Date: 24/03/2025 Question Paper Code

T25 523

Corporate Office : AESL, 3rd Floor, Incuspaze Campus-2, Plot-13, Sector-18, Udyog Vihar,
Gurugram, Haryana-122015

Time: 2 Hrs.
BIOLOGY Max. Marks: 80

(Science Paper 3)
ICSE Board Class X Exam (2025)
Answers & Solutions

GENERAL INSTRUCTIONS

Read the following instructions very carefully and follow them:

(i) Duration for the Test is 2 hours.

(ii) Maximum Marks for Section-A and B is 40 each.

(iii) The intended marks for questions or parts of questions are given in brackets [ ].

(iv) Section A is compulsory. Attempt all questions from this section.

(v) Attempt any four questions from Section B.

(vi) Use of calculator is not permitted.

(vii) It is mandatory to use Blue/Black ballpoint pen to write the answer.

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 Biology (Science Paper 3) ICSE - Class X

SECTION-A (40 Marks)

(Attempt all questions from this Section.)
1. Select the correct answers to the questions from the given options. [15]
(Do not copy the questions, write the correct answer only).
(i) The number of live births per thousand people per year is called:
(a) Mortality (b) Population density
(c) Population growth rate (d) Natality
Answer (d) [1]
(ii) The structure that lies at the junction of the choroid and the iris and is itself a part of the choroid is called:
(a) Ciliary body (b) Suspensory ligament
(c) Pupil (d) Lens
Answer (a) [1]
(iii) Assertion (A): Seminal vesicles pour an alkaline secretion into the semen as it passes through the ureter.
Reason (R): The female vagina is acidic and needs to be neutralized for sperm survival.
(a) (A) is true and (R) is false (b) (A) is false and (R) is true
(c) Both (A) and (R) are true (d) Both (A) and (R) are false
Answer (b) [1]
(iv) The hormone that induces vigorous contractions of the uterus in a pregnant mother is
(a) Oestrogen (b) Prolactin
(c) Oxytocin (d) Progesterone
Answer (c) [1]
(v) A scientist wanted to conduct a genetic experiment on mice. He cut the tails of all the mice and made them
reproduce. What will be the phenotype of the offsprings?
(a) All the offsprings will be tailless. (b) There will be a mix of tailed and tailless offsprings.
(c) All the offsprings will have tails. (d) Tail of the offsprings cannot be predicted.
Answer (c) [1]
(vi) Assertion (A): A turgid plant cell is in a balanced state.
Reason (R): In a turgid cell, turgor pressure and wall pressure are equal and in the same direction.
(a) (A) is true and (R) is false. (b) (A) is false and (R) is true.
(c) Both (A) and (R) are true. (d) Both (A) and (R) are false.
Answer (a) [1]
(vii) The optimum temperature for photosynthesis is:
(a) 10 – 15°C
(b) 60 – 65°C
(c) 40 – 45°C
(d) 25 – 35°C
Answer (d) [1]

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Biology (Science Paper 3) ICSE - Class X
(viii) Ajay and Vijay are siblings. Ajay can roll his tongue while Vijay cannot. What is the genotype of their
parents?
(a) Both the parents are homozygous dominant.
(b) Both the parents are homozygous recessive.
(c) One parent is homozygous dominant, and the other is homozygous recessive.
(d) Both the parents are heterozygous dominant.
Answer (d) [1]
(ix) Assertion (A): Deficiency of Antidiuretic hormone causes an increase in urination.
Reason (R): Antidiuretic hormone acts on the kidney to reabsorb water from the kidney tubules.
(a) (A) is true and (R) is false. (b) (A) is false and (R) is true.
(c) Both (A) and (R) are true. (d) Both (A) and (R) are false.
Answer (c) [1]
(x) A phase of cell division where the spindle fibres disappear is:
(a) Telophase (b) Prophase
(c) Metaphase (d) Anaphase
Answer (a) [1]
(xi) Assertion(A): Arachnoid layer helps in speeding up the transmission of nerve impulses along the axons.
Reason(R): Axon endings at the synapse secrete acetylene.
(a) (A) is true and (R) is false. (b) (A) is false and (R) is true.
(c) Both (A) and (R) are true. (d) Both (A) and (R) are false.
Answer (d) [1]
(xii) Many nuclear power plants are constructed near water sources. They use water for cooling their machinery
and release it back into the water stream, Identify the kind of pollution caused.
(a) Radiation pollution (b) Water pollution
(c) Industrial pollution (d) Thermal pollution
Answer (d) [1]
(xiii)

