Most Important MCQs for CBSE Class 11 Biology Students

(NCERT-Based | Exam-Focused | High-Weightage Questions with Detailed Explanations)

Section A: Diversity in Living World (10 MCQs)

Q1. The basic unit of classification is:
A. Genus
B. Family
C. Species
D. Order

Answer: C. Species
Explanation: Species is the smallest and most specific unit of classification, comprising similar organisms capable of interbreeding.

Q2. Which of the following is NOT a taxonomic category?
A. Class
B. Phylum
C. Order
D. Variety

Answer: D. Variety
Explanation: Variety is not a major taxonomic rank in the Linnaean system.

Q3. Cell wall of bacteria is made up of:
A. Cellulose
B. Chitin
C. Peptidoglycan
D. Lignin

Answer: C. Peptidoglycan
Explanation: Bacterial cell walls contain peptidoglycan, also called murein.

Q4. Which kingdom includes unicellular eukaryotes?
A. Monera
B. Protista
C. Fungi
D. Plantae

Answer: B. Protista
Explanation: Protista includes unicellular eukaryotic organisms.

Q5. Lichens indicate:
A. Water pollution
B. Soil fertility
C. Air pollution
D. Climate change

Answer: C. Air pollution
Explanation: Lichens are sensitive to SO₂ and indicate air quality.

Q6. Viruses are considered living only when they are:
A. Outside host
B. In crystalline form
C. Inside host cells
D. In water

Answer: C. Inside host cells
Explanation: Viruses show life-like properties only inside host cells.

Q7. Which group lacks a true nucleus?
A. Protista
B. Fungi
C. Monera
D. Plantae

Answer: C. Monera
Explanation: Monerans are prokaryotic organisms.

Q8. Bryophytes are known as amphibians of plant kingdom because they:
A. Live in water
B. Need water for reproduction
C. Have vascular tissues
D. Produce seeds

Answer: B. Need water for reproduction
Explanation: Water is essential for fertilization in bryophytes.

Q9. Which plant group bears naked seeds?
A. Angiosperms
B. Bryophytes
C. Pteridophytes
D. Gymnosperms

Answer: D. Gymnosperms
Explanation: Seeds are not enclosed within fruits in gymnosperms.

Q10. The correct sequence of taxonomic hierarchy is:
A. Kingdom → Phylum → Class → Order
B. Phylum → Kingdom → Class → Order
C. Class → Phylum → Order → Family
D. Species → Genus → Order → Family

Answer: A. Kingdom → Phylum → Class → Order
Explanation: This sequence follows decreasing complexity.

Section B: Structural Organisation in Animals & Plants (10 MCQs)

Q11. Which tissue provides mechanical strength to plant stems?
A. Parenchyma
B. Collenchyma
C. Sclerenchyma
D. Xylem

Answer: C. Sclerenchyma
Explanation: Thick lignified walls give strength and rigidity.

Q12. Xylem transports:
A. Food
B. Water and minerals
C. Hormones
D. Gases

Answer: B. Water and minerals
Explanation: Xylem conducts water upward from roots.

Q13. Blood is classified as:
A. Epithelial tissue
B. Muscular tissue
C. Connective tissue
D. Nervous tissue

Answer: C. Connective tissue
Explanation: Blood connects different body systems by transport.

Q14. Which muscle is involuntary and non-striated?
A. Skeletal muscle
B. Cardiac muscle
C. Smooth muscle
D. Striated muscle

Answer: C. Smooth muscle
Explanation: Found in internal organs like intestine.

Q15. The functional unit of kidney is:
A. Neuron
B. Alveolus
C. Nephron
D. Sarcomere

Answer: C. Nephron
Explanation: Nephron filters blood and forms urine.

Q16. Which tissue joins bone to bone?
A. Tendon
B. Ligament
C. Cartilage
D. Areolar tissue

Answer: B. Ligament
Explanation: Ligaments are elastic connective tissues.

Q17. RBCs lack nucleus to:
A. Increase flexibility
B. Increase oxygen-carrying capacity
C. Reduce size
D. Store nutrients

Answer: B. Increase oxygen-carrying capacity
Explanation: Absence of nucleus allows more haemoglobin.

Q18. The outermost layer of dicot stem is:
A. Cortex
B. Endodermis
C. Epidermis
D. Pericycle

Answer: C. Epidermis
Explanation: Epidermis protects plant organs.

Q19. Which tissue is responsible for food transport in plants?
A. Xylem
B. Cambium
C. Cortex
D. Phloem

Answer: D. Phloem
Explanation: Phloem transports sugars and organic solutes.

Q20. The structural and functional unit of muscle contraction is:
A. Myofibril
B. Sarcomere
C. Actin
D. Myosin

Answer: B. Sarcomere
Explanation: Shortening of sarcomeres causes contraction.

Section C: Cell Structure & Function (10 MCQs)

Q21. Who discovered the cell?
A. Schleiden
B. Schwann
C. Robert Hooke
D. Virchow

Answer: C. Robert Hooke
Explanation: He observed cork cells in 1665.

Q22. Which organelle is involved in lipid synthesis?
A. RER
B. SER
C. Golgi body
D. Lysosome

Answer: B. SER
Explanation: Smooth ER synthesizes lipids.

Q23. Ribosomes are composed of:
A. DNA and protein
B. RNA and lipid
C. RNA and protein
D. Only protein

Answer: C. RNA and protein
Explanation: Ribosomes are ribonucleoprotein particles.

Q24. Which organelle is absent in animal cells?
A. Mitochondria
B. Ribosome
C. Lysosome
D. Chloroplast

Answer: D. Chloroplast
Explanation: Chloroplasts are found only in plant cells.

