Biology MCQs

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Biology MCQs

Practice complete Biology MCQs covering Introduction to Biology, Cell Biology, Cell Structure, Cell Division, Biomolecules, Plant Physiology, Human Physiology, Genetics, Evolution, Biotechnology, Ecology, Classification of Living Organisms, Plant Kingdom, Animal Kingdom, Microbiology, Human Diseases, Nutrition, Reproduction, Environmental Biology, and all other important topics. Includes chapter-wise and exam-oriented multiple-choice questions with detailed answers and explanations for JKSSB, SSC, Banking, Railway, UPSC, CUET, NEET, State PSCs, and other competitive exams.

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Page 66 of 103
Question #1301
The enzyme that catalyzes the removal of the RNA primer during DNA replication is:
A. Helicase
B. DNA polymerase I
C. Ligase
D. DNA polymerase III
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Correct Answer: Option B

Explanation:
DNA polymerase I has 5' to 3' exonuclease activity to remove RNA primers and fill gaps with DNA. In eukaryotes, RNase H removes primers.
This question belongs to: Science Biology
Question #1302
The scientist who discovered the concept of 'natural killer' cells was:
A. Peter Doherty
B. Macfarlane Burnet
C. Rolf Kiessling
D. Rolf Zinkernagel
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Correct Answer: Option C

Explanation:
Natural killer (NK) cells were discovered in the 1970s by Rolf Kiessling and others. They are part of innate immunity, killing virus-infected and tumor cells.
This question belongs to: Science Biology
Question #1303
The vitamin that is required for the synthesis of ATP from ADP is:
A. Riboflavin
B. Niacin
C. Thiamine
D. Pantothenic acid
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Correct Answer: Option B

Explanation:
Niacin is part of NAD⁺/NADH, which donates electrons to the electron transport chain to generate the proton gradient for ATP synthesis. All B vitamins contribute indirectly.
This question belongs to: Science Biology
Question #1304
The process of movement of water from a hypotonic solution to a hypertonic solution across a semipermeable membrane is:
A. Diffusion
B. Active transport
C. Osmosis
D. Facilitated diffusion
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Correct Answer: Option C

Explanation:
Osmosis is the net diffusion of water through a selectively permeable membrane from a region of low solute (high water potential) to high solute (low water potential).
This question belongs to: Science Biology
Question #1305
Which branch of biology deals with the study of bees?
A. Apiology
B. Myrmecology
C. Entomology
D. Malacology
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Correct Answer: Option A

Explanation:
Apiology is the specific branch of zoology dedicated to the scientific study of bees, including their biology, ecology, and behavior. Malacology studies mollusks, myrmecology focuses on ants, and entomology is the broader study of all insects. Exam tip: Remember 'Api' relates to Apis, the genus of honeybees.
This question belongs to: Science Biology
Question #1306
The scientific name of the common garden pea, extensively used by Mendel, is:
A. Cicer arietinum
B. Lathyrus sativus
C. Phaseolus vulgaris
D. Pisum sativum
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Correct Answer: Option D

Explanation:
The common garden pea is scientifically named Pisum sativum. It belongs to the family Fabaceae. Mendel chose this plant for his genetic experiments because it has easily distinguishable contrasting traits, a short generation time, and is primarily self-pollinating. Cicer arietinum is chickpea, and Phaseolus vulgaris is the common bean.
This question belongs to: Science Biology
Question #1307
In binomial nomenclature, the 'type specimen' collected during the original discovery of a species is called the:
A. Syntype
B. Isotype
C. Paratype
D. Holotype
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Correct Answer: Option D

Explanation:
The holotype is the single physical specimen designated by the original author when the species is first formally described. It serves as the ultimate reference point for that species name. An isotype is a duplicate of the holotype, syntypes are multiple specimens cited when no holotype was designated, and paratypes are additional specimens cited in the original description.
This question belongs to: Science Biology
Question #1308
Which organelle is primarily responsible for the detoxification of lipid-soluble drugs and toxins in liver cells?
A. Golgi Apparatus
B. Smooth Endoplasmic Reticulum
C. Rough Endoplasmic Reticulum
D. Lysosome
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Correct Answer: Option B

