Nuclear Force
    • While other forces hold things together, a weak nuclear force plays a greater role in making things fall apart. Although a stronger force than gravity, it is only effective at very short distances. The theory of weak nuclear force was first proposed by Enrico Fermi and was known at that time as Fermi’s interaction. Following are a few of the properties of weak force:
      • It is the only kind of reaction that can change one kind of quark to other
      • Weak forces are propagated by carrier particles that have significant masses.
      • It violates parity-symmetry
      • It violates charge-parity symmetry
  • Gravitation
    • Gravitational force is the weakest of all. It is the force that decides how much we weigh and how far a basketball travels when it is thrown before it returns to the surface. When two objects are gravitationally locked, their gravitational force is centered in an area that is not the center of either of the objects, rather at the barycentre of the system.
Electromagnetic Force
Gravitational Force
Strong Nuclear Force
Weak Nuclear Force

Q. Consider the following phenomena:

  1. Size of the sun at dusk
  2. Colour of the sun at dawn
  3. Moon being visible at dawn
  4. Twinkle of stars in the sky
  5. Polestar being visible in the sky

Which of the above are optical illusions?

(a) 1, 2 and 3 only
(b) 3, 4 and 5 only
(c) 1, 2 and 4 only
(d) 2, 3 and 5 only

Answer: (c) 1, 2 and 4 only

Optical Illusion
  • Optical Illusions are images or pictures that are perceived differently than they really are. So in a  way, Optical Illusions occur when our eyes see something and send the signals to our brain which perceives it to be something unreal. In other words, what you see does not match the reality of what actually is to be seen. 
    • When images look different from the Real one, it is called ‘optical illusion’ (or visual illusion).
    • Optical Illusion can be of three main types – Verbal, Physical and Cognitive. They are often used as mental exercises for adults and children.
    • In this process, visual illusions arise to human beings, this shows the process of simultaneous functioning of eyes and brain. We live in a three-dimensional (3D) world. Therefore, the brain helps us to present the complete information of its depth, shading, lighting and position in relation to an object seen by it in the form of an image.
    • Mirage is an optical phenomenon, in which the ray of light is incident at the bottom of the medium at such an angle that its reflection takes place in the same medium, which is called Total internal reflection. Generally, this happens when light enters the rare medium through a dense medium and the angle of incidence is greater than the ‘critical angle’. In this event, there is the illusion of water on the roads or on the deserts. It can usually be seen during high sunlight.
  • Size of the sun at dusk: The size of the sun at different intervals of the day will appear different because of optical illusion. It will appear large during the morning time because we see it with other objects in the environment. It will appear smaller in noon time because of the presence of clear sky and appears more clear during evening time.
  • Color of the Sun at dawn: The color of the sun resembles optical illusion throughout the day. Light is composed of many colors and out of all those colors, red color travels farthest in the atmosphere and appears to be seen at last. During noon time, Sun appears whitish and yellowish in color.
  • The twinkle of stars in the sky: Stars have their own light and as a result cause an optical illusion. This happens when light travels through various layers of the atmosphere before reaching human eyes.
  • Moon being visible at Dawn: It is not an optical illusion because the moon is visible at dawn during the half of the cycle of Full Moon to just before New Moon.
  • Polestar being visible in the sky: It is not an optical illusion as Polestars appears in North or South pole which completely depends on earth rotation.

Q. Due to improper/indiscriminate disposal of old and used computers or their parts, which of the following are released into the environment as e-waste?

  1. Beryllium
  2. Cadmium
  3. Chromium
  4. Heptachlor
  5. Mercury
  6. Lead
  7. Plutonium

Select the correct answer using the codes given below:

(a) 1, 3, 4, 6 and 7 only
(b) 1, 2, 3, 5 and 6 only
(c) 2, 4, 5 and 7 only
(d) 1, 2, 3, 4, 5, 6 and 7

