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Biology & Human Body — UPSC Prelims Science & Environment previous year questions

213 solved previous year questions on Biology & Human Body, papers from 1993 to 2023, drawn from UPSC CSE Prelims, UPPCS, UPSC CDS. Each carries the printed answer key and the explanation from the source compilation.

1. #1UPSC CSE Prelims 2022
   Consider the following statements in respect of probiotics: 1. Probiotics are made of both bacteria and yeast. 2. The organisms in probiotics are found in foods we ingest but they do not naturally occur in our gut. 3. Probiotics help in the digestion of milk sugars.Which of the statements given above is/are correct?
   • A1 only
   • B2 only
   • C1 and 3
   • D2 and 3
   Answer: (C) 1 and 3
   Explanation

   Option c is the correct answer. Probiotics are live microorganisms that are intended to have health benefits when consumed or applied to the body. They can be found in yogurt and other fermented foods, dietary supplements, and beauty products. Statement l is correct: Probiotics are a combination of live beneficial bacteria and/or yeasts. Statement 2 is incorrect: Probiotics live naturally in your body. L. acidophilus is a probiotic bacteria that naturally occurs in the human gut. The most common place linked to beneficial microbes is your gut (mostly large intestines), but there are other places like mouth, urinary tract, skin lungs etc where these probiotics are found. Statement 3 is correct: Yogurt is a well-known food source of probiotics. Certain strains of bacteria in yogurt have which is an enzyme that helps break down lactose in dairy products into the sugars glucose and galactose

2. #2UPSC CSE Prelims 2022
   Which one of the following statements best describes the role of B cells and T cells in the human body?
   • AThey protect the body from environmental allergens
   • BThey alleviate the body's pain and inflammation
   • CThey act as immunosuppressants in the body
   • DThey protect the body from the diseases caused by pathogens
   Answer: (D) They protect the body from the diseases caused by pathogens
   Explanation

   Option d is the correct answer Lymphocytes are a type of white blood cells. They play a critical role in keeping us healthy. Without them, we can't survive. T cells protect us from infection. In our daily lives, we're constantly exposed to pathogens, such as bacteria, viruses and fungi. Without T lymphocytes, also called T cells, every exposure could be life-threatening. T cells can wipe out infected or cancerous cells. They also direct the immune response by helping B lymphocytes to eliminate invading pathogens. B cells create antibodies. B lymphocytes, also called B cells, create a type of protein called an antibody. These antibodies bind to pathogens or to foreign substances, such as toxins, to neutralize them. For example, an antibody can bind to a virus, which prevents it from entering a normal cell and causing infection. B cells can also recruit other cells to help destroy an infec

3. #3UPSC CSE Prelims 2021
   With reference to furnace oil, consider the following statements: 1. It is a product of oil refineries. 2. Some industries use it to generate power. 3. Its use causes sulphur emissions into the environment.Which of the statements given above are correct?
   • A1 and 2 only
   • B2 and 3 only
   • C1 and 3 only
   • D1, 2 and 3 14
   Answer: (D) 1, 2 and 3 14
   Explanation

   Option d is the correct 1 is correct: Furnace oil is a dark viscous obtained by blending mainly heavier crude distillation unit. Crude distillation unit is of an oil refinery that separates crude oil into based on their boiling 2 is correct: Some industries use furnace generate power by burning it in boilers or oil is used as a fuel for industrial heating and because it is cheaper than diesel or natural gas. 1'1 3 is correct: Furnace oil contains sulphur, released into the atmosphere when it is burned. can cause acid rain, air pollution, and for humans and animals

4. #4UPSC CSE Prelims 2019
   With reference to the recent developments in science, which one of the following statements is not correct?
   • AFunctional chromosomes can be created by joining segments of DNA taken from cells of different species
   • BPieces of artificial functional DNA can be created in laboratories
   • CA piece of DNA taken out from an animal cell can be made to replicate outside a living cell in a laboratory
   • DCells taken out from plasma and animals can be made to undergo cell division in laboratory petri dishes
   Answer: (A) Functional chromosomes can be created by joining segments of DNA taken from cells of different species
   Explanation

   Option a is the correct a is incorrect. The joining of DNA two cells of different species is possible but making chromosome out of it has not been bis correct. Unlike DNA synthesis in living gene synthesis does not require template virtually any DNA sequence to be synthesized c is correct. A piece of DNA from an animal be made to replicate outside a living cell in a d is correct. Given appropriate plant and animal cells can live, multiply, and differentiated properties in a tissue-culture cells can be watched continuously under the analyzed biochemically, and the effects of adding specific molecules, such as hormones or can be explored

