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Top 30 Biology MCQs for Competitive Exams – 16 March 2024

பல்வேறு போட்டித் தேர்வுகளில்  உயிரியல் முக்கியப் பங்காற்றுகிறது, விண்ணப்பதாரர்களுக்கு அவர்களின் தயாரிப்பில் உதவ, நாங்கள் 30 கேள்விகளை (MCQs)  தொகுத்துள்ளோம். உங்கள் உயிரியல் அறிவை மேம்படுத்துவதற்கும், வரவிருக்கும் தேர்வுகளுக்கு உங்களை சிறப்பாக தயார்படுத்துவதற்கும் ஒவ்வொரு கேள்விக்கும் சரியான பதில் உள்ளது.

Top 30 Biology MCQs

Q1. The rhythmic contraction of the lining of muscles of the canal to push the food along the gut is called ______.

(a) Peristalsis

(b) Facilitation

(c) Guttation

(d) No option is correct


Q2. Which of the following is a CORRECT relation between the length of small intestines of an herbivore and a carnivore?

(a) Herbivore = Carnivore

(b) Herbivore < Carnivore

(c) Herbivore > Carnivore

(d) No option is correct.


Q3. Lymph carries digested and absorbed fat from ______.

(a) Lungs 

(b) Intestine

(c) Stomach

(d) Kidney


Q4. Alveoli are balloon-like structures within the ______.

(a) Lungs 

(b) Kidney

(c) Liver

(d) Heart


Q5. The alimentary canal is a long tube that extends from ______.

(a) mouth to stomach

(b) stomach to the large intestine

(c) small intestine to the anus

(d) mouth to anus 


Q6. What is regulated by the sphincter muscle in the stomach?

 (a) Exit of the food from the stomach

 (b) Entry of food in the stomach

 (c) Mixing of food in the stomach

 (d) Exit of food from the large intestine


Q7. What are the organs similar in basic structure/shape, modified to perform different functions called?

(a) Analogous organs

 (b) Homologous organs

 (c) Heterogeneous organs

 (d) Homogenous organs


Q8. Which is the longest part of alimentary canal?

(a) Esophagus

(b) Small intestine

(c) Large intestine

(d) Buccal cavity 


Q9. Which of the following is/are the function(s) of bile juice released from the liver?

  1. Make the food coming from the stomach alkaline.
  2. Conversion of proteins into amino acids.

III. Breakdown of fats into smaller globules.

(a) Only I

(b) Only II and III

(c) Only I and III

(d) All I, II and III


Q10. The voluntary muscles are also called ______ muscles.

(a) Striated

(b) Smooth

(c) Cardiac

(d) Unstriated

Q11. Which is the anti-coagulant substance in blood?

(a) Fibrinogen

(b) Heparin

(c) Thrombin

(d) Globin


Q12. Which of the following is not connective tissue?

(a) Bone

(b) Cartilage

(c) Blood

(d) Skeletal muscle


Q13. Which one of the following substances is normally found in urine?

(a) Blood proteins

(b) Creatinine

(c) Red blood cells

(d) White blood cells


Q14. Blood group AB has –

(a) No antigen

(b) No antibody

(c) Neither antigen nor antibody

(d) Both antigen and antibody


Q15. Blood group was discovered by

(a) Alexander Fleming

(b) William Harvey

(c) Landsteiner

(d) Paulov


Q16. Blood is red in color due to the presence of __________.

(a) Cytochrome

(b) Chlorophyll

(c) Hemocyanin

(d) Haemoglobin


Q17. An instrument for measuring blood pressure is called –

(a) Barometer

(b) Spirometer

(c) Sphygmomanometer

(d) Haemocytometer


Q18. Haemoglobin is an important component of _______.

(a) White Blood Cells

(b) Red Blood Cells

(c) Plasma

(d) All options are correct


Q19. Which of the following carries oxygen to various parts of the human body?

(a) Red blood cells

(b) White blood cells

(c) Plasma

(d) Nerves


Q20. Another name for Platelets is?

(a) Leucocytes

(b) Erythrocytes

(c) Lymphocytes

(d) Thrombocytes


Q21. Which hormone controls the quantity of urine from kidney?

(a) TSH

(b) ACTH

(c) FSH

(d) ADH


Q22. Which of the following is a key difference between hormones and enzymes?