Explanation:
The Smooth Endoplasmic Reticulum (SER) in liver hepatocytes contains enzymes like cytochrome P450 that detoxify lipid-soluble drugs, metabolic waste, and toxins by making them water-soluble for excretion. Rough ER is involved in protein synthesis, the Golgi apparatus in packaging and secretion, and lysosomes in intracellular digestion. Exam tip: SER is abundant in liver and adrenal cortex cells.
This question belongs to: Science Biology
Question #1309
Glyoxysomes are specialized organelles found primarily in:
A. Fungal spores
B. Animal liver cells
C. Germinating oil seeds
D. Mature plant leaves
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Correct Answer: Option C

Explanation:
Glyoxysomes are specialized peroxisomes found in the fat-storing cotyledons of germinating seeds. They contain enzymes for the beta-oxidation of fatty acids and the glyoxylate cycle, which converts stored lipids into carbohydrates (gluconeogenesis) to nourish the growing seedling. This metabolic pathway is absent in animal cells. Exam tip: Glyoxysomes eventually transform into chloroplasts as the plant matures.
This question belongs to: Science Biology
Question #1310
The '9+2' arrangement of microtubules is characteristic of:
A. Cilia and flagella
B. Centrioles and basal bodies
C. Intermediate filaments
D. Mitotic spindle fibers
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Correct Answer: Option A

Explanation:
The '9+2' arrangement refers to nine doublets of microtubules surrounding a central pair, which is the classic axoneme structure of motile cilia and flagella. Centrioles and basal bodies possess a '9+0' arrangement (nine triplets, no central pair). Mitotic spindle fibers are single microtubules, and intermediate filaments lack a tubular microtubule structure entirely.
This question belongs to: Science Biology
Question #1311
During which phase of the cell cycle does the centrosome duplicate?
A. S phase
B. G1 phase
C. M phase
D. G2 phase
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Correct Answer: Option A

Explanation:
The centrosome, which contains two centrioles, duplicates during the S phase of the cell cycle, concurrent with DNA replication. This ensures that by the time the cell enters mitosis, it has two fully formed centrosomes to organize the mitotic spindle. G1 is for growth, G2 is for preparation for M phase, and M phase is for actual division.
This question belongs to: Science Biology
Question #1312
The enzyme telomerase is highly active in which type of cells?
A. Somatic cells
B. Neurons
C. Stem cells and cancer cells
D. Mature red blood cells
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Correct Answer: Option C

Explanation:
Telomerase is a ribonucleoprotein enzyme that adds repetitive nucleotide sequences to the ends of chromosomes (telomeres), preventing them from shortening during DNA replication. It is highly active in germ cells, stem cells, and most cancer cells, granting them replicative immortality. In most normal somatic cells, telomerase is inactive, leading to gradual telomere shortening and cellular aging.
This question belongs to: Science Biology
Question #1313
Chiasmata, the visible points of crossing over, become clearly visible during which sub-stage of Prophase I?
A. Diplotene
B. Zygotene
C. Leptotene
D. Pachytene
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Correct Answer: Option A

Explanation:
Chiasmata become clearly visible during the diplotene stage of Prophase I. While the actual exchange of genetic material (crossing over) occurs during the pachytene stage, the homologous chromosomes begin to repel each other and move apart in diplotene, remaining connected only at the sites of crossing over, which appear as X-shaped chiasmata. Exam tip: Pachytene = crossing over; Diplotene = chiasmata visible.
This question belongs to: Science Biology
Question #1314
Which of the following Archaebacteria is responsible for the production of biogas from animal waste?
A. Methanogens
B. Cyanobacteria
C. Halophiles
D. Thermoacidophiles
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Correct Answer: Option A

