Class 11 Half Yearly Question Paper 2025-26 Biology

CBSE CLASS 11
Half Yearly Question Paper
Session 2025-26

BIOLOGY

Exam CBSE Class 11
Subject Biology
Session 2025-26
Document Type Half Yearly Question Paper

Notes · Sample Papers · Previous Year Papers · Mock Tests

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Question Paper
HALF YEARLY EXAMINATION
SESSION: 2025-2026 ag
CLASS: XI MAXIMUM MARKS: 70
SUBJECT: BIOLOGY TIME: 03 Hours
General Instructions:
(i) All questions are compulsory.
(ii) The question paper has five sections and 33 questions.

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(iii) Section–A has 16 questions of 1 mark each; Section–B has 5 questions of 2 marks each; Section– C has

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7 questions of 3 marks each; Section– D has 2 case-based questions of 4 marks each; and Section–E has 3

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questions of 5 marks each.

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(iv) There is no overall choice. Answer all 33 questions. However, internal choices have been provided in

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some questions. A student has to attempt only one of the alternatives in such questions.
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(v) Wherever necessary, neat and properly labeled diagrams should be drawn.
SECTION - A
Q. No. 1 to 12 are multiple choice questions. Only one of the choices is correct. Select and write the
correct choice as well as the answer to these questions.
1. Recognize the following flow diagram and find the correct option according to the taxonomic 1
hierarchy

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g la 5-Hominidae, 6- Primata
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A. 1-Canis, 2- Felis, 3- Homo, 4- Felidae,
B. 1-Canidae, 2- Felidae, 3- Hominidae, 4-Carnivora, 5- Primata, 6- Mammalia
C. 1-Canidae, 2- Felidae, 3- Hominidae, 4-Carnivora, 5- Mammalia, 6- Chordata
D. 1-Canis, 2- Felis, 3- Homo, 4- Carnivora, 5- Primata, 6-Mammalia
2. Identify the correct pair of combination. 1
I. Albugo-Coenocytic hyphae-Parasite on mustard
II. Alternaria-Conidia-Rust disease
III. Aspergillus-Sac fungi-Meiosis occurs in asci

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IV. Agaricus-Basidiomycetes-Smut disease.

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A. I and II

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B. II and III

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C. III and IV
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D. I and III

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3. How many of the following organisms belong to the second largest phylum?
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a Apple snail, Pearl oyster, Anopheles, Culex, Aedes, Star fish, Sea urchin, Cuttlefish, Sea
cucumber, Squid, Lamprey
A. 9
B. 8
C. 10
D. 5

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4. Which of the following statements is correct? 1
I. In Linnaeus time, two kingdom system of classification with Plantae and Animalia
kingdoms was developed that included all plants and animals respectively.
II. Aristotle was the earliest to attempt a more scientific basis of classification and he used
simple morphological characters to classify plants into trees, shrubs and herbs.
III. The three-domain system has also been proposed that divides the kingdom Monera into
three domains.
IV. R.H. Whittaker proposed a five kingdom classification that included Monera, Protista,
Fungi, Plantae and Animalia.
Choose the correct option.
A. I, III
B. II, IV
C. I, II, IV
D. I, II, III, IV
5. The figures given below show the types of coelom. Select the correct types from the following:- 1

A. A-Eucoelom, B-Pseudocoelom, C-Acoelom
B. A-Pseudocoelom, B-Eucoelom, C-Acoelom
C. A-Acoelom, B-Pseudocoelom, C-Eucoelom
D. A-Eucoelom, B-Acoelom, C-Pseudocoelom

6. Identify the correct pairing of plants and their characteristics. 1
I. Cassia-Imbricate aestivation
II. Lady finger- Twisted aestivation
III. Calotropis- Vexillary aestivation
IV. Lily- Epipetalous stamens
V. Alstonia-Whorled phyllotaxy
VI. Silk cotton- Pinnately compound leaf
A. I, II, V
B. I, II, V, VI
C. II, IV, V, VI
D. III, IV, V, VI
7. Read the following statements and choose the correct option. 1
A. The Golgi cisternae are concentrically arranged near the nucleus with distinct concave
cis or the forming face and convex trans or the maturing face.
B. The Golgi cisternae are concentrically arranged near the nucleus with distinct convex cis
or the maturing face and concave trans or the forming face.
C. The Golgi apparatus principally performs the function of packaging materials, to be
delivered either to the intracellular targets or secreted outside the cell.
D. Number of proteins synthesised by ribosomes on the endoplasmic reticulum are
modified in the cisternae of the Golgi apparatus before they are released from its cis
face.

