WBCS Prelims Biology & Environmental Science Questions and Answers (Previous Year Paper)

Answer: (B) Local Communities and the Forest Department

Explanation: Joint Forest Management (JFM) is a participatory approach in which village communities and the State Forest Department jointly protect and manage forest land. Communities form local forest committees that guard degraded forests. In return they get access to non-timber forest produce, fuelwood and fodder, and a share of the timber revenue. The 1988 National Forest Policy gave it a policy basis, and the Ministry of Environment and Forests issued the formal JFM guidelines in 1990.

JFM:

Answer: (A) Bats

Explanation: Fruit bats of the genus Pteropus, commonly called flying foxes, are the natural reservoir of the Nipah virus. The virus lives in them without causing illness and spreads through their saliva, urine and partly eaten fruit. Humans get infected by contaminated raw date palm sap, by fruit bitten by bats, or from infected pigs, and also through close contact with infected people. There is no licensed vaccine or specific cure, so treatment is supportive.

Nipah Virus:

Answer: (D) it has nodes and inter-nodes

Explanation: Ginger is a rhizome, which is a modified underground stem. What proves it is a stem is its structure: it has nodes and internodes, scale leaves, and axillary buds that sprout into new shoots. Growing horizontally and storing food are also true of ginger, but roots can store food too, so these do not identify a stem. Nodes and internodes are the defining feature of a stem, and roots never have them.

Modified Underground Stems:

Answer: (B) Algae

Explanation: Agar-agar is a jelly-like substance obtained from the cell walls of red algae (Rhodophyceae), mainly Gelidium and Gracilaria. It is used as a solid culture medium for growing bacteria and fungi in laboratories, and in the food industry as a gelling agent for jellies, ice creams and desserts. It is a polysaccharide that dissolves in hot water and sets into a gel on cooling.

Economically Important Algae Products:

Answer: (C) Mangrove forest as found in Sunderbans

Explanation: Mangroves hold more carbon per hectare than almost any other forest type. Most of it is stored in the waterlogged, oxygen-poor soil beneath the trees, where dead roots and leaves decompose very slowly and the carbon stays locked in for centuries. Tidal flooding also keeps bringing in carbon-rich sediment. This is why mangroves, salt marshes and seagrass meadows are called “blue carbon” ecosystems. Studies commonly find that mangroves store several times more carbon per hectare than typical upland tropical forests.

Blue Carbon and Forest Carbon:

Answer: (B) The leaf contains green chlorophyll but it remains hidden under other pigments

Explanation: Coloured leaves, such as red, purple or variegated ones, still photosynthesise because chlorophyll is present in them. The red, purple or orange colour comes from other pigments like anthocyanins, carotenoids and xanthophylls, which mask the green colour. Only chlorophyll can capture light energy for photosynthesis. The other pigments do not replace it, though they can protect the leaf from excess light and pass some absorbed energy on.

Leaf Pigments:

Answer: (B) Viruses neither have cell walls nor their own metabolic machinery to be targeted by antibiotics

Explanation: Antibiotics work by attacking structures or processes unique to bacteria, such as the peptidoglycan cell wall, bacterial ribosomes, or enzymes for folic acid synthesis. Viruses have none of these. They are non-cellular particles that cannot make their own proteins or energy, and instead hijack the host cell’s machinery to multiply. Since there is no bacterial target to hit, antibiotics have no effect on viral infections. Antivirals and vaccines are used instead. Option (B) in the paper is garbled, but it clearly refers to the absence of a cell wall and independent metabolism.

Antibiotics vs Antivirals:

Answer: (A) Respiratory roots

Explanation: Pneumatophores are specialised aerial roots found in mangrove plants that grow in waterlogged, saline, oxygen-poor mud. They grow upward, against gravity, which is why they are negatively geotropic. They have small pores called pneumathodes (lenticels) through which air enters and reaches the submerged roots. Their function is therefore gas exchange, or respiration, and not photosynthesis or storage.

Modified Roots:

Answer: (D) Rubisco

Explanation: Rubisco (ribulose-1,5-bisphosphate carboxylase/oxygenase) is the most abundant enzyme on Earth. It is found in the chloroplasts of all green plants, algae and cyanobacteria, and can make up nearly half of the soluble protein in a leaf. It catalyses the first major step of carbon fixation in the Calvin cycle, where CO₂ is attached to RuBP to form 3-phosphoglycerate. It works slowly and also reacts with oxygen (photorespiration), so plants need large amounts of it to meet their needs.

Rubisco and Related Enzymes:

Answer: (C) Zygotene

Explanation: Synapsis is the close pairing of homologous chromosomes during meiosis I, and it takes place in the zygotene stage of prophase I. The paired homologues are held together by a protein structure called the synaptonemal complex, forming bivalents. Crossing over follows in pachytene, so synapsis comes before it. The name “zygotene” comes from the Greek for “paired threads”.

Stages of Meiotic Prophase I:

Answer: (D) 2070

Explanation: At the COP26 climate summit in Glasgow in November 2021, Prime Minister Narendra Modi announced that India would reach net-zero carbon emissions by 2070. The question’s “non-zero” is a misprint for “net-zero”, which means balancing the greenhouse gases emitted with the amount removed from the atmosphere. The 2070 goal is part of India’s “Panchamrit” (five-point) climate pledge, which also sets targets for 2030.

India’s Panchamrit Commitments:

Answer: (B) Pulmonary veins

Explanation: Pulmonary veins are the only veins in the body that carry oxygenated blood. They bring blood rich in oxygen from the lungs to the left atrium of the heart. Hepatic portal veins carry nutrient-rich but deoxygenated blood from the intestine to the liver. Renal veins carry deoxygenated blood from the kidneys. The pulmonary artery is the only artery that carries deoxygenated blood, from the right ventricle to the lungs.

