Biology MCQs

Question #1401

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In biotechnology, 'Bt brinjal' is a genetically modified crop developed to provide resistance against:

A. Herbicides

B. The fruit and shoot borer (Leucinodes orbonalis)

C. Viral diseases

D. Fungal infections

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Correct Answer: Option B

Explanation:
Bt brinjal is a transgenic eggplant (brinjal) developed by inserting the cry1Ac gene from the soil bacterium Bacillus thuringiensis (Bt). This gene codes for a crystal protein that is toxic to the larvae of the brinjal fruit and shoot borer (Leucinodes orbonalis), a major pest that causes significant yield loss. When the insect ingests the plant tissue, the alkaline gut activates the toxin, creating pores in the gut lining and killing the pest.

This question belongs to: Science Biology

Question #1402

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The 'Humulin' was the first genetically engineered human therapeutic product approved for clinical use. It is:

A. Human Albumin

B. Human Growth Hormone

C. Human Insulin

D. Human Interferon

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Correct Answer: Option C

Explanation:
Humulin is the trade name for the first genetically engineered human insulin, approved by the FDA in 1982. Prior to this, insulin for diabetic patients was extracted from the pancreases of pigs and cows, which could cause allergic reactions. Humulin is produced by inserting the human insulin genes into Escherichia coli bacteria, which then synthesize the exact amino acid sequence of human insulin, eliminating the risk of animal-derived immune reactions.

This question belongs to: Science Biology

Question #1403

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In animal husbandry, 'composite fish culture' is a technique used in inland fisheries where:

A. Only one species of fish is reared at a very high density

B. A combination of five or six different fish species with different feeding habits are reared together in a single pond

C. Fish and prawns are reared together exclusively

D. Fish are reared in the ocean cages

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Correct Answer: Option B

Explanation:
Composite fish culture is a highly productive system used in inland fisheries (ponds) in India. It involves stocking a single pond with a combination of 5-6 different indigenous and exotic fish species that have complementary feeding habits (e.g., Catla are surface feeders, Rohu are column feeders, Mrigal and Common Carp are bottom feeders). This ensures that all available food resources in the different zones of the pond are utilized efficiently without interspecific competition, maximizing total yield.

This question belongs to: Science Biology

Question #1404

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The scientist who first observed and described living microorganisms (animalcules) using a single-lens microscope was:

A. Matthias Schleiden

B. Robert Hooke

C. Antonie van Leeuwenhoek

D. Rudolf Virchow

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Correct Answer: Option C

Explanation:
Antonie van Leeuwenhoek, a Dutch tradesman, is credited as the 'father of microbiology'. In the 1670s, using his own handcrafted, high-quality single-lens microscopes (which could magnify up to 270x), he was the first person to observe and describe living, single-celled organisms, which he called 'animalcules'. These included bacteria, protozoa, and spermatozoa. Robert Hooke observed dead cells (cork) and coined the term 'cell'.

This question belongs to: Science Biology

Question #1405

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The 'Fluid Mosaic Model' of the cell membrane was proposed in 1972 by:

A. Danielli and Davson

B. Singer and Nicolson

C. Watson and Crick

D. Robertson

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Correct Answer: Option B

Explanation:
The Fluid Mosaic Model is the universally accepted model for the structure of the plasma membrane. It was proposed by S. Jonathan Singer and Garth Nicolson in 1972. It describes the membrane as a dynamic, fluid lipid bilayer in which globular proteins are embedded (integral) or attached to the surface (peripheral), creating a 'mosaic' pattern. The lipids and proteins can move laterally within the plane of the membrane. Danielli and Davson proposed the earlier 'sandwich model'.

This question belongs to: Science Biology

Question #1406

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In the human body, the 'Islets of Langerhans' are found in the:

A. Liver

B. Spleen

C. Pancreas

D. Kidneys

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Correct Answer: Option C

Explanation:
The Islets of Langerhans are the endocrine (hormone-producing) portions of the pancreas. They are clusters of cells scattered throughout the pancreatic tissue, comprising about 1-2% of the pancreas's mass. They contain several cell types, primarily alpha cells (secreting glucagon), beta cells (secreting insulin), delta cells (secreting somatostatin), and F cells (secreting pancreatic polypeptide). These hormones are crucial for regulating blood glucose levels.

This question belongs to: Science Biology

Question #1407

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The 'Haversian canal' in compact bone contains:

A. Cartilage and fat

B. Red bone marrow

C. Osteocytes and lacunae

D. Blood vessels, nerves, and lymphatic vessels

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Correct Answer: Option D

Explanation:
The Haversian canal (central canal) is the core of the osteon (Haversian system) in compact bone. It runs parallel to the long axis of the bone and contains the blood vessels (arterioles, venules, capillaries), nerve fibers, and lymphatic vessels that supply the bone tissue. The concentric lamellae surround this canal. Osteocytes are housed in lacunae between the lamellae, and red bone marrow is found in the medullary cavity of long bones or the spaces of spongy bone.