Answer: (b) 1, 2, 3, 5 and 6 only

  • Electronic waste (e-waste), is a generic term used to describe all types of old, end-of-life or discarded electrical and electronic equipment, such as household appliances, office information and communications equipment etc.
    • E-waste contains numerous toxic chemicals including metals such as lead, cadmium, mercury, and nickel.
  • Invisible e-waste: Invisible e-waste refers to electronic waste that often goes unnoticed due to its nature or appearance, causing consumers to overlook its recyclable potential.
    • There are Numerous electronic items falling under this category, such as cables, e-toys, e-cigarettes, e-bikes, power tools, smoke detectors, USB sticks, wearable health devices, and smart home gadgets.
  • India currently ranks third among the largest generators of e-waste globally, behind only China and the US.
    • The volume of e-waste in India has witnessed a significant surge to 1.6 million tonnes in 2021-22.
    • The 65 cities in India generate more than 60% of the total generated e-waste, whereas 10 states generate 70% of the total e-waste.
  • Following are some examples of the e-waste components:
    • Cathode ray tubes
    • Printed circuit boards
    • Chips and other gold plated components
    • Plastics from printers, keyboards, monitors, etc.
    • Computer wires
  • Various issues related to e-waste:
    • Health risks: E-waste when dismantled and shredded, release dust or large particles into the immediate environment and affects the respiratory health of workers. Further, unregulated burning of e-waste releases toxins, such as dioxins which are potent and damaging to both human (neurological disease and impact on immune system) and animal health.
    • Water pollution: Water is contaminated by e-waste in landfills that are not properly designed to contain e-waste and due to improper recycling and subsequent disposal of e-waste. Groundwater is polluted by e-waste as heavy metals and other persistent chemicals leach from landfills and illegal dump sites into ground water tables.
    • Soil pollution: Soil is contaminated by e-waste through direct contact with contaminants from e-waste or the by-products of e-waste recycling and disposal and indirectly through irrigation through contaminated water. Contaminated soils have adverse impact on microbes and plants and the pollutants pass to higher animals and humans along the food chain.
    • Air pollution: Most of the discarded products are set into open fire, which melts and releases harmful elements to the atmosphere. Carcinogens and neurotoxins when released into the air pollute and create smog which is very obnoxious.
ElementsHarmful effects
Leadaffects the nervous system that leads to behavioural changes, lower IQ, also has a negative impact on kidneys
Mercuryexposure to mercury causes dermatitis, sensory impairment, memory loss, muscle weakness, reduced fertility, etc.
Cadmiumit is the cause of severe lung and kidney damages, and in children, it may cause learning and neuromotor defects
Chromium it has carcinogenic properties and may also result in damaging of DNA.
Beryllium it can cause beryllium sensitization, chronic beryllium disease, acute beryllium disease, and lung cancer.
PVC (Polyvinyl chloride)the bioaccumulation of chlorine over a period of time results in air, water, and soil pollution; and can lead to reproductive and developmental health effects.
PFOA (Perfluorooctanoic  acid)it has severe impact on the pregnant women as it may lead to spontaneous abortions, stillbirth, low birth weight, etc.
Sulphurit can damage the heart, kidneys, and liver.
BFRs (Brominated Flame Retardants) it may lead to thyroid problems, liver problems, improper development of nervous system, etc.

Q. The efforts to detect the existence of Higgs boson particle have become frequent news in the recent past. What is/are the importance (s) of discovering this particle?

  1. It will enable us to understand as to why elementary particles have mass.
  2. It will enable us in the near future to develop the technology of tranferring matter from one point to another without traversing the physical space between them.
  3. It will enable us to create better fuels for nuclear fission.

Select the correct answer using the codes given below.

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (a) 1 only

Higgs boson
  • It is the fundamental force-carrying particle associated with the Higgs field, a field that gives mass to other fundamental particles such as electrons and quarks. 
  • It is one of the 17 elementary particles that make up the Standard Model of particle physics, which is scientists’ best theory about the behaviors of the universe’s most basic building blocks.
  • Higgs boson plays such a fundamental role in subatomic physics that it is sometimes referred to as the “God particle.”
  • It was proposed in 1964 by Peter Higgs, François Englert, and four other theorists to explain why certain particles have mass.
  • The particle was finally discovered on July 4, 2012, by researchers at the Large Hadron Collider (LHC).
  • Features:
    • The Higgs boson has a mass of 125 billion electron volts  —  meaning it is 130 times more massive than a proton , according to CERN.
    • It is also chargeless with zero spin  —  a quantum mechanical equivalent to angular momentum.
    • The Higgs Boson is the only elementary particle with no spin.
    • Its a “force carrier” particle that comes into play when particles interact with each other, with a boson exchanged during this interaction.
  • When the Higgs field doesn’t provide mass to particles then there will be no gravity and no life.
Large Hadron Collider (LHC)
  • It is the world’s largest and most powerful particle accelerator.
  • LocationNear GenevaSwitzerland; across the border of France and Switzerland.
  • The LHC, built by the European Organisation for Nuclear Research (CERN), is on the energy frontier of physics research, conducting experiments with highly energised particles.
  • The LHC can reproduce the conditions that existed within a billionth of a second of the Big Bang.
  • The colossal accelerator allows scientists to collide high-energy subatomic particles in a controlled environment and observe the interactions.
  • One of the most significant LHC breakthroughs came in 2012 with the discovery of the Higgs Boson.