(a) Enzymes are predominantly proteins, while Hormones can be made up of proteins, amino acids, or steroids.

(b) Enzymes are steroids, while hormones are made up of proteins and amino acids. 

(c) Hormones are made up of amino acids, while enzymes can be made up of proteins, steroids, or amino acids. 

(d) Enzymes and hormones are both made up of amino acids.


Q23. Which hormone is responsible for the regulation of the sleep-wake cycle? 

(a) Melatonin 

(b) Adrenaline 

(c) Thyroxine 

(d) Estrogen


Q24. Which endocrine gland is responsible for producing cortisol, the stress hormone? 

(a) Adrenal gland 

(b) Thyroid gland 

(c) Pituitary gland 

(d) Pancreas


Q25. What is the consequence of iodine deficiency in our diet? 

(a) Hyperthyroidism 

(b) Goitre 

(c) Diabetes 

(d) Cushing’s syndrome


Q26. Which of the following is a common co-factor required for the activity of many enzymes? 

(a) Calcium ions 

(b) Magnesium ions 

(c) Zinc ions 

(d) All of the above


Q27. Which of the following statements about enzymes is FALSE? 

(a) Enzymes are biological catalysts 

(b) Enzymes increase the activation energy of a chemical reaction 

(c) Enzymes are usually specific for a particular substrate 

(d) Enzymes can be affected by temperature and pH


Q28. Which of the following is an example of an enzyme? 

(a) Lactose 

(b) Glucose 

(c) Amylase 

(d) Sucrose


Q29. Which of the following is NOT a factor that affects enzyme activity? 

(a) Temperature 

(b) pH 

(c) Substrate concentration 

(d) Gender


Q30. Which of the following hormones reduces cellular glucose uptake and utilization and is responsible for hyperglycemia?

(a) Insulin 

(b) Thyroxine 

(c) Glucagon 

(d) Adrenaline



Sol. Peristalsis is a particular, wave-like kind of muscle contraction because its purpose is to move solids or liquids along within the tube-like structures of the digestive and urinary tracts.

  • Facilitation is the process of making something easier or more possible. It is not related to the movement of food in the gut.
  • Guttation is the process by which water is exuded from the pores or hydathodes on the leaves of plants. It is not related to the digestive system.



Sol. Herbivores require a longer digestive tract to break down the cellulose in plant matter, which is more difficult to digest than the protein and fat found in animal matter. 

  • The small intestine is a major site of nutrient absorption in the digestive system, so herbivores typically have longer small intestines than carnivores to extract as much nutrition as possible from their food.
  • In contrast, carnivores require a shorter digestive tract because animal protein and fat are more easily digestible, and they need to expel undigested material quickly to avoid putrefaction in their short intestines.


Sol. Lymph is a fluid that is similar to blood plasma, but it is colorless and does not contain red blood cells. 

  • One of the main functions of the lymphatic system is to absorb fats and fat-soluble vitamins from the small intestine.
  • Lymphatic vessel is present in the intestinal villi.
  • It acts as a reservoir of digested food and water.

S4. Ans.(a)

Sol. Alveoli are structures within the Lungs. 

  • Alveoli are small, balloon-like structures in the lungs that are responsible for gas exchange. They are the site of oxygen and carbon dioxide exchange between the lungs and the bloodstream.
  • When we breathe in, air enters the lungs through the trachea and bronchi, which then branch out into smaller airways called bronchioles. 
  • At the end of the bronchioles are the alveoli, which are tiny air sacs lined with a thin layer of cells that are in direct contact with the bloodstream.


Sol. The alimentary canal is the whole passage along which food passes through the body from mouth to anus during digestion.

  • It is the pathway through which food travels in the body, and where the process of digestion and absorption of nutrients takes place.
  • The alimentary canal is composed of several organs that are connected in a continuous tube, including the mouth, pharynx, esophagus, stomach, small intestine, large intestine, and anus.

S6. Ans.(a)

Sol. The sphincter muscle in the stomach regulates the exit of food from the stomach. 

  • The sphincter muscle in the stomach is called the pyloric sphincter, and it is located at the lower end of the stomach where it joins the small intestine. 
  • It is a ring of muscle that controls the release of partially digested food, known as chyme, from the stomach into the small intestine. 