Owls are nocturnal animals. They are active at night and hunt small animals for food. Owls have large eyes
and can see well at night. This is due to:
(a) Cones and Rhodopsin (b) Rods and lodopsin
(c) Rods and Rhodopsin (d) Cones and lodopsin
Answer (c) [1]

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 Biology (Science Paper 3) ICSE - Class X
(xiv) Sunil tried to match the tropic movements in plants with the stimulus they respond to. The tabulation is
given below:

Tropism Stimulus

P Thigmotropism Touch

Q Geotropism Water

R Chemotropism Chemicals

S Phototropism Gravity

Identify the correct pair:

(a) P and R (b) Q and S

(c) R and S (d) P and R

Answer (a, d) [1]

(xv) Observe the following picture, identify the defect and the cause of the defect.

(a) Simple goitre, under secretion of thyroxine.

(b) Ex-ophthalmic goitre, over secretion of thyroxine.

(c) Simple goitre, over secretion of thyroxine.

(d) Ex-ophthalmic goitre, under secretion of thyroxine.

Answer (b) [1]

2. (i) Name the following: [5]

(a) The fully developed part of the ovary containing a mature ovum.

(b) A waxy layer on the upper epidermis of leaves meant to reduce Transpiration.

(c) The ear ossicle which opens into the oval window of Cochlea.

(d) The physiological process which is the starting point of all food chains.

(e) An insect which is a classic example of natural selection due to industrial melanism.

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Biology (Science Paper 3) ICSE - Class X
(ii) Given below is the diagram of a human heart. Read the information below the diagram and fill in the blanks:

[5]

The human heart pumps blood throughout the body. It is the size of a large fist. The heart is located between

the lungs in the thoracic cavity. It has four chambers. The heart functions all through the lifespan of a person

and is responsible for the survival of the person.

The heart is enclosed by a membrane called (a) _______. The ventricles give rise to two large blood vessels

called (b) _______ and (c)_______. The flaps of the cuspid valves are kept in position by (d) _______.

(e) _______ arteries supply oxygenated blood to the walls of the heart.

(iii) Arrange the terms in each group in the correct order. Write them in a logical sequence beginning with the

term that is underlined. [5]

(a) Palisade cells, Cuticle, Upper epidermis, Spongy cells.

(b) Hepatic portal vein, Stomach, Hepatic vein, Liver.

(c) Cyton, Dendrites, Synaptic cleft, Axon endings.

(d) Insulin release, High blood sugar, Lowers blood sugar, Stimulates glucose uptake from blood.

(e) Sperm duct, Seminiferous tubule, Epididymis, Efferent ducts.

(iv) Read the explanations given below and name the structures: [5]

Example: The tubules which produce sperms.

Answer: Seminiferous tubules

(a) The canal through which the testes descend down into the scrotum just before the birth of a male

baby.

(b) The part of the brain that regulates the peristaltic movement of the alimentary canal.

(c) A structure that collects the soundwaves and conducts them through the external auditory canal.

(d) The point of attachment of two chromatids of a chromosome.

(e) Regulation of the opening and closing of stomata.

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 Biology (Science Paper 3) ICSE - Class X
(v) Given below is an outline of the human body showing the important endocrine glands. Match the glands
marked (a) to (e) with their correct functions: [5]

Example: (f)-6. Secretes Testosterone.

Endocrine glands Functions

1. Prepares the body to face stress.

2. Secretes tropic hormones

3. Secretes Oestrogens

4. Maintains blood sugar level

5. Regulates basal metabolism

6. Secretes Testosterone.

Sol. (i) (a) Graafian follicle.