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Identify the correct sequence of events during Prophase I of meiosis: 1

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I. Synapsis of homologous chromosomes
II. Chromosomes become gradually visible under microscope
III. Crossing over between non-sister chromatids of homologous chromosomes
IV. Terminalisation of chiasmata
V. Dissolution of synaptonemal complex
Choose the correct answer from the options given below:
A. I, II, III, IV, V
B. II, III, IV, V, I
C. II, I, III, V, IV

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D. I, III, IV, V, II

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9. In the graphical representation of pulmonary volumes and capacities, 'x' and ‘y’ denotes 1

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A. Inspiratory reserve volume and expiratory reserve volume.
B. Inspiratory capacity and total lung capacity.
C. Expiratory capacity and inspiratory capacity.

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D. Inspiratory capacity and vital capacity.
10. Breathing, an important step of the respiratory system, is a two-part process involving- 1

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inhalation and exhalation. During the process of breathing, the thorax region shows some

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changes. Identify the statement/s from below that is/are related to the exhalation process.

I.
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External intercostal muscles contract
II. Pressure in the lungs increases
III. Diaphragm contracts
IV. The volume of thorax cavity decreases
A. II and IV only
B. I, II and III only
C. II and III only
D. I, II, III and IV

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11. Read the following statements and find out the incorrect statement. 1

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A. Though the heart is autoexcitable, its functions can be moderated by neural and
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hormonal mechanisms.

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B. Angina pectoris can occur in men and women of any age but it is more common among
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the middle-aged and elderly.

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C. Heart failure is same as cardiac arrest or heart attack.
D. CAD is caused by deposits of calcium, fat, cholesterol and fibrous tissues, which makes
the lumen of arteries narrower.
12. Which of the following is the correct pathway through which impulse travels in the heart is 1
A. SA node → AV node → Purkinje fibres → Bundle of His Heart muscles
B. AV node → SA node → Bundle of His → Purkinje fibres Heart muscles
C. AV node → SA node → Purkinje fibres → Bundle of His Heart muscles
D. SA node → AV node → Bundle of His → Purkinje fibres Heart muscles

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Question No. 13 to 16 consist of two statements – Assertion (A) and Reason (R). Answer these questions
selecting the appropriate option given below:
A. Both A and R are true and R is the correct explanation of A.
B. Both A and R are true and R is not the correct explanation of A.
C. A is true but R is false.
D. A is False but R is true.
13. Assertion (A): Members of Phylum - Porifera are generally marine and asymmetrical. Reason 1
(R): They have a water transport or canal system that helps in food gathering, respiratory
exchange, and removal of waste material.
14. Assertion (A): Meiosis II is known as equational division. 1
Reason (R): Meiosis II results in the separation of sister chromatids, maintaining the
chromosome number.
15. Assertion (A): The exchange of gases in the alveoli is a passive process. 1
Reason (R): It occurs mainly due to the pressure/concentration gradient.
16. Assertion (A): An ECG is a graphical representation of the electrical activity of the heart. 1
Reason (R): The P-wave in an ECG represents the repolarization of the atria.
SECTION – B
17. Name the type of placentation shown in the given figures (a) and (b) and give one example of 2
each.

18. Differentiate between:- 2
Racemose and Cymose Inflorescence
Apocarpous and Syncarpous ovary
19. What happens to homologous chromosomes during 2
A. Zygotene
B. Pachytene
C. Diplotene
D. Metaphase I
OR
Differentiate between anaphase I and anaphase II of meiosis based on what is being separated
and the ploidy of cells if the parent cell was diploid?
20. Why is the diffusion of gases across the alveolar membrane in the lungs so efficient? State two 2
reasons.
OR
A person's vital capacity is 4600 mL, expiratory reserve volume is 1000 mL, and inspiratory
reserve volume is 3000 mL. Calculate their tidal volume and inspiratory capacity.
21. What is erythroblastosis foetalis? How can it be prevented? 2
SECTION – C
22. What are the four fundamental processes that form the basis of taxonomy? How does 3
systematics differ from taxonomy in its scope and approach?
23. How does sexual reproduction occur in Ascomycetes? Mention one useful fungi and its use 3
which belongs to the same group.

