Class 11 BiologyImportant Questions for Board Exams 2025-26

What is binomial nomenclature? State the rules to be followed while writing scientific names. Give two examples.

Define taxonomy. What are the different taxonomic categories? Arrange them in hierarchical order from species to kingdom.

Distinguish between growth in living organisms and growth in non-living things. Give one example of each.

What is a herbarium? How is it useful in taxonomical studies?

Which of the following is NOT a characteristic feature of living organisms? (a) Metabolism (b) Growth (c) Crystallisation (d) Reproduction

Give an account of R.H. Whittaker's five-kingdom classification. What are the criteria used for this classification?

What are viruses? Describe the structure of a bacteriophage with a well-labelled diagram.

Distinguish between archaebacteria and eubacteria. Give two examples of each.

What are lichens? Why are they considered good indicators of air pollution?

Name the kingdom to which Mycoplasma belongs. State two characteristics of Mycoplasma.

Describe the general characteristics of bryophytes. Why are they called amphibians of the plant kingdom?

Distinguish between gymnosperms and angiosperms with four points. Give two examples of each.

What is alternation of generations? Explain with reference to the life cycle of a bryophyte.

Name the three classes of algae and state one characteristic pigment and one storage food product for each.

The plant body in mosses represents the _____ generation. (a) Sporophytic (b) Gametophytic (c) Diploid (d) Mixed

Give the salient features and two examples each of Porifera, Coelenterata, and Platyhelminthes.

What are the distinguishing characters of phylum Chordata? Name the three sub-phyla.

Distinguish between Chondrichthyes and Osteichthyes with four distinguishing points.

What is metamerism? In which phylum is it observed? Name one example.

Which of the following is an acoelomate organism? (a) Earthworm (b) Tapeworm (c) Starfish (d) Cockroach

What are the different types of root modifications? Give one example and state one function of each type.

Describe the structure of a typical dicotyledonous seed with a well-labelled diagram.

What is phyllotaxy? Name the three types and give one example of each.

Write the floral formula for the family Fabaceae. Draw and label its floral diagram.

Distinguish between simple and compound leaves. Give one example of each type.

Draw and label a transverse section of a dicot stem. How does it differ from a monocot stem? List three differences.

Describe the different types of simple permanent tissues in plants with their functions.

What is secondary growth? Describe the role of vascular cambium in secondary growth of a dicot stem.

Distinguish between xylem and phloem with four points.

Which tissue is responsible for the increase in girth of a plant stem? (a) Apical meristem (b) Lateral meristem (c) Intercalary meristem (d) Epidermis

Describe the different types of epithelial tissues with their location and one function each.

Draw a well-labelled diagram of the digestive system of a cockroach.

Distinguish between striated, unstriated, and cardiac muscle with their location and function.

What is areolar tissue? Where is it found in the body? State two functions.

Name the type of tissue that forms the inner lining of kidney tubules. Name one other location of this tissue.

Draw a well-labelled diagram of a plant cell as seen under an electron microscope.

Describe the structure and functions of mitochondria with a labelled diagram. Why is it called the 'powerhouse of the cell'?

What is the fluid mosaic model of the cell membrane? Who proposed it? Describe the arrangement of lipids and proteins.

Distinguish between rough endoplasmic reticulum (RER) and smooth endoplasmic reticulum (SER) with two points.

What are the functions of lysosomes? Why are they called 'suicidal bags'?

Describe the structure of DNA. Draw a diagram showing the double helix model. How does it differ from RNA?

What are enzymes? Describe the induced-fit model of enzyme action. How does it differ from the lock-and-key model?

Distinguish between competitive and non-competitive inhibition of enzymes with suitable examples.

What are co-factors? Distinguish between coenzymes and prosthetic groups with one example each.

Name the monomer of proteins. What is a peptide bond? How is it formed?

Describe the various stages of mitosis with labelled diagrams. What is the significance of mitosis?

Draw labelled diagrams of (a) Metaphase I of meiosis and (b) Metaphase of mitosis. State two differences.

Distinguish between mitosis and meiosis. Explain with any four points.

Define synapsis and crossing over. During which stages of meiosis do they occur?

What major event occurs during the S phase of the cell cycle? What is its significance?

What is water potential? How does it influence the direction of water movement in plants? What are its components?

Describe the cohesion-tension theory of ascent of sap. Who proposed it? What evidence supports it?

Explain the pressure-flow hypothesis of phloem translocation. Name the scientist who proposed it.

What is plasmolysis? Under what conditions does it occur? Draw a labelled diagram showing a plasmolysed cell.

Differentiate between apoplast and symplast pathways of water movement in plants.

