ICSE Class 10 Biology — All Questions

diffusion

Reason — Diffusion is the movement of molecules from a region of their higher concentration to a region of their lower concentration. The scent molecules of the freshly cut grass move from the region where they are concentrated into the surrounding air, just as the fragrance of a lighted incense stick spreads through a room.

Excessive perspiration

Reason — While playing on a hot afternoon, a large amount of water and salts is lost from the body as sweat. This loss leads to dehydration, which causes dizziness. An oral rehydration solution replaces the water and salts that have been lost.

Both (A) and (R) are true and (R) is the correct explanation of (A).

Reason — Plants have neither sense organs nor a nervous system, yet they respond to stimuli such as light, gravity and water. These responses are brought about by phytohormones like auxins. Hence the hormonal system correctly explains why plants are able to respond to stimuli.

Renal Artery - High; Renal Vein - Low

Reason — The excess amino acids of a protein meal are deaminated in the liver to form urea. The renal artery brings this urea rich blood to the kidney, where urea is filtered out and removed in the urine. So the blood leaving the kidney through the renal vein contains much less urea.

passes very little urine due to severe dehydration.

Reason — In cholera, a large quantity of water is lost from the body through severe diarrhoea and vomiting. To conserve the little water that is left, the kidney tubules reabsorb more water, so only a small quantity of concentrated urine is passed.

Q and S

Reason — Guttation is the loss of water as droplets along the margins of leaves through hydathodes. It can be observed in many plants and is quite common in banana, nasturtium and strawberry so Q is correct. ADP is converted to ATP during the light dependent phase of photosynthesis, so S is correct. P is wrong because stomatal opening takes place by potassium ion exchange and not by cobalt ions. R is wrong because duplicated chromosomes are joined at the centromere and not at the centrosome.

exosmosis

Reason — The salt sprinkled on the cucumber makes the solution outside the cells more concentrated, that is hypertonic. Water therefore moves out of the cucumber cells through their semipermeable membranes and collects in the bowl. This outward movement of water is called exosmosis.

Renal Cortex – 1, 2, 3, 4, 5; Renal Medulla – 6, 7

Reason — In the figure, 1 is the afferent arteriole, 2 the glomerulus, 3 the efferent arteriole, 4 the proximal convoluted tubule and 5 the distal convoluted tubule. All of these lie in the renal cortex. The loop of Henle (6) and the collecting duct (7) run down into the renal medulla.

acquired reflex

Reason — Watering of the mouth at the mere sound of the school bell is a learnt response, formed by associating the bell with food. Such learnt responses are called acquired or conditioned reflexes, as shown by Pavlov in his experiment on a dog.

Right auricle, Right ventricle, Pulmonary artery, Lungs, Pulmonary veins, Left auricle.

Reason — In pulmonary circulation, deoxygenated blood is pumped from the right ventricle through the pulmonary artery to the lungs. After being oxygenated in the lungs, the blood returns to the left auricle through the pulmonary veins.

primary consumer

Reason — A rabbit is a herbivore and feeds directly on green plants, which are the producers. Organisms that feed directly on producers occupy the position of primary consumers in a food chain.

Both (A) and (R) are true, but (R) is not the correct explanation of (A).

Reason — Pericardial fluid is present between the heart wall and the pericardium, and the human heart does have four chambers. However, the number of chambers has nothing to do with the presence of this fluid. The pericardial fluid protects the heart from shocks and reduces friction during its beating.

50%

Reason — Arun cannot roll his tongue, so he is homozygous recessive (tt). His wife is a carrier, so she is heterozygous (Tt). The cross tt × Tt gives 50% Tt children, who can roll their tongue, and 50% tt children, who cannot.

climate change

Reason — A long term change in the pattern of rainfall and temperature, leading to crop failure and water shortage, is an effect of climate change brought about by global warming.

P and R

Reason — Root hairs are very fine and numerous, which gives them a large surface area for absorption. The cell sap inside them is more concentrated than the soil water, so water enters by endosmosis. Q is wrong because the cell sap is more concentrated, not less, and S is wrong because the cell membrane of the root hair is semipermeable, not freely permeable.

(a) Lenticels

(b) Aqueous humour

(c) Inguinal canal

(d) Meiosis

(e) Acetylcholine

(a) ova

(b) ovulation

(c) fertilisation

(d) uterus

(e) 40

(a) Odd term — Monocyte
Category of the remaining terms — Granulocytes.

(b) Odd term — ADH
Category of the remaining terms — Hormones secreted by the anterior lobe of the pituitary gland.

(c) Odd term — Tongue
Category of the remaining terms — Vestigial organs.

(d) Odd term — Haemoglobin
Category of the remaining terms — Components involved in blood clotting.

(e) Odd term — Endometrium
Category of the remaining terms — Parts of the male reproductive system.

(a) Eustachian tube.

(b) Ossicles.

(c) Organ of Corti.

(d) The tiny hairs, along with the wax secreting glands of the auditory canal, prevent dust and other small foreign particles from entering the ear and reaching the ear drum.

(e) The auditory nerve carries nerve impulses from the inner ear to the brain, for hearing and for maintaining body balance.