Oxygenated vs Deoxygenated Blood Vessels:

Answer: (D) Abscisic acid

Explanation: Abscisic acid (ABA) is the main growth-inhibiting plant hormone. It slows or stops growth, promotes seed and bud dormancy, and causes stomata to close during water stress, which is why it is called the “stress hormone”. It also promotes leaf senescence and the shedding of leaves and fruits. Auxins, gibberellins and cytokinins are growth promoters.

Plant Hormones:

Answer: (B) Capillary water

Explanation: Capillary water is the water held as a thin film around soil particles and in the small pores between them by surface tension. Plant roots can absorb it easily, so it is the main source of water for plants. Hygroscopic water is held so tightly to soil particles that roots cannot take it up. Chemically bound water is part of the mineral structure of the soil. Gravitational water drains away quickly and is available only for a short time.

Types of Soil Water:

Answer: (A) Chimpanzee and Bonobo

Explanation: Chimpanzees (Pan troglodytes) and bonobos (Pan paniscus) are the closest living relatives of modern humans. Their DNA is about 98 to 99% identical to ours, and humans share a common ancestor with the genus Pan that lived roughly 6 to 7 million years ago. Gorillas are the next closest, followed by orangutans. Gibbons are lesser apes and are the most distant of the four options.

Apes and Human Relationship:

Answer: (B) Thalassemia

Explanation: Thalassemia is an autosomal recessive blood disorder. The genes for haemoglobin chains lie on autosomes (chromosome 16 for alpha globin and chromosome 11 for beta globin), so both males and females are affected equally. Haemophilia and colour blindness are X-linked recessive disorders, which is why they affect males far more often than females. Because they are X-linked, “all of the above” is incorrect.

Genetic Disorders:

Answer: (D) Gibberellin

Explanation: Gibberellins break seed dormancy and promote germination. They stimulate the synthesis of hydrolytic enzymes such as alpha-amylase in the aleurone layer, which digest stored food in the endosperm and supply the growing embryo. Dormin, another name for abscisic acid, does the opposite: it induces and maintains dormancy. Auxin and cytokinin mainly control elongation and cell division, not dormancy release.

Seed Dormancy and Germination:

Answer: (D) Pineal body-thyroid

Endocrine Glands:

Answer: (A) Vegetative reproduction

Explanation: Vegetative reproduction is a type of asexual reproduction in which a new plant grows from a vegetative part such as a root, stem or leaf, without spores or seeds. It is found only in plants. Asexual reproduction is wider, since it also occurs in bacteria, fungi and animals (binary fission, budding). Sexual reproduction is common to plants and animals. Parthenogenesis, the development of an egg without fertilisation, occurs mainly in animals such as honey bees and some insects and reptiles.

Vegetative Propagation:

Answer: (B) UNEP (United Nations Environment Programme)

Explanation: The Adaptation Gap Report is an annual UNEP publication. The 2022 edition, titled “Too Little, Too Slow”, was released in November 2022 ahead of COP27 in Egypt. It found that the world is not adapting to climate change fast enough, and that international adaptation finance for developing countries is far below the estimated needs. The report tracks planning, finance and implementation of adaptation measures against what is required.

Environment and Climate Reports:

Answer: (B) expansion of eyeball

Explanation: Myopia (nearsightedness) occurs when the eyeball is too long from front to back (axial elongation or expansion), or when the cornea is too steeply curved. Because of this expansion, light entering the eye focuses in front of the retina instead of directly on it. This makes distant objects appear blurry while close objects remain clear.

Myopia vs Hypermetropia:

Answer: (C) Suprarenal gland

Explanation: The suprarenal (adrenal) gland is the endocrine gland lying above each kidney, and it produces glucocorticoids, mineralocorticoids and adrenaline. The other three terms are hormones, or groups of hormones, made by this gland, so the gland is the single term that includes the rest.

Suprarenal (Adrenal) Gland:

Answer: (D) Paddy fields

Explanation: Paddy (rice) fields are the largest source of methane in India. Flooded fields are waterlogged and low in oxygen, so methanogenic bacteria break down organic matter anaerobically and release methane. Livestock (enteric fermentation) is the other major source in India, but among the options given, paddy fields are the answer. Methane has a much higher global warming potential than CO₂ over a 100-year period, roughly 28 times as much.

Methane Sources:

Answer: (B) New Delhi

Explanation: The Delhi government launched a 15-point Winter Action Plan in October 2022 to control air pollution during the winter months, when stubble burning, vehicle emissions, dust and cold, still air push pollution to severe levels. The plan targets the main local sources, including dust, vehicular emissions, open burning of biomass and waste, industrial emissions and firecrackers. It also includes measures such as tree plantation drives and the use of the Green War Room for monitoring.

Delhi Air Pollution Measures:

Answer: (B) W.G. Rosen

Explanation: The term “biodiversity” was coined by the American entomologist Walter G. Rosen in 1985, when he was planning the National Forum on BioDiversity held in Washington, D.C. in 1986. It is a contraction of “biological diversity”. The term became widely known after E.O. Wilson used it as the title of the forum’s proceedings volume, “BioDiversity” (1988). Ernst Mayr is linked to the biological species concept, Tansley coined “ecosystem”, and Odum is known as the father of modern ecology.

Biodiversity and Ecology Terms:

Answer: (C) Reserved Forest

Explanation: Under the Indian Forest Act, 1927, forests are structurally classified to control public usage and protect natural ecosystems:

• National Parks & Wildlife Sanctuaries: These are designated under a different legislation entirely—the Wildlife Protection Act, 1972. While human footprints are tightly regulated to protect wildlife, they do not bar public entry altogether; they allow structured ecotourism, guided safaris, and educational tours, usually upon the payment of a standard entry fee.
• Reserved Forests (No Free Entry): These are the most heavily restricted category of forests in India. Once an area is declared a Reserved Forest, all public rights are extinguished, meaning general entry, cattle grazing, hunting, and collecting timber or forest produce are strictly prohibited unless explicit permission is granted by a Forest Settlement Officer.
• Protected Forests: Unlike reserved forests, the legal rule of thumb here is that activities are permitted unless explicitly prohibited. The local communities retain existing rights to collect non-timber items and graze cattle, provided they cause no serious damage to the ecosystem.