S7. Ans.(b)

Sol. Homologous organs are similar in basic structure/shape, modified to perform different functions. Homologous organs are similar in structure and share a common ancestry, but they may have different functions in different organisms. For example, the forelimbs of mammals, birds, reptiles, and amphibians are all homologous structures, despite being modified for different functions.

  • Analogous organs, on the other hand, are organs that have similar functions in different organisms, but different structures and evolutionary origins. (e.g., wings of birds and insects). 
  • Heterogeneous and homogenous organs are not typically used to describe biological structures.


Sol. The Small Intestine is the largest and longest part of the alimentary canal. The small intestine is the longest part of the alimentary canal, measuring around 6 meters in length. It plays a crucial role in digestion and nutrient absorption.

  • Esophagus – a muscular tube that connects the mouth to the stomach. It is part of the digestive system, but it is relatively short and measures around 25 cm in length.
  • Large intestine – also known as the colon, is a shorter segment of the alimentary canal that follows the small intestine. It is around 1.5 meters in length and its main function is to absorb water and electrolytes and to store and eliminate feces.
  • Buccal Cavity – also known as the oral cavity, is the opening at the start of the alimentary canal. It contains the tongue, teeth, and salivary glands and plays a role in the initial mechanical and chemical digestion of food.


S9. Ans.(c)

Sol. Bile juice released from the liver has two primary functions:

  1. Make the food coming from the stomach alkaline. 
  2. Breakdown of fats into smaller globules. Thus, Statement I & III is correct.
  • Bile juice does not convert proteins into amino acids. Protein digestion occurs mainly in the stomach and small intestine through the action of enzymes such as pepsin and trypsin. Thus, Statement II is incorrect.

Note: Bile breaks down large fat globules into smaller globules in the small intestine so that the pancreatic enzymes can easily act on them. This process is known as emulsification of fats.

S10. Ans.(a)

Sol. The voluntary muscles are also called Striated muscles.

  • Striated muscles are so named because they have a striped appearance due to the presence of alternating light and dark bands (or striations) under the microscope. 
  • These muscles are called voluntary muscles because they are under conscious control and can be contracted or relaxed at will, allowing us to perform movements such as walking, running, and lifting weights.
  • Smooth muscles, on the other hand, are involuntary muscles found in the walls of internal organs such as the stomach, intestines, and blood vessels. They do not have striations and are not under conscious control.
  • Cardiac muscles are a type of striated muscle found only in the heart, and they are also involuntary.

S11. Ans.(b)

Sol. Heparin is an anticoagulant substance that is naturally present in the body, particularly in mast cells and basophils. It helps to prevent blood clots from forming by inhibiting the activity of clotting factors, specifically thrombin, and factor Xa.

  • Fibrinogen is a clotting factor in the blood that is converted to fibrin during the coagulation process. Thrombin is an enzyme that helps to convert fibrinogen to fibrin and plays a key role in the formation of blood clots. Globin, on the other hand, is a protein found in hemoglobin, which is responsible for transporting oxygen in the blood.

S12. Ans.(d)

Sol. Skeletal muscle is not a connective tissue. It is a type of muscle tissue that is responsible for voluntary movements of the body. 

  • Connective tissue is a group of tissues in the body that maintain the form of the body and its organs and provide cohesion and internal support. 
  • Examples of connective tissue include adipose, cartilage, bone, tendons, and blood. Bone, cartilage, and blood are all examples of connective tissue. 


S13. Ans.(b)

Sol. Creatinine is normally found in urine. High levels of creatinine in the bloodstream and urine can be an indicator of kidney disease.

  • Creatinine is a waste product that is produced by the muscles from the breakdown of creatine, a compound used for energy storage in muscle cells. 
  • Creatinine is filtered out of the blood by the kidneys and excreted in the urine. 
  • The amount of creatinine in the urine can be used to estimate the glomerular filtration rate (GFR), which is a measure of how well the kidneys are functioning.


S14. Ans.(b)

Sol. Group AB has both A and B antigens on red cells but neither A nor B antibodies in the plasma.

  • Blood group AB has both A and B antigens on the surface of its red blood cells, which means that it can receive blood from individuals with blood groups A, B, AB, or O. However, it does not produce any antibodies against either A or B antigens.

