Biology MCQs

Question #1

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Which of the following is NOT a characteristic of living organisms?

A. Metabolism

B. Crystallization

C. Reproduction

D. Growth

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Correct Answer: Option B

Explanation:
Crystallization is a property of non-living substances where molecules arrange in a definite pattern, e.g., salt crystals. Living organisms exhibit growth, reproduction, metabolism, cellular organization, and consciousness. Metabolism is a defining feature of all living organisms, occurring even in unicellular forms. Reproduction, though absent in sterile organisms like mules, is generally a characteristic. Growth in living beings is internal and intrinsic, unlike extrinsic accumulation in non-living things. Hence, crystallization is not a characteristic of life.

This question belongs to: Science Biology

Question #2

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Who introduced the binomial nomenclature system?

A. Gregor Mendel

B. Charles Darwin

C. Carolus Linnaeus

D. Robert Hooke

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Correct Answer: Option C

Explanation:
Carolus Linnaeus, a Swedish botanist, introduced the binomial nomenclature system in his book 'Species Plantarum' (1753). This system assigns a two-part scientific name—genus and species—to every organism. For example, Homo sapiens. Darwin proposed natural selection, Hooke discovered cells, and Mendel laid the foundation of genetics. Linnaeus is also known as the father of taxonomy. Binomial names are universally accepted and italicized in print.

This question belongs to: Science Biology

Question #3

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Which branch of biology deals with the study of fungi?

A. Mycology

B. Phycology

C. Bryology

D. Pteridology

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Correct Answer: Option A

Explanation:
Mycology is the study of fungi, including yeasts and molds. Phycology deals with algae, bryology with mosses and liverworts, and pteridology with ferns. Fungi are eukaryotic, heterotrophic organisms with chitinous cell walls. The term mycology derives from Greek 'mykes' meaning mushroom. Alexander Fleming's discovery of penicillin from the fungus Penicillium notatum revolutionized medicine. Mycology is crucial for understanding fungal diseases and antibiotic production.

This question belongs to: Science Biology

Question #4

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Which of the following is an example of a living thing showing autotrophic nutrition?

A. Rhizopus

B. Mushroom

C. Spirogyra

D. Mucor

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Correct Answer: Option C

Explanation:
Spirogyra is a filamentous green alga containing chloroplasts, performing photosynthesis, hence autotrophic. Mushroom, Mucor, and Rhizopus are fungi, which are heterotrophic saprophytes or parasites. Autotrophs synthesize their own food using light or chemical energy. Spirogyra belongs to algae, classified under Plantae in five-kingdom classification. Its ribbon-shaped chloroplast aids in photosynthesis. This question tests the concept of nutrition modes.

This question belongs to: Science Biology

Question #5

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The term 'cell' was coined by:

A. Robert Brown

B. Rudolf Virchow

C. Antonie van Leeuwenhoek

D. Robert Hooke

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Correct Answer: Option D

Explanation:
Robert Hooke observed thin slices of cork under a microscope he designed and saw honeycomb-like compartments which he termed 'cells' in his 1665 book 'Micrographia'. Leeuwenhoek discovered living cells (bacteria, protozoa). Brown discovered the nucleus (1831), and Virchow proposed that all cells arise from pre-existing cells (1855). Hooke's cells were dead, empty cell walls of cork.

This question belongs to: Science Biology

Question #6

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Which of the following is a defining feature of prokaryotic cells?

A. Linear chromosomes

B. Absence of cell wall

C. Presence of membrane-bound nucleus

D. Presence of 70S ribosomes only

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Correct Answer: Option D

Explanation:
Prokaryotic cells lack a true nucleus; their genetic material is located in a nucleoid region. They possess 70S ribosomes (50S+30S subunits), whereas eukaryotic cells have 80S ribosomes. Prokaryotes generally have a cell wall (except Mycoplasma) and circular DNA, not linear. Membrane-bound organelles like mitochondria, ER are absent. Examples: bacteria and blue-green algae. This distinction is fundamental in cell biology.

This question belongs to: Science Biology

Question #7

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Which organelle is known as the 'powerhouse of the cell'?