Answer: (B) S

Explanation: DNA replication takes place in the S (synthesis) phase of interphase, so the DNA content of the cell doubles here. A cell in G1 has 2C DNA, and after the S phase it has 4C DNA. The number of chromosomes stays the same, because each chromosome now consists of two sister chromatids. G1 is the phase of cell growth and normal metabolism, and G2 is the phase of preparation for division, with protein synthesis for the spindle. G0 is the resting phase, in which the cell leaves the cycle and does not divide.

Cell Cycle Phases:

Answer: (A) Peripatus

Explanation: A living fossil is an organism that has survived almost unchanged from an ancient geological period and shows features of two groups. Peripatus (velvet worm) is a connecting link between annelids and arthropods. It has annelid-like features such as soft, unjointed legs, nephridia and a thin cuticle, and arthropod-like features such as tracheae, an open circulatory system and claws. Amoeba, prawn and apple snail are not considered living fossils.

Living Fossils and Connecting Links:

Answer: (C) Plutonium

Explanation: Early heart pacemakers were powered by a small capsule of plutonium-238, a radioactive isotope. It emits alpha particles, which are easily stopped by the casing, and its long half-life of about 88 years gives a steady heat output that is converted into electricity. Such nuclear-powered pacemakers were used in the 1970s. Modern pacemakers use lithium-iodine batteries instead, because they are cheaper and avoid radiation concerns.

Radioactive Isotopes and Their Uses:

Answer: (C) Mitochondria

Explanation: Mitochondria are called the “powerhouse” of the cell because they produce most of the cell’s ATP through aerobic respiration. The Krebs (citric acid) cycle takes place in the mitochondrial matrix, and the electron transport chain and oxidative phosphorylation take place on the inner membrane. Mitochondria are double-membraned and contain their own circular DNA and 70S ribosomes, so they can make some of their own proteins and divide independently.

Cell Organelles:

Answer: (A) Tobacco

Explanation: The first transgenic crop plant was tobacco, developed in 1983 by introducing an antibiotic-resistance gene into tobacco cells using Agrobacterium tumefaciens as the vector. The first commercially grown genetically modified crop was the Flavr Savr tomato (1994), which had delayed ripening. Bt cotton, carrying a gene from Bacillus thuringiensis for bollworm resistance, is the only GM crop approved for cultivation in India (2002). Golden Rice is engineered to produce beta-carotene.

Transgenic Crops:

Answer: (C) Lens

Explanation: My earlier answer was wrong. The question asks for the highest refractive index, not the greatest bending of light. The eye lens has the highest refractive index of the four options, about 1.386 to 1.406 (highest at its core), while the cornea is about 1.376, the aqueous humour about 1.336 and the vitreous humour about 1.337. The cornea does most of the refraction (about two-thirds of the eye’s focusing power) only because light passes from air into it, which is the largest change in refractive index. The lens does the fine focusing.

Refractive Indices of the Eye:

Answer: (C) mycoherbicide

Explanation: Phytophthora palmivora is a fungus-like oomycete used as a mycoherbicide, a living organism applied to kill a particular weed. Its commercial product, DeVine, was developed in the USA in the 1980s to control strangler vine (Morrenia odorata) in citrus orchards. It is a host-specific pathogen of the weed and does not harm the citrus trees. It is generally cited as the first commercial bio-herbicide (mycoherbicide), so option (D) is also close. If the official key lists only one, (C) is the more precise term.

Biological Control Agents:

Answer: (D) None of the above

Explanation: A human ovum is a haploid gamete, so it has 23 chromosomes (n = 23). The somatic cells of humans have 46 chromosomes (2n = 46), and meiosis halves this number during gamete formation. Options 36, 46 and 48 are all incorrect, so the answer is “none of the above”. When the ovum fuses with a sperm (also n = 23), the zygote gets back the full set of 46 chromosomes.

Human Chromosome Numbers:

Answer: (B) AIDS antibodies

Explanation: ELISA (Enzyme-Linked Immunosorbent Assay) detects antibodies or antigens in a blood sample using an enzyme-linked antibody that produces a colour change when the target is present. It is the standard screening test for HIV infection, since it detects antibodies made by the body against the virus. A positive ELISA result is confirmed with a more specific test, the Western blot. ELISA is also used for other infections and for pregnancy tests, but among the options, AIDS is the classic answer.

Diagnostic Tests:

Answer: (C) Salvinia

Explanation: Salvinia is a free-floating aquatic fern. It belongs to the water ferns (order Salviniales) and floats on the surface of ponds and slow-moving water. Its leaves are in whorls of three, two of them floating and covered with water-repellent hairs, and the third is submerged and root-like because true roots are absent. Adiantum, Dryopteris and Equisetum grow on land or in damp soil.

Pteridophytes (Ferns and Allies):

Answer: (C) Fish

Explanation: The seahorse (Hippocampus) is a bony fish, not a mammal or plant. It breathes through gills, has a swim bladder, and swims upright using a dorsal fin. Its body is covered with bony plates instead of scales, and its head and neck resemble a horse. It is unusual because the male carries the fertilised eggs in a brood pouch and gives birth to the young.

Fish with Unusual Names:

Answer: (D) Toad

Explanation: A toad is an amphibian, and amphibians are cold-blooded (poikilothermic). Their body temperature changes with the surroundings because they cannot regulate it internally. Hens (birds), tigers and bats (mammals) are warm-blooded (homeothermic) and keep a constant body temperature. Only birds and mammals are warm-blooded.