(b) Cuticle

(c) Stapes

(d) Photosynthesis

(e) Moth [5×1=5]

(ii) (a) Pericardium

(b) Pulmonary artery

(c) Aorta

(d) Chordae tendineae

(e) Coronary arteries [5×1=5]

(iii) (a) Cuticle, Upper epidermis, Palisade cells, Spongy cells.

(b) Stomach, Hepatic portal vein, Liver, Hepatic vein.

(c) Dendrites, Cyton, Axon endings, Synaptic cleft.

(d) High blood sugar, Insulin release, Stimulates glucose uptake from blood, Lowers blood sugar.

(e) Seminiferous tubule, Efferent ducts, Epididymis, Sperm duct. [5×1=5]

(iv) (a) Inguinal canal

(b) Medulla oblongata

(c) Ear pinna

(d) Centromere

(e) Guard cells [5×1=5]

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Biology (Science Paper 3) ICSE - Class X

(v) Endocrine glands Functions

(a) 2. Secretes tropic hormones

(b) 5. Regulates basal metabolism

(c) 1. Prepares the body to face stress

(d) 4. Maintains blood sugar level

(e) 3. Secretes oestrogens [5×1=5]

SECTION-B (40 Marks)

(Attempt any four questions from this Section.)
3. (i) Write the overall chemical equation for photosynthesis. [1]
(ii) Ramesh is a farmer who has a vineyard and cultivates grapes. To improve the shape of the grapes and
make them elongated he sprays a particular phytohormone at the time of fruiting. [2]

(a) Name the phytohormone that Ramesh sprays on the plant at the time of fruiting.
(b) These grapes are said to be seedless. What is the technical term for the formation of such fruits?
(iii) Mention the two pairs of nitrogenous bases that are present in a DNA strand and pair with each other by
hydrogen bonds. [2]
(iv) State any two disadvantages of living close to an airport. [2]
(v) Draw a neat, labelled diagram of an animal cell showing Metaphase with four chromosomes. [3]
Sol. (i) Chemical equation for photosynthesis :

6CO2 + 6H2O ⎯⎯⎯⎯⎯

Chlorophyll
Sunlight
→ C6H12O6 + 6O2 [1]
Carbon dioxide Water Glucose Oxygen

(ii) (a) Gibberellin [1]

(b) Parthenocarpy [1]
(iii) Adenine(A) always pairs with thymine(T) through two hydrogen bonds ,while guanine (G) always pairs with
cytosine(C) through three hydrogen bonds. [2×1]
(iv) Disadvantages of living close to an airport are
(a) It interferes in communication.
(b) It interrupts concentration of thought and disturbs peace of mind.
(c) It lowers efficiency of work.
(d) It disturbs sleep and leads to nervous irritability.
(e) A sudden loud sound can damage eardrum and prolonged noise can even lead to deafness.
(f) Life of animals like birds gets disturbed by aircrafts landing or taking off from the airports.
(Any two) [2×1]

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 Biology (Science Paper 3) ICSE - Class X
(v)

[3]
4. (i) What is the structure of DNA as proposed by Watson and Crick? [1]
(ii) Name the white blood cells that: [2]
(a) show phagocytosis
(b) produce antibodies
(iii) Complete the food chain by mentioning the names of the organisms in (c) and (d): [2]

(iv) State any two harmful effects of acid rain. [2]

(v) Given below is a picture of a tree. Mention the scientific phenomena occurring in the parts labelled (a), (b)
and (c). [3]

Sol. (i) J.D. Watson and F.H.C. Crick proposed a double helical model of DNA. DNA molecule consists of two
polynucleotide strands coiled around a common axis, forming a double helix. Each helical turn has a length
of 3.4 nm in which ten nucleotides are present. [1]

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Biology (Science Paper 3) ICSE - Class X
(ii) (a) Neutrophils or monocytes. (Any one) [1]
(b) Lymphocytes [1]

(iii)

[2×1]