Q. Many transplanted seedlings do not grow because

(a) the new soil does not contain favourable minerals

(b) most of the root hairs grip the new soil too hard

(c) most of the root hairs are lost during transplantation

(d) leaves get damaged during transplantation

Answer: (c) most of the root hairs are lost during transplantation

  • Transplantation is the process in which the plant is grown in other places by replacing it from its original place.
  • In this process, most of the time root hairs are lost because dry soil present during transplantation takes away all the moisture from the plant. Hence option 3 is correct.
  • Transplantation helps in selecting healthy plants.
  • It allows deeper penetration of the roots in the soil.
  • It provides a good amount of sunlight, water, minerals, and nutrient to the plant.
  • Leaves sometimes got damaged during transplantation but it doesn’t affect the plants’ growth.

Q. Recombinant DNA technology (Genetic Engineering) allows genes to be transferred

  1. Across different species of plants
  2. From animals to plants
  3. From microorganisms to higher organisms

Select the correct answer using the codes given below.

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

Recombinant DNA Technology
  • Recombinant DNA technology (RDT), often referred to as Genetic Engineeringis an in-vitro (lab) method of manipulating genes (DNA fragments) by using a set of tools and techniques. The primary aim of RDT is to produce “Transgene (recombinant DNA) and its product (recombinant protein), to be applied across different fields of biotechnology.
    • The RDT is a continuously evolving technology due to the advancement in its tools and techniques, such as the discovery of the CRISPR-Cas9 gene editing tool.
  • Process involved in Recombinant DNA Technology:
    • Recombinant DNA technology undergoes through the following steps:
      • Isolation of Genetic Material: The extraction of genetic material is performed from the source organism’s DNA, such as bacteria, plants, or animals.
      • Selection of a Suitable Cloning Vector: Vectors are carrier molecules used to introduce rDNA into a host organism.
        • Plasmids, which are small, circular DNA molecules, are commonly used vectors. They can replicate independently within a host cell, allowing for the propagation of the foreign DNA.
        • The vectors can also be non-self replicating (for example, viral vectors). 
      • Cutting of DNA at Specific Locations: It uses the specialized enzymes known as restriction endonucleases (RE) or restriction enzymes, which recognize specific DNA sequences (recognition sites) and cleave the DNA at those precise locations.
        • The RE cuts the target DNA as well as Plasmid, producing “sticky ends” that are complementary to each other.
      • Joining of DNA Fragments by Ligation:
        • The isolated DNA fragments are combined with a vector, which is typically a plasmid or a viral genome modified to accept foreign DNA.
        • DNA ligase is used to catalyze the formation of phosphodiester bonds, effectively sealing the gaps and fusing the DNA fragments with the vector.
        • Now the rDNA is ready for gene transfer (for in-vivo gene cloning) or for the PCR. 
      • Gene Transfer: There are several methods which are employed in the process of Gene Transfer- physical, chemical, and biological. RDT uses the biological means of gene transfer.
        • Physical methods: Gene gun or Biolistics, Electroporation, Microinjection, etc., which make the direct entry of the rDNA into the host’s cell.
        • Chemical methods: Using Lipofection, calcium phosphate, etc. make it easier for the rDNA to enter into the host’s cell.
        • Biological methods: This is an indirect method of gene transfer, using vectors (for example, bacteria) as a means.
      • Gene Cloning: Once inside the host, the rDNA replicates itself independently (due to self-replicating plasmid). This is called Gene Cloning. It can also be done using the PCRmethod for amplifying a gene of interest.
      • Polymerase Chain Reaction (PCR): PCR is a tool that allows for the amplification of the target DNA sequences outside the cell. It needs much less time than the traditional cloning methods.
      • Selection and Screening of Transformed Cells: This step involves identifying and isolating cells that have successfully taken up the recombinant DNA.
        • Selectable markers, such as antibiotic resistance genes carried by the vector, are often used to distinguish transformed cells from non-transformed ones.
      • Validation of Recombinant DNA Integration: To ensure that the recombinant DNA has integrated into the host genome as intended, various techniques may be employed.
        • For example, nucleic acid hybridization, blue-white screening, etc.
  • Applications of Recombinant DNA Technology:
    • Recombinant DNA Technology stands as a cornerstone of modern science with far-reaching applications across numerous fields.
      • Advancement in Medicine:
        • It enables the production of vital biopharmaceuticals, particularly therapeutic proteins like insulin, growth hormone, and clotting factors.
        • Customized Therapeutics enables the production of personalised medicines tailored to an individual’s genetic makeup, leading to more effective and targeted treatments.
      • Gene Therapy:
        • It offers the potential to treat genetic disorders by replacing or repairing faulty genes.
        • It is helpful in treating a wide range of diseases, like cystic fibrosismuscular dystrophy, and certain types of cancer.
      • Recombinant Vaccines: RDT can be used to develop vaccines for a variety of diseases, using vectors like bacteria, yeasts, viruses (phage), etc. 
      • Immunotherapy: RDT contributes to the development of immunotherapies for example, T-cell therapy, which harnesses the body’s own immune system to target and destroy cancer cells.
      • Agricultural Advancements:
        • It is used to cultivate Genetically modified (GM) crops that have transformed agriculture. Example: BT cotton.
        • These crops possess traits like pest resistancedrought tolerance, and improved nutritional content.
      • Bioremediation and Environmental Protection:
        • Environmental biotechnology indicates that Genetically-modified microbes such as bacteria, yeast and filamentous fungi can remove heavy metals from aqueous solutions.
        • For example, Escherichia coli strain JM109 has the ability to remove mercury from contaminated water or soil.
      • Targeted Drug Delivery: 
        • It enables the design and production of drug-delivery systems that can precisely target specific tissues or cells within the body.
        • This increases the effectiveness of treatments while minimizing side effects.
      • Molecular diagnosis (RDT plus PCR):
        • It plays a critical role in diagnostic techniques, allowing for the detection of specific DNA sequences associated with diseases or pathogens.
        • It is helpful in early detection and monitoring of various conditions.
      • Industrial Applications:
        • It is used in the production of recombinant enzymes to produce sugarcheese, biofuels, important chemicals, etc.
Process involved in Recombinant DNA Technology