5. #5UPSC CSE Prelims 2018
   Consider the following statements: 1. Light is affected by gravity. 2. The Universe is constantly expanding. 3. Matter warps its surrounding space-time.Which of the above is/are the prediction/ predictions of Albert Einstein's General Theory of Relativity, often discussed in media?
   • A1 and 2 only
   • B3 only
   • C1 and 3 only
   • D1, 2 and 3
   Answer: (D) 1, 2 and 3
   Explanation

   Option d is the correct answer. According to Albert Einstein's General Theory of Relativity, Light will be affected the same way matter is affected by gravity. Based on this theory, Hubble found that distant galaxies move away faster than those that are relatively nearby and the universe is indeed expanding. According to this theory, gravity is caused by a warping of space and time. Gravity is the curvature of the universe, caused by massive bodies, which determines the path that objects travel

6. #6UPSC CSE Prelims 2013
   Which of the following statements is/are correct:? I. 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. 1 ] '
   • A1 only
   • B2 and 3 only
   • C1 and 3 only
   • D1, 2 and 3
   Answer: (A) 1 only
   Explanation

   Option a is the correct lack metabolic enzymes and thus they their own energy. They cannot be cultured synthetic medium as they require a growth living mechanical vector carries a pathogen on its body host to another, not as an infection. A biological a pathogen from one host to another after itself. Thus, Viruses are transmitted from to another not only by biological vectors but mechanical vectors

7. #7Previous year
   A married couple adopted a male child. A few years later, twin boys were born to them. The blood group of the couple is AB positive and O negative. The blood group of the three sons is A positive, B positive, and 0 positive. The blood group of the adopted son is? [UPSC CSE Pre
   • A0 positive
   • BA positive
   • CB positive
   • DCannot be determined on the basis of the given data
   Answer: (A) 0 positive
   Explanation

   Option a is the correct biological parent donates one of two ABO genes child. The A and B genes are dominant and the O recessive. For example, if an O gene is paired with an the blood type will be with blood group consist of and O negative blood group consist of 0- gene. gene over O gene which results in blood group child. gene is dominant over 0- gene which results blood group in other child. Therefore, the blood group adopted son would be

8. #8UPSC CSE Prelims 2011
   Regular intake of fresh fruits and vegetables is recommended in the diet since they are a good source of antioxidants. How do antioxidants help a person maintain health and promote longevity?
   • AThey activate the enzymes necessary for vitamin synthesis in the body and help prevent vitamin deficiency ]
   • BThey prevent excessive oxidation of carbohydrates, fats, and proteins in the body and help avoid unnecessary wastage of energy
   • CThey neutralize the free radicals produced in the body during metabolism
   • DThey activate certain genes in the cells of the body and help delay the aging process
   Answer: (C) They neutralize the free radicals produced in the body during metabolism
   Explanation

   Option c is the correct play a crucial role in maintaining health longevity by neutralizing harmful free the body. Free radicals are highly reactive during metabolism, and they can damage cells contributing to various diseases and the aging counteract this damage by donating stabilize free radicals, preventing cellular harm. diet rich in antioxidants, primarily found in fruits helps protect cells, reduce oxidative stress, overall health and longevity

9. #9Previous year
   King Cobra is the only snake that makes its own nest. Why does it make its nest? [UPSC CSE Pre 2010)
   • AIt is a snake-eater, and the nest helps attract other snakes
   • BIt is a viviparous snake and needs a nest to give birth to its offspring
   • CIt is an oviparous snake and lays its eggs in the nest and guards the nest until they are hatched
   • DIt is a large, cold-blooded animal and needs a nest to hibernate in the cold season
   Answer: (C) It is an oviparous snake and lays its eggs in the nest and guards the nest until they are hatched
   Explanation

   Option c is the correct King Cobra is an oviparous snake, meaning it lays than giving birth to live offspring. It to protect and incubate its eggs. The nest provides environment where the eggs can be kept safe from potential threats. The King Cobra guards until the eggs hatch, ensuring the survival of its behavior is essential for the reproductive success snakes like the King Cobra