S15. Ans.(c)

sol. Karl Landsteiner discovered the blood group.

  • Karl Landsteiner was an Austrian immunologist and pathologist who discovered the ABO blood group system in 1901. 
  • He found that there are different blood types, based on the presence or absence of specific antigens on the surface of red blood cells. His discovery made it possible to perform safe blood transfusions without the risk of a transfusion reaction.
  • Landsteiner was awarded the Nobel Prize in Physiology or Medicine in 1930 for his discovery.
  • Alexander Fleming – a Scottish microbiologist, discovered Penicillin. 
  • William Harvey – an English physician, described the circulation of blood in the body in the 17th century. 
  • Pavlov – Russian physiologist known for his work on classical conditioning.


Sol. Blood is red in color due to the presence of Haemoglobin.

  • Haemoglobin is a protein found in red blood cells that is responsible for carrying oxygen from the lungs to the tissues of the body. It contains iron, which gives blood its red color. When oxygen binds to the iron in hemoglobin, the molecule changes shape and becomes brighter red, and when it releases oxygen in the tissues, it becomes darker red.
  • Cytochrome is a protein that is involved in the electron transport chain in the mitochondria. 
  • Chlorophyll is a green pigment found in plants that is responsible for photosynthesis.
  • Hemocyanin is a copper-containing protein found in the blood of some invertebrates.

S17. Ans.(c)

Sol. Sphygmomanometer is an instrument for measuring blood pressure.

Instrument Basic Function
Barometer Measure atmospheric pressure to predict weather conditions
Spirometer Measure lung capacity and function for respiratory conditions
Haemocytometer Count blood cells for research and clinical settings


S18. Ans.(b)

Sol. Hemoglobin is the protein molecule in red blood cells. 

  • Hemoglobin is responsible for carrying oxygen from the lungs to the body’s tissues and organs.
  • It is an iron-containing protein that binds to oxygen in the lungs and releases it in the body’s tissues. 
  • Hemoglobin levels are measured in blood tests and can indicate various medical conditions such as anemia, polycythemia, or sickle cell disease.


S19. Ans.(a)

Sol. Red blood cells carry oxygen to various parts of the human body. 

  • They contain the protein hemoglobin, which binds to oxygen in the lungs and carries it to the body’s tissues and organs.
  • Red blood cells are produced in the bone marrow and circulate in the bloodstream. 
  • White blood cells are involved in the immune response and help fight infections.
  • Plasma is a fluid component of blood that contains proteins, hormones, and other substances. 
  • A nerve cell, also known as a neuron, is a specialized type of cell found in the nervous system which is responsible for transmitting information throughout the body in the form of electrical impulses.

S20. Ans. (d)

Sol. Platelets, also called thrombocytes are a component of blood whose function (along with the coagulation factors) is to stop bleeding by clumping and clotting blood vessel injuries.

  • Leucocytes: Also known as white blood cells, these are involved in the immune response and help fight infections.
  • Erythrocytes: Also known as red blood cells, these contain the protein hemoglobin and are responsible for carrying oxygen to the body’s tissues and organs.
  • Lymphocytes: These are a type of white blood cell that play a role in the immune response and help the body fight off infections.

S21. Ans.(d)

Sol. ADH (anti-diuretic hormone) controls the quantity of urine from the kidney by increasing the reabsorption of water from the distal tubules of the nephrons. This results in less urine formation and more concentrated urine. 

  • TSH (Thyroid Stimulating Hormone) stimulates the synthesis and secretion of thyroid hormones from the thyroid gland.
  • ACTH (Adrenocorticotropic Hormone) stimulates the synthesis and secretion of steroid hormones called glucocorticoids from the adrenal cortex. 
  • FSH (Follicle Stimulating Hormone) stimulates the growth and development of the ovarian follicles in females and stimulates spermatogenesis in males.

S22. Ans.(a)

Sol. Enzymes are predominantly proteins, while Hormones can be made up of proteins, amino acids, or steroids.