Q. Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to

  1. resist drought and increase absorptive area
  2. tolerate extremes of pH
  3. resist disease infestation

Select the correct answer using the codes given below.

(a) 1 only
(b) 2 and 3 only
(c) 1 and 3 only
(d) 1, 2 and 3

Answer: (d) 1, 2 and 3

  • Mycorrhiza are symbiotic associations between plant roots and certain soil fungi which play a key role in nutrient cycling in the ecosystem and also protect plants against environmental and cultural stress.
    • The plant makes organic molecules by photosynthesis and supplies them to the fungus in the form of sugars or lipids, while the fungus supplies the plant with water and mineral nutrients, such as phosphorus, taken from the soil.
    • Mycorrhizas are located in the roots of vascular plants, but mycorrhiza-like associations also occur in bryophytes.
  • They greatly increase the efficiency of nutrient and water uptake, enhance resistance to pathogens, and buffer plant species against several environmental stresses and drought resistance. Mycorrhizae also improve plant growth and survival in soils contaminated by heavy metals.
  • Mycorrhiza fungi act as a bio-fertilizer and help in maintaining soil biology and chemistry. These are of 2 types:​
    • Endo mycorrhizae – Example with orchids.
    • Ecto mycorrhizae – Example with pines, mushrooms, etc.
Nutrient exchanges and communication between a mycorrhizal fungus and plants.
Nutrient exchanges and communication between a mycorrhizal fungus and plants.
  • A fungus is any member of the group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms.
    • These organisms are classified as one of the traditional eukaryotic kingdoms, along with Animalia, Plantae and either Protista or Protozoa and Chromista.
  • A characteristic that places fungi in a different kingdom from plants, bacteria, and some protists is chitin in their cell walls. Fungi, like animals, are heterotrophs; they acquire their food by absorbing dissolved molecules, typically by secreting digestive enzymes into their environment. Fungi do not photosynthesize.
  • Growth is their means of mobility, except for spores (a few of which are flagellated), which may travel through the air or water. Fungi are the principal decomposers in ecological systems.
    • Many fungi are free-living in soil or water; others form parasitic or symbiotic relationships with plants or animals.
  • Fungi are heterotrophic organisms; therefore, they rely on photosynthetic carbon to produce energy, and some species get this carbon from plant root exudates. Together, plants and fungi perform a process called soil carbon sequestration, capturing carbon from the atmosphere and storing it into the soil for decades if not hundreds of years.
    • This important process not only improves soil fertility as it can also help reduce the excess carbon human activities have put into the atmosphere.
  • Importance of fungi
    • Together with bacteria, fungi are responsible for breaking down organic matter and releasing carbon, oxygen, nitrogen, and phosphorus into the soil and the atmosphere.
    • Fungi are important contributors to the soil carbon stock. They play a major part in the carbon cycle through the soil food web.
    • Fungi have been found to help degrade various pollutants from the environment, such as plastic and other petroleum-based products, pharmaceuticals and personal care products, and oil.
    • Fungi are essential to many household and industrial processes, notably the making of bread, wine, beer, and certain cheeses.
    • Fungi are also used as food; for example, some mushrooms, morels, and truffles are epicurean delicacies, and mycoproteins (fungal proteins), derived from the mycelia of certain species of fungi, are used to make foods that are high in protein.