10. #10Previous year
    In dry cells, which of the following are used as electrolytes? [UPSC CSE Pre 2009)
    • AAmmonium Chl or ide and Zinc Chl or ide
    • BSodium Chl or ide and Calcium Chl or ide
    • CMagnesium Chl or ide and Zinc Chl or ide
    • DAmmonium Chl or ide and Calcium Chl or ide
    Answer: (A) Ammonium Chl or ide and Zinc Chl or ide
    Explanation

    Option a is the correct Chloride and Zinc Chloride serve in dry cells, a battery type employing a with minimal moisture to facilitate current electrodes. Unlike wet cells, dry cells can function any orientation without leakage due to the absence liquid. The zinc-carbon battery, the most cell, features a zinc anode, a carbon cathode, and paste consisting of ammonium chloride chloride. Ammonium chloride, a water-soluble chosen for its conductivity and non-reactive nature and carbon electrodes. Similarly, zinc chloride, salt, is included as an electrolyte to electrode corrosion. During operation, the zinc the carbon cathode reduces, generating flow through the external circuit to power the time, the zinc anode is depleted, rendering the inoperative. Dry cells find widespread application devices, such as flashlights, radios, toys, and lighting systems

11. #11UPSC CSE Prelims 2008
    In which one of the following kinds of organisms is the phenomenon found wherein the female kills the male after copulation?
    • ADragonfly
    • BHoneybee
    • CSpider
    • DPit Viper
    Answer: (C) Spider
    Explanation

    Option c is the correct some species of spiders, the female eats the male This behavior is known as sexual cannibalism has been observed in over I 00 spiders, including black widows, brown widows, spiders. Scientists believe that sexual a number of benefits to the female spider. eating the male can provide the female nutrients, which can help her to produce Sexual cannibalism can also help the female to risk of being infected with parasites or diseases from Important Tips Cannibalism in Spiders: Males Eating Females: Some species, like Allocosa brasiliensis, Evarcha culicivora, and Argyronetia aquatica, exhibit males consuming females. This behavior is associated with male-biased sexual dimorphism, and male water spiders (Argyronetia aquatica) tend to mate with larger females while cannibalizing smaller Sacrificial Mothers: In species like Stegodyphus lineatus, offspring practice matriph

12. #12Previous year
    Which among the following one lays eggs and does not produce young ones directly? [UPSC CSE Pre 2008)
    • AEchidna
    • BKangaroo
    • CPorcupine
    • DWhale
    Answer: (A) Echidna
    Explanation

    Option a is the correct are monotremes, which means that they mammals. The other three animals listed question, kangaroos, porcupines, and whales, are mammals, which means that they give birth young. Echidnas are medium-sized, solitary with coarse hair and spines. The spines are and are made of keratin. Echidnas lay a single which they incubate in a pouch on their egg hatches after about 10 days, and the baby puggle, stays in the pouch for another 50-60 days Echidnas produce milk to feed their young, do not have nipples. Instead, the milk oozes patches of skin in the pouch. Echidnas are found and New Guinea. They are nocturnal animals on ants and termites

13. #13Previous year
    Which one of the following parts of the human brain is the regulating centre for swallowing and vomiting? [UPSC CSE Pre 2007)
    • ACerebellum
    • BCerebrum
    • CMedulla oblongata
    • DPons
    Answer: (C) Medulla oblongata
    Explanation

    Option c is the correct medulla oblongata is the part of the brain stem many vital functions, such as swallowing, heartbeat, etc. Important Tips Some of the other functions of the medulla oblongata are: It manages heart, circulation and breathing. Your medulla is where your cardiovascular and respiratory systems link together into a united system that controls your heart rate, breathing, blood pressure and more. It manages other automatic processes. These are things that your body often does without you having to think about them. Some examples include coughing, sneezing, swallowing, vomiting and maintaining your balance. It relays nerve signals between the brain and spinal cord. The vast majority of major nerves converge at your spine, carrying signals to and from your brain. That means those signals must pass through your medulla. It coordinates body movements. The medulla is the locat

14. #14Previous year
    In the human body, which one of the following hormones regulates blood calcium and phosphate? [UPSC CSE Pre 2007)
    • AGlucagon
    • BGrowth hormone
    • CParathyroid hormone
    • DThyroxine
    Answer: (C) Parathyroid hormone
    Explanation