(a) Placenta - Allows diffusion of glucose from maternal blood into foetal blood

(b) Umbilical cord - A tube-like structure that transports substances to and from the foetus

(c) Amnion - Protective membrane surrounding the foetus

(d) Amniotic fluid - Cushions the foetus and absorbs mechanical shocks

(e) Cervix - Site of fertilisation

Transpiration

Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant, mainly from the leaves.

On a rainy day the atmosphere is highly humid. As there is very little difference between the amount of water vapour inside the leaf and that in the surrounding air, the diffusion of water vapour out of the leaf becomes slow. Hence the rate of transpiration is much lower on a rainy day.

The primary pores are the stomata.
They are present mainly on the surface of the leaves and also on young green stems.

Three adaptations in plants to reduce transpiration are:

1. A thick waxy cuticle develops over the epidermis, as in the banyan tree.
2. The number of stomata is reduced and they are placed on the lower surface of the leaf.
3. The stomata are sunken in pits and covered with hair, as in Nerium.

(a) Adrenal virilism.

(b) Cortical hormones, that is the sex corticoids or androgens, are responsible for this disorder. They are secreted by the adrenal gland.

(c) Hormones are chemical messengers secreted in very small amounts by the ductless or endocrine glands directly into the blood. They are carried by the blood to the target organs, where they regulate physiological processes.

(d) 1. TSH — Thyroid Stimulating Hormone
2. ACTH — Adreno Cortico Tropic Hormone

A neat, labelled diagram of a turgid root hair cell is shown below:

The picture shows a large number of factories giving out smoke into the air. It conveys the message that factories should not be built close to residential areas, and that industrial growth should not be allowed to spoil the environment.

Air pollution and water pollution.

Two reasons for population explosion in India are:

1. High birth rate.
2. Lack of education and awareness about family planning methods.

Two health problems that the residents may face are:

1. Respiratory diseases such as asthma and bronchitis.
2. Allergies and skin infections.

Three resources that come under pressure due to rising population are:

1. Food
2. Fossil fuels
3. Minerals

Mitosis

Each cell of the human body contains 46 chromosomes, that is 23 pairs.
The wound heals by mitosis, in which the daughter cells receive the same number of chromosomes as the parent cell. So each daughter cell will also contain 46 chromosomes.

Mendel’s Law of Segregation of gametes states that during the formation of gametes (sperm or eggs), the two alleles for a given gene separate, or segregate, so that each gamete carries only one allele for each gene. When gametes fuse during fertilization, the resulting offspring inherits one allele from each parent, restoring the diploid number of alleles for that gene.

Haemophilia is a sex linked recessive disorder carried on the X chromosome. A female has two X chromosomes, so she will suffer from the disease only if both of them carry the recessive gene. If only one X chromosome carries it, the normal dominant gene on the other X chromosome suppresses the disease and she remains a carrier. A male has only one X chromosome, so a single recessive gene expresses itself and he shows the disease. This is why haemophilia is uncommon in human females.

A neat, labelled diagram of an animal cell having 4 chromosomes in the metaphase stage is shown below:

The aim of the experiment is to prove that carbon dioxide is necessary for photosynthesis.

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

The mineral element essential for the formation of chlorophyll is magnesium.

In plant X, the potassium hydroxide kept in the watch glass absorbed all the carbon dioxide present inside the bell jar. In the absence of carbon dioxide, photosynthesis could not take place, so no starch was formed and the leaves did not turn blue black with iodine.

In the control plant Y, carbon dioxide was available, so photosynthesis took place and starch was formed. Hence its leaves turned blue black with iodine.

This proves that carbon dioxide is essential for photosynthesis.

Auxin is the hormone that promotes the growth of plants towards sunlight.
This tropic movement is called phototropism.

Below diagram shows the stomatal apparatus found in the epidermis of leaves with all the different parts labelled:

Charles Darwin

Two characteristic features of Australopithecus are:

1. Absence of chin.
2. Body covered with hair.

Hyperopia or hypermetropia is caused either by the shortening of the eyeball from front to back or by the lens becoming too flat. As a result, the image of nearby objects is formed behind the retina and near vision becomes blurred.

It is corrected by using spectacles with convex (biconvex) lenses.

One difference between identical twins and fraternal twins is:

A neat, labelled diagram of a human blood smear is shown below:

R and S

Reason — Malaria and Cholera are not genetic disorders. They are caused by plasmodium and bacteria respectively. Haemophilia, Colour blindness and Albinism are genetic disorders.

P-close and Q-open

Reason — The atrioventricular valves close to prevent the backflow of blood into the atria, and the semilunar valves open to allow blood to be pumped into the pulmonary artery and aorta.

(A) is true and (R) is false

Reason — A thick cuticle helps to reduce transpiration because it forms a protective, waxy barrier on the leaf surface and reduces water loss. Therefore, Assertion (A) is true.

The Reason (R) is false because desert plants do not have large, thin leaves. They usually have small leaves or leaves modified into spines to reduce water loss through transpiration.

Therefore, (A) is true and (R) is false.

75

Reason

If Guanine = 75, then cytosine = 75
So, Guanine + Cytosine = 75 + 75 = 150

Remaining bases = 300 - 150 = 150

Adenine + Thymine = 150

Since, Adenine = Thymine
So, we will divide 150 equally between them.

150/2 = 75

So, Adenine = Thymine = 75

Both (A) and (R) are true and (R) is the correct explanation of (A).