This question belongs to: Science Biology

Question #1408

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The 'Rh factor' was first discovered in the blood of which animal, giving it its name?

A. Reindeer

B. Rabbit

C. Rat

D. Rhesus monkey

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Correct Answer: Option D

Explanation:
The Rh factor (Rhesus factor) is an inherited protein found on the surface of red blood cells. It was discovered in 1940 by Karl Landsteiner and Alexander Wiener. They immunized rabbits and guinea pigs with the red blood cells of the Rhesus monkey (Macaca mulatta). The serum produced contained antibodies that agglutinated the red blood cells of about 85% of humans. These individuals were designated Rh-positive, and the rest Rh-negative.

This question belongs to: Science Biology

Question #1409

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In plant tissue culture, the process of forming an unorganized, undifferentiated mass of cells from an explant is called:

A. Micropropagation

B. Callus formation

C. Protoplast fusion

D. Somatic embryogenesis

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Correct Answer: Option B

Explanation:
In plant tissue culture, when an explant (a piece of plant tissue) is placed on a nutrient medium containing specific plant hormones (like auxins and cytokinins), the cells dedifferentiate and undergo rapid, unorganized division to form a mass of cells called a callus. This callus is undifferentiated. Under appropriate hormonal conditions, this callus can then be induced to redifferentiate and form organized structures like shoots and roots (organogenesis) or somatic embryos.

This question belongs to: Science Biology

Question #1410

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The 'Green Revolution' in India, which led to a massive increase in wheat and rice production, was primarily led by the efforts of:

A. Both B and C

B. Verghese Kurien

C. Norman Borlaug

D. M.S. Swaminathan

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Correct Answer: Option A

Explanation:
The Green Revolution in India was a period of significant agricultural transformation. Norman Borlaug, the 'father of the Green Revolution' globally, developed high-yielding, disease-resistant dwarf wheat varieties in Mexico. M.S. Swaminathan, known as the 'father of the Green Revolution in India', adapted these varieties to Indian conditions and led the scientific and administrative efforts to introduce these high-yielding varieties (along with improved irrigation and fertilizers) to Indian farmers, drastically increasing wheat and rice production.

This question belongs to: Science Biology

Question #1411

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In the human respiratory system, the 'Surfactant' is a lipoprotein complex secreted by which cells to reduce surface tension in the alveoli?

A. Goblet cells

B. Alveolar macrophages

C. Type II alveolar cells

D. Type I alveolar cells

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Correct Answer: Option C

Explanation:
Pulmonary surfactant is a complex mixture of lipids (primarily dipalmitoylphosphatidylcholine) and proteins secreted by Type II alveolar cells (septal cells) in the lungs. Its primary function is to reduce the surface tension of the fluid lining the alveoli. Without surfactant, the alveoli would collapse at the end of expiration (atelectasis) due to high surface tension, making it extremely difficult to re-inflate the lungs during inspiration.

This question belongs to: Science Biology

Question #1412

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The 'Spleen' in the human body is primarily located in the:

A. Abdominal cavity, in the upper left quadrant

B. Cranial cavity

C. Thoracic cavity

D. Pelvic cavity

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Correct Answer: Option A

Explanation:
The spleen is the largest lymphoid organ in the body. It is located in the abdominal cavity, specifically in the upper left quadrant, tucked between the stomach and the diaphragm, protected by the rib cage (ribs 9-11). It functions primarily in filtering blood, removing old or damaged red blood cells, storing platelets, and mounting immune responses against blood-borne pathogens. It is not located in the thoracic, pelvic, or cranial cavities.

This question belongs to: Science Biology

Question #1413

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In the human eye, the defect of vision where the eyeball is too long or the cornea is too curved, causing light to focus in front of the retina, is called:

A. Astigmatism

B. Myopia (Nearsightedness)

C. Presbyopia

D. Hypermetropia (Farsightedness)

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Correct Answer: Option B

Explanation:
Myopia, or nearsightedness, is a refractive error where distant objects appear blurry, but near objects are clear. It occurs when the eyeball is elongated (axial myopia) or the cornea/lens is too curved (refractive myopia), causing light rays from distant objects to focus in front of the retina instead of directly on it. It is corrected using a concave (diverging) lens. Hypermetropia is the opposite, corrected with a convex lens.