    Option c is the correct hormone is a small protein that calcium and phosphate homeostasis, as well as Parathyroid hormone has effects antagonistic of calcitonin, which is another hormone that and phosphate levels in the blood Important Tips Glucagon is a peptide hormone, produced by alpha cells of the pancreas. It works to raise the concentration of glucose in the bloodstream. Grnwth hormone (GH), also known as human growth hormone, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. Thyroxine is an iodine-containing hormone, released from the thyroid Jt regulates the metabolic and development of lhc )dy

15. #15UPSC CSE Prelims 2005
    Consider the following statements: Assertion (A): All the proteins in our food are digested in small intestine only. Reason The protein-digesting enzyme from the pancreas is released into the small intestine. Code
    • ABoth (A) and (R) are individually true and (R) is the correct explanation of (A)
    • BBoth (A) and (R) are individually true, but (R) is not a correct explanation of (A)
    • C(A) is true, but (R) is false
    • D(A) is false, but (R) is true
    Answer: (D) (A) is false, but (R) is true
    Explanation

    Option d is the correct (A) is false: Not all proteins are digested small intestine. Some protein digestion begins in due to the action of the enzyme pepsin, optimally in the acidic environment of the some protein digestion occurs before the food small (R) is true: The pancreas releases protein digesting enzymes such as trypsin, chymotrypsin, into the small intestine to further proteins. These enzymes are essential for the of proteins in the small intestine

16. #16UPSC CSE Prelims 2002
    With reference to the blood in a normal person, which one of the following statements is correct?
    • ACompared to arteries, veins are less numerous and hold less of the body's blood at any given time
    • BBlood cells constitute about 70 percent of the total volume of the blood
    • CWhite blood cells (WBC) are made by lymph nodes only
    • DThe blood has more platelets than WBC
    Answer: (D) The blood has more platelets than WBC
    Explanation

    Option d is the correct is a specialized body fluid. It has four plasma, red blood cells, white blood cells The blood has more platelets than WBC. A count ranges from 150,000 to 450,000 platelets of blood

17. #17UPSC CSE Prelims 2002
    With reference to the work of human kidney, consider the following statements: 1. After the waste is removed in the kidney, the cleaner blood is sent back through the renal artery. 2. From Bowman's capsule, the filtered liquid passes through tiny tubes where much of the glucose is reabsorbed and sent back to the blood in the renal vein.Which of these statements is/are correct?
    • A1 only
    • B2 only
    • CBoth 1 and 2
    • DNeither 1 nor 2
    Answer: (B) 2 only
    Explanation

    Option b is the correct l c l is incorrect: After the waste products in the kidney, the cleaned blood is sent back through the renal vein, not the renal 2 is correct: After the initial filtration in capsule, the filtered liquid, which is now filtrate, moves through a series of tiny tubules in In these tubules, important substances like and water are reabsorbed back into the bloodstream

18. #18UPSC CSE Prelims 2002
    Among living organisms, which one of the following is the most responsible factor for bringing about the origin of a new species?
    • AIsolation
    • BMutation
    • CNatural selection
    • DSexual reproduction
    Answer: (B) Mutation
    Explanation

    Option b is the correct is the ultimate source of all new genes which are the units of heredity. Mutations can or be induced by environmental as radiation or chemicals. When a mutation a reproductive cell, it can be passed down to can be harmful, beneficial, or neutral. can lead to disease or death. Beneficial give organisms an advantage in their environment, making them more resistant to disease or better able for food. Neutral mutations have no effect on fitness. l,IFor

19. #19UPSC CSE Prelims 2002
    With reference to the human body, consider the following statements: 1. The production of somatotropin goes up when a person exercises. 2. Men's testes produce progesterone. 3. Women's adrenal glands secrete testosterone. 4. Stress causes the adrenals to release very less amount of cortisol than usual.Which of these statements are correct?
    • A1, 2, 3 and 4
    • B1, 2 and 3
    • C2, 3 and 4
    • D1 and 4
    Answer: (B) 1, 2 and 3
    Explanation

    Option bis the correct l is correct: The production of up when a person exercises, as exercise release of growth hormone-releasing hormone the hypothalamus, which causes GH to be produced anterior pituitary 2 is correct: Men's testes produce a of progesterone, which helps balance the effects and 3 is correct: Women's adrenal glands which helps maintain muscle mass, bone libido. It also produces a small amount of estrogen However, the ovaries are the main source female sex hormones. Statement 4 is incorrect: Stress causes the adrenals to amount of cortisol than usual, not less. This is helps the body cope with stress by increasing levels, blood pressure, and muscle strength. stress can lead to high levels of cortisol, which problems such as decreased immune function risk of infection

