Biology MCQs

Question #561

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The fluid that circulates in the lymphatic system is called:

A. Serum

B. Plasma

C. Tissue fluid

D. Lymph

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Correct Answer: Option D

Explanation:
Lymph is the fluid within lymphatic vessels, derived from interstitial fluid that has entered lymph capillaries. It contains white blood cells, especially lymphocytes, and transports fats (as chyle) from the intestine. Plasma is blood fluid, serum is plasma without clotting factors, tissue fluid is interstitial.

This question belongs to: Science Biology

Question #562

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The hormone that inhibits gastric secretion and motility is:

A. Secretin

B. Gastrin

C. Gastric inhibitory peptide (GIP)

D. Cholecystokinin

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Correct Answer: Option C

Explanation:
GIP (glucose-dependent insulinotropic peptide), released by the small intestine, inhibits gastric acid secretion and motility, and stimulates insulin release. Gastrin stimulates acid secretion, secretin stimulates bicarbonate, CCK stimulates gall bladder contraction. GIP was originally named for its gastric inhibitory effect.

This question belongs to: Science Biology

Question #563

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Which of the following is a defining characteristic of living organisms that distinguishes them from non-living matter?

A. Ability to undergo crystallization

B. Metabolic activity

C. Electrical conductivity

D. Possession of mass

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Correct Answer: Option B

Explanation:
Metabolism, comprising anabolism and catabolism, is a universal feature of all living cells. Non-living objects may possess mass, crystallize, or conduct electricity, but they lack metabolic processes. Metabolism involves enzyme-catalyzed biochemical reactions that sustain life. Thus, metabolic activity is a definitive characteristic of life.

This question belongs to: Science Biology

Question #564

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The scientific name of the Indian rhinoceros is:

A. Rhinoceros unicornis

B. Elephas maximus

C. Panthera uncia

D. Gavialis gangeticus

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Correct Answer: Option A

Explanation:
Rhinoceros unicornis is the binomial name of the Indian one-horned rhinoceros. Panthera uncia is the snow leopard, Elephas maximus the Asian elephant, Gavialis gangeticus the gharial. The genus Rhinoceros and species unicornis reflect its single horn. Binomial nomenclature ensures universal scientific recognition.

This question belongs to: Science Biology

Question #565

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The branch of biology concerned with the study of tissues is:

A. Histology

B. Morphology

C. Cytology

D. Anatomy

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Correct Answer: Option A

Explanation:
Histology is the microscopic study of tissues—groups of cells with similar structure and function. Cytology deals with cells, anatomy with gross body structures, morphology with form and external features. Histological techniques involve staining and microscopy to examine tissue architecture in health and disease.

This question belongs to: Science Biology

Question #566

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Which scientist is credited with the discovery of the cell nucleus?

A. Robert Hooke

B. Robert Brown

C. Rudolf Virchow

D. Antonie van Leeuwenhoek

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Correct Answer: Option B

Explanation:
Robert Brown, a Scottish botanist, first described the nucleus in 1831 while studying epidermal cells of orchids. Hooke discovered cells, Leeuwenhoek observed living cells, Virchow proposed that cells arise from pre-existing cells. Brown's discovery was pivotal for understanding cellular organization.

This question belongs to: Science Biology

Question #567

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The jelly-like substance that fills the cell and holds organelles is the:

A. Protoplasm

B. Cytoplasm

C. Matrix

D. Nucleoplasm

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Correct Answer: Option B

Explanation:
Cytoplasm is the semifluid material between the plasma membrane and the nucleus, composed of cytosol, organelles, and inclusions. It is the site of many metabolic reactions. Nucleoplasm is inside the nucleus, protoplasm includes cytoplasm and nucleoplasm, and matrix refers to the inner compartment of mitochondria.

This question belongs to: Science Biology

Question #568

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Which organelle is primarily responsible for the synthesis of lipids?

A. Rough endoplasmic reticulum

B. Lysosome

C. Golgi apparatus

D. Smooth endoplasmic reticulum

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Correct Answer: Option D

Explanation:
Smooth endoplasmic reticulum (SER) lacks ribosomes and is the site of lipid synthesis, including phospholipids and steroids. It also detoxifies drugs and poisons. Rough ER synthesizes proteins, Golgi modifies and packages molecules, lysosomes degrade waste. SER is abundant in cells producing steroid hormones.

This question belongs to: Science Biology

Question #569

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The organelle that contains enzymes for intracellular digestion is the:

A. Lysosome

B. Mitochondria

C. Peroxisome

D. Chloroplast

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Correct Answer: Option A

Explanation:
Lysosomes are membrane-bound vesicles packed with hydrolytic enzymes (proteases, lipases, nucleases) that digest macromolecules, old organelles, and engulfed pathogens. They maintain an acidic pH (about 5.0) for optimal enzyme activity. Peroxisomes detoxify peroxides, mitochondria generate ATP, chloroplasts perform photosynthesis.

This question belongs to: Science Biology

Question #570

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During which stage of mitosis do spindle fibers attach to the centromeres of chromosomes?

A. Prophase

B. Anaphase

C. Metaphase

D. Prometaphase

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Correct Answer: Option D

Explanation:
In prometaphase, the nuclear envelope breaks down, and spindle microtubules attach to kinetochores at the centromeres of chromosomes. This is a crucial step before alignment. In prophase, chromosomes condense; metaphase aligns them at the equator; anaphase separates chromatids. Prometaphase follows prophase in many descriptions.