(iv) • Acid rain causes damage to crops, buildings and many others things. [1]
• Acid rain water accumulates in river causing death of aquatic life. [1]
(v) • The scientific phenomena occurring in the part labelled (a) is absorption. [1]
• The scientific phenomena occurring in the part labelled (b) is transpirational pull. [1]
• The scientific phenomena occurring in the part labelled (c) is transpiration. [1]
5. (i) What is Micturition? Explain. [1]
(ii) What are biomedical wastes? Give an example. [2]
(iii) Differentiate between the functions of Urethra and Uterus. [2]
(iv) Rachna is an expert gymnast on the balance beam. She has been vigorously practising for the Olympic
Games. Lately, she has been experiencing dizziness and losing her balance during the practise sessions.
[2]

(a) Which part of the membranous labyrinth is responsible for maintaining the body balance on the beam?
(b) Which type of balance is maintained by the structure mentioned in (a)?
(v) Draw a neat, labelled diagram to show that oxygen is released during photosynthesis. [3]
Sol. (i) The process of expelling urine from the urinary bladder through the urethra is called micturition. [1]
(ii) The wastes generated by hospitals, clinics, laboratories, nursing homes, etc. are referred to as biomedical
wastes. [1]
Examples : Needles, syringes, dirty dressing, gloves, surgery wastes, etc. (Any one) [1]
(iii) Differences between urethra and uterus are :

Urethra Uterus

1. It is a part of male and female 1. It is a part of female reproductive system.

excretory systems.

2. It is a tube that carries urine from 2. It is a hollow muscular organ where a fertilised
urinary bladder to outside of the body. egg implants and a fetus develops. [2×1]

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 Biology (Science Paper 3) ICSE - Class X
(iv) (a) The vestibular apparatus is concerned with the maintenance of body balance. [1]
(b) Both static as well as the dynamic balances are maintained by the vestibular apparatus. [1]
(v)

[3]

Fig. : Photosynthesis in a green leaf

6. (i) Where are Hydathodes located? [1]
(ii) What are Vestigial organs? Give one example of a vestigial structure in the human mouth. [2]
(iii) Ahmed had a severe throat infection. After a few days he developed an earache too. What could be the
reason for the pain in his ears? Explain [2]
(iv) Mr. Sharma is a 76 year old man. His vision was gradually becoming blurred. He consulted an eye doctor
and it was diagnosed as cataract. [2]

(a) Which part of the eye does cataract affect?

(b) Why does the vision become blurred?
(v) Given below is the diagram of a plasmolysed cortical cell of a root. [3]

Copy the diagram and label the following parts in the diagram:
(a) Cytoplasm
(b) Hypertonic solution
(c) Plasma membrane

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Biology (Science Paper 3) ICSE - Class X
Sol. (i) Hydathodes are present at the tips of veins in leaves. [1]
(ii) Vestigial organs – Those organs which are non-functional in the possessor but were functional in the
ancestors are known as vestigial organs. [1]
Wisdom tooth is an example of vestigial organ in human body. [1]
(iii) Ahmed is suffering from tonsillitis. [1]
The ear pain occurs due to irritation in nerves that are connected to both throat and ears. [1]
(iv) (a) Eye lens. [1]
(b) It occurs because the eye lens turns opaque. [1]
(v)

(b)

(a)

(c )

[3×1]

7. (i) Define the term Allele. [1]

(ii) In the last century, the human population has increased tremendously. Death rate has reduced and life
expectancy has increased. This rapid growth has placed significant pressure on resources. Global
cooperation is needed for environmental preservation. [2]

(a) Mention any one reason for reduction in the death rate.
(b) Name any one resource that is under pressure due to population explosion.
(iii) Mention any two functions of amniotic fluid. [2]
(iv) Expand the following abbreviations : [2]
(a) CFC
(b) CNG

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 Biology (Science Paper 3) ICSE - Class X
(v) Vineet’s day begins with a cup of piping hot coffee. Caffeine is a stimulant present in coffee which increases
the circulation of Adrenaline in the body. Vineet feels refreshed, alert and focussed. [3]