Explanation:
Methanogens are strict anaerobic Archaebacteria that produce methane (biogas) as a metabolic byproduct in hypoxic environments. They are commonly found in the guts of ruminant animals (like cows and buffaloes) and in anaerobic sludge digesters. Halophiles thrive in high salt, thermoacidophiles in hot acidic environments, and cyanobacteria are photosynthetic Eubacteria.
This question belongs to: Science Biology
Question #1315
Diatomaceous earth, used in filtration and polishing, is formed from the cell walls of:
A. Dinoflagellates
B. Euglenoids
C. Diatoms
D. Green algae
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Correct Answer: Option C

Explanation:
Diatomaceous earth is a siliceous, sedimentary rock formed from the fossilized remains of diatoms. Diatoms have unique, highly resistant cell walls called frustules, made of hydrated silicon dioxide (silica). Over millions of years, these frustules accumulate on ocean and lake floors, forming diatomaceous earth, which has numerous industrial applications due to its abrasive and porous nature.
This question belongs to: Science Biology
Question #1316
The red tides in the ocean are primarily caused by the rapid multiplication of:
A. Green algae
B. Diatoms
C. Dinoflagellates
D. Cyanobacteria
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Correct Answer: Option C

Explanation:
Red tides are harmful algal blooms caused primarily by the rapid multiplication of certain marine dinoflagellates, such as Gonyaulax. These blooms discolor the water red or brown and release potent toxins (like saxitoxin) that can kill marine life and cause paralytic shellfish poisoning in humans who consume contaminated seafood. Cyanobacteria can cause freshwater blooms, but not marine red tides.
This question belongs to: Science Biology
Question #1317
Which class of fungi includes the common bread mold, Rhizopus stolonifer?
A. Basidiomycetes
B. Phycomycetes
C. Ascomycetes
D. Deuteromycetes
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Correct Answer: Option B

Explanation:
Rhizopus stolonifer belongs to the class Phycomycetes (or Zygomycetes). These fungi are characterized by a coenocytic (multinucleate, aseptate) mycelium and reproduce asexually by forming motile or non-motile spores in sporangia. Ascomycetes (sac fungi) have septate hyphae and produce ascospores in asci. Basidiomycetes (club fungi) produce basidiospores on basidia. Deuteromycetes are imperfect fungi lacking a known sexual stage.
This question belongs to: Science Biology
Question #1318
The causative agent of ergotism, a disease affecting rye and other cereals, is:
A. Alternaria solani
B. Ustilago maydis
C. Claviceps purpurea
D. Puccinia graminis
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Correct Answer: Option C

Explanation:
Ergotism is caused by the fungus Claviceps purpurea, which infects the ovaries of rye and other grasses, replacing the seeds with hard, dark sclerotia (ergots). These sclerotia contain potent alkaloids (like ergotamine) that cause severe vasoconstriction and neurological symptoms in humans and animals consuming contaminated grain. Ustilago causes smut, and Puccinia causes rust.
This question belongs to: Science Biology
Question #1319
In the plant kingdom, the 'amphibians' refer to:
A. Pteridophytes
B. Gymnosperms
C. Algae
D. Bryophytes
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Correct Answer: Option D

Explanation:
Bryophytes (mosses, liverworts, hornworts) are often called the 'amphibians of the plant kingdom' because, although they can live on land, they absolutely require water for the completion of their life cycle, specifically for the swimming of male gametes (antherozoids) to reach the female gamete (egg) during fertilization. Algae are mostly aquatic, while pteridophytes and gymnosperms are better adapted to terrestrial life.
This question belongs to: Science Biology
Question #1320
Which of the following is a vascular cryptogam?
A. Pinus
B. Marchantia
C. Selaginella
D. Funaria
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Correct Answer: Option C

Explanation:
Vascular cryptogams are plants that possess vascular tissues (xylem and phloem) but reproduce via spores rather than seeds. Pteridophytes, such as Selaginella (spike moss), ferns, and Equisetum, fit this description. Funaria and Marchantia are bryophytes (non-vascular cryptogams), and Pinus is a gymnosperm (a vascular phanerogam or seed-producing plant).
This question belongs to: Science Biology

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