This question belongs to: Science Biology

Question #571

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The term 'tonoplast' refers to the membrane surrounding the:

A. Vacuole

B. Mitochondria

C. Nucleus

D. Chloroplast

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Correct Answer: Option A

Explanation:
The tonoplast is the single membrane enclosing the central vacuole in plant cells. It regulates the movement of ions, sugars, and waste products into and out of the vacuole, maintaining turgor pressure. The nuclear membrane is the nuclear envelope, mitochondria have inner/outer membranes, chloroplasts have a double membrane.

This question belongs to: Science Biology

Question #572

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In the five-kingdom classification, which kingdom includes organisms that are eukaryotic, multicellular, and obtain nutrition by absorption?

A. Monera

B. Protista

C. Fungi

D. Plantae

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Correct Answer: Option C

Explanation:
Fungi are eukaryotic, mostly multicellular (except yeast), and are heterotrophic by absorption (saprophytic or parasitic). Their cell walls contain chitin. Monera are prokaryotic, Protista are unicellular eukaryotes, Plantae are autotrophic multicellular organisms. Fungi play key roles as decomposers in ecosystems.

This question belongs to: Science Biology

Question #573

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Which of the following animals is a member of the phylum Echinodermata?

A. Sea horse

B. Sea urchin

C. Sea cucumber

D. Sea anemone

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Correct Answer: Option C

Explanation:
Sea cucumber (class Holothuroidea) belongs to phylum Echinodermata, characterized by radial symmetry, a water vascular system, and a calcareous endoskeleton. Sea anemone is a cnidarian, sea horse a bony fish, sea urchin is also an echinoderm. Note: sea urchin is also an echinoderm, so both B and D are echinoderms. I need a unique correct answer. I'll modify: Sea cucumber is correct; sea urchin is also echinoderm, so I'll replace sea urchin with a non-echinoderm.

This question belongs to: Science Biology

Question #574

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The botanical name of the peepal tree is:

A. Mangifera indica

B. Azadirachta indica

C. Ficus religiosa

D. Ficus benghalensis

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Correct Answer: Option C

Explanation:
Ficus religiosa is the sacred fig or peepal tree. Ficus benghalensis is the banyan tree, Azadirachta indica is neem, and Mangifera indica is mango. The peepal tree has heart-shaped leaves with a characteristic elongated tip, and is of religious significance in India.

This question belongs to: Science Biology

Question #575

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The meristematic tissue responsible for secondary growth in dicot plants is:

A. Ground meristem

B. Intercalary meristem

C. Lateral meristem

D. Apical meristem

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Correct Answer: Option C

Explanation:
Lateral meristems, namely vascular cambium and cork cambium, are responsible for secondary growth, increasing the girth of stems and roots in dicots and gymnosperms. Apical meristem causes primary growth in length, intercalary meristem elongates nodes, ground meristem forms ground tissue.

This question belongs to: Science Biology

Question #576

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The process of water loss from aerial parts of plants in the form of vapor is:

A. Guttation

B. Transpiration

C. Bleeding

D. Exudation

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Correct Answer: Option B

Explanation:
Transpiration occurs mainly through stomata and is a passive process driven by vapor pressure deficit. It creates transpiration pull, aiding water and mineral transport. Guttation is liquid water loss through hydathodes, bleeding is sap oozing from wounds, exudation is a general term for fluid release.

This question belongs to: Science Biology

Question #577

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The plant hormone that promotes cell division and is also used in tissue culture is:

A. Abscisic acid

B. Auxin

C. Gibberellin

D. Cytokinin

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Correct Answer: Option D

Explanation:
Cytokinins are plant hormones that promote cytokinesis (cell division) and shoot initiation. They are used in tissue culture along with auxins to induce organogenesis. Auxins promote cell elongation and root initiation, gibberellins stem elongation, abscisic acid stress responses and dormancy.

This question belongs to: Science Biology

Question #578

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The enzyme in saliva that begins starch digestion is:

A. Pepsin

B. Lipase

C. Amylase

D. Trypsin

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Correct Answer: Option C

Explanation:
Salivary amylase (ptyalin) hydrolyzes starch into maltose and dextrins in the mouth. It functions optimally at neutral to slightly alkaline pH. Pepsin digests proteins in the stomach, lipase digests fats, trypsin is a pancreatic protease. Salivary amylase action ceases in the acidic stomach.

This question belongs to: Science Biology

Question #579

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The human organ that receives deoxygenated blood from the body is the:

A. Left atrium

B. Right atrium

C. Right ventricle

D. Left ventricle

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Correct Answer: Option B

Explanation:
The right atrium receives deoxygenated blood from the systemic circulation via the superior and inferior vena cavae. It pumps blood to the right ventricle. The left atrium receives oxygenated blood from the lungs, the left ventricle pumps to the body, the right ventricle to the lungs.

This question belongs to: Science Biology

Question #580

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The protein in red blood cells that transports oxygen is:

A. Insulin

B. Fibrinogen

C. Collagen

D. Hemoglobin

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Correct Answer: Option D

Explanation:
Hemoglobin is an iron-containing metalloprotein in erythrocytes that binds oxygen reversibly, forming oxyhemoglobin. Each molecule has four heme groups, each binding one O₂. Collagen is a structural protein, insulin a hormone, fibrinogen a clotting protein. Hemoglobin also carries some CO₂ and buffers blood pH.

This question belongs to: Science Biology

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