Reason — During drought stress, abscisic acid signals the guard cells to close stomata, which reduces transpiration and prevents excessive water loss.
Therefore, Both (A) and (R) are true (R) is the correct explanation of (A).

(A) is false and (R) is true

Reason — (A) is false because leukoderma is not blood cancer; it is a skin condition in which loss of pigmentation occurs. Blood cancer is called leukaemia, and it involves an abnormal increase in the number of white blood cells. Therefore, (R) is true.

Hence, (A) is false and (R) is true.

P, R and S

Reason — For educating the rural audience about population control through visually engaging methods, the most effective options are:

• Posters (P) – attract attention through pictures and short messages.
• Film shows (R) – provide information in an interesting visual form.
• Street plays (S) – are easy to understand and highly effective in rural areas.

Loudspeakers (Q) only provide audio and are not visually engaging.

Therefore, the correct combination is P, R and S.

50%

Reason —

Bronchodilation

Reason — When Bharat panicked after missing the bus, his sympathetic nervous system became active. This prepared the body for an emergency situation by widening the air passages so that more air could enter the lungs and more oxygen could be supplied to the muscles. This widening of the air passages is called bronchodilation.

In such situations, the coronary arteries dilate, the muscles become more active, and the respiration rate increases.

Right Atrium → Right Ventricle → Lungs → Left Atrium → Left Ventricle → Body tissues

Reason — Deoxygenated blood from the body enters the right atrium, then goes to the right ventricle. From there, it is pumped to the lungs for oxygenation. Oxygenated blood returns to the left atrium, passes into the left ventricle, and is then pumped to the body tissues.

Medulla oblongata

Reason — The pupil constricts in bright light due to a reflex action. Reflex centres for such involuntary actions are controlled by parts of the brainstem. If, after a head injury, the pupils lose the ability to constrict in bright light, it indicates damage to the medulla oblongata, which helps control involuntary reflexes.
Suspensory ligaments hold the eye lens in position for focus.
Eye lens only helps in focusing light on the retina and not the size of the pupil.
Eyelids protect the eye and control opening/closing of the eye.

Albuminuria

Reason — The presence of proteins in urine is called albuminuria. It occurs due to kidney damage, when proteins leak into the urine. Haematuria is the presence of blood in urine. Glycosuria is the presence of glucose in urine. Anaemia is a condition in which the haemoglobin level is lower than normal.

Improved sanitation and solid waste management.

Reason — Swachh Bharat Abhiyan is a national cleanliness campaign aimed at improving hygiene, sanitation and waste management across India. The mission focuses on protecting the environment, not destroying forests. It aims to reduce waste generation and manage it properly, not simply increase landfill areas. The programme encourages cleanliness and waste reduction, not increasing pollution or waste.

B and D

Reason —

• A – Salt does not enhance the colour of the pickle.
• C – Salt does not increase the nutritional value; it mainly acts as a preservative.
• B – Salt inhibits the growth of microorganisms by drawing water out of their cells and causing plasmolysis.
• D – Salt creates a hypertonic medium that helps prevent microbial growth.

Therefore, B and D are correct.

Menstrual phase

Reason — The shedding of the endometrium occurs when fertilisation does not take place, leading to menstruation. This happens during the menstrual phase. In the follicular phase, Follicle Stimulating Hormone stimulates the growth of ovarian follicles. In the ovulatory phase, the mature ovum is released from the ovary. In the luteal phase, after ovulation, the empty follicle becomes the corpus luteum, which releases progesterone and maintains the uterine lining for possible pregnancy. If fertilisation does not occur, the lining breaks down at the end of this phase.

(a) Thigmotropism

(b) Astigmatism

(c) Biomedical waste

(d) Tubectomy

(e) Speciation

(a) Acrosome

(b) Hyaluronidase

(c) 23

(d) Mitochondria

(e) Semen

(a) Odd one : Oxytocin
Auxin, Gibberellin, Cytokinin - Plant hormones

(b) Odd one : Vasopressin
Growth Hormone, Thyroid Stimulating Hormone, Gonadotropic Hormone - Anterior pituitary gland secretions

(c) Odd one : Nucleic acid
Urochrome, Urea, Uric acid - Excretory waste products

(d) Odd one : Cervix
Chordae Tendinea, Papillary Muscles, Sinoatrial node - Parts of heart

(e) Odd one : Oviduct Morula, Blastocyst, Foetus - Stages of embryonic development

(a) Diabetes mellitus

(b) Insulin

(c) Pancreas

(d) Frequent urination

(e) Regular physical exercise

(a) Renal cortex

(b) Renal artery

(c) Ureter

(d) Renal medulla

(e) Renal vein

(f) Pelvis

Interphase is the resting but metabolically active stage of the cell cycle.

Binocular vision provides better depth perception and helps in accurately judging distance.

There are 44 autosomes and 2 allosomes in a human body cell.

(a) Transpiration

(b) Temperature

The scientific name of modern man is Homo sapiens sapiens.

(a) In the cerebrum, the Cytons are present in the outer gray matter, while the Axons are present in the inner white matter.

(b) In the spinal cord, the Cytons are present in the inner gray matter, while the Axons are present in the outer white matter.

(a) The theory of Natural Selection was proposed by Charles Darwin.

(b) The organism used to explain industrial melanism is Biston betularia.

Difference between Plasmolysis and Deplasmolysis:

(a) The prostate gland is located just below the urinary bladder, surrounding the urethra close to its origin from the bladder.