20. #20UPSC CSE Prelims 2001
    Which organelle in the cell, other than the nudeus, contains DNA?
    • ACentriole
    • BGolgi apparatus
    • CLysosome
    • DMitochondria
    Answer: (D) Mitochondria
    Explanation

    Option d is the correct answer. Peroxisome Lysosorne Chromatin Microtubule Ribosome Mitochondrial Ccntrosomc membrane endoplasmic endoplnsmic reticulum reticulum Proteasome Golgi apparatus are organelles that contain their own mitochondrial DNA or thought to be the descendants of ancient bacteria that entered into a symbiotic relationship with eukaryotic are responsible for producing most of or ATP (Adenosine triphosphate) in the cell process called cellular respiration. Important Tips Centrioles are structures made of microtubules that help in cell division and the formation of cilia and flagella. They do not contain DNA. Golgi apparatus is an organelle that modifies, sorts, and packages proteins and other molecules for transport within or outside the cell. It does not contai DNA. Lysosomes are organelles that contain digestive enzymes that break down various biomolecules and waste mate

21. #21UPSC CSE Prelims 2001
    The cellular and molecular control of programmed cell death are known as
    • AApoptosis
    • BAgeing
    • CDegeneration
    • DNecrosis
    Answer: (A) Apoptosis
    Explanation

    Option a is the correct answer. is the process of programmed cell death may occur in multicellular organisms. lead to characteristic cell changes and changes include blebbing, cell shrinkage, chromatin condensation, and plays an important role in development, disease. For example, the differentiation of fingers in a developing human embryo occurs because the fingers apoptose; the result is that the digits is different from necrosis, which is the death of caused by external factors such as trauma or is marked by swelling, rupture, and the dying cells

22. #22UPSC CSE Prelims 2001
    Which of the following features of DNA makes it uniquely suited to store and transmit genetic information from generation to generation?
    • AComplementarity of the two strands
    • BDouble helix
    • CNumber of base-pairs per turn
    • DSugar-phosphate backbone
    Answer: (A) Complementarity of the two strands
    Explanation

    Option a is the correct of the two strands makes DNA to store and transmit genetic information to generation. This feature of DNA allows replication and transmission of genetic one generation to the next. The complementary in the DNA double helix ensures that each serve as a template for the synthesis of a new double helix, the number of base-pairs per turn, sugar-phosphate backbone are also important features but they are not unique to DNA or essential for transmitting genetic information

23. #23UPSC CSE Prelims 2001
    Consider the following statements: 1. Tapeworm is a hermaphrodite. 2. Roundworm has separate sexes. 3. Filaria is caused by a nematode. 4. Guineaworm is an annelid.Which of these are correct?
    • A1 and 2 only
    • B1, 2 and 3 only
    • C3 and 4 only
    • D2, 3 and 4 only
    Answer: (B) 1, 2 and 3 only
    Explanation

    Option b is the correct 1 is correct: Tapeworms are that they have both male and female Tapeworms are parasites that live in the animals. They are flat, segmented worms that can grow several feet long. Tapeworms can cause a variety of including malnutrition and weight 2 is correct: Roundworms have separate that there are male and female are parasites that cause infections. humans can lead to diarrhea and 3 is correct: Filaria is a disease caused by of nematode, which is a type of roundworm. spread by blood-feeding insects such as black flies They belong to the group of diseases These parasites exist in the wild in of southern Asia, Africa, the South Pacific, and South America. One does not acquire them in like Europe or the United 4 is incorrect: Guinea worm is a and not an annelid. Guinea worm neglected tropical disease (NTD), is caused by Dracunculus medinensis. The disease affects in

24. #24UPSC CSE Prelims 2000
    Consider the following statements: Assertion (A): In human being, the females play a major role in determining the sex of the offspring. Reason Women have two chromosomes. Code
    • ABoth (A) and (R) are true, and (R) is the correct explanation of (A)
    • BBoth (A) and (R) are true, but (R) is not the correct explanation of (A)
    • C(A) is true, but (R) is false
    • D(A) is false, but (R) is true
    Answer: (D) (A) is false, but (R) is true
    Explanation

    Option d is the correct (A) is false: It is not the females but the males a major role in determining the sex of the is because the male sperm cell can carry either an X Y chromosome, while the female egg cell typically an X chromosome. Therefore, the sex chromosome male sperm carries determines whether the offspring into a male or a (R) is true: Women do have two X inherited from each parent. This is represented as "XX". This is in men, who typically have one X chromosome and one represented as "XY"