(a) Name the organ that is stimulated by caffeine which makes Vineet alert and focussed.
(b) Give the collective term for the protective membranes of the organ mentioned in (a).
(c) Which part of the autonomic nervous system increases the secretion of Adrenaline?
Sol. (i) Allele represents the two alternative forms of a unit factor (or a gene). [1]
(ii) (a) The main factors that contribute to the decline in death rate in a population are as :
• Protection from natural risks : Living in houses protected man from wild animals, heat, cold,
rain, etc.
• Advancement in agriculture : Improved agricultural techniques increased food output for the
rising population.
• Storage facility : Better storage facility made food available all the year round. It has also
minimised the loss of grain by pests.
• Control of diseases : Control of communicable diseases with antibiotics, elimination of
epidemics and sound public health measures reduced the death rate.
(Any one) [1]
(b) A population explosion puts immense pressure on resources like water, land, food, energy, etc.
(Any one) [1]
(iii) Functions of amniotic fluid are :
• It prevents desiccation of the embryo.
• It supports fetal movement.
• It maintains stable temperature. (Any two) [2×1]
(iv) (a) CFC – Chlorofluorocarbon [1]
(b) CNG – Compressed natural gas [1]
(v) (a) Brain [1]
(b) Meninges [1]
(c) Sympathetic nervous system. [1]
8. (i) Explain the term Excretion. [1]
(ii) State the difference between Nephron and Neuron. [2]
(iii) Mention any two objectives of Swachh Bharat Abhiyan. [2]
(iv) Give any two characteristic features of a Cro-Magnon man. [2]

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Biology (Science Paper 3) ICSE - Class X
(v) A farmer cultivates a unique species of tomato plants. The two traits selected for breeding were: Colour of
the fruits and height of the plants. The farmer initially crosses a homozygous tall plant bearing red fruit
(TTRR) with a dwarf plant bearing yellow fruit (ttrr) and the genotype of all the offspring of the F1 generation
was TtRr. Next, he crosses two F1 generation plants (TtRr). [3]

(a) Explain the phenotype of the offsprings of the F1 generation obtained from the initial cross.

(b) Mention the phenotypic ratio of the F2 generation offsprings.

(c) State Mendel’s Law of Independent Assortment.

Sol. (i) The process by which harmful metabolic waste products are eliminated from the body is called
excretion. [1]
(ii) Differences between nephron and neuron are :

Nephron Neuron

(a) It is the structural and functional unit of the It is the structural and functional unit of
kidneys. neural system. [1]

(b) It is responsible for filtration of blood and It is responsible for transmitting electrical
urine production. signals (impulses) within the body. [1]

(iii) Objectives of Swachh Bharat Abhiyan are :

(a) Eliminating open defecation through the construction of household-owned and community-owned
toilets.
(b) Establishing an accountable mechanism of monitoring toilet use. [2×1]
(iv) Characteristics of a Cro-Magnon man are :
• The Cro-Magnon man had, like us, about 1.8 metres tall, well-built body.
• His face was perfectly orthognathous with an arrow, elevated nose, broad and arched forehead,
moderate brow-ridges, strong jaws with man-like dentition, and a well developed chin.
• His cranial capacity was, however, somewhat more than ours, being about 1650 c.c. It is, therefore,
believed that Cro-Magnon man was somewhat more intelligent and cultured than the man of today.
• It could walk and run faster and lived with families in caves.
• It made excellent tools and even ornaments, not only of stones and bones, but also of elephant tusks.
• Its tools included spears, bows and arrows, as he was omnivorous.
• Use of the skin clothes by this man is also confirmed. (Any two) [2×1]

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 Biology (Science Paper 3) ICSE - Class X
(v)

(a) All the plants obtained in the F1 generation will be tall with red fruits (TtRr). [1]

(b) Phenotypic ratio of the F2 generation offsprings is 9 : 3 : 3 : 1. [1]

(c) Law of Independent Assortment :

This law states that the alleles of two different characters/traits segregate or assort independently i.e.,
the segregation of alleles of a trait in the gametes is independent of the segregation of alleles of the
other trait. [1]

❑ ❑ ❑

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