(b) The prostate gland produces an alkaline secretion to neutralise the acidity of the urethra and vagina.

(c) The structure that regulates the flow of urine from the urinary bladder into the urethra is the internal urethral sphincter.

The advantages of RBCs not having nuclei are:

1. It allows more space for haemoglobin, the oxygen-carrying pigment.
2. It helps the RBC to maintain a biconcave shape, which increases the surface area for faster gas exchange.

(a) Algae → Mosquito larvae → Small fish → Kingfisher

(b) Green leaves → Snail → Frog → Crow

(a) One function of the placenta is the exchange of materials between the mother and the foetus, such as supplying oxygen and nutrients to the foetus and removing waste products from it.

(b) The structure that connects the placenta to the foetus is the umbilical cord.

Two secondary sexual characteristics in a 15-year-old boy are:

1. Growth of facial hair such as moustache and beard.
2. Deepening of the voice due to enlargement of the larynx.

(a) The eye disorder is presbyopia.

(b) It can be corrected by using a convex lens.

(c) In this defect, the image is formed behind the retina.

Population density is the number of people living per square kilometre at a given time.

(a) Hypersecretion of androgens from the adrenal cortex results in adrenal virilism in human females.

(b) One symptom of this disorder is excessive growth of facial and body hair.

(a) The plant was placed in the dark for 48 hours to destarch it, so that the stored starch would be used up in respiration.

(b) The leaf is boiled in alcohol to remove chlorophyll so that the colour change with iodine can be clearly observed.

(a) The structure shown is a cross-section of the spinal cord.

(b) Gray matter and White matter is labelled in the below diagram:

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

(a) Nicotinamide Adenine Dinucleotide Phosphate

(b) Adenosine Diphosphate

(a) A synapse is the junction between the terminal branches of the axon of one neuron and the dendrites or cell body of another neuron, separated by a minute gap.

(b) The neurotransmitter responsible for transmission across the synapse is acetylcholine.

(a) Leydig cells produce testosterone, which controls the development of male secondary sexual characteristics and supports sperm formation.

(b) Seminiferous tubules are the sites where sperms are produced in the testes.

(a) One significant problem caused by the reduction in urban greenery is an increase in air pollution.

(b) Green plants improve air quality by absorbing carbon dioxide during photosynthesis, releasing oxygen, and trapping dust and pollutants on their leaves.

(c) As a citizen, I can help by planting more trees, protecting existing plants in my surroundings, avoiding unnecessary cutting of trees, and supporting green initiatives.

The term for the pressure exerted by the cell contents on the cell wall is Turgor pressure.

(a) The fluid present between the meninges in the spinal cord is cerebrospinal fluid.

(b) It acts as a shock-proof cushion and forms a medium for the exchange of food materials, waste products and respiratory gases with neurons.

The labelled diagram is given below:

Decaying fruits and newspapers are two biodegradable wastes.

(a) Membranous labyrinth.

(b) Organ of Corti.

(c) Noise pollution.

Sperm Duct

Reason — The surgical method of sterilisation in males is called vasectomy. In this operation a small cut is made in the scrotum, the vas deferens (sperm duct) is ligated and a small piece between the two ligatures is removed, so that the semen contains no spermatozoa.

Oxygen

Reason — Carbon dioxide and water are the raw materials of photosynthesis and temperature affects the enzymes involved, so all three influence the rate of photosynthesis. Oxygen is an end product of the process and is not a factor that controls its rate.

Pancreas

Reason — Pancreas is a heterocrine gland. As an exocrine gland it pours pancreatic juice into the duodenum through a duct, and as an endocrine gland its Islets of Langerhans secrete insulin, glucagon and somatostatin directly into the blood.

By making informed choices about family planning methods.

Reason — Population growth can be checked by voluntary family planning. When women are educated and make informed choices about the methods of contraception available to them, the number and spacing of children can be regulated and the birth rate comes down.

Organ of Corti

Reason — The organ of Corti lies inside the cochlea and carries the sensory hair cells of hearing. Vibrations of the basilar membrane stimulate these cells, which send impulses to the brain through the auditory nerve.

Both (A) and (R) are true and (R) is the correct explanation of (A).

Reason — Light intensity is a limiting factor for photosynthesis. Plants growing in shade receive less light, so they develop a larger leaf surface area to trap the maximum amount of the available sunlight.

Ethylene

Reason — Ethylene is a gaseous phytohormone which aids in the ripening of fruits. In a closed rice bin the ethylene given out by the fruit is trapped around it, so the mangoes ripen faster.

Both (A) and (R) are true and (R) is the correct explanation of (A).

Reason — Water and sodium ions are reabsorbed along the loop of Henle. By varying the quantity of water returned to the blood, the loop of Henle decides whether the urine leaving the nephron is concentrated or dilute.

Survival of the fittest

Reason — Darwin observed that more offspring are produced than can survive, which leads to a struggle for existence. Individuals with favourable variations are better fitted to their surroundings, survive and reproduce. This is the survival of the fittest, which drives natural selection.

opens, closes

Reason — During atrial systole the atria contract and push blood into the ventricles, so the tricuspid and bicuspid valves open. The semilunar valves at the base of the pulmonary artery and aorta remain closed at this stage to prevent blood from flowing back into the ventricles.

