Punjab School Education Board
Class 11th – September Examination 2026-27
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) Ramesh saw that salt crystals on his window kept increasing in size and thought they were alive since they were "growing." As a biology student, which defining characteristic would you use to correct him?
(ii) Which of the following taxonomic sequences represents the scientifically correct descending hierarchy?
(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) A unicellular organism is eukaryotic, photosynthetic, and instead of a rigid cell wall, it possesses a flexible protein-rich pellicle. Under which kingdom should it be grouped?
(v) Which of the following algae is an example of a colonial green alga?
(vi) Which pair correctly matches the algae with its commercially extracted phycocolloid product?
(vii) Which of the following is not a characteristic of Chordates?
(viii) Which class of vertebrate chordates possesses a cartilaginous endoskeleton, ventral mouth, and placoid scales?
(ix) A gynoecium with multiple carpels fused together is called:
(x) In Opuntia, the flattened, green photosynthetic structure is an anatomical modification of the:
(xi) In a dicot stem, the sequence of tissues from the periphery to the centre is:
(xii) The ventricle of a frog's heart contains:
(xiii) Which of the following is a double membrane-bound cell organelle?
(xiv) The chemical bond linking amino acids together in a protein molecule is:
(xv) Which of the following carbohydrates is a non-reducing sugar?
(xvi) During which phase of mitosis do chromosomes align along the equatorial plate?
(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 are capable of surviving under extremely harsh environmental conditions like high temperatures and salinity.
Reason (R): They possess a distinct cell wall structure with branched-chain lipids in their plasma membrane that confers extreme resistance.
(xviii) Assertion (A): Interphase is considered the most metabolically active stage of the cell cycle.
Reason (R): During interphase, the cell synthesizes RNA, duplicates cell organelles, and replicates 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 Differentiate between eubacteria and archaebacteria on the basis of their cell wall composition and habitat. [2]
Q.3 Why are bryophytes referred to as "amphibians of the plant kingdom"? State why water is necessary for their sexual reproduction. [2]
Q.4 Distinguish between open and closed circulatory systems with one animal example for each. [2]
Mention any two morphological or physiological adaptations observed in parasitic flatworms (Platyhelminthes). [2]
Q.5 Distinguish between racemose inflorescence and cymose inflorescence on the basis of growth of the main axis and order of flower opening. [2]
Q.6 Give reasons: Why is sweet potato considered a modified root, while potato is considered a modified stem? [2]
Differentiate between a pinnately compound leaf and a palmately compound leaf with one suitable example of each. [2]
Q.7 Study the schematic diagrams of vascular bundles given below:
(a) Identify which figure represents an open vascular bundle and which represents a closed vascular bundle.
(b) In which plant organs (dicot stem or monocot stem) are these types typically found? [2]
Q.8 Why does a frog require thin and moist skin for its survival? Explain its role during respiration underwater. [2]
State two physiological differences between the red blood cells (RBCs) of a frog and those of a human. [2]
Q.9 Mention two structural and functional differences between Rough Endoplasmic Reticulum (RER) and Smooth Endoplasmic Reticulum (SER). [2]
Q.10 Differentiate between DNA and RNA based on their nitrogenous bases and pentose sugars. [2]
Q.11 DNA replication occurs during the S phase of interphase. Explain what would happen if a cell divides without completing the S phase. [2]
What is crossing over? Name the stage of Meiosis I in which it occurs and state its significance. [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 List three fundamental chordate characters. Why are mammals considered the most evolutionarily advanced group among vertebrates? [3]
Compare Class Pisces and Class Amphibia on the basis of: (a) Body covering/skin, (b) Respiratory organs, and (c) Structure of heart. [3]
Q.14 Study the placentation patterns shown in the diagrams below:
(a) Identify the types of placentation shown in Pattern (A) and Pattern (B).
(b) Give one plant example exhibiting pattern (A) and one exhibiting pattern (B).
(c) How does marginal placentation differ from these patterns? [3]
Q.15 Explain how a dorsiventral leaf is adapted for efficient photosynthesis and gaseous exchange. Why are stomata typically more abundant on the lower epidermis? [3]
Q.16 Explain the functional interrelationship between the Nucleus, Endoplasmic Reticulum, and Golgi apparatus in the synthesis, modification, and packaging of proteins. [3]
State three prominent structural differences between a plant cell and an animal cell based on cell boundary and cell organelles. [3]
Q.17 A student prepared a temporary mount of an onion root tip to study mitotic stages under a microscope:
(a) Identify the mitotic stage where sister chromatids separate and move to opposite poles.
(b) Name the stage where two daughter nuclei are organized at the poles.
(c) State the biological significance of mitosis in growth and repair. [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) Describe the salient features of gymnosperms with respect to their plant body, vascular tissues, and naked seeds.
(b) What is heterospory? Explain its evolutionary significance towards seed habit. [2+2 = 4]
(a) Describe the life cycle of a moss, showing alternation of generations between gametophyte and sporophyte.
(b) Differentiate between the protonema stage and the leafy stage of mosses. [2+2 = 4]
Q.19
(a) Draw a neat and labelled diagram showing the transverse section (T.S.) of a typical dicot stem.
(b) Describe the functions of: (i) Collenchymatous hypodermis, (ii) Endodermis (starch sheath), and (iii) Cambium.
(c) Why does secondary growth take place in dicot stems but not in monocot stems? [2+2+1 = 5]
(a) Draw a neat and labelled diagram of the transverse section (T.S.) of a dicot root.
(b) State two anatomical differences between a dicot root and a monocot root based on the number of xylem bundles and pith development.
(c) What is the function of the Casparian strip present in the endodermal cells? [2+2+1 = 5]
Q.20 A biochemical test was conducted on three food samples: boiled rice suspension (Sample X), egg white solution (Sample Y), and mustard oil (Sample Z).
* Addition of iodine solution turned Sample X blue-black.
* Addition of Biuret reagent turned Sample Y violet.
* Addition of Sudan III stain turned Sample Z into red droplets.
(a) Identify the primary biomolecule present in Sample X, Sample Y, and Sample Z.
(b) Explain why starch turns blue-black upon reaction with iodine solution.
(c) Name the building blocks of proteins and the chemical bond linking them.
(d) State two biological functions of lipids in living cells. [1.5+1+1+1.5 = 5]
(a) What are enzymes? Why are they referred to as biocatalysts?
(b) Explain how enzymes increase the rate of chemical reactions by lowering activation energy.
(c) Describe the effect of temperature and substrate concentration on enzyme activity.
(d) Differentiate between competitive and non-competitive enzyme inhibition. [1+1+2+1 = 5]