Q25. The membrane surrounding the vacuole is called:
A. Tonoplast
B. Plasmalemma
C. Cell wall
D. Cristae

Answer: A. Tonoplast
Explanation: Tonoplast regulates movement of ions.

Q26. The fluid mosaic model describes:
A. Cell wall
B. Plasma membrane
C. Nuclear membrane
D. Mitochondrial membrane

Answer: B. Plasma membrane
Explanation: Proposed by Singer and Nicolson.

Q27. Prokaryotic cells lack:
A. Ribosomes
B. Cytoplasm
C. Plasma membrane
D. Membrane-bound organelles

Answer: D. Membrane-bound organelles
Explanation: Prokaryotes have no true organelles.

Q28. Cristae are found in:
A. Chloroplast
B. Golgi body
C. Mitochondria
D. Nucleus

Answer: C. Mitochondria
Explanation: Cristae increase surface area for respiration.

Q29. Which cell organelle is called suicidal bag?
A. Ribosome
B. Lysosome
C. Golgi body
D. ER

Answer: B. Lysosome
Explanation: Contains hydrolytic enzymes.

Q30. The largest cell in human body is:
A. Nerve cell
B. Muscle cell
C. Ovum
D. RBC

Answer: C. Ovum
Explanation: Human ovum is the largest cell.

Section D: Plant Physiology (10 MCQs)

Q31. Movement of water across semi-permeable membrane is called:
A. Diffusion
B. Active transport
C. Osmosis
D. Mass flow

Answer: C. Osmosis
Explanation: Driven by water potential gradient.

Q32. Opening and closing of stomata depends on:
A. Epidermal cells
B. Guard cells
C. Root hairs
D. Companion cells

Answer: B. Guard cells
Explanation: Turgidity changes control stomatal movement.

Q33. Transpiration pull theory was proposed by:
A. Dixon and Joly
B. Priestley
C. Sachs
D. Darwin

Answer: A. Dixon and Joly
Explanation: Explains ascent of sap in tall trees.

Q34. Which pigment is essential for photosynthesis?
A. Carotene
B. Xanthophyll
C. Chlorophyll a
D. Phycobilin

Answer: C. Chlorophyll a
Explanation: Primary photosynthetic pigment.

Q35. Light reaction of photosynthesis occurs in:
A. Stroma
B. Thylakoid
C. Cytoplasm
D. Matrix

Answer: B. Thylakoid
Explanation: Light energy is trapped in thylakoids.

Q36. End product of glycolysis is:
A. Acetyl CoA
B. Pyruvate
C. CO₂
D. ATP only

Answer: B. Pyruvate
Explanation: Glucose breaks down into pyruvate.

Q37. Which hormone promotes cell elongation?
A. Cytokinin
B. Ethylene
C. Auxin
D. ABA

Answer: C. Auxin
Explanation: Auxins promote stem elongation.

Q38. Respiration without oxygen is called:
A. Aerobic respiration
B. Oxidative phosphorylation
C. Anaerobic respiration
D. Photorespiration

Answer: C. Anaerobic respiration
Explanation: Produces less ATP.

Q39. Which mineral is part of chlorophyll?
A. Iron
B. Magnesium
C. Calcium
D. Potassium

Answer: B. Magnesium
Explanation: Central atom of chlorophyll.

Q40. The process of loss of water in plants is called:
A. Translocation
B. Respiration
C. Transpiration
D. Guttation

Answer: C. Transpiration
Explanation: Occurs mainly through stomata.

Section E: Human Physiology (10 MCQs)

Q41. Functional unit of lung is:
A. Bronchus
B. Bronchiole
C. Alveolus
D. Trachea

Answer: C. Alveolus
Explanation: Gas exchange occurs here.

Q42. The enzyme in saliva is:
A. Pepsin
B. Trypsin
C. Amylase
D. Lipase

Answer: C. Amylase
Explanation: Digests starch.

Q43. Universal donor blood group is:
A. A
B. B
C. AB
D. O

Answer: D. O
Explanation: Lacks A and B antigens.

Q44. Pacemaker of heart is:
A. AV node
B. SA node
C. Purkinje fibres
D. Bundle of His

Answer: B. SA node
Explanation: Initiates heartbeat.

Q45. Hormone regulating blood sugar level is:
A. Thyroxine
B. Adrenaline
C. Insulin
D. Estrogen

Answer: C. Insulin
Explanation: Lowers blood glucose.

Q46. Main nitrogenous waste in humans is:
A. Ammonia
B. Uric acid
C. Urea
D. Creatinine

Answer: C. Urea
Explanation: Humans are ureotelic.

Q47. Which vitamin helps in blood clotting?
A. Vitamin A
B. Vitamin B
C. Vitamin C
D. Vitamin K

Answer: D. Vitamin K
Explanation: Required for clotting factors.

Q48. The hormone responsible for fight or flight response is:
A. Insulin
B. Adrenaline
C. Cortisol
D. Thyroxine

Answer: B. Adrenaline
Explanation: Prepares body for emergencies.

Q49. Which part of brain controls balance?
A. Cerebrum
B. Medulla
C. Cerebellum
D. Hypothalamus

Answer: C. Cerebellum
Explanation: Coordinates posture and balance.

Q50. The functional unit of muscle contraction is:
A. Myosin
B. Actin
C. Sarcomere
D. Myofibril

Answer: C. Sarcomere
Explanation: Shortening causes contraction.

✅ These most important NCERT-aligned MCQs cover high-weightage Class 11 Biology concepts and are ideal for school exams and quick revision.