Hypotonic, Endosmosis

Reason — The pudding around the raisins has a lower solute concentration than the cell sap of the dried raisins, so it is hypotonic to them. Water therefore moves into the raisins through their semi-permeable membranes by endosmosis and they swell up.

Telophase

Reason — Telophase is essentially the reverse of prophase. The chromosomes reach the poles and uncoil, the nucleolus reappears and a new nuclear membrane is formed around each group of chromosomes.

Cerebellum

Reason — The cerebellum maintains posture, equilibrium and muscle tone and coordinates voluntary muscular movements. Under the influence of alcohol the cerebellum cannot coordinate these movements, so balance and walking are affected.

Q and S

Reason — Diabetes insipidus is caused by the hyposecretion of ADH (vasopressin). As very little water is reabsorbed, the patient passes frequent and copious urine and consequently suffers from excessive thirst. No glucose is lost in the urine of such patients.

(A) is false and (R) is true.

Reason — Transpiration adds water vapour to the air and therefore increases the moisture of the atmosphere, so (A) is false. It is because of this large-scale loss of water vapour that a dense forest raises the humidity of the region and helps in bringing rainfall, so (R) is true.

(a) Haemoglobin

(b) Portal veins (e.g. hepatic portal vein)

(c) Cornea

(d) Meninges

(e) Hydathodes (water stomata)

The outer ear consists of the projecting part (a) pinna and the passage auditory canal leading to the (b) tympanum. The middle ear contains three bones and a (c) eustachian tube which connects the cavity of the middle ear with the throat. The three bones are collectively called the (d) ossicles. The inner ear has three parts. One of them is spiral-shaped and looks like a snail shell which is called the (e) cochlea.

(a) Odd one — Mitochondria. The others are parts of the hereditary material (chromosome and DNA).

(b) Odd one — Bile. The others are nitrogenous excretory wastes.

(c) Odd one — Pulmonary artery. The others are arteries carrying oxygenated blood.

(d) Odd one — Starch. The others are small, diffusible substances which can pass through a semi-permeable membrane.

(e) Odd one — Heart. The others are excretory organs of the human body.

(a) Transpiration

(b) Water loss occurs mainly from the leaves, through the stomata.

(c) The loss of water vapour from the leaves creates a suction force called transpiration pull. This pull draws a continuous column of water upwards through the xylem from the roots to the leaves, bringing about the ascent of sap.

(d) High temperature.

(e) If transpiration stops, the transpiration pull will be lost and the upward conduction of water and dissolved minerals will slow down. The plant will also not be able to cool itself, and excess water in the plant may be given out as droplets by guttation.

Pituitary gland – (d) secretes vasopressin

Adrenal glands – (e) secretes adrenaline

Pancreas – (b) secretes glucagon

Ovaries – (c) secretes oestrogen

Testicles – (a) secretes testosterone

Mutation is a sudden random change in the genetic material of a cell that may cause it to differ in appearance or behaviour from the normal type.

(a) 50% of their sons will be colour blind. The mother gives either X^o or X, while the father gives Y to all sons, so half the sons are X^oY (colour blind) and half are XY (normal).

(b) Yes. The father passes X^o to every daughter, so a daughter who receives X^o from the mother will be X^oX^o and colour blind, and a daughter who receives X from the mother will be XX^o and a carrier. Therefore half the daughters will be colour blind and half will be carriers.

(a) Scrotum — It is a pouch of skin that holds the testes outside the abdominal cavity and keeps them at a temperature about 2°C lower than the body temperature, which is necessary for the production of sperms.

(b) Epididymis — It is a highly coiled tube in which the spermatids mature into functional spermatozoa. It also serves as a temporary storage site for the sperms.

(a) It is natural (inborn) reflex action, as it is an automatic protective response which is not learnt.

(b) Medulla oblongata

(c) Ear

Law of dominance states that when a pair of contrasting characters is present together, only one of them is able to express itself in the F₁ generation while the other remains suppressed. The character that is expressed is called the dominant character and the suppressed one is called the recessive character.

(a) TSH — Thyroid Stimulating Hormone

(b) CNG — Compressed Natural Gas

In summer a large amount of water is lost from the body as sweat, in order to keep the body temperature normal.
To make up for this loss, the kidneys reabsorb more water from the filtrate. As a result less urine is formed, we urinate fewer times, and the urine that is passed is more concentrated or thicker.

The cell organelle responsible for photosynthesis is the chloroplast. Below diagram shows the structure of a chloroplast with its parts labelled:

Parturition is the childbirth in viviparous mammals, i.e. the expulsion of the fully developed young one from the uterus of the mother at the end of the gestation period. In humans it occurs after about 280 days and is brought about by labour pains caused by the contraction of the uterine wall.

(a) Guttation

(b) Hydathodes (water stomata)

Two objectives of Swachh Bharat Abhiyan are:

1. To eliminate open defecation: The mission aims to ensure that all households have access to toilets and promote the construction and use of sanitary latrines.
2. To promote cleanliness and hygiene: It seeks to create awareness about sanitation and cleanliness practices, improve waste management systems, and maintain cleanliness in public spaces.

(a) Abscisic acid — It acts as a growth inhibitor. It prevents or slows down seed germination, causes closure of stomata and promotes the abscission of leaves, flowers and fruits. It also increases the tolerence of plants to various kinds of stresses. Therefore it is also called the "stress harmone".