25. #25UPSC CSE Prelims 1998
    Which one of the following type of microorganisms is most widely used in industries?
    • ABacteria
    • BBacteria and fungi
    • CBacteria and algae
    • DBacteria, microalgae and fungi
    Answer: (D) Bacteria, microalgae and fungi
    Explanation

    Option d is the correct answer microalgae, and fungi are the most widely in industries. They are used to produce variety of products, including: Food and beverages: Bacteria are used to produce yogurt, cheese, bread, beer, and wine. Microalgae are used to produce spirulina, chlorella, and other health foods. Fungi are used to produce mushrooms and yeast Pharmaceuticals: Bacteria are used to produce antibiotics, vaccines, and other drugs. Fungi are used to produce penicillin and other antibiotics. Biofuels: Microalgae and bacteria are used to produce biodiesel and ethanol. Chemicals: Bacteria and fungi are used to produce a variety of chemicals, such as organic acids, enzymes, plastics. Environmental remediation: Bacteria are used to clean up oil spills and other environmental pollution

26. #26UPSC CSE Prelims 1998
    Which one of the following statements regarding starch and cellulose is not correct?
    • ABoth of them are of plant or igin
    • BBoth of them are polymers
    • CBoth of them give colour with iodine
    • DBoth of them are made up of glucose molecules
    Answer: (C) Both of them give colour with iodine
    Explanation

    Option c is the correct gives a blue-black color with iodine, while not. Amylose present in starch is the reason for in its colour to blue black. Iodine is not soluble so it is dissolved along with potassium iodide a triiodide molecule which enters the helical amylose and changes the colour of starch. Cellulose color when subjected to iodine solution. This is cannot hold iodine. Since there are no in cellulose, it can't coil around iodine. Source Planl Plant s 1-4 1-4 1-4 amt 1-6 1-4 and No No Y8s

27. #27UPSC CSE Prelims 1997
    Corpus luteum is a mass of cells found in
    • ABrain
    • BOvary
    • CPancreas
    • DSpleen
    Answer: (B) Ovary
    Explanation

    Option b is the correct corpus luteum is a temporary structure that the ovary after an egg is released during ovulation. hormones such as progesterone that are reproductive health and fertility. Important Tips Brain: The brain is the central organ of the human nervous system, and with the spinal cord makes up the central nervous system. The brain consists of the cerebrum, the brainstem and the cerebellum. The brain controls many functions such as thought, memory, emotion, vision, breathing, temperature and hormone secretion. The brain is composed of gray matter and white matter, which have different roles in processing and transmitting information. Pancreas: The pancreas is an organ that has both endocrine and exocrine functions. The pancreas is located in the abdomen, behind the stomach. As an endocrine gland, it produces hormones such as insulin and glucagon that regulate blood sugar l

28. #28UPSC CSE Prelims 1997
    Oxygen transportation in a human body takes place through: 1. Blood 2. Lungs 3. Tissue The correct sequence of transportation is:?
    • A1, 2, 3
    • B3, 1, 2
    • C2, 1, 3
    • D1, 3, 2
    Answer: (C) 2, 1, 3
    Explanation

    Option c is the correct correct sequence of oxygen transportation in a is Lungs, Blood, Tissue. Oxygen first enters the binds to hemoglobin in the blood, and finally tissues where it is used for cellular respiration. Important Tips How oxygen is transported in the human body? Oxygen is poorly soluble in plasma, so that less than 2 percent of oxygen is transported dissolved in plasma. The vast majority of oxygen, 98.5 percent, is bound to a protein called hemoglobin and carried to the tissues. Hemoglobin is a protein molecule found in red blood cells (erythrocytes) made of four subunits: two alpha subunits and two beta subunits. Each subunit surrounds a central heme group that contains iron and binds one oxygen molecule, allowing each hemoglobin molecule to bind four oxygen molecules. The quantity of oxygen bound to hemoglobin is dependent on the partial pressure of oxygen in the lung. Wh

29. #29UPSC CSE Prelims 1997
    The working principle of a washing machine is
    • ACentrifugation
    • BDialysis
    • CReverse osmosis
    • DDiffusion
    Answer: (A) Centrifugation
    Explanation