What are macro- and micronutrients? Give two examples of each and state their role in plant metabolism.

Describe biological nitrogen fixation. What is the role of leghaemoglobin in root nodules?

What are the criteria for essentiality of a mineral element? State all three criteria.

What is hydroponics? Give one advantage of this technique.

Name the element that plays an important role in biological nitrogen fixation. State its function.

Draw a well-labelled diagram of a chloroplast. Where do the light reactions and dark reactions occur?

Explain the Calvin cycle (C3 pathway) with a diagram. Name the key enzyme and the CO₂ acceptor molecule.

Distinguish between C3 and C4 plants with respect to (i) primary CO₂ acceptor (ii) primary fixation product (iii) cells involved (iv) photorespiration.

What is the Z-scheme of electron flow? Describe the roles of Photosystem I and Photosystem II.

What is photorespiration? Under what conditions does it occur? Why is it absent in C4 plants?

Describe glycolysis. Where does it occur? What is the net gain of ATP and NADH in this process?

Explain the Krebs cycle with a labelled diagram. Where does it occur? What are the net products per cycle?

What is the respiratory quotient (RQ)? Calculate the RQ for glucose and for a fat. What does RQ less than 1 indicate?

What is fermentation? Give the end products of (a) alcoholic fermentation and (b) lactic acid fermentation.

What is oxidative phosphorylation? Explain the chemiosmotic hypothesis for ATP synthesis in mitochondria.

What are plant growth regulators? Describe the physiological roles of auxins with examples.

What is photoperiodism? Distinguish between short-day plants and long-day plants with examples. What is the critical photoperiod?

What is vernalisation? What is its significance for plants? Give one example.

What role does abscisic acid play in plants under drought stress conditions?

Which plant hormone promotes fruit ripening and is released as a gas? (a) Auxin (b) Cytokinin (c) Ethylene (d) Gibberellin

Draw a well-labelled diagram of the human digestive system.

Describe the process of digestion of proteins in the human digestive tract. Name the enzymes involved at each stage.

What is the role of the liver in digestion? What is bile and what does it contain?

What is emulsification? Which substance is responsible for it and where does it occur?

Name the enzyme present in saliva, the substrate it acts upon, and the products of its action.

Draw a well-labelled diagram of the human respiratory system.

Describe the transport of oxygen in blood. What is the Bohr effect? Draw the oxyhaemoglobin dissociation curve.

Define vital capacity. Name the lung volumes that make up vital capacity.

How is CO₂ transported in blood? Explain any two mechanisms with their approximate percentages.

What is emphysema? What causes it and what is its effect on breathing?

Draw a well-labelled diagram of the human heart and describe its structure and function.

Describe the cardiac cycle. What is cardiac output? How is it calculated?

What is an ECG? What do the P wave, QRS complex, and T wave represent?

Distinguish between blood and lymph with four points.

Why is the SA node called the pacemaker of the heart? What happens if it fails?

Draw a well-labelled diagram of a nephron and describe the process of urine formation.

Explain the counter-current mechanism in the loop of Henle and vasa recta. How does it help in concentration of urine?

What is glomerular filtration rate (GFR)? What is its normal value? What factors affect it?

Distinguish between ammonotelism, ureotelism, and uricotelism. Give one example of each.

What is the role of ADH (vasopressin) in kidney function? What happens when ADH secretion is deficient?

Describe the sliding filament theory of muscle contraction. What is the role of calcium ions?

Draw a well-labelled diagram of a sarcomere. Identify the A-band, I-band, H-zone, and Z-line.

What are the different types of synovial joints? Give one example of each type.

Distinguish between red muscle fibres and white muscle fibres with three points.

What is osteoporosis? Name the age group most commonly affected and one causative factor.

Draw a well-labelled diagram of the human brain and describe the functions of its major parts.

Describe the mechanism of conduction of a nerve impulse. Explain action potential with reference to Na+/K+ ion movements.

Draw a well-labelled diagram of a reflex arc and explain the mechanism of reflex action.

Draw a labelled diagram of the human eye and describe the mechanism of vision. How are rods and cones involved?

What is synaptic transmission? Describe the events that occur at a chemical synapse.

Name the hormones secreted by the anterior pituitary gland and state the function of each hormone.

Describe the role of the adrenal gland in the body. Name the hormones secreted by the adrenal cortex and adrenal medulla and state one function of each.

Explain the mechanism of action of steroid hormones. How does it differ from the mechanism of action of peptide hormones?

What is diabetes mellitus? Distinguish between Type I (insulin-dependent) and Type II (non-insulin-dependent) diabetes.

What is the role of insulin in blood glucose regulation? What hormonal imbalance leads to diabetes mellitus?