A. Mitochondria

B. Golgi apparatus

C. Ribosome

D. Nucleus

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Correct Answer: Option A

Explanation:
Mitochondria produce ATP through oxidative phosphorylation in the inner membrane. They are double-membrane organelles with their own DNA (mtDNA) and 70S ribosomes, supporting the endosymbiotic theory. The Krebs cycle occurs in the mitochondrial matrix. Nucleus controls cell activities, ribosomes synthesize proteins, Golgi apparatus packages and modifies proteins. Mitochondria are abundant in energy-demanding cells like muscle cells.

This question belongs to: Science Biology

Question #8

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Assertion (A): Mitochondria and chloroplasts are considered semi-autonomous organelles. Reason (R): They possess their own DNA and ribosomes, and can synthesize some of their own proteins.

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

B. A is false, but R is true.

C. A is true, but R is false.

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

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Correct Answer: Option D

Explanation:
Mitochondria and chloroplasts contain circular DNA and 70S ribosomes, enabling them to transcribe and translate some proteins independently, though they rely on nuclear genes for most proteins. This partial autonomy supports the endosymbiotic origin hypothesis. The presence of their own genetic material and protein synthesis machinery qualifies them as semi-autonomous. Thus, both assertion and reason are correct, and the reason correctly explains the assertion.

This question belongs to: Science Biology

Question #9

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Which cell organelle is responsible for the formation of lysosomes?

A. Endoplasmic Reticulum

B. Mitochondria

C. Golgi apparatus

D. Nucleus

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Correct Answer: Option C

Explanation:
Lysosomes are membrane-bound vesicles containing hydrolytic enzymes formed by the Golgi apparatus. The Golgi modifies, sorts, and packages proteins from the rough ER into vesicles; some become lysosomes. These organelles function in intracellular digestion and autophagy. Rough ER synthesizes enzymes, but the final packaging into lysosomes occurs at the Golgi. Hence, Golgi is sometimes called the 'traffic police' of the cell.

This question belongs to: Science Biology

Question #10

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During which phase of the cell cycle does DNA replication occur?

A. S phase

B. G1 phase

C. M phase

D. G2 phase

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Correct Answer: Option A

Explanation:
The cell cycle consists of interphase (G1, S, G2) and M phase. DNA synthesis or replication occurs during the S (synthesis) phase, resulting in each chromosome having two sister chromatids. G1 is for cell growth and RNA/protein synthesis; G2 is for preparation for mitosis. M phase includes mitosis and cytokinesis. Accurate DNA replication in S phase is crucial for genetic continuity.

This question belongs to: Science Biology

Question #11

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Which of the following features differentiates mitosis from meiosis?

A. Synapsis and crossing over

B. Spindle fibre formation

C. Separation of sister chromatids

D. Chromosome duplication

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Correct Answer: Option A

Explanation:
Synapsis (pairing of homologous chromosomes) and crossing over (exchange of genetic material) occur during prophase I of meiosis, not in mitosis. Mitosis involves one division producing two genetically identical diploid daughter cells. Meiosis involves two divisions producing four haploid gametes with genetic variation. Chromosome duplication and sister chromatid separation occur in both. Spindle fibres form in both divisions. Thus, synapsis and crossing over are unique to meiosis.

This question belongs to: Science Biology

Question #12

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In the five-kingdom classification, bacteria are placed in the kingdom:

A. Monera

B. Plantae

C. Fungi

D. Protista

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Correct Answer: Option A

Explanation:
R.H. Whittaker's five-kingdom classification (1969) categorizes organisms into Monera, Protista, Fungi, Plantae, and Animalia. Monera includes all prokaryotes—bacteria, cyanobacteria, and archaebacteria—characterized by lack of true nucleus and membrane-bound organelles. Protista includes unicellular eukaryotes. Fungi are multicellular saprophytes. Plantae are autotrophic eukaryotes. Monera is the only kingdom of prokaryotes in this system.

This question belongs to: Science Biology

Question #13

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Which among the following is an example of an invertebrate chordate?

A. Earthworm

B. Amphioxus

C. Starfish

D. Cockroach

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Correct Answer: Option B

Explanation:
Amphioxus (Branchiostoma) is a primitive chordate possessing a notochord, dorsal nerve cord, and pharyngeal slits throughout life, but lacking a vertebral column; hence it is an invertebrate chordate. Earthworm is an annelid, cockroach an arthropod, starfish an echinoderm—all non-chordates. Vertebrate chordates include fishes, amphibians, reptiles, birds, and mammals. Amphioxus is studied for evolutionary insights into vertebrate origins.