    Option a is the correct working principle of a washing machine This is the process of separating different densities by spinning them at high speed in container. When we load dirty clothes, water, into the machine, it agitates to clean the it rinses and then employs rapidly to force water out of the clothes. spin effectively "throws" water out through drainage system. Important Tips Dialysis: This is the process of removing waste and excess fluid from the blood when the kidneys are not working properly. It involves passing the blood through a semipermeable membrane that filters out the unwanted substances and returns the clean blood to the body. For example, dialysis is used to treat people with chronic kidney disease or acute kidney injury. Reverse osmosis: This is the process of purifying water by forcing it through a semipermeable membrane that blocks the passage of dissolved solutes

30. #30UPSC CSE Prelims 1996
    Which of the following are more likely to nm the risk of a permanent change in their cell's DNA? 1. Researchers using carbon 14 isotope 2. X-ray technician 3. Coal miner 4. Dyer and painterSelect the correct answer by using the codes given below
    • A2 only
    • B1, 2 and 3 only
    • C1, 2 and 4 only
    • D1, 3, and 4 only
    Answer: (C) 1, 2 and 4 only
    Explanation

    Option c is the correct using carbon 14 isotope, X-ray dyer and painter are exposed to ionizing which can cause mutations in their DNA. Coal miners, other hand, are not likely to face a permanent change cell's DNA because the amount of carbon 14 in coal low

31. #31UPSC CSE Prelims 1996
    It is possible to produce seedless tomato fruits by
    • AApplying trace elements in tomato fruits
    • BSpraying mineral solution on plants
    • CSpraying hormones on flowers
    • DApplying fertilizers containing radioactive elements
    Answer: (C) Spraying hormones on flowers
    Explanation

    Option c is the correct tomato fruits can be produced by spraying of the plant with hormones such as gibberellins These hormones prevent the development of inhibiting the fertilization of the ovules. This process

32. #32UPSC CSE Prelims 1995
    Which one of the following hormones contains iodine?
    • AThyroxine
    • BTestosterone
    • CInsulin
    • DAdrenaline
    Answer: (A) Thyroxine
    Explanation

    Option a is the correct is a hormone that contains four iodine its molecular structure. Iodine is essential for of thyroxine, which is produced by the Thyroxine regulates the metabolism, growth, of the body

33. #33UPSC CSE Prelims 1995
    Which of the following elements are present in all proteins? 1. Carbon 2. Hydrogen 3. Oxygen 4. Nitrogen Code
    • A2 and 3 only
    • B1, 2 and 4 only
    • C1, 3 and 4 only
    • D1, 2, 3 and 4
    Answer: (D) 1, 2, 3 and 4
    Explanation

    Option d is the correct are complex macromolecules composed of These amino acids share a common which includes carbon hydrogen and nitrogen Therefore, all four elements hydrogen, oxygen, and nitrogen - are present proteins. Additionally, proteins may also contain and sometimes other elements, but the core in all proteins are and N

34. #34UPSC CSE Prelims 1994
    Even though an animal is fed with carbohydrates rich diet, its blood sugar concentration tends to remain constant. This is on account of the fact that is the case of an animal
    • AHormones of pituitary glands control metabolic process
    • BHormones of pancreas cause such a condition
    • CBlood sugar is readily absorbed by the liver
    • DGlucose undergoes autolysis
    Answer: (B) Hormones of pancreas cause such a condition
    Explanation

    Option b is the correct pancreas is an organ that produces two and glucagon, that regulate blood glucose lowers blood glucose by stimulating cells to glucose from the blood and store it as glycogen or raises blood glucose by stimulating the liver down glycogen and release glucose into the hormones work together to maintain blood a narrow range, regardless of the dietary intake

35. #35UPSC CSE Prelims 1994
    If the blood group of father is A and mother is then what will be the blood group of son
    • AB
    • BAB
    • C0
    • DAB or 0
    Answer: (C) 0
    Explanation

    Option c is the correct blood group of a person is determined by the the ABO gene on chromosome. There are three A, B and 0. The A and B alleles are that they both express their antigens on the cells. The O allele is recessive, meaning that it produce any father has blood group A and the mother has 0. This means that the father has either AA or and the mother has 00 genotype. The of alleles that the son can inherit from are shown below. Father's Mother's Son's niood Allele Allele Genotype A 0 AO A 0 0 00 the son can have either blood group A or 0, depending on which allele he inherits from