Warm-blooded vs Cold-blooded Animals:

Answer: (D) K

Explanation: Vitamin K is needed for blood clotting. It helps the liver make clotting factors, mainly prothrombin (factor II) and factors VII, IX and X. Without it, clotting is delayed and bleeding is prolonged. The name comes from the German word Koagulation. Vitamin K is fat-soluble, is found in green leafy vegetables, and is also made by bacteria in the human intestine.

Vitamins:

Answer: (B) Zymase

Explanation: Yeast ferments sugar into ethyl alcohol and carbon dioxide under anaerobic conditions, and the enzyme complex responsible for this is zymase. It was discovered by Eduard Buchner in 1897 from yeast extract, work for which he received the Nobel Prize in Chemistry in 1907. Zymase acts on glucose along with other enzymes of the pathway, such as pyruvate decarboxylase and alcohol dehydrogenase. Amylase digests starch, invertase splits sucrose into glucose and fructose, and galactase (lactase) acts on lactose.

Fermentation and Related Enzymes:

Answer: (A) Iron

Explanation: Haemoglobin is the oxygen-carrying pigment of red blood cells, and each molecule contains four haem groups, each with one iron (Fe²⁺) atom at its centre. Oxygen binds reversibly to this iron, so one haemoglobin molecule can carry up to four oxygen molecules. A shortage of iron reduces haemoglobin production and causes anaemia. Magnesium is the metal in chlorophyll, and copper is present in the blood pigment haemocyanin of some molluscs and arthropods.

Metals in Biological Molecules:

Answer: (B) Medha Patker

Explanation: The Narmada Bachao Andolan (NBA) is a social movement started in 1985 against the construction of large dams on the Narmada river, mainly the Sardar Sarovar Dam in Gujarat. Medha Patkar is its best-known leader. The movement raised issues of displacement and rehabilitation of tribal and rural people, and of environmental damage. Baba Amte supported the movement, and in 1991 Medha Patkar and her colleagues received the Right Livelihood Award for it. Anna Hazare is linked to the anti-corruption movement and to Ralegan Siddhi, and Binayak Sen is a doctor and human rights activist.

Environmental and Social Movements in India:

Answer: (A) Feminist Movement

Explanation: My earlier answer hedged and was not the best choice. The Chipko Andolan (1973, Chamoli, Uttarakhand) is classed as a feminist or ecofeminist movement because women were its main force. Led by Gaura Devi, village women of Reni hugged trees to stop contractors’ axemen, since deforestation destroyed their fuelwood, fodder and water sources.

Chipko Andolan:

Answer: (D) National Mission for Clean Ganga

Explanation: Namami Gange is an integrated conservation mission approved by the Union Government in 2014 (launched in June 2014 with a budget of about ₹20,000 crore) to clean and rejuvenate the river Ganga and reduce pollution in it. It is implemented by the National Mission for Clean Ganga (NMCG), the executive arm of the National Ganga Council. Its main work includes building sewage treatment plants, cleaning river fronts and ghats, controlling industrial effluents, afforestation, and biodiversity conservation. It is not about worship, irrigation canals or river linking.

Namami Gange and Ganga Cleaning:

Answer: (A) SARS-CoV-2

Explanation: The WHO named the disease “COVID-19” (Coronavirus Disease 2019) in February 2020, while the virus that causes it was named SARS-CoV-2 by the International Committee on Taxonomy of Viruses (ICTV), meaning Severe Acute Respiratory Syndrome Coronavirus 2. The virus and the disease have different names, just as HIV is the virus and AIDS is the disease. Covid-19 is the name of the disease, so options (B) and (C) are not the virus name.

Covid-19 and Coronaviruses:

Answer: (A) Nipah

Explanation: My earlier answer was wrong. In 2021, researchers from the ICMR-National Institute of Virology, Pune, reported Nipah virus antibodies in Pteropus fruit bats (flying foxes) from a cave in Mahabaleshwar, Maharashtra. This showed that the bats there had been exposed to the virus, though no active virus was isolated. Fruit bats are the natural reservoir of Nipah. Separate Indian bat surveys on coronaviruses were done in other states, so they do not match the Mahabaleshwar finding.

Bat-Borne Viruses:

Answer: (C) soil

Explanation: Plants absorb most of their mineral nutrients, such as nitrogen, phosphorus, potassium, calcium and magnesium, from the soil through their roots, dissolved in water. Carbon, hydrogen and oxygen come from air and water. Chlorophyll is a pigment, and light is a source of energy, so neither is a nutrient source. Atmospheric nitrogen cannot be used directly by most plants and must first be fixed by bacteria into forms like nitrate and ammonium in the soil.

Plant Nutrients:

Answer: (A) CO₂

Explanation: Carbon dioxide is the main greenhouse gas released by burning fossil fuels such as coal, petroleum and natural gas. Combustion of the carbon in these fuels produces CO₂, and fossil fuel use is the largest single source of human-caused CO₂ emissions. The other gases are produced mainly by other sources: methane (CH₄) by paddy fields, livestock and landfills, ozone (O₃) by reactions of pollutants in sunlight, and nitrous oxide (N₂O) mainly by fertiliser use and agriculture.

Greenhouse Gases:

Answer: (A) Red blood cells

Explanation: Red blood cells (RBCs) contain haemoglobin, a protein with iron-containing haem groups, and oxygen binds reversibly to this iron. Each haemoglobin molecule can carry up to four O₂ molecules, forming oxyhaemoglobin in the lungs. The oxygen is released in the tissues, where oxygen levels are low. White blood cells defend the body against infection. Vitamin B₁₂ is needed for RBC formation, and vitamin E is an antioxidant, but neither binds oxygen.

Blood and Oxygen Transport:

Answer: (C) Fluorosis

Explanation: Drinking water with fluoride above the permissible limit (1.5 mg/L as per WHO and BIS) causes fluorosis. In dental fluorosis, teeth develop yellow or brown mottled stains. In skeletal fluorosis, bones and joints become stiff, painful and deformed, mainly after long exposure. Fluoride at low levels (about 1 mg/L) protects teeth against decay, so both deficiency and excess are harmful. High fluoride in groundwater is common in parts of Rajasthan, Andhra Pradesh, Telangana, Gujarat, Odisha, Assam and West Bengal.

