Biology MCQs

Question #301

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Which of the following is an example of a modified stem that stores food?

A. Sweet potato

B. Radish

C. Potato

D. Carrot

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Correct Answer: Option C

Explanation:
Potato is a modified stem (tuber) that stores starch. The 'eyes' on a potato are axillary buds, confirming it as a stem. Sweet potato is a modified root (tuberous root), carrot is a taproot, radish is a modified root. Other modified stems include ginger (rhizome), onion (bulb, though bulb is a modified stem with fleshy leaf bases), and garlic.

This question belongs to: Science Biology

Question #302

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The pigment that gives plants their characteristic green color and is the main pigment for photosynthesis is:

A. Chlorophyll b

B. Xanthophyll

C. Carotene

D. Chlorophyll a

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Correct Answer: Option D

Explanation:
Chlorophyll a is the primary photosynthetic pigment, essential for converting light energy into chemical energy. It directly participates in the light reactions. Chlorophyll b, carotenes, and xanthophylls are accessory pigments that capture additional wavelengths and transfer energy to chlorophyll a. These accessory pigments also protect chlorophyll from photo-oxidation.

This question belongs to: Science Biology

Question #303

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The scientist who proposed the cell theory that 'all cells arise from pre-existing cells' is:

A. Theodor Schwann

B. Robert Hooke

C. Matthias Schleiden

D. Rudolf Virchow

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Correct Answer: Option D

Explanation:
Rudolf Virchow, in 1855, added the third tenet to the cell theory: 'Omnis cellula e cellula', meaning all cells arise from pre-existing cells. Schleiden and Schwann proposed that plants and animals are composed of cells (first two tenets). Robert Hooke discovered cells. Virchow's concept refuted spontaneous generation and established the continuity of life.

This question belongs to: Science Biology

Question #304

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The technique of separating molecules based on their size and charge is:

A. Centrifugation

B. Spectrophotometry

C. Chromatography

D. Electrophoresis

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Correct Answer: Option D

Explanation:
Gel electrophoresis, especially agarose gel electrophoresis, separates DNA, RNA, or protein fragments based on size and charge under an electric field. Smaller fragments move faster through the gel matrix. Centrifugation separates by density, chromatography by differential partitioning, spectrophotometry measures light absorption. Electrophoresis is a fundamental tool in molecular biology.

This question belongs to: Science Biology

Question #305

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Which of the following is a correct statement about sponges (phylum Porifera)?

A. They have tissues and organs.

B. They have a well-developed nervous system.

C. They are multicellular with a cellular level of organization.

D. They are exclusively terrestrial.

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Correct Answer: Option C

Explanation:
Sponges are the simplest multicellular animals with a cellular level of organization (no true tissues or organs). They are mostly marine, sessile, filter feeders. Water enters through numerous pores (ostia) into a spongocoel and exits through the osculum. They lack a nervous system. They possess specialized cells like choanocytes and amoebocytes but no coordination.

This question belongs to: Science Biology

Question #306

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The inheritance of skin color in humans is an example of:

A. Polygenic inheritance

B. Multiple alleles

C. Co-dominance

D. Pleiotropy

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Correct Answer: Option A

Explanation:
Polygenic inheritance is when multiple genes (polygenes) contribute to a single trait, resulting in continuous variation. Human skin color is controlled by at least three genes, showing a spectrum of phenotypes. Pleiotropy is one gene affecting multiple traits. Multiple alleles refer to more than two alleles for a gene (e.g., ABO blood groups). Co-dominance is when both alleles express equally.

This question belongs to: Science Biology

Question #307

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The 'Red Data Book' keeps records of:

A. All living organisms

B. Endangered and threatened species

C. Fossil records

D. Human population

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Correct Answer: Option B

Explanation:
The IUCN Red List (Red Data Book) documents the conservation status of plants, animals, and fungi, categorizing species from Extinct to Least Concern. It highlights species at risk of global extinction. It is a critical tool for conservation policy and action. Endangered species like the Bengal tiger and snow leopard are listed. The Red Data Book was first published by IUCN in 1964.

This question belongs to: Science Biology

Question #308

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Which of the following is an abiotic component of an ecosystem?

A. Consumers

B. Soil

C. Producers

D. Decomposers

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Correct Answer: Option B

Explanation:
Abiotic components are non-living physical and chemical factors of an ecosystem, including soil, water, temperature, light, and minerals. Biotic components include producers (plants), consumers (animals), and decomposers (bacteria, fungi). The interaction between abiotic and biotic components drives ecosystem functions. Soil provides nutrients and a medium for plant growth.

This question belongs to: Science Biology

Question #309

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The enzyme used to join DNA fragments in genetic engineering is:

A. Restriction enzyme

B. Helicase

C. DNA polymerase

D. DNA ligase

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Correct Answer: Option D

Explanation:
DNA ligase seals the phosphodiester bonds between adjacent DNA fragments, joining them together. In recombinant DNA technology, it is used to ligate the gene of interest into a vector. Restriction enzymes cut DNA, DNA polymerase synthesizes DNA, and helicase unwinds the double helix. Ligase is essential for finalizing the recombinant DNA molecule.

This question belongs to: Science Biology

Question #310

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Which of the following is a benefit of using biopesticides over chemical pesticides?

A. They are target-specific and environmentally friendly.

B. They increase soil salinity.

C. They are non-biodegradable and persist in the environment.

D. They are broad-spectrum and kill all insects.

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Correct Answer: Option A

Explanation:
Biopesticides, such as Bacillus thuringiensis (Bt), neem extracts, and Trichoderma, are generally target-specific, affecting only certain pests while sparing beneficial organisms, humans, and the environment. They are biodegradable and do not accumulate. Chemical pesticides often kill a wide range of species, persist, and cause pollution. Biopesticides are key in Integrated Pest Management (IPM).

This question belongs to: Science Biology

Question #311

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The transgenic cow 'Rosie' was known for producing milk enriched with:

A. Human insulin

B. Antithrombin

C. Human alpha-lactalbumin

D. Bovine growth hormone

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Correct Answer: Option C

Explanation:
Rosie, the first transgenic cow, produced milk containing human alpha-lactalbumin, a protein important for infant nutrition. This was achieved by introducing the human gene for the protein into the cow. Human insulin is produced in E. coli or yeast, growth hormone in some transgenic animals, and antithrombin in goat milk (ATryn). Transgenic animals are used as bioreactors.

This question belongs to: Science Biology

Question #312

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The scientist who first observed the nucleus in plant cells was:

A. Matthias Schleiden

B. Robert Hooke

C. Antonie van Leeuwenhoek

D. Robert Brown

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Correct Answer: Option D

Explanation:
Robert Brown, a Scottish botanist, discovered the nucleus in 1831 while studying orchid cells under a microscope. He named it 'nucleus'. Hooke discovered cells, Leeuwenhoek observed living cells, Schleiden proposed that all plants are made of cells. Brown's discovery was crucial for understanding cell structure and function.

This question belongs to: Science Biology

Question #313

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The natural place of an organism where it lives and reproduces is called its:

A. Niche

B. Biome

C. Ecosystem

D. Habitat

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Correct Answer: Option D

Explanation:
Habitat refers to the physical environment where an organism lives (address), whereas niche refers to its functional role in the ecosystem (profession), including interactions and resource use. Ecosystem is the community plus abiotic factors, biome is a large ecological area with similar climate and vegetation. A pond habitat can have various niches.

This question belongs to: Science Biology

Question #314

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Which of the following is an example of a chemical mutagen?

A. Nitrous acid

B. UV radiation

C. Gamma rays

D. X-rays

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Correct Answer: Option A

Explanation:
Nitrous acid (HNO₂) is a chemical mutagen that can deaminate bases (e.g., cytosine to uracil), causing base-pair changes and mutations. X-rays, UV radiation, and gamma rays are physical mutagens (ionizing and non-ionizing radiation). Chemical mutagens include base analogs, alkylating agents, and intercalating agents. Mutagens increase the rate of mutations beyond natural levels.

This question belongs to: Science Biology

Question #315

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The term 'malnutrition' refers to:

A. Only deficiency of nutrients

B. Adequate nutrition

C. Only excess of nutrients

D. Both deficiency and excess of nutrients leading to health problems

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Correct Answer: Option D

Explanation:
Malnutrition includes undernutrition (deficiency of calories, protein, or micronutrients) and overnutrition (excess intake leading to obesity and related diseases). Both result in physiological disorders. Examples: marasmus and kwashiorkor (deficiency), obesity (excess). A balanced diet prevents malnutrition. It is a significant global health issue, especially in developing countries.

This question belongs to: Science Biology

Question #316

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The hormone that stimulates the growth of the thyroid gland and secretion of thyroxine is:

A. Adrenocorticotropic hormone (ACTH)

B. Thyroid-stimulating hormone (TSH)

C. Growth hormone (GH)

D. Prolactin

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Correct Answer: Option B

Explanation:
TSH, released from the anterior pituitary, binds to receptors on thyroid follicular cells, stimulating the synthesis and release of thyroxine (T₄) and triiodothyronine (T₃). TSH release is regulated by thyrotropin-releasing hormone (TRH) from the hypothalamus and feedback inhibition by thyroid hormones. ACTH stimulates adrenal cortex, GH growth, prolactin milk production.

This question belongs to: Science Biology

Question #317

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The process by which plants lose water in the form of vapour mainly through stomata is:

A. Evaporation

B. Transpiration

C. Condensation

D. Guttation

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Correct Answer: Option B

Explanation:
Transpiration is the evaporative loss of water from the aerial parts of plants, primarily through stomata. It creates transpiration pull, aiding water and mineral transport. Guttation is loss of liquid water droplets from hydathodes. Evaporation is a physical process from any surface. Condensation is change from vapour to liquid. Transpiration also cools the plant.

This question belongs to: Science Biology

Question #318

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Which of the following diseases is caused by the bacterium Clostridium tetani?

A. Diphtheria

B. Tetanus

C. Botulism

D. Pertussis (whooping cough)

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Correct Answer: Option B

Explanation:
Tetanus (lockjaw) is caused by the neurotoxin of Clostridium tetani, a soil bacterium that enters through wounds. The toxin causes muscle spasms and rigidity. Diphtheria is by Corynebacterium diphtheriae, pertussis by Bordetella pertussis, botulism by Clostridium botulinum (also a neurotoxin, but from food poisoning). Vaccination with DPT/tetanus toxoid prevents tetanus.

This question belongs to: Science Biology

Question #319

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The number of autosomes in a normal human sperm cell is:

A. 46

B. 22

C. 44

D. 23

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Correct Answer: Option B

Explanation:
Human somatic cells have 46 chromosomes: 44 autosomes and 2 sex chromosomes (XX or XY). Sperm cells are haploid (n=23), containing 22 autosomes and one sex chromosome (either X or Y). The ovum also has 22 autosomes and one X. Fertilization restores 44 autosomes plus XX or XY. So sperm has 22 autosomes.

This question belongs to: Science Biology

Question #320

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Which of the following is a correct statement about the human brain?

A. The cerebellum controls memory and intelligence.

B. The cerebrum is the centre for balance and coordination.

C. The medulla oblongata regulates heart rate and breathing.

D. The hypothalamus controls voluntary muscle movements.

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Correct Answer: Option C

Explanation:
The medulla oblongata contains vital centers that control involuntary functions like heart rate, breathing, and blood pressure. The cerebrum is responsible for memory, intelligence, and voluntary movements; the cerebellum coordinates balance and movement; the hypothalamus regulates body temperature, hunger, and hormone secretion.

This question belongs to: Science Biology

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