Solved 2025 Question Paper ICSE Class 10 Biology

The number of live births per thousand people per year is called:

1. Mortality
2. Population density
3. Population growth rate
4. Natality

Answer

Natality

Reason — Natality refers to the birth rate, or the number of live births per thousand people per year.

The structure that lies at the junction of the choroid and the iris and is itself a part of the choroid is called:

1. Ciliary body
2. Suspensory ligament
3. Pupil
4. Lens

Answer

Ciliary body

Reason — The ciliary body is a part of the choroid, located at the junction between the choroid and the iris. It plays key roles in producing aqueous humour and controlling the shape of the lens.

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.

1. A is True and R is False
2. A is False and R is True
3. Both A and R are True
4. Both A and R are False

Answer

A is False and R is True

Reason — Seminal vesicles secrete an alkaline fluid, but semen does not pass through the ureter. The ureter is part of the urinary system, carrying urine from the kidneys to the bladder, it is not related to the reproductive pathway. Semen passes through the ejaculatory duct and urethra, not the ureter.

The hormone that induces vigorous contractions of the uterus in a pregnant mother is:

1. Oestrogen
2. Prolactin
3. Oxytocin
4. Progesterone

Answer

Oxytocin

Reason — Oxytocin is the hormone responsible for stimulating strong uterine contractions during labour and childbirth.

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?

1. All the offsprings will be tailless.
2. There will be a mix of tailed and tailless offsprings.
3. All the offsprings will have tails.
4. Tail of the offsprings cannot be predicted.

Answer

All the offsprings will have tails.

Reason — Cutting a mouse’s tail is not an inheritable feature. As the procedure does not alter the DNA in the germ cells, the change cannot be inherited by the next generation. Therefore, every offspring produced will possess a normal tail.

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.

1. A is True and R is False
2. A is False and R is True
3. Both A and R are True
4. Both A and R are False

Answer

A is True and R is False

Reason — In a turgid cell, turgor pressure pushes outward from inside the cell, while wall pressure pushes inward from the cell wall. They are equal in magnitude but act in opposite directions, balancing each other and keeping the cell firm. Therefore, the assertion is correct, but the reason is incorrect because the pressures are not in the same direction.

The optimum temperature for photosynthesis is:

1. 10 – 15°C
2. 60 – 65°C
3. 40 – 45°C
4. 25 – 35°C

Answer

25 – 35°C

Reason — Photosynthesis is most efficient at moderate warm temperatures. Temperatures between 25 – 35°C provide the best conditions for the enzymes involved in photosynthesis to work effectively.

Ajay and Vijay are siblings. Ajay can roll his tongue while Vijay cannot. What is the genotype of their parents?

1. Both the parents are homozygous dominant.
2. Both the parents are homozygous recessive.
3. One parent is homozygous dominant, and the other is homozygous recessive.
4. Both the parents are heterozygous dominant.

Answer

Both the parents are heterozygous dominant.

Reason — Tongue rolling is controlled by a single gene: the dominant allele R allows rolling, while the recessive allele r prevents it.

• Ajay can roll his tongue, so he carries at least one dominant allele (R).
• Vijay cannot roll his tongue, so his genotype must be rr.

For Vijay to receive two recessive alleles (rr), each parent must contribute an r. At the same time, because each parent can roll the tongue themselves, they must also carry an R. Therefore, both parents must be heterozygous Rr.

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.

1. A is True and R is False
2. A is False and R is True
3. Both A and R are True
4. Both A and R are False

Answer

Both A and R are True

Reason — ADH helps the kidneys reabsorb water, so less urine is made. If there’s not enough ADH, water isn’t reabsorbed properly, causing more urine to be produced.

A phase of cell division where the spindle fibres disappear is:

1. Telophase
2. Prophase
3. Metaphase
4. Anaphase

Answer

Telophase

Reason — During telophase, chromosomes arrive at opposite poles of the cell and the spindle fibres disappear as the nuclear envelopes re-form, marking the end of mitosis before cytokinesis begins.

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.

1. A is True and R is False
2. A is False and R is True
3. Both A and R are True
4. Both A and R are False

Answer

Both A and R are False

Reason — The arachnoid layer is the middle meningeal membrane surrounding the brain and spinal cord; it has no role in increasing the speed of impulse conduction. The structure that actually speeds impulse transmission is the myelin sheath around many axons.
Axon terminals at most synapses release the neurotransmitter acetylcholine not acetylene. Hence the stated Reason is incorrect.

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.

1. Radiation pollution
2. Water pollution
3. Industrial pollution
4. Thermal pollution

Answer

Thermal pollution

Reason — Nuclear power plants use large amounts of water for cooling, and when this heated water is released back into rivers or lakes, it raises the water temperature. This sudden increase in temperature harms aquatic life by reducing oxygen levels and disrupting ecosystems. This type of pollution is called thermal pollution.

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:

1. Cones and Rhodopsin
2. Rods and Iodopsin
3. Rods and Rhodopsin
4. Cones and Iodopsin

Answer

Rods and Rhodopsin

Reason — Owls see well at night because their eyes have many rods, which work in dim light. Rods contain rhodopsin, a pigment that helps detect light in the dark.

Sunil tried to match the tropic movements in plants with the stimulus they respond to. The tabulation is given below:

Identify the correct pair:

1. P and R
2. Q and S
3. R and S
4. P and S

Answer

P and R

Reason — Thigmotropism (P) is the response to touch.
Chemotropism (R) is the response to chemicals.
Geotropism (Q) responds to gravity, not water.
Phototropism (S) responds to light, not gravity.

Observe the following picture, identify the defect and the cause of the defect.

1. Simple goitre, under secretion of thyroxine.
2. Ex-ophthalmic goitre, over secretion of thyroxine.
3. Simple goitre, over secretion of thyroxine.
4. Ex-ophthalmic goitre, under secretion of thyroxine.

Answer

Ex-ophthalmic goitre, over secretion of thyroxine.

Reason — Ex-ophthalmic goitre is caused by the over secretion of thyroxine hormone from the thyroid gland. It results in symptoms like protruding eyes, increased metabolism, swelling in the neck (goitre).

Name the following:

(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.

Answer

(a) Graafian follicle

(b) Cuticle

(c) Stapes

(d) Photosynthesis

(e) Peppered moth (Biston betularia)

Given below is the diagram of a human heart. Read the information below the diagram and fill in the blanks:

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.

Answer

The heart is enclosed by a membrane called (a) Pericardium . The ventricles give rise to two large blood vessels called (b) Pulmonary artery and (c) Aorta . The flaps of the cuspid valves are kept in position by (d) Chordae tendineae . (e) Coronary arteries supply oxygenated blood to the walls of the heart.

Arrange the terms in each group in the correct order. Write them in a logical sequence beginning with the term that is underlined.

(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.

Answer

(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.

Read the explanations given below and name the structures:

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.

Answer

(a) Inguinal canal

(b) Medulla oblongata

(c) Pinna

(d) Centromere

(e) Guard cells

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:

Example: (f) – 6. Secretes Testosterone.

Answer

(a) → (2)

(b) → (5)

(c) → (1)

(d) → (4)

(e) → (3)

Explanation

(a) is Pituitary gland, its function is (2) Secretes tropic hormones.
Tropic hormones stimulate other endocrine glands to secrete their hormones; for example, TSH from the pituitary activates the thyroid to release thyroxine.

(b) is Thyroid gland, its function is (5) Regulates basal metabolism.
The thyroid gland produces hormones (like thyroxine) that regulate basal metabolism, the rate at which the body uses energy at rest to maintain vital functions like breathing and heartbeat.

(c) is Adrenal gland, its function is (1) Prepares the body to face stress.
The adrenal gland releases hormones like adrenaline, which help the body respond to stress by increasing heart rate, breathing, and energy supply, preparing the body for "fight or flight" action.

(d) is Pancreas, its function is (4) Maintains blood sugar level.
The pancreas produces hormones like insulin and glucagon, which help maintain blood sugar levels by lowering or raising the glucose in the blood as needed.

(e) is Ovaries, its function is (3) Secretes Oestrogens.
The ovaries produce the hormone oestrogen, which helps in the development of female secondary sexual characteristics and regulates the menstrual cycle and reproductive functions.

Write the overall chemical equation for photosynthesis.

Answer

$6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow[\text{chlorophyll}]{\text{light energy}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{H}_2\text{O} + 6\text{O}_2 \uparrow$

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.

(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?

Answer

(a) Gibberellins

(b) Parthenocarpy

Mention the two pairs of nitrogenous bases that are present in a DNA strand and pair with each other by hydrogen bonds.

Answer

1. Adenine (A) pairs with Thymine (T): – Connected by 2 hydrogen bonds.

2. Guanine (G) pairs with Cytosine (C): – Connected by 3 hydrogen bonds.

State any two disadvantages of living close to an airport.

Answer

1. Noise Pollution — Constant sound from airplanes taking off and landing can disturb sleep, lower efficiency of work and disturb peace of mind.

2. Air Pollution — Emissions from aircraft and airport traffic can lead to poor air quality, affecting respiratory health over time.

Draw a neat, labelled diagram of an animal cell showing Metaphase with four chromosomes.

Answer

What is the structure of DNA as proposed by Watson and Crick?

Answer

Watson and Crick proposed the double helical model of DNA composed of two complementary strands wound around each other in a double helix. Each strand has a sugar-phosphate backbone with nitrogenous bases in the center.

Name the white blood cells that:

(a) Show phagocytosis

(b) Produce antibodies

Answer

(a) Neutrophils

(b) Lymphocytes

Complete the food chain by mentioning the names of the organisms in (c) and (d):

Answer

(c) Snake

(d) Hawk

State any two harmful effects of acid rain.

Answer

1. Damages Plants and Crops: Acid rain harms leaves, reduces photosynthesis, and weakens plant growth by polluting soil.

2. Pollutes Water Bodies: It makes lakes and rivers acidic, which can kill fish and other aquatic life.

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

Answer

(a) Absorption of water

(b) Transportation of water

(c) Transpiration

What is Micturition? Explain.

Answer

Micturition is the process by which urine is expelled from the urinary bladder out of the body through the urethra. It occurs when the bladder muscles contract and the sphincter muscles relax.

What are biomedical wastes? Give an example.

Answer

Biomedical wastes are the wastes generated from hospitals, clinics, laboratories, and other healthcare facilities during diagnosis, treatment, or immunization of humans or animals.
Example: Used syringes and needles.

Differentiate between the functions of Urethra and Uterus.

Answer

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 practice sessions.

(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)?

Answer

(a) The semicircular canals.

(b) Dynamic balance.

Draw a neat, labelled diagram to show that oxygen is released during photosynthesis.

Answer

Below labelled diagram shows that oxygen is released during photosynthesis:

Where are Hydathodes located?

Answer

Hydathodes are located at the tips or edges of leaves.

What are Vestigial organs? Give one example of a vestigial structure in the human mouth.

Answer

Vestigial organs are those organs that have ceased to be of any use to the possessor but still persist generation after generation in a reduced form.

Example in the human mouth — Wisdom teeth.

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.

Answer

Ahmed’s earache after a throat infection is likely because the infection spread from his throat to the middle ear through the eustachian tube (which connects the throat and the middle ear). This causes inflammation and fluid buildup in the middle ear, leading to pain and discomfort.

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.

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

(b) Why does the vision become blurred?

Answer

(a) Lens

(b) The vision becomes blurred because the lens becomes cloudy or opaque, preventing light from passing clearly to the retina.

Given below is the diagram of a plasmolysed cortical cell of a root.

Copy the diagram and label the following parts in the diagram:

(a) Cytoplasm

(b) Hypertonic solution

(c) Plasma membrane

Answer

The labelled diagram is shown below:

Define the term Allele.

Answer

Alternative forms of a gene, occupying the same position on homologous chromosomes and depicting different forms of the same character are called alleles.

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.

(a) Mention any one reason for reduction in the death rate.

(b) Name any one resource that is under pressure due to population explosion.

Answer

(a) Improved healthcare and medical facilities.

(b) Freshwater

Mention any two functions of amniotic fluid.

Answer

1. Protects the foetus by cushioning it against jerks or mechanical shocks.
2. Keeps an even pressure all around the embryo.

Expand the following abbreviations:

(a) CFC

(b) CNG

Answer

(a) CFC – Chlorofluorocarbon

(b) CNG – Compressed Natural Gas

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.

(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?

Answer

(a) Brain

(b) Meninges

(c) Sympathetic nervous system

Explain the term Excretion.

Answer

Excretion is the removal of harmful and unwanted nitrogenous waste products from the body.

State the difference between Nephron and Neuron.

Answer

Mention any two objectives of Swachh Bharat Abhiyan.

Answer

1. To eliminate open defecation through the construction of individual, cluster and community toilets.
2. To improve overall cleanliness and hygiene in towns and rural areas.

Give any two characteristic features of a Cro-Magnon man.

Answer

1. Cranial capacity 1450-1600 cm³.
2. Large skull, broad face, rounded forehead and a prominent chin.

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 fruits (TTRR) with a dwarf plant bearing yellow fruits (ttrr) and the genotype of all the offsprings of the F₁ generation was TtRr. Next, he crosses two F₁ generation plants (TtRr).

(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.

Answer

(a) All F₁ plants are tall with red fruits, because the alleles for tallness (T) and red fruit colour (R) are dominant over dwarfness (t) and yellow colour (r).

(b) 9 : 3 : 3 : 1

(c) Mendel's Law of Independent Assortment states that when there are two pairs of characters, the distribution of the alleles of one character into the gametes is independent of the distribution of the alleles of the other character.