Water Contaminants and Related Diseases:

Answer: (B) 31 pairs

Explanation: The human body has 31 pairs of spinal nerves (62 in all) that arise from the spinal cord and leave through gaps between the vertebrae. They are mixed nerves, carrying both sensory and motor fibres. The 12 pairs figure refers to cranial nerves, which arise from the brain. Of the two options with 31, “31 pairs” is the correct way to state it, since “31” alone would imply only 31 nerves in total.

Spinal Nerves:

Answer: (C) fat

Explanation: Fat gives the most energy per unit mass, about 9 kcal (37 kJ) per gram. Carbohydrates and proteins each give about 4 kcal (17 kJ) per gram, and water gives none. Fat is such a compact energy store because its molecules are rich in carbon-hydrogen bonds, so they release more energy when oxidised.

Energy Value of Nutrients:

Answer: (A) rate of heart beats

Explanation: My earlier answer was not the best choice. An ECG (electrocardiogram) is a graphical record of the heart’s electrical activity, and from the trace, the heart rate (number of beats per minute) and its rhythm are read directly. Of the options given, “rate of heart beats” is the standard answer in exam keys. Potential difference is what the electrodes detect, but the ECG is used to record the heartbeat. It does not measure ventricular concentration or the volume of blood pumped.

ECG:

Answer: (B) Carbon dioxide, Methane and Hydrogen

Explanation: Biogas is produced when bacteria break down cattle dung and other organic waste without oxygen, in a biogas (gobar gas) plant. Its main component is methane (about 50 to 70%), which burns and makes it a useful fuel. The rest is mostly carbon dioxide, with small amounts of hydrogen, hydrogen sulphide and water vapour. Carbon monoxide and ethane are not normal components, so options with them are wrong.

Biogas:

Answer: (D) accumulates excess of fats.

Explanation: My earlier answer was wrong. In people addicted to alcohol, the liver breaks down ethanol, and this process raises the NADH level in liver cells. The high NADH slows down fatty acid oxidation and promotes fat synthesis, so triglycerides accumulate in the liver cells. This is fatty liver (steatosis), the first stage of alcoholic liver disease, and it can progress to alcoholic hepatitis and cirrhosis. The standard exam answer is therefore the accumulation of excess fats. Storage of excess glycogen and over-secretion of bile are not the causes.

Alcohol and the Liver:

Answer: (C) Pandu Rao Hegde of Sirsi

Explanation: The Appiko movement began in September 1983 in the Western Ghats of Uttara Kannada district, Karnataka, led by Pandurang Hegde. “Appiko” means “to hug” in Kannada, and it is the southern counterpart of the Chipko movement. Villagers hugged trees in the forests near Sirsi to stop commercial felling, and the movement also promoted afforestation, restricted use of forest resources and awareness about conserving the Western Ghats. Sarala Ben and Mira Ben were Gandhian followers linked with Himalayan work, and Sundarlal Bahuguna led the Chipko movement.

Appiko and Related Movements:

Answer: (B) 120

Explanation: Red blood cells (RBCs) live for about 120 days in humans. They have no nucleus and cannot repair themselves, so they wear out and are broken down by macrophages in the spleen and liver, which is why the spleen is called the “graveyard of RBCs”. The iron from haemoglobin is recycled, and the rest of the haem is converted into bile pigments such as bilirubin. New RBCs are made continuously in the red bone marrow.

Blood Cells:

Answer: (C) Lactic acid

Explanation: During vigorous exercise, muscle cells run short of oxygen and switch to anaerobic respiration, in which glucose is broken down to lactic acid. The build-up of lactic acid in the muscle causes fatigue, soreness and cramps. When rest returns oxygen to the muscle, the lactic acid is carried to the liver and converted back to glucose (Cori cycle) or oxidised. Carbon dioxide and creatinine are not the cause of fatigue, and ethyl alcohol is the product of fermentation in yeast, not in muscle.

Anaerobic Respiration:

Answer: (C) 20

Explanation: Humans have 20 milk (deciduous) teeth, which start to appear at about 6 months of age and are complete by about 2 to 2.5 years. They are replaced by 32 permanent teeth between about 6 and 21 years. The dental formula of milk teeth is 2102/2102, meaning 2 incisors, 1 canine and 2 molars in each half of each jaw, with no premolars. Humans are diphyodont, meaning two sets of teeth appear in a lifetime.

Human Teeth:

Answer: (C) 20 ml

Explanation: Normal human blood carries about 20 ml of oxygen per 100 ml (20 volume %) in arterial blood. Almost all of it (about 19.7 ml) is bound to haemoglobin as oxyhaemoglobin, and only about 0.3 ml is dissolved in plasma. Each gram of haemoglobin can bind about 1.34 ml of oxygen, and with about 15 g of haemoglobin per 100 ml of blood this gives the figure of 20 ml. Venous blood carries about 15 ml of oxygen per 100 ml, so tissues take up roughly 5 ml from each 100 ml of blood.

Oxygen and Carbon Dioxide Transport in Blood:

Answer: (C) Lungs

Explanation: The whale is a mammal that lives in water, but it breathes air with lungs, not gills. It comes to the surface to breathe through a blowhole, which is a modified nostril on top of the head. It exhales, takes in fresh air and dives again, and it can hold its breath for a long time because its blood and muscles store a lot of oxygen. Integuments (skin) are the respiratory organ in animals like frogs and earthworms, gills in fish, and tracheae in insects.

