CLASS XI — BIOLOGY (THEORY) — ANNUAL EXAMINATION PRACTICE PAPER (2026–2027)

Maximum Marks: 70

Instructions to Candidates

(Candidates are allowed an additional 15 minutes for only reading the paper. They must NOT start writing during this time.)

This paper is divided into four sections — A, B, C and D.
Answer all questions.
Section A consists of one question of one mark / two marks each.
Section B consists of seven questions of two marks each.
Section C consists of seven questions of three marks each, and
Section D consists of three questions of five marks each.
Internal choices have been provided in one question each in Section B, Section C and Section D.
The intended marks for questions or parts of questions are given in brackets [ ].

Syllabus: Full book — Diversity of Living Organisms; Structural Organisation in Animals and Plants; Cell: Structure and Function; Plant Physiology; Human Physiology.

SECTION A — 20 MARKS

Question 1

Answer the following questions briefly.

I) The scientific name of mango is correctly written as: [1]
(a) Mangifera Indica
(b) Mangifera indica
(c) mangifera Indica
(d) mangifera indica

II) The mushroom Agaricus belongs to the class: [1]
(a) Zygomycetes
(b) Ascomycetes
(c) Basidiomycetes
(d) Deuteromycetes

III) The type of vascular bundle present in a dicot stem is: [1]
(a) radial
(b) conjoint, collateral and open
(c) conjoint, collateral and closed
(d) conjoint and bicollateral

IV) The class of enzymes that catalyses the interconversion of isomers is: [1]
(a) hydrolases
(b) ligases
(c) isomerases
(d) lyases

V) In which phase of the cell cycle does DNA replication take place? [1]
(a) G₁ phase
(b) S phase
(c) G₂ phase
(d) M phase

VI) In a C₄ plant, name (a) the primary acceptor of CO₂ and (b) the first stable product formed. [2]

VII) The respiratory quotient (RQ) when fat is used as the respiratory substrate is about: [1]
(a) 1.0
(b) 0.7
(c) 1.5
(d) infinity

VIII) Assertion: The oxygen dissociation curve of haemoglobin is sigmoid in shape. [1]
Reason: The binding of oxygen to one haem unit increases the affinity of the remaining units for oxygen.
(a) Both Assertion and Reason are true, and Reason is the correct explanation for Assertion.
(b) Both Assertion and Reason are true, but Reason is not the correct explanation for Assertion.
(c) Assertion is true and Reason is false.
(d) Both Assertion and Reason are false.

IX) The pacemaker of the human heart is the: [1]
(a) AV node
(b) SA node
(c) Purkinje fibres
(d) bundle of His

X) A person has a stroke volume of 70 mL and a heart rate of 72 beats per minute. Calculate the cardiac output in litres per minute. [2]

XI) Define ureotelism and uricotelism. Give one example of an animal for each. [2]

XII) State any two functions of the smooth endoplasmic reticulum (SER). [2]

XIII) Name the plant growth regulator responsible for each of the following: [2]
(a) bolting in rosette plants
(b) apical dominance
(c) ripening of fruits
(d) closure of stomata during water stress

XIV) Name the sub-phylum of chordates in which the notochord is present only in the larval tail. [1]

XV) Name the class of fishes that has a cartilaginous endoskeleton. [1]

SECTION B — 14 MARKS

Question 2

State two differences between Gram-positive and Gram-negative bacteria. [2]

Question 3

Differentiate between racemose and cymose inflorescence on the basis of any two points. Give one example of each. [2]

Question 4

Differentiate between a tap root system and a fibrous root system on the basis of any two points. [2]

Question 5

What are co-factors? Name any two types of co-factors. [2]

Question 6

Differentiate between an absorption spectrum and an action spectrum. [2]

Question 7

Define hypogeal germination and epigeal germination. Give one example of each. [2]

Question 8

A. Define tidal volume and inspiratory reserve volume (IRV). [2]

B. What is an electrocardiogram (ECG)? Name the three main waves of a normal ECG and state the event that each represents. [2]

SECTION C — 21 MARKS

Question 9

State any three distinguishing features of the class Aves. [3]

Question 10

(i) State any three differences between a dicot root and a monocot root. [3]

(ii) Describe the structure, location and function of collenchyma. [3]

Question 11

Describe the ultrastructure of a mitochondrion and state its function. [3]

Question 12

State any three differences between mitosis and meiosis. [3]

Question 13

What is photorespiration? Explain the role of RuBisCO in this process and state why photorespiration is considered a wasteful process. [3]

Question 14

(a) Define C-value. [1]
(b) Name the three stages of interphase in a cell cycle and state the main event of each. [2]

Question 15

Describe the digestive system of a frog in brief. [3]

SECTION D — 15 MARKS

Question 16

(a) State Blackman's Law of Limiting Factors. [1]
(b) State two differences between cyclic and non-cyclic photophosphorylation. [2]
(c) Explain the chemiosmotic hypothesis of ATP synthesis in the chloroplast. [2]

Question 17

(i)
(a) Define stroke volume. [1]
(b) Describe the blood flow through the heart during auricular systole and ventricular systole. [2]
(c) What is double circulation? State its significance. [2]

(ii)
(a) Define glomerular filtration rate (GFR) and state its approximate value in a healthy adult. [1]
(b) Explain the process of selective reabsorption in the proximal convoluted tubule (PCT). [2]
(c) Explain the role of ADH in regulating the function of the kidney. [2]

Question 18

(a) Name the contractile proteins of a skeletal muscle. [1]
(b) Explain the sliding filament theory of muscle contraction. [2]
(c) Differentiate between red and white muscle fibres on the basis of any two points. [2]