Criteria Hormones Enzymes
Composition Can be made up of amino acids, peptides, or steroids Proteins, but may also contain other components such as metal ions or cofactors
Function Chemical messengers that trigger various bodily processes and affect target tissues or cells Act as catalysts to facilitate chemical reactions
Mode of Action Travel through the bloodstream to reach target cells or tissues Act locally on molecules near the enzyme
Regulation Secreted by glands in response to various stimuli, and their production and secretion are tightly regulated Produced in cells and their activity is regulated by various factors, including substrate concentration and environmental conditions
Examples Insulin, growth hormone, testosterone, estrogen Amylase, catalase, lactase


S23. Ans.(a)

Sol. The hormone responsible for the regulation of the sleep-wake cycle is Melatonin.

  • Melatonin is a hormone produced by the pineal gland in the brain. Melatonin is involved in the regulation of the sleep-wake cycle, and its production increases in response to darkness, promoting sleep. In contrast, exposure to light inhibits melatonin production, promoting wakefulness.
  • Adrenaline is a hormone produced by the adrenal glands and is involved in the body’s “fight or flight” response to stress. 
  • Thyroxine is a hormone produced by the thyroid gland that regulates metabolism. 
  • Estrogen is a hormone primarily associated with female reproductive functions, but it also plays a role in bone health and other physiological processes.


S24. Ans.(a)

Sol. The endocrine gland responsible for producing cortisol, the stress hormone, is the Adrenal gland.

  • The adrenal glands are small, triangular-shaped glands located on top of each kidney. They produce several hormones, including cortisol. Cortisol is a steroid hormone that is released in response to stress and helps the body respond to stressful situations by increasing blood sugar levels, suppressing the immune system, and increasing blood pressure.
  • The thyroid gland produces hormones that regulate metabolism.
  • The pituitary gland produces several hormones that control other endocrine glands in the body.
  • The pancreas produces hormones such as insulin and glucagon, which regulate blood sugar levels.

 S25. Ans.(b)

Sol. The consequence of iodine deficiency in our diet is Goitre.

  • Goitre is a visible swelling of the thyroid gland in the neck, which can cause discomfort, difficulty swallowing, and difficulty breathing. It is more common in areas where the soil and water are low in iodine, and the population’s diet is deficient in iodine. In severe cases, iodine deficiency can lead to mental retardation and developmental delays, particularly in infants and children.
  • Hyperthyroidism is a condition characterized by the overproduction of thyroid hormones.
  • Diabetes is a condition characterized by high blood sugar levels.
  • Cushing’s syndrome is a condition caused by the excessive production of cortisol, a hormone produced by the adrenal gland.


S26. Ans.(d)

Sol. The common co-factor required for the activity of many enzymes is All of the above – calcium ions, magnesium ions, and zinc ions.

  • Co-factors are non-protein chemical compounds that are required for the activity of many enzymes. 
  • They are essential for the proper functioning of enzymes and can be inorganic ions, such as calcium, magnesium, and zinc, or organic molecules, such as vitamins or coenzymes.

S27. Ans.(b)

Sol.  The FALSE statement about enzymes is (b) Enzymes increase the activation energy of a chemical reaction.

  • Enzymes are biological catalysts that accelerate chemical reactions by reducing the activation energy required for the reaction to occur. Enzymes do this by stabilizing the transition state of a reaction, which lowers the energy required for reactant molecules to form products.


S28. Ans.(c)

Sol. The example of an enzyme is Amylase.

  • Amylase is an enzyme that catalyzes the breakdown of complex carbohydrates, such as starch and glycogen, into simpler sugars, such as glucose and maltose. 
  • Lactose is composed of glucose and galactose, while sucrose is composed of glucose and fructose. They are not enzymes.
  • Glucose is a simple sugar that is an important source of energy for the body. 

S29. Ans.(d)

Sol. The factor that is NOT a factor that affects enzyme activity is Gender.

  • Enzyme activity can be affected by several factors, including temperature, pH, substrate concentration, enzyme concentration, and the presence of inhibitors or activators but not gender. 


S30. Ans.(c)

Sol. Glucagon reduces cellular glucose uptake and utilization, leading to hyperglycemia.

  • The main role of glucagon is to maintain glucose homeostasis in the body, ensuring that there is a constant supply of glucose to meet the energy demands of the body. When blood glucose levels drop, such as during fasting or exercise, glucagon is released to stimulate the liver to break down glycogen into glucose, which is then released into the bloodstream.
  • In contrast, insulin is a hormone produced by the beta cells in the pancreas that lowers blood glucose levels.


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