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A. A limbless amphibia
B. A cold blooded animal
C. A warm blooded animal
D. An animal possessing dry and cornified skin
E. An animal having canal system and spicules
F. An animal with cnidoblasts
OR
List four characteristic features of the Phylum Arthropoda. Give one example of an arthropod
that is a living fossil and one that is a vector for diseases.

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25. You are observing two flower buds from distinct plant species: 3

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Flower bud A shows petals arranged such that one margin of an appendage consistently
overlaps the next one, and so on, in a spiral, regular fashion.
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Flower bud B shows petals with overlapping margins, but this overlap occurs without any
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specific or consistent direction, appearing irregular.
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A. Identify the type of aestivation in both buds.
B. Differentiate between these two types of aestivation based on their pattern. Give one example
of each.
26. Explain the transport of following molecules across the membrane 3
A. Neutral solutes
B. Polar molecules
C. Na+ / K+ ion
27. Explain how the partial pressures of gases play a crucial role in the exchange of gases at the 3
alveolar and tissue levels.

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28. When an injury is caused to a blood vessel bleeding starts which is stopped by a process called 3

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blood clotting or blood coagulation. Describe the process of blood clotting through a flow chart.

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SECTION – D
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29.
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A diploid somatic cell of an organism contains 16 chromosomes. This cell is allowed to undergo 4

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mitotic divisions in a culture medium.
A. What will be the number of chromosomes in the cell at the end of prophase of mitosis?
(1)
Attempt either subpart B or C
B. What will be the amount of DNA (in C units, assuming 2C at G1 phase) in each
daughter cell at the end of mitosis? (1)
OR
C. How many chromosomes will be present per cell immediately after karyokinesis? (1)
D. If 5 such cells were allowed to undergo 3 successive mitotic divisions, how many total

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cells would be produced? What would be the total number of chromosomes in all these

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cells combined at the end of the third division? (2)

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30. A patient is experiencing metabolic acidosis (a condition where the blood becomes too acidic). 4

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A. How would this affect their oxygen-hemoglobin dissociation curve?
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(1)

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B. What would be the consequence of this shift on oxygen delivery to their tissues?(1)

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Attempt either subpart C or D
a C. Mention the factors that help in oxygen delivery to the tissues.
OR
(2)

D. How much oxygen (in ml) is delivered to the tissues for a person having a stroke volume
of 100 ml and heart beat of 72? (2)
SECTION – E

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31. Write the functions of the following terms- 5
A. Nuclear pores
B. Inclusion bodies
C. Mesosome
D. Plasmid
E. Contractile vacuole
OR
A. The 'fluidity' aspect of the fluid mosaic model helps the membrane to perform important
functions. Mention any four such functions.
B. Explain how the various components of the endomembrane system work in a
coordinated manner to perform their functions.
C. What is the tonoplast?
32. Below is a partially labelled diagram showing a stage of Meiosis I in a plant cell under the 5
microscope:

Answer the following:

A. Identify the sub-stage of Prophase I shown in the diagram. Give two reasons for your
identification based on features visible in the diagram.
B. Label the parts marked as A, B, and C in the diagram.
C. Explain the significance of the structure labelled ‘B’ in the diagram.
D. If the diploid number of the organism is 8n and DNA content is 8C in G1 phase, how
these parameters will change after completion of S phase of cell cycle?
OR
Define the G0 (quiescent) phase of the cell cycle. Describe the sequence of events that take
place during the interphase of the cell cycle. Explain the difference between cytokinesis in an
animal cell and cytokinesis in a plant cell.
33. A. In the joint diastole of cardiac cycle write down the state of atrium and ventricles(blood 5
flow); atrio-ventricular septum and semilunar valve (whether open or closed). In case the
cardiac output needs to be increased how that can be achieved?
What is atherosclerosis?
OR
B. Study the diagram of the human heart. Identify the labeled parts of the nodal tissue and
describe the function of each in the cardiac cycle. State the reason of first and second heart
sound.

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