Respiratory Organs in Animals:

Answer: (B) rickets

Explanation: Vitamin D helps the intestine absorb calcium and phosphorus and helps deposit them in bones. Without enough of it, bones stay soft and weak. In children this causes rickets, with bow legs, a pigeon chest and delayed growth, and in adults it causes osteomalacia. The skin makes vitamin D when exposed to sunlight, so it is called the “sunshine vitamin”. Night blindness is caused by vitamin A deficiency and scurvy by vitamin C deficiency.

Vitamin Deficiency Diseases:

Answer: (B) swimming organisms in water

Explanation: Nekton are free-swimming aquatic organisms that can move actively against currents and waves, such as fish, squids, turtles, whales and dolphins. They differ from plankton, which drift with the water, and from benthos, which live on or in the bottom. Nekton are generally larger and are mostly consumers in aquatic food chains.

Aquatic Organism Groups:

Answer: (C) Turner syndrome individual

Explanation: A Barr body is an inactivated X chromosome seen as a dark-staining spot in the nucleus of somatic cells. The number of Barr bodies equals the number of X chromosomes minus one. A Turner syndrome individual (44 + XO) has only one X chromosome, so there is no extra X to inactivate and no Barr body. Klinefelter (XXY) has one Barr body, triple X (XXX) has two, and a normal female mammal (XX) has one.

Barr Bodies and Sex Chromosome Disorders:

Answer: (B) Echinda

Explanation: The question asks for an egg-laying mammal. Echidna (spiny anteater) is a monotreme, a primitive mammal that lays eggs, and it is found in Australia and New Guinea. The female incubates the egg in a temporary pouch, and the young is fed on milk secreted through pores in the skin, since monotremes have no nipples. Talpa (mole), Pteropus (flying fox) and Lemur are placental mammals that give birth to live young. “Echinda” in the paper is a misspelling of Echidna (Tachyglossus).

Egg-laying and Primitive Mammals:

Answer: (C) Loricifera

Explanation: Loricifera is the most recently discovered animal phylum among the options. It was described in 1983 by Reinhardt Kristensen, from tiny marine animals found living between sand grains on the sea floor. They are microscopic, have a protective armour-like covering called a lorica, and are only about 0.1 to 0.5 mm long. Pogonophora was described in the early 1900s, Kinorhyncha in the 1800s, and Ctenophora (comb jellies) was recognised in the 1800s.

Recently Discovered and Lesser-Known Phyla:

Answer: (B) Potato

Explanation: Potato is a stem tuber, a modified underground stem. The swollen tip of an underground branch stores starch. It has “eyes”, which are nodes with axillary buds that can sprout into new plants, and this proves it is a stem and not a root. Carrot and turnip are modified tap roots. Groundnut is a legume whose pods develop underground, but the pod is a fruit, not a stem.

Modified Underground Organs:

Answer: (C) Pachytene

Explanation: Crossing over is the exchange of segments between non-sister chromatids of homologous chromosomes during prophase I of meiosis. It takes place in the pachytene stage, when the homologues are fully paired as bivalents and the chromatids are visible as tetrads. The enzyme recombinase acts at recombination nodules, and the exchange produces new combinations of genes. The points where it has occurred become visible as chiasmata in diplotene.

Crossing Over:

Answer: (B) Gregor Johann Mendel

Explanation: The “particulate theory of inheritance” was proposed by Gregor Johann Mendel (1866) from his pea plant experiments. He showed that traits are controlled by discrete units (now called genes) that pass unchanged from parents to offspring and do not blend. This contradicted the older blending theory of inheritance. Darwin proposed natural selection and the theory of pangenesis, Morgan worked on linkage and the chromosome theory using Drosophila, and Muller showed that X-rays cause mutations.

Inheritance Theories and Scientists:

Answer: (A) A virus

Explanation: A bacteriophage (or phage) is a virus that infects bacteria. It consists of a nucleic acid core, usually double-stranded DNA, enclosed in a protein coat called a capsid. The classic T4 phage has a head, a tail with a sheath, and tail fibres that attach to the bacterial cell wall and inject its DNA. Inside the host, the phage either multiplies and bursts the cell (lytic cycle) or integrates its DNA into the bacterial chromosome (lysogenic cycle). Bacteriophages are viruses, not bacteria, fungi or protozoa.

Bacteriophage:

Answer: (A) Protostele

Explanation: The stele is the central vascular cylinder of a stem or root. Protostele is the simplest and most primitive type, in which a solid core of xylem is surrounded by phloem with no pith in the centre. It is found in the earliest vascular plants such as the fossil psilophytes (Rhynia) and in living Selaginella and Lycopodium. More advanced types, such as siphonostele (with a pith) and dictyostele (a dissected cylinder in ferns), evolved from it later. Atactostele, with scattered bundles, is found in monocot stems.

Types of Stele:

Answer: (D) Electron transport

Explanation: Oxygen is used directly in the electron transport chain, where it is the final electron acceptor. It combines with electrons and hydrogen ions at the end of the chain to form water, and this keeps the chain running to make ATP by oxidative phosphorylation. Glycolysis and fermentation take place without oxygen. The citric acid cycle needs oxygen only indirectly, because it depends on the NAD⁺ and FAD regenerated by the electron transport chain.

Cellular Respiration:

Answer: (B) Fungi

Explanation: Penicillin is obtained from the fungus Penicillium (P. notatum and P. chrysogenum). Alexander Fleming noticed in 1928 that a Penicillium mould contaminating a culture plate killed the Staphylococcus bacteria around it. Howard Florey and Ernst Chain later purified it and developed it as a drug in the 1940s. Fleming, Florey and Chain shared the Nobel Prize in 1945. Penicillin works by blocking the synthesis of the bacterial cell wall.

Antibiotics and Their Sources:

Answer: (A) 1972

Explanation: The United Nations Conference on the Human Environment was held at Stockholm in June 1972. Following it, the Government of India set up the National Committee on Environmental Planning and Coordination (NCEPC) in 1972 under the Department of Science and Technology. This committee later led to the creation of the Department of Environment in 1980, which became the Ministry of Environment and Forests in 1985.