36. #36UPSC CSE Prelims 1994
    Which of the following are characteristics shown in a breast-fed baby when compared to a bottle-fed baby? 1. It is less obese. 2. It shows greater capacity to resist diseases. 3. It gets more vitamins and protein. 4. Its growth in height is abnormal. Code
    • A1, 2 and 3
    • B1, 2 and 4
    • C1, 3 and 4
    • D2, 3 and 4
    Answer: (A) 1, 2 and 3
    Explanation

    Option a is the correct l is correct: Breast milk is naturally balanced appropriate nutrition, which helps regulate a more effectively than formula, Breast-fed babies have a iower risk of obesity in chiidhood and iater in 2 is correct: Breast milk contains other immune-boosting factors that help protect from various infections and illnesses. This often results in fewer illnesses and faster they do get 3 is correct: Breast milk provides including vitamins and proteins, the baby's needs. Itfa highly digestible and efficient absorption of 4 is incorrect: Breast milk supports and development, including normal height gain. It is carefully balanced to promote while minimizing the risk of overgrowth or

37. #37UPSC CSE Prelims 1994
    Which one of the following animal's stores waters in the intestine?
    • AMoloch
    • BCamel
    • CZebra
    • DUromastix
    Answer: (B) Camel
    Explanation

    Option b is the correct are known for their ability to go for long time without water. They do this by storing water intestines. Camel intestines can hold up to 30 water. When a camel drinks water, it quickly absorbs into its bloodstream. The water is then transported intestines, where it is stored. The camel can then water as needed. Important Tips In addition to storing water in their intestines, camels also have a number of other adaptations that help them to conserve water. For example, camels have very thick fur, which helps to insulate them from the heat. Camels also have very long eyelashes and slit nostrils, which help to keep sand out of their eyes and nose. A camel's hump does not hold water at all - it actually stores fat. The camel uses it as nourishment when food is scarce. If a camel uses the fat inside the hump, the hump will become limp and droop down. With proper food an

38. #38UPSC CSE Prelims 1993
    Which one of the following is a man-made cereal, not found in nature?
    • ADwarf wheat
    • BHybrid maize
    • CTri tic ale
    • DSoybean
    Answer: (C) Tri tic ale
    Explanation

    Option c is the correct is a man-made cereal, not found in nature. It hybrid of wheat and rye. Triticale was first developed 19th century, but it did not become commercially viable until the Triticale has a number of advantages and rye. It is more resistant to pests and it can be grown in a wider range of climates. also a good source of protein and fiber. Triticale is make a variety of food products, including bread, breakfast cereals. It is also used as animal feed. Important Tips Dwarf wheat is a variety of wheat that has been bred to be shorter in stature. This makes it less susceptible to lodging, which is when the plants fall over due to strong winds or heavy rain. Hybrid maize is a type of maize that has been bred to produce higher yields. Hybrid maize is produced by crossing two different varieties of maize. Soybeans are a type of legume, not a cereal. Legumes are plants that prod

39. #39UPSC CSE Prelims 1993
    Poison gland of snakes is homologous to
    • AElectric organ offishes
    • BStings of rays
    • CSebaceous glands of mammals
    • DSalivary gl and of vertebrates
    Answer: (D) Salivary gl and of vertebrates
    Explanation

    Option dis the correct poison gland of snakes is homologous to the of vertebrates. This means that both the same evolutionary origin, but they have serve different functions. The salivary gland which helps to moisten the mouth and break The poison gland produces venom, which is subdue prey or defend against predators. While may differ, the structural and genetic the poison gland in snakes and the in vertebrates indicate their common ancestry relationship

40. #40UPPCS 2020
    Consider the following statements about human brain: 1. The brain is responsible for regulating the heartbeat. 2. It is responsible for balancing the body.Select the correct answer using the codes given below
    • AOnly 1 is correct
    • BOnly 2 is correct
    • C1 and 2 both are correct
    • DNeither 1 nor 2 is correct
    Answer: (C) 1 and 2 both are correct
    Explanation

    Option c is the correct brain is a complex organ that controls many processes body, such as movement, thinking, emotion, and more. The brain is composed of three the cerebrum, the cerebellum, and the l is correct: The brainstem is the the brain and the spinal cord. It controls such as heartbeat, breathing, blood pressure, It also regulates sleep, arousal, and 2 is correct: The cerebellum is located at the the brain and is involved in coordinating balance, voluntary movements. It also plays a role in and cognitive functions

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