Punjab School Education Board
Class 11th – September Examination 2026-27 (Set 2)
Subject: Biology (Theory)
- There shall be one theory paper comprising 20 questions. All questions are compulsory.
- Section A: Question No. 1 consists of 18 sub-parts carrying 1 mark each (16 MCQs and 2 Assertion-Reasoning questions).
- Section B: Question Nos. 2 to 11 are Very Short Answer Type carrying 2 marks each. Internal choice is provided in 4 questions.
- Section C: Question Nos. 12 to 17 are Short Answer Type carrying 3 marks each. Internal choice is provided in 2 questions.
- Section D: Question Nos. 18 to 20 are Long Answer Type carrying 5 marks each (adjusted to 70 total). All questions carry internal choice.
- No True/False, Fill in the Blanks, or Comprehension-based questions are included.
- Draw neat, properly labelled diagrams wherever necessary.
Q.1 Select and write the most appropriate option out of the four given choices for each sub-part (i to xvi). Sub-parts (xvii) and (xviii) are Assertion-Reasoning based. (18 × 1 = 18 Marks)
(i) A student while preparing notes on taxonomy wrote: "The person who laid the foundation of taxonomy is also called its father." Who is this scientist?
(ii) While visiting an orchard, a label on a tree reads Mangifera indica L. The letter "L." in this scientific name signifies:
(iii) Scientists exploring hot geothermal springs at 80°C isolated a unicellular prokaryote with an unusual cell wall structure. To which group does it belong?
(iv) Which of the following statements truly explains why viruses are said to stand at the borderline of living and non-living things?
(v) The juvenile, haploid, green, filamentous stage in the life cycle of mosses that develops directly from a germinating spore is called:
(vi) Which of the following plants is monoecious with both male and female cones borne on the same tree?
(vii) The specialized stinging cells containing toxic capsules used for defense and prey capture in phylum Cnidaria are:
(viii) Which class of vertebrate chordates possesses a cartilaginous endoskeleton, ventral mouth, and placoid scales?
(ix) In Opuntia, the flattened, green photosynthetic structure is an anatomical modification of the:
(x) Casparian strips are characteristic suberized band-like structures found specifically in the:
(xi) In dicot roots, lateral root branches originate endogenously from which internal tissue layer?
(xii) Frogs belong to class Amphibia of phylum Chordata and are poikilothermic animals. They show winter sleep and summer sleep respectively known as:
(xiii) Which cell organelle is commonly referred to as the "protein factory" of the cell?
(xiv) Which of the following carbohydrates is a non-reducing sugar?
(xv) Which of the following is a water-soluble vitamin?
(xvi) During eukaryotic cell division, the disc-shaped protein structures on the centromere to which spindle fibres attach are:
(A) Both (A) and (R) are true, and (R) is the correct explanation of (A).
(B) Both (A) and (R) are true, but (R) is NOT the correct explanation of (A).
(C) (A) is true, but (R) is false.
(D) (A) is false, but (R) is true.
(xvii) Assertion (A): Archaebacteria can survive under extreme conditions like hot springs and high salinity.
Reason (R): They possess a distinctive cell wall structure and branched-chain membrane lipids that provide resistance against harsh environments.
(xviii) Assertion (A): Interphase is an active phase of the cell cycle.
Reason (R): During interphase, the cell undergoes continuous biochemical growth, protein synthesis, and replication of nuclear DNA during the S phase.
Answer the following Very Short Answer Type questions (Q. Nos. 2 to 11 carry 2 Marks each). (10 × 2 = 20 Marks)
Q.2 Why are lichens recognized as sensitive biological indicators of industrial air pollution? Name the two symbiotic components constituting a lichen. [2]
Q.3 Differentiate between homosporous and heterosporous plants with one suitable example for each. [2]
Q.4 Differentiate between diploblastic and triploblastic animals on the basis of embryonic germ layers. Give one animal phylum representing each condition. [2]
Why is Phylum Arthropoda considered the largest and most ecologically dominant group in Kingdom Animalia? Mention two key morphological features responsible for their evolutionary success. [2]
Q.5 Differentiate between axile placentation and parietal placentation based on the position of the placenta and ovule attachment within the ovary. [2]
Q.6 Why is a maize grain morphologically described as a caryopsis rather than a typical true seed? Explain with reference to its pericarp and seed coat. [2]
Describe two distinguishing floral characteristics of Family Solanaceae with respect to its calyx and gynoecium. [2]
Q.7 Study the schematic flowchart showing xylem tissue differentiation given below:
Identify the missing biological terms labelled as (A), (B), (C), and (D). [2]
Q.8 Why is the circulatory system of an adult frog termed an "incomplete double circulation"? Name the specific heart chamber where mixing of oxygenated and deoxygenated blood occurs. [2]
Name the two seasonal dormancy phenomena shown by frogs to survive extreme cold and heat. Mention the primary mode of respiration employed during these dormant states. [2]
Q.9 Explain why the plasma membrane is described as a "fluid mosaic" model. Name the two principal biomolecular components forming this framework. [2]
Q.10 Differentiate between the primary and secondary structural conformations of protein molecules. [2]
Q.11 What are the primary cellular events that occur during the G1 and G2 phases of interphase in a proliferating eukaryotic cell? [2]
A cytogeneticist treats dividing plant cells with a chemical agent that prevents spindle fibre assembly during mitosis. Predict the stage at which division will arrest and state the chromosomal consequence in the cell. [2]
Answer the following Short Answer Type questions (Q. Nos. 12 to 17 carry 3 Marks each). (6 × 3 = 18 Marks)
Q.12 Compare the modes of nutrition found in Kingdom Monera, Kingdom Protista, and Kingdom Fungi with one suitable example of each. [3]
Q.13 Compare Phylum Annelida and Phylum Arthropoda based on the following structural criteria:
(a) Nature of body segmentation
(b) Locomotory organs / appendages
(c) Type of circulatory system [3]
Describe three unique anatomical or physiological characteristics of Phylum Echinodermata with reference to their body symmetry, habitat, and water vascular system. [3]
Q.14 Study the schematic diagram illustrating the transverse section of a dicot leaf (dorsiventral leaf) given below:
(a) How is the mesophyll tissue differentiated in a dorsiventral leaf?