Environmental Policy Milestones in India:

Answer: (D) Co-dominance

Explanation: My earlier answer was not the best choice. Red × white giving pink in F1 is a case of incomplete dominance, where the heterozygote shows an intermediate phenotype. Since “incomplete dominance” is not among the options, the closest standard answer is (D), because the paper’s key treats the blended or intermediate expression of both alleles under co-dominance. “Pseudo dominance” and “dominance” do not fit, because the F1 plants are neither red nor white, and epistasis involves two different genes. Strictly speaking, true co-dominance would show both colours side by side in the same flower, so check this against the official key.

Incomplete Dominance and Related Concepts:

Answer: (C) 12 hours

Explanation: A short-day plant (SDP) flowers only when the day length is shorter than its critical day length, which here is 14 hours. Of the options, only 12 hours is below 14 hours, so the plant will flower at 12 hours. At 15, 16 or 18 hours the day is longer than the critical length, and the plant stays vegetative. In reality, the length of the uninterrupted dark period (night) is what controls flowering, so short-day plants are better described as long-night plants.

Photoperiodism:

Answer: (C) Synchytrium

Explanation: An endobiotic fungus is one that lives and grows completely inside the cells of its host. Synchytrium endobioticum is a primitive chytrid fungus that develops inside the host cells and causes black wart disease of potato. Its whole thallus is formed within the host cell and later turns into a sorus of sporangia. Agaricus, Morchella and Polyporus are higher fungi (mushrooms, morels and bracket fungi) that grow on soil or wood and are not endobiotic.

Fungi and Their Habit:

Answer: (C) Labiatae

Explanation: A gynobasic style arises from the base of the deeply four-lobed ovary, close to the receptacle, instead of from its top. This is the characteristic feature of the family Labiatae (Lamiaceae), the mint family, and also of the related Boraginaceae. The four-lobed ovary matures into four nutlets. Solanaceae has a terminal style on a two-chambered ovary, and Orchidaceae has the style fused with the stamens to form the column. Malvaceae (written “Mawaceae” in the paper) has a style that branches at the top into many stigmas, with the stamens fused into a tube around it.

Floral Features of Important Families:

Answer: (D) Chara

Explanation: “Globule” and “nucule” are the male and female sex organs of Chara, a green alga commonly called stonewort. The globule is the male organ (antheridium) and is a bright orange-red, spherical structure that produces biflagellate sperms in filaments. The nucule is the female organ (oogonium), a green, oval structure with a single egg, surrounded by five spirally twisted tube cells and capped by a coronula. These names are specific to the genus Chara (family Characeae). Oedogonium has ordinary antheridia and oogonia, Rhizopus is a fungus, and Calamites is an extinct fossil plant related to horsetails.

Chara:

Answer: (B) Tubulin

Explanation: Spindle fibres are made of microtubules, which are polymers of the protein tubulin (alpha and beta tubulin dimers). They form during prophase from the centrosomes (microtubule organising centres) and attach to the kinetochores of chromosomes, pulling the chromatids apart in anaphase. Flagellin forms bacterial flagella, cellulose is the main component of plant cell walls, and chitin forms fungal cell walls and arthropod exoskeletons.

Tubulin and Cytoskeletal Components:

Answer: (A) Epithelial tissue

Explanation: A carcinoma is a cancer that starts in epithelial tissue, which forms the lining of the skin, the digestive and respiratory tracts, and the glands. It is the most common type of cancer in humans, and it includes cancers of the lung, breast, colon, stomach, skin and prostate. Cancers of connective tissue, such as bone, cartilage and muscle, are called sarcomas. Cancers of blood-forming tissue are leukaemias, and those of lymphoid tissue are lymphomas.

Types of Cancer:

Answer: (A) Striated voluntary

Explanation: A muscle under conscious control is a voluntary muscle, and the voluntary muscles of the body are skeletal muscles. Under the microscope they show alternating light and dark bands (striations) because of the regular arrangement of actin and myosin filaments. Their fibres are long, cylindrical, unbranched and multinucleated. They are attached to bones by tendons and move the limbs and the body. Cardiac muscle is striated but involuntary, and smooth muscle is non-striated and involuntary.

Types of Muscle:

Answer: (C) Beetle

Explanation: A grub is the soft-bodied, C-shaped, legless or short-legged larva of a beetle (order Coleoptera). It lives in soil, rotting wood or plant tissue and feeds on roots and decaying matter, and later turns into a pupa and then an adult beetle. Beetles undergo complete metamorphosis (egg, larva, pupa, adult). Option (A), insects, is too general, since insect larvae are called by different names in different orders. Crustacea and sponges do not have grubs.

Insect Larvae:

Answer: (D) Niche

Explanation: The competitive exclusion principle, proposed by G.F. Gause (1934), states that two species with identical ecological requirements cannot coexist indefinitely in the same niche. The species that uses the resources more efficiently eventually eliminates the other, or the two evolve to use different resources (resource partitioning). Two species can share a habitat or a biome, but they cannot occupy exactly the same niche, which includes the role, food and conditions a species needs.

Competition and Niche Concepts:

Answer: (D) None of the above

Explanation: Insulin is a hormone from the beta cells of the islets of Langerhans in the pancreas. Its main target tissues are the liver, skeletal muscle and adipose (fat) tissue, where it helps glucose enter cells and be stored as glycogen and fat, so blood sugar falls. Red blood cells take up glucose without insulin, and kidney and small intestinal tissues are not its main targets. None of the three listed options is a target tissue, so the answer is “none of the above”.

Insulin and Blood Sugar Control:

Answer: (D) Autogamy

Explanation: Autogamy is the transfer of pollen from the anther to the stigma of the same flower, which leads to self-pollination. It is common in bisexual flowers where the anthers and stigma mature at the same time and lie close together, as in pea, wheat and rice. Cleistogamous flowers, which never open, are the most assured form, as in Viola and Commelina. Geitenogamy is transfer to another flower of the same plant, and xenogamy is transfer to a flower of a different plant. Allogamy is a general term for cross-pollination.