This question belongs to: Science Biology

Question #14

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Which plant hormone is primarily responsible for apical dominance?

A. Cytokinin

B. Auxin

C. Ethylene

D. Gibberellin

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Correct Answer: Option B

Explanation:
Auxin (indole-3-acetic acid) produced at the shoot apex suppresses the growth of lateral buds, a phenomenon called apical dominance. Removing the apex allows lateral buds to grow. Cytokinin promotes cell division and counteracts apical dominance. Gibberellin stimulates stem elongation, and ethylene is involved in fruit ripening and senescence. The auxin-cytokinin ratio determines root and shoot differentiation in tissue culture.

This question belongs to: Science Biology

Question #15

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Which tissue is responsible for the increase in the girth of a dicot stem?

A. Lateral meristem

B. Intercalary meristem

C. Apical meristem

D. Epidermis

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Correct Answer: Option A

Explanation:
Lateral meristems—vascular cambium and cork cambium—are responsible for secondary growth, increasing the girth (diameter) of dicot stems and roots. Apical meristem at root and shoot tips causes primary growth in length. Intercalary meristem at nodes helps in elongation in grasses. Epidermis is a protective outer layer. Secondary growth is absent in most monocots due to lack of vascular cambium.

This question belongs to: Science Biology

Question #16

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In photosynthesis, oxygen is released from:

A. Glucose

B. Carbon dioxide

C. Chlorophyll

D. Water

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Correct Answer: Option D

Explanation:
During the light reactions of photosynthesis, photolysis of water occurs at photosystem II, splitting water into protons, electrons, and molecular oxygen. The oxygen comes from water, not CO₂. This was demonstrated by using isotopically labeled oxygen (H₂O¹⁸). Glucose is formed in the Calvin cycle. Chlorophyll absorbs light but does not provide oxygen. The overall equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O.

This question belongs to: Science Biology

Question #17

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Transpiration in plants mainly occurs through:

A. Hydathodes

B. Stomata

C. Lenticels

D. Cuticle

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Correct Answer: Option B

Explanation:
Stomatal transpiration accounts for about 80-90% of total water loss from plants. Stomata are microscopic pores on leaves, surrounded by guard cells. Cuticular transpiration occurs through the cuticle but is minimal. Lenticular transpiration is through lenticels on woody stems. Hydathodes are involved in guttation, not transpiration. Transpiration creates transpiration pull essential for water ascent in xylem.

This question belongs to: Science Biology

Question #18

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Which of the following is the primary product of the light-dependent reactions of photosynthesis?

A. Oxygen only

B. Glucose

C. Water

D. ATP and NADPH

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Correct Answer: Option D

Explanation:
Light reactions occur in the thylakoid membranes, converting light energy into chemical energy in the form of ATP and NADPH, with oxygen as a by-product. These energy-rich molecules are used in the Calvin cycle (light-independent reactions) to fix CO₂ into carbohydrates. Glucose is a final product of the Calvin cycle. Oxygen is released but not the primary product. Thus ATP and NADPH are the main outputs.

This question belongs to: Science Biology

Question #19

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Root hairs are modifications of which type of cells?

A. Cortical cells

B. Epidermal cells

C. Endodermal cells

D. Pericycle cells

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Correct Answer: Option B

Explanation:
Root hairs are tubular extensions of epidermal cells in the zone of maturation of roots. They increase surface area for absorption of water and minerals. Cortical cells form the ground tissue, endodermis is the innermost layer of cortex with Casparian strip, and pericycle gives rise to lateral roots. Root hairs are unicellular in angiosperms, living for a short period and constantly replaced.

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Question #20

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Which of the following is an example of a rabi crop?

A. Sugarcane

B. Rice

C. Maize

D. Wheat

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Correct Answer: Option D

Explanation:
Rabi crops are sown in winter (October-December) and harvested in spring (March-April). Wheat, gram, mustard, pea are common rabi crops. Rice, maize, and sugarcane are kharif crops, sown with the onset of monsoon and harvested in autumn. This distinction is based on seasonal cultivation patterns in Indian agriculture. Rabi crops require cool growing season and warm harvest season.

This question belongs to: Science Biology

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