(b) Why are stomata typically more numerous on the lower epidermis than on the upper epidermis?
(c) State the function of the bundle sheath cells surrounding the vascular bundle. [3]
Q.15 Describe the endomembrane system of a eukaryotic cell. Name the four membrane-bound organelles that coordinate functionally to constitute this system, and explain why mitochondria and chloroplasts are excluded from it. [3]
Explain the structure of a eukaryotic nucleus with special reference to the nuclear envelope, nuclear pores, nucleoplasm, and nucleolus. State one primary function of the nucleolus. [3]
Q.16 A student observing mitotic stages in onion root meristematic cells notices three distinct cellular events under different microscope fields:
* Field 1: Chromatin condenses into distinct chromosomes, and the nucleolus and nuclear envelope begin to disintegrate.
* Field 2: Thick, distinct chromosomes are aligned precisely across the equatorial plane of the spindle.
* Field 3: Centromeres split simultaneously, and sister chromatids separate toward opposite poles.
(a) Identify the specific mitotic stages observed in Field 1, Field 2, and Field 3.
(b) Why is the stage observed in Field 2 considered best for studying chromosomal morphology?
(c) What would be the consequence if the event in Field 3 fails to occur symmetrically? [3]
Q.17 What is crossing over? Name the sub-stage of Prophase I of meiosis during which it occurs, and explain why it is essential for producing genetic variations in sexually reproducing organisms. [3]
Answer the following Long Answer Type questions (Q. No. 18 carries 4 Marks; Q. Nos. 19 & 20 carry 5 Marks each). (1 × 4 + 2 × 5 = 14 Marks)
Q.18
(a) Give a comparative account of Chlorophyceae, Phaeophyceae, and Rhodophyceae based on major photosynthetic pigments, stored food material, and cell wall composition.
(b) Explain why members of Rhodophyceae can thrive in deep ocean waters where other photosynthetic plants cannot survive. [3+1 = 4]
(a) Describe the salient morphological and reproductive features of Pteridophytes.
(b) Define homospory and heterospory with an example of each. Why is heterospory considered a crucial evolutionary precursor to seed habit? [2+2 = 4]
Q.19
(a) Draw a neat and labelled diagram representing the transverse section (T.S.) of a monocotyledonous stem.
(b) Describe three distinctive anatomical differences between a monocot stem and a dicot stem with respect to ground tissue, arrangement of vascular bundles, and presence of cambium.
(c) Why are the vascular bundles in a monocot stem described as "conjoint, collateral, and closed"? [2+2+1 = 5]
(a) Draw a neat, labelled diagram showing the alimentary canal and digestive glands of an adult frog (Rana tigrina).
(b) Describe the digestion and absorption of food inside the stomach and intestine of a frog.
(c) State the role of the cloaca in physiological waste elimination and reproduction in amphibians. [2+2+1 = 5]
Q.20 An athlete collapses during an intense marathon due to sudden muscular exhaustion and hypoglycemia. Medical responders administer immediate intravenous glucose solution rather than complex dietary starches or proteins to rapidly revive the runner.
(a) Why is glucose chosen over complex polysaccharides like starch or glycogen for immediate clinical energy recovery?
(b) Classify carbohydrates into monosaccharides, disaccharides, and polysaccharides, giving one biological example for each category.
(c) Differentiate between reducing and non-reducing sugars with one example of each.
(d) What structural polysaccharide provides mechanical rigidity and support to plant cell walls? [1+1.5+1.5+1 = 5]
(a) Describe the sequential stages of Meiosis I in detail, highlighting the chromosomal behavior occurring during Prophase I (Leptotene, Zygotene, Pachytene, Diplotene, and Diakinesis).
(b) Explain the formation and significance of the synaptonemal complex, bivalents, and chiasmata.
(c) State two points of biological significance of meiosis in sexually reproducing organisms. [2.5+1.5+1 = 5]