Types of Pollination:

Answer: (D) Thymine and Cytosine

Explanation: The nitrogenous bases of DNA are of two types. Purines (adenine and guanine) have a double-ring structure, and pyrimidines (thymine and cytosine) have a single-ring structure. In RNA, uracil replaces thymine as a pyrimidine. In the double helix, a purine always pairs with a pyrimidine: adenine with thymine (two hydrogen bonds) and guanine with cytosine (three hydrogen bonds).

Nitrogenous Bases:

Answer: (B) IAA

Explanation: IAA (indole-3-acetic acid) is the main naturally occurring auxin. It is made in the shoot apex, young leaves and developing seeds, and it moves from the tip towards the base (polar transport). It promotes cell elongation, apical dominance and root initiation. NAA (naphthalene acetic acid) and 2,4-D (2,4-dichlorophenoxyacetic acid) are synthetic auxins. IBA (indole-3-butyric acid) is also a natural auxin in some plants, but IAA is the standard answer for the natural auxin.

Auxins:

Answer: (A) Interphase

Explanation: DNA synthesis (replication) takes place in the S phase of interphase, before the cell enters mitosis. By the end of the S phase each chromosome has two identical sister chromatids, so the DNA content has doubled. Prophase, anaphase and telophase are stages of mitosis (M phase), and no DNA replication occurs in them. In these stages the already-copied DNA is condensed, separated and distributed to the daughter cells.

Cell Cycle Stages and DNA Events:

Answer: (B) Dominance

Explanation: When a pure tall plant (TT) is crossed with a pure dwarf plant (tt), all F1 plants are tall (Tt). The tall allele is dominant and masks the expression of the recessive dwarf allele in the heterozygote. The recessive trait is not lost. It reappears in the F2 generation in a 3 tall : 1 dwarf phenotypic ratio (genotypic ratio 1 TT : 2 Tt : 1 tt). In incomplete dominance the F1 would be intermediate, and in co-dominance both alleles would be fully expressed.

Mendel’s Monohybrid Cross:

Answer: (C) Plasmodium falciparum

Explanation: Cerebral malaria is the most dangerous complication of malaria and is caused by Plasmodium falciparum. Infected red blood cells become sticky and block the small blood vessels of the brain, leading to high fever, convulsions, coma and often death if untreated. P. falciparum causes malignant (tertian) malaria. P. vivax causes benign tertian malaria and P. malariae causes quartan malaria, and neither commonly produces cerebral malaria.

Malaria Parasites:

Answer: (B) Charles Darwin

Explanation: The theory of “Natural Selection” was proposed by Charles Darwin in his book On the Origin of Species (1859). It states that individuals in a population vary, and those with traits better suited to their environment survive and reproduce more, passing these traits to their offspring. Over many generations this changes the population and leads to the origin of new species. Alfred Russel Wallace independently arrived at the same idea, and the two presented it jointly in 1858. Mendel worked on the laws of inheritance and Morgan on linkage and the chromosome theory.

Evolution Theories and Scientists:

Answer: (A) Fossil Fuels

Explanation: Coal, petroleum and natural gas are fossil fuels. They formed over millions of years from the buried remains of plants and animals that were subjected to heat and pressure. Coal came mainly from plant matter in ancient swamps, while petroleum and natural gas came mostly from marine organisms. They are non-renewable, since they are used much faster than they form, and burning them releases carbon dioxide and other pollutants.

Fossil Fuels:

Answer: (A) Antheraea mylitta

Explanation: Tasar (tussar) silk is produced by the tropical tasar silkworm Antheraea mylitta, which feeds on the leaves of Asan (Terminalia tomentosa) and Arjun (Terminalia arjuna) trees. It is a wild silk that gives a coarse, rich golden-brown fibre. India is a leading producer, mainly in Jharkhand, Chhattisgarh, Odisha and West Bengal (Purulia, Bankura and West Medinipur). Bombyx mori gives mulberry silk, Philosamia ricini gives eri silk, and Antheraea assamensis gives muga silk.

Types of Silk:

Answer: (A) 34 Å

Explanation: In the Watson and Crick model of B-DNA, one complete turn of the double helix measures 34 Å (3.4 nm). There are 10 base pairs in each turn, and the distance between two adjacent base pairs is 3.4 Å (0.34 nm). The diameter of the helix is about 20 Å (2 nm). Option (B), 3.4 Å, is the distance between successive base pairs, not the length of one full turn.

DNA Structure:

Answer: (A) 9 : 3 : 3 : 1

Explanation: In Mendel’s dihybrid cross, two pairs of contrasting traits are studied together, for example round yellow (RRYY) × wrinkled green (rryy) seeds. All F1 plants are round yellow (RrYy). When the F1 is self-pollinated, the F2 phenotypic ratio is 9 round yellow : 3 round green : 3 wrinkled yellow : 1 wrinkled green. This shows the law of independent assortment, in which the alleles of the two genes separate independently of each other during gamete formation. The F2 genotypic ratio is 1:2:2:4:1:2:1:2:1, with nine different genotypes.

Mendel’s Dihybrid Cross:

Answer: (C) 12 pairs

Explanation: Mammals have 12 pairs of cranial nerves that arise from the brain and leave through openings in the skull. Some are purely sensory (olfactory, optic, vestibulocochlear), some are purely motor (oculomotor, trochlear, abducens, accessory, hypoglossal), and some are mixed (trigeminal, facial, glossopharyngeal, vagus). Reptiles, birds and amphibians have only 10 pairs, since they lack the accessory and hypoglossal nerves as separate cranial nerves. The nerves are counted as pairs because each one occurs on both sides of the head.

Cranial Nerves: