Biology MCQs

Question #101

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In poultry farming, the term 'broilers' refers to birds raised for:

A. Ornamental purposes

B. Feathers

C. Meat production

D. Egg production

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Correct Answer: Option C

Explanation:
Broilers are chickens bred and raised specifically for meat, reaching market weight in 6-8 weeks. Layers are hens raised for egg production. Broilers require high-protein diet and management to maximize growth. Poultry farming is an important sector for protein supply. Some breeds like Rhode Island Red are dual-purpose. Cobb and Ross are popular broiler strains.

This question belongs to: Science Biology

Question #102

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The silkworm used in sericulture is the larva of:

A. Bombyx mori

B. Labeo rohita

C. Apis mellifera

D. Drosophila melanogaster

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Correct Answer: Option A

Explanation:
Bombyx mori is the domesticated silkworm, whose caterpillar spins a silk cocoon. The silk thread is obtained by boiling cocoons. Apis mellifera is the honeybee, Labeo rohita is a fish (rohu), Drosophila is fruit fly used in genetics. Sericulture involves mulberry cultivation, silkworm rearing, and reeling of silk. India is the second largest silk producer.

This question belongs to: Science Biology

Question #103

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Who was the first scientist to observe bacteria using a single-lens microscope?

A. Louis Pasteur

B. Robert Hooke

C. Joseph Lister

D. Antonie van Leeuwenhoek

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Correct Answer: Option D

Explanation:
Antonie van Leeuwenhoek (1670s) constructed high-quality single-lens microscopes and was the first to observe bacteria, protozoa, sperm cells, and red blood cells, describing them as 'animalcules'. Hooke observed cells in cork. Pasteur disproved spontaneous generation, Lister introduced antiseptic surgery. Leeuwenhoek's pioneering work laid the foundation for microbiology.

This question belongs to: Science Biology

Question #104

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Which of the following statements is correct regarding cell theory?

A. Only plant cells contain cell walls.

B. All living organisms are composed of cells and products of cells.

C. Cells arise spontaneously.

D. All cells have a nucleus.

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Correct Answer: Option B

Explanation:
Modern cell theory states that all living organisms are composed of cells and cell products, the cell is the basic unit of structure and function, and all cells arise from pre-existing cells (Omnis cellula e cellula). Not all cells have a nucleus (e.g., prokaryotes, mature RBCs). Cell theory was formulated by Schleiden, Schwann, and Virchow. Spontaneous generation was disproved.

This question belongs to: Science Biology

Question #105

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Which structure is common to both prokaryotic and eukaryotic cells?

A. Golgi apparatus

B. Ribosomes

C. Nuclear membrane

D. Mitochondria

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Correct Answer: Option B

Explanation:
Ribosomes are the only organelles common to both prokaryotes and eukaryotes, though sizes differ: 70S in prokaryotes, 80S in eukaryotes. Nuclear membrane, mitochondria, and Golgi are absent in prokaryotes. Ribosomes are the site of protein synthesis. This commonality supports the universal role of protein synthesis in all life forms. Mycoplasma, the smallest prokaryote, also has ribosomes.

This question belongs to: Science Biology

Question #106

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In which phase of mitosis do chromosomes align at the equatorial plate?

A. Metaphase

B. Telophase

C. Anaphase

D. Prophase

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Correct Answer: Option A

Explanation:
During metaphase, chromosomes are maximally condensed and align at the cell equator (metaphase plate) attached to spindle fibers via kinetochores. This alignment ensures equal segregation. In prophase, chromosomes condense; anaphase, sister chromatids separate; telophase, nuclear envelope reforms. Metaphase is the best stage for studying chromosome morphology for karyotyping.

This question belongs to: Science Biology

Question #107

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The infoldings of the inner mitochondrial membrane are called:

A. Grana

B. Cristae

C. Cisternae

D. Thylakoids

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Correct Answer: Option B

Explanation:
Cristae are the numerous infoldings of the inner mitochondrial membrane that increase surface area for oxidative phosphorylation and ATP synthesis. They contain ATP synthase complexes. Thylakoids are membrane structures in chloroplasts; grana are stacks of thylakoids. Cisternae are flattened membrane sacs of ER and Golgi. Cristae give the inner membrane its characteristic folded appearance.

This question belongs to: Science Biology

Question #108

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Which of the following organisms lacks a cell wall?

A. Fungi

B. Bacteria

C. Mycoplasma

D. Plant cells

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Correct Answer: Option C

Explanation:
Mycoplasma is a genus of bacteria that naturally lack a cell wall; they are the smallest known free-living organisms. Their membrane contains sterols providing some rigidity. Other bacteria typically have peptidoglycan cell walls. Fungi have chitinous walls, plant cells have cellulose walls. The absence of cell wall makes Mycoplasma pleomorphic and resistant to antibiotics targeting cell wall synthesis like penicillin.

This question belongs to: Science Biology

Question #109

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The gametes in humans are haploid, containing how many chromosomes?

A. 46

B. 44

C. 23

D. 22

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Correct Answer: Option C

Explanation:
Human somatic cells are diploid (2n = 46), with 23 pairs of homologous chromosomes. Gametes (sperm and egg) are haploid (n = 23), containing one set of chromosomes. Fertilization restores diploidy. The haploid number is 23. Option 22 would be autosomes plus one sex chromosome, but the total count is 23. 44 is the number of autosomes in somatic cells.

This question belongs to: Science Biology

Question #110

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Assertion (A): Viruses are considered obligate parasites. Reason (R): Viruses lack their own metabolic machinery and require a host cell to replicate.

A. A is true, but R is false.

B. Both A and R are true, but R is not the correct explanation.

C. A is false, but R is true.

D. Both A and R are true, and R is the correct explanation of A.

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Correct Answer: Option D

Explanation:
Viruses are non-living outside a host cell and cannot carry out metabolism or reproduce independently. They hijack the host cell's machinery to replicate. Hence they are obligate intracellular parasites. The reason correctly explains the assertion. Even though some debate exists on whether viruses are living, the statement that they are obligate parasites and lack metabolic machinery is accurate.

This question belongs to: Science Biology

Question #111

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Which of the following is an example of a saprophytic angiosperm?

A. Drosera

B. Cuscuta

C. Monotropa

D. Pitcher plant

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Correct Answer: Option C

Explanation:
Monotropa (Indian pipe) is a saprophytic angiosperm that obtains nutrition from dead organic matter through mycorrhizal association. Cuscuta is a parasitic plant (dodder), Drosera (sundew) and pitcher plant are insectivorous plants. Saprophytes lack chlorophyll and are heterotrophic. Monotropa belongs to the family Ericaceae. Saprophytism is uncommon in angiosperms.

This question belongs to: Science Biology

Question #112

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The symbiotic nitrogen-fixing bacterium found in root nodules of legumes is:

A. Rhizobium

B. Azotobacter

C. Nitrosomonas

D. Clostridium

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Correct Answer: Option A

Explanation:
Rhizobium species infect legume roots, leading to root nodule formation, where they fix atmospheric N₂ into ammonia using nitrogenase enzyme. They are symbiotic, receiving carbohydrates from the plant. Azotobacter and Clostridium are free-living nitrogen fixers. Nitrosomonas is a nitrifying bacterium. Legume-Rhizobium symbiosis is crucial in sustainable agriculture, reducing the need for nitrogen fertilizers.

This question belongs to: Science Biology

Question #113

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Which part of the flower develops into fruit?

A. Ovary

B. Petal

C. Ovule

D. Anther

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Correct Answer: Option A

Explanation:
After fertilization, the ovary of the flower develops into fruit, while the ovule develops into seed. The ovary wall becomes the pericarp (fruit wall). Petals, sepals, and stamens usually wither. Some fruits are parthenocarpic (without fertilization, e.g., banana). The fruit protects seeds and aids in dispersal. Anther produces pollen grains. Thus, fruit is a mature ovary.

This question belongs to: Science Biology

Question #114

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Which of the following is a characteristic feature of cardiac muscle?

A. Voluntary control

B. Spindle-shaped cells

C. Multinucleated syncytium

D. Branched fibres with intercalated discs

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Correct Answer: Option D

Explanation:
Cardiac muscle cells are striated, branched, and connected by intercalated discs containing gap junctions for synchronized contraction. They are involuntary. Multinucleated syncytium is typical of skeletal muscle. Spindle-shaped non-striated cells characterize smooth muscle. Voluntary control is for skeletal muscle. Intercalated discs allow rapid ion passage, enabling the heart to function as a syncytium.

This question belongs to: Science Biology

Question #115

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The release of an ovum from the ovary is termed:

A. Fertilization

B. Implantation

C. Menstruation

D. Ovulation

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Correct Answer: Option D

Explanation:
Ovulation is the rupture of the mature Graafian follicle and release of a secondary oocyte from the ovary, typically around day 14 of a 28-day menstrual cycle, triggered by LH surge. Menstruation is the shedding of uterine lining. Fertilization is fusion of sperm and ovum, implantation is embedding of blastocyst in the endometrium.

This question belongs to: Science Biology

Question #116

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Which of the following is an example of a sexually transmitted disease (STD)?

A. Malaria

B. Typhoid

C. Gonorrhea

D. Tuberculosis

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Correct Answer: Option C

Explanation:
Gonorrhea is an STD caused by the bacterium Neisseria gonorrhoeae. Tuberculosis is airborne bacterial disease, malaria is vector-borne protozoan, typhoid is waterborne bacterial. Other STDs include syphilis, chlamydia, HIV/AIDS, genital herpes. STDs can be prevented by safe sex practices. Gonorrhea causes urethritis, discharge, and can lead to PID if untreated.

This question belongs to: Science Biology

Question #117

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The deficiency of iodine in the diet leads to:

A. Scurvy

B. Rickets

C. Goiter

D. Anemia

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Correct Answer: Option C

Explanation:
Iodine is essential for synthesis of thyroxine (T₄) and triiodothyronine (T₃). Deficiency leads to enlargement of the thyroid gland, known as goiter, as the gland tries to compensate. Anemia is due to iron deficiency, rickets to vitamin D deficiency, scurvy to vitamin C deficiency. Iodized salt is a public health measure to prevent goiter.

This question belongs to: Science Biology

Question #118

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Which of the following is a correct match regarding vitamin and its deficiency disease?

A. Vitamin C - Scurvy

B. Vitamin D - Pellagra

C. Vitamin B₁ - Scurvy

D. Vitamin A - Beriberi

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Correct Answer: Option A

Explanation:
Vitamin C deficiency causes scurvy, marked by bleeding gums, poor wound healing, and anemia. Vitamin A deficiency causes night blindness. Vitamin B₁ deficiency causes beriberi. Vitamin D deficiency causes rickets/osteomalacia. Pellagra is due to niacin deficiency. Thus, the correct match is Vitamin C - Scurvy.

This question belongs to: Science Biology

Question #119

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During transcription, the enzyme RNA polymerase binds to the:

A. Start codon

B. Enhancer

C. Terminator

D. Promoter

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Correct Answer: Option D

Explanation:
RNA polymerase recognizes and binds to the promoter region of DNA, which is located upstream of the coding sequence. This initiates transcription. The terminator signals the end of transcription. Start codon (AUG) is on mRNA where translation begins. Enhancers are regulatory DNA sequences that increase transcription but are not the primary binding site for polymerase.

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Question #120

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In a double-stranded DNA, adenine pairs with thymine by how many hydrogen bonds?

A. One

B. Four

C. Two

D. Three

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Correct Answer: Option C

Explanation:
Adenine (A) pairs with thymine (T) via two hydrogen bonds. Guanine (G) pairs with cytosine (C) via three hydrogen bonds. This base pairing (complementarity) is key to the double helix structure and ensures accurate replication and transcription. The higher number of bonds between G-C contributes to DNA stability; GC-rich regions are harder to denature.

This question belongs to: Science Biology

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