This question belongs to: Science Biology

Question #1414

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The 'Hormone Relaxin' is secreted by the corpus luteum and the placenta during pregnancy primarily to:

A. Stimulate milk production

B. Stimulate uterine contractions

C. Increase blood glucose levels

D. Relax the smooth muscles of the uterus and soften the pelvic ligaments and pubic symphysis for childbirth

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Correct Answer: Option D

Explanation:
Relaxin is a peptide hormone produced by the corpus luteum and the placenta during pregnancy. Its primary roles are to relax the smooth muscles of the uterus (inhibiting contractions to maintain pregnancy) and to soften and increase the flexibility of the connective tissues in the pelvis, specifically the pelvic ligaments and the pubic symphysis. This relaxation and widening of the pelvic joints facilitate the passage of the baby through the birth canal during delivery.

This question belongs to: Science Biology

Question #1415

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In the context of human diseases, 'Elephantiasis' is caused by the filarial worm Wuchereria bancrofti, which is transmitted by the bite of the female:

A. Anopheles mosquito

B. Tsetse fly

C. Culex mosquito

D. Aedes mosquito

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Correct Answer: Option C

Explanation:
Lymphatic filariasis, commonly known as elephantiasis, is a parasitic disease caused by nematode worms, primarily Wuchereria bancrofti. The infective larvae (microfilariae) are transmitted to humans through the bite of an infected female Culex mosquito (primarily Culex pipiens fatigans). The adult worms lodge in the lymphatic vessels, causing severe inflammation, blockage, and the characteristic massive swelling (elephantiasis) of the limbs and genitals. Anopheles transmits malaria, Aedes transmits dengue.

This question belongs to: Science Biology

Question #1416

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The 'Vaccine' for Rabies was first developed by Louis Pasteur using:

A. A subunit of the rabies virus

B. Killed rabies virus

C. Live attenuated rabies virus

D. Weakened virus obtained from the spinal cord of infected rabbits

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Correct Answer: Option D

Explanation:
In 1885, Louis Pasteur developed the first effective vaccine against rabies. He achieved this by serially passaging the rabies virus (obtained from the saliva of infected dogs) through the spinal cords of rabbits. This process attenuated (weakened) the virus for rabbits but made it virulent for dogs. He then dried the infected spinal cords to further weaken the virus and used this attenuated material to successfully inoculate and protect a boy, Joseph Meister, who had been bitten by a rabid dog.

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Question #1417

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In genetics, the 'Operon model' was proposed by:

A. McClintock

B. Watson and Crick

C. Beadle and Tatum

D. Jacob and Monod

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Correct Answer: Option D

Explanation:
The Operon model, specifically the lac operon model, was proposed by French scientists François Jacob and Jacques Monod in 1961 to explain the regulation of gene expression in prokaryotes (bacteria). They proposed that genes are organized into functional units called operons, consisting of a promoter, an operator, and structural genes, controlled by a regulatory gene. They were awarded the Nobel Prize in Physiology or Medicine in 1965 for this discovery. Beadle and Tatum proposed the 'one gene-one enzyme' hypothesis.

This question belongs to: Science Biology

Question #1418

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In plant anatomy, the 'Casparian strip' is a band of cell wall material made of suberin and lignin found in the:

A. Endodermis of the root

B. Cortex of the stem

C. Pericycle of the root

D. Epidermis of the root

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Correct Answer: Option A

Explanation:
The Casparian strip is a waterproof band of suberin and lignin found in the radial and transverse cell walls of the endodermis (the innermost layer of the cortex) in plant roots. It acts as a barrier to the passive flow of water and dissolved minerals through the cell walls (the apoplastic pathway). This forces water and solutes to cross the selectively permeable plasma membrane and enter the symplastic pathway, allowing the plant to control and filter what enters the vascular cylinder (stele).

This question belongs to: Science Biology

Question #1419

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The 'Emerson enhancement effect' demonstrated that photosynthesis is more efficient when:

A. Plants are kept in complete darkness

B. Plants are exposed to both red and far-red light simultaneously

C. Plants are exposed to only red light

D. Plants are exposed to only far-red light

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Correct Answer: Option B

Explanation:
The Emerson enhancement effect, discovered by Robert Emerson in 1957, provided crucial evidence for the existence of two distinct photosystems (PSI and PSII) in photosynthesis. He observed that the rate of photosynthesis (measured by oxygen evolution) under far-red light (>680 nm) alone was very low. However, when far-red light was combined with shorter wavelength red light (

This question belongs to: Science Biology

Question #1420

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In the human circulatory system, the 'Hepatic portal vein' carries blood from the digestive tract to the:

A. Heart

B. Kidneys

C. Liver

D. Lungs

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Correct Answer: Option C

Explanation:
The hepatic portal vein is a unique blood vessel in the circulatory system that carries nutrient-rich, but potentially toxin-laden, blood from the gastrointestinal tract (stomach, intestines), spleen, and pancreas directly to the liver, rather than to the heart. This allows the liver to process absorbed nutrients, store glycogen, detoxify harmful substances, and regulate blood composition before the blood enters the systemic circulation via the hepatic veins to the inferior vena cava.

This question belongs to: Science Biology

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