(b) Gibberellins — They bring about elongation of the internodes of the stem, overcome genetic dwarfism in plants and help in breaking the dormancy of seeds and buds.

(a) Myopia (short-sightedness or near-sightedness)

(b) The image of a distant object is formed in front of the retina, either because the eyeball has become elongated from front to back or because the lens has become too convex.

(c) Concave lens

Birth rate, also called natality, is the number of births per 1000 individuals in a population per year.

Two differences between Fraternal twins and Identical twins are:

The phenomenon taking place is osmosis, more precisely endosmosis.
Osmosis is the net movement of water molecules from a region of their higher concentration to a region of their lower concentration through a semi-permeable membrane. Here water from the beaker passes through the cellophane paper into the sugar solution, so the level in the thistle funnel rises.

(a) A rubber sheet is impermeable, so water molecules cannot pass through it. No osmosis will take place and the level of the sugar solution in the thistle funnel will not rise.

(b) A muslin cloth is freely permeable, so both water and sugar molecules can pass through it in either direction. Osmosis will not take place; the sugar solution will simply diffuse out into the beaker and the level in the thistle funnel will not rise.

(a) All the plants of the F₁ generation bear red flowers, as red is dominant over white.

(b) The monohybrid phenotypic ratio of the F₂ generation is 3 red : 1 white, i.e. 3 : 1.

(c) The genotypes obtained in the F₂ generation are RR, Rr and rr in the ratio 1 : 2 : 1.

Fertilisation is the fusion of a haploid male gamete (sperm) with a haploid female gamete (ovum) to form a diploid cell called the zygote. In human beings fertilisation is internal and usually takes place in the ampulla of the fallopian tube.

(a) Epididymis

(b) In the epididymis the spermatids mature into functional spermatozoa. It also acts as a temporary storage site for the sperms before they pass into the vas deferens.

Two vestigial organs found in humans are:

1. Vermiform appendix
2. Wisdom teeth

(a) Corn → Rat → Fox → Eagle

(b) Nectar → Bee → Lizard → Crow

Below diagram shows the anaphase stage of mitosis in an animal cell having 4 chromosomes, with all the parts labelled:

There are 12 pairs of cranial nerves in a man.

(a) A is the cerebellum.

(b) The cerebellum maintains posture, equilibrium and muscle tone of the body, and coordinates the voluntary muscular movements initiated by the cerebrum.

The two main processes in urine formation are:

1. Ultrafiltration — In the glomerulus the blood is filtered under pressure, so that water, mineral salts, glucose, amino acids and nitrogenous wastes pass into the Bowman's capsule while blood cells and large molecules like proteins are retained.
2. Selective reabsorption — As the filtrate passes along the renal tubule, useful materials such as most of the water, all the glucose and amino acids and some mineral salts are taken back into the surrounding blood capillaries.

(a) Amniotic fluid is present inside the amnion, the sac which surrounds and encloses the developing embryo in the uterus.

(b) Fovea centralis, also called the yellow spot, is present on the retina of the eye, directly behind the centre of the lens along the visual axis.

(a) Air pollution

(b) Smog is a thick haze formed near the ground when smoke and other particulate pollutants of the air mix with fog. It reduces visibility and causes breathing problems.

(c) Carbon monoxide (CO)

Erythropenia

Reason — Erythropenia refers to an abnormally low number of red blood cells (RBCs) in the blood.

Ethylene

Reason — Ethylene is a gaseous plant hormone that promotes the ripening of fruits. Ripe mangoes release ethylene, which speeds up ripening in nearby unripe mangoes.

Both (A) and (R) are true and (R) is the correct explanation of (A).

Reason — Photolysis occurs in the thylakoid membranes during the light-dependent stage, producing oxygen.

Adrenaline

Reason — Adrenaline is the stress hormone secreted by the adrenal glands. It prepares the body for "fight or flight" during stressful situations. It increases heart rate, blood pressure, and energy supply.

Phagocytosis

Reason — Neutrophils are a type of white blood cell. Their main function is to engulf and destroy pathogens like bacteria (phagocytosis).

(A) is true and (R) is false.

Reason — The pituitary gland is called the master gland because it controls the activity of many other endocrine glands.
The pituitary gland does not regulate exocrine glands (which have ducts and secrete substances like sweat or saliva). It regulates endocrine glands ( which are ductless like the thyroid, adrenal, etc.).

Adaptation of eyes

Reason — Adaptation of eyes is the ability of the eyes to adjust to changes in light intensity.

Require no conscious thought, allowing rapid responses.

Reason — Reflex actions are automatic and quick responses to stimuli. They bypass the brain's conscious areas, allowing the body to react rapidly, which is necessary for survival (e.g., pulling your hand away from something hot).

In polluted areas, became darker in colour for better camouflage.

Reason — Industrial melanism means moths in polluted areas became darker to blend in better and avoid predators.

Progesterone

Reason — Progesterone maintains the thickened lining of the uterus (endometrium) during pregnancy. This helps support and nourish the developing embryo.

Menarche

Reason — Menarche refers to the first occurrence of menstruation in girls, marking the onset of puberty and reproductive maturity.

22 pairs of autosomes, 1 pair of allosome

Reason — Humans have 23 pairs of chromosomes in total. 22 pairs are autosomes (non-sex chromosomes). 1 pair is allosomes (sex chromosomes — X and Y). So, the human cell contains 22 pairs of autosomes and 1 pair of allosomes.

Tool making, Agricultural, Scientific and Industrial

Reason — Early humans started making tools, improving survival. Farming began, leading to food surplus and population growth. Advances in science and industry boosted living standards and population further.

R, P, S, Q

Reason

R – Menstrual Phase: Day 1 to about Day 5.
P – Follicular Phase: After menstruation, roughly Day 5 to Day 12.
S – Ovulatory Phase: Around Day 13 or 14 (when ovulation occurs).
Q – Luteal Phase: After ovulation, Day 15 to Day 28.

(a) Smog

(b) Endometrium

(c) Root pressure

(d) Stroma

(e) Cerebrospinal fluid (CSF)

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

(a) Odd term — Oxygen
Category of the remaining terms — Air Pollutants.

(b) Odd term — Pons
Category of the remaining terms — Plant tissues.

(c) Odd term — Malleus
Category of the remaining terms — Parts of outer ear.

(d) Odd term — Uterus
Category of the remaining terms — Parts of Excretory system.

(e) Odd term — Root hairs
Category of remaining terms — Structures involved in transpiration in plants.

(a) Tears.

(b) Cone cells.

(c) Optic nerve.

(d) Iris.

(e) Pupil.

(a) Secrete Testosterone – Interstitial cells (Leydig cells)

(b) Transports sperms to Epididymis – Efferent ducts

(c) Stores sperms till maturation – Epididymis

(d) Transport sperms to urethra – Vas deferens

(e) Produce sperms – Seminiferous tubules

It is the first occurrence of menstruation in a human female, marking the onset of puberty and the beginning of her reproductive life. It usually occurs between the ages of 10 to 15 years.

Transpiration — Water is lost in the form of water vapour through stomata.

Guttation — Water is lost in the form of liquid droplets from the tips or edges of leaves through hydathodes.

(a) Cerebrum

(b) Cerebellum

(a) Cell membrane — Semipermeable

(b) Cell wall — Freely permeable

Excretion is the biological process by which harmful nitrogenous waste products are removed from the body.

Diabetes mellitus occurs due to hyposecretion of insulin whereas Diabetes insipidus occurs due to hyposecretion of Antidiuretic hormone (ADH).

Common name — Garden pea

Scientific name — Pisum sativum

Endosmosis occurs when a cell is placed in a hypotonic solution.

Exosmosis occurs when a cell is placed in a hypertonic solution.

(a) Abscisic acid, Ethylene

(b) Auxin

(c) Pea plant

Non-biodegradable wastes are substances that cannot be broken down naturally by microorganisms (like bacteria or fungi) into harmless products. These wastes persist in the environment for a long time and can cause pollution. E.g., Plastics.

1. To eliminate open defecation by constructing toilets and promoting sanitation practices in both rural and urban areas.
2. To promote proper solid waste management through the collection, segregation, and disposal of garbage to keep surroundings clean.

(a) Algae, Mosquito larvae, Small fish, Penguin, Seal.

(b) Cabbage, Caterpillar, Wood pecker, Fox, Mountain lion.

Cranial nerves: – 12 pairs

Spinal nerves: – 31 pairs

(a) The green parts of the variegated leaf will turn blue-black because they contain chlorophyll and can produce starch.

(b) It shows that chlorophyll is essential for photosynthesis because only the parts with chlorophyll produce starch (which turns blue-black with iodine).

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

Law of Dominance — Out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed. The one that expresses is the dominant character and the one that is unexpressed is the recessive one.

(a) More atmospheric humidity — Transpiration rate decreases.

(b) Hot and dry air — Transpiration rate increases.

(a) ACTH — Adreno Cortico Tropic Hormone

(b) ADH — Antidiuretic Hormone

The part of the ear that equalizes air pressure on either side of the eardrum is the Eustachian tube.
It is located in the middle ear.

(a) The genotypes of the parent plants that Santosh originally planted were heterozygous dominant (Rr).
Since all plants in the first generation (F1) had round seeds, the parents must have been pure round-seeded (RR) and wrinkled-seeded (rr) plants. Crossing RR (round, homozygous dominant) × rr (wrinkled, homozygous recessive) produces all Rr (heterozygous round) plants in F1.

(b) Round seeds are dominant over wrinkled seeds, because the F1 plants (Rr) all show the round seed phenotype.

(c) 1:2:1

Natality (or birth rate) is the number of live births per 1000 people of population per year.

Sympathetic system increases heartbeat whereas Parasympathetic system decreases heartbeat and makes it normal.

(a) Transpiration

(b) Transpiration is the loss of water in the form of water vapour from the aerial parts (mainly leaves) of a plant.

Glomerulus — Cortex (outer region) of the kidney.

Henle's loop — Medulla (inner region) of the kidney.

Ozone layer depletion allows more harmful UV rays from the sun to reach Earth. This causes skin cancer, cataract, and weakens the immune system in humans. It also harms plants, animals, and marine life and reduces crop yields.

Two body features of Australopithecus are:

1. Projecting eyebrow ridges.
2. Absence of chin.

Identical twins are formed when a single fertilized egg (zygote) splits into two embryos. Since they come from the same egg and sperm, they have exactly the same genetic material, including the sex chromosomes.

Inserting sharp objects into the ear can damage the delicate eardrum or ear canal, causing pain, infection, or even permanent hearing loss. It can also push the earwax deeper, making the problem worse

(a) Phototropism

(b) Roots grow downward due to positive geotropism. They grow towards the gravitational pull to anchor the plant and absorb water and minerals from the soil.

(c) Auxins

Natality

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

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.

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.

Oxytocin

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

(a) Graafian follicle

(b) Cuticle

(c) Stapes

(d) Photosynthesis

(e) Peppered moth (Biston betularia)

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.

(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.

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.

(a) Inguinal canal

(b) Medulla oblongata

(c) Pinna

(d) Centromere

(e) Guard cells

(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.

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

(a) Gibberellins

(b) Parthenocarpy

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

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

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.

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.

(a) Neutrophils

(b) Lymphocytes

(c) Snake

(d) Hawk

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.

(a) Absorption of water

(b) Transportation of water

(c) Transpiration

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.

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.

(a) The semicircular canals.

(b) Dynamic balance.

Below labelled diagram shows that oxygen is released during photosynthesis:

Hydathodes are located at the tips or edges of leaves.

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’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.

(a) Lens

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

The labelled diagram is shown below:

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

(a) Improved healthcare and medical facilities.

(b) Freshwater

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

(a) CFC – Chlorofluorocarbon

(b) CNG – Compressed Natural Gas

(a) Brain

(b) Meninges

(c) Sympathetic nervous system

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

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.

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

(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.

Deplasmolysis

Reason — Deplasmolysis is the process where a plasmolysed cell (shrunken due to water loss) gains water through endosmosis, causing the cell membrane to return to its normal position close to the cell wall.

Sneezing

Reason — Sneezing is a natural (inborn) reflex that occurs automatically in response to irritation in the nasal passages. It doesn’t require learning or conscious effort.

50%

Reason — A mother always gives an X chromosome, and the father can give either X or Y. If the father gives X, the child is a girl (XX). If he gives Y, the child is a boy (XY).
So, there's a 50% chance of having a daughter.

Both (A) and (R) are true.

Reason — Veins from the intestines do not open directly into the inferior vena cava. Instead, they join to form the hepatic portal vein, which first carries nutrient-rich blood to the liver for processing before it enters the general circulation.

Centrosome

Reason — Nerve cell lack a centrosome, which is why neurons cannot divide.

46, 46

Reason — Somatic cells are body cells and have a diploid number of chromosomes, which is 46 in humans. During mitosis, the cell divides to form two identical daughter cells, each with the same number of chromosomes as the parent cell. The number of chromosomes before and after mitosis remains 46.

Ammonia

Reason — Urea, uric acid, and creatinine are organic nitrogenous wastes. Ammonia is an inorganic compound. Although most ammonia is converted to urea in the liver, a small amount is excreted unchanged in urine.

(A) is false and (R) is true.

Reason — It was Gregor Mendel, not Darwin, who conducted genetic experiments using pea plants. Also, pea plants are bisexual, they have both male and female reproductive organs in the same flower.

2, 3 and 4

Reason — Water is mainly reabsorbed in the proximal convoluted tubule, loop of Henle, and distal convoluted tubule of the nephron to help the body save water and prevent dehydration. The glomerulus only filters blood, it doesn't reabsorb water.

Crossing over

Reason — Crossing over (exchange of genetic material between homologous chromosomes) occurs only in meiosis, increasing genetic variation.

(A) is true and (R) is false.

Reason — The bicuspid (mitral) valve separates the left atrium and left ventricle, not the tricuspid valve. The tricuspid valve is between the right atrium and right ventricle.

Increased leaf surface area

Reason — Desert plants have small or fewer leaves to reduce water loss. Increasing leaf surface area would cause more water to evaporate, so they do not have this adaptation.

Both (A) and (R) are true.

Reason — Pesticides and insecticides don’t break down easily and can wash into water sources, causing pollution.

Glomerulus

Reason — Ultrafiltration happens in the glomerulus, where blood is filtered to form the filtrate that enters the nephron.

P and R

Reason

P is correct — Night blindness is caused by Vitamin A deficiency.

Q is incorrect — Utriculus helps in static balance, not dynamic.

R is correct — A neuron is a single nerve cell.

S is incorrect — Fossil fuels are exhaustible, not inexhaustible.

(a) Leydig cells

(b) Amniotic fluid

(c) Swachh Bharat Abhiyan

(d) Auxin

(e) Organ of Corti

Pieces of dried (a) cobalt chloride paper are fixed to the two surfaces of a leaf. The leaf should remain attached to the plant. The plant is exposed to bright sunlight for a few hours. The colour of the paper on the lower surface of the leaf turns (b) pink faster than the one on the upper surface. This proves that more (c) transpiration occurs from the (d) lower surface of the leaf as it has a greater number of (e) stomata.

(a) Menstrual phase, Follicular phase, Ovulatory phase, Luteal phase.

(b) Auditory canal, Ear ossicles, Oval window, Cochlea.

(c) Eyeball, Sclera, Choroid, Retina.

(d) Artery, Arterioles, Capillaries, Vein.

(e) Ovulation, Fertilisation, Implantation, Parturition.

(a) → (5)

(b) → (3)

(c) → (4)

(d) → (2)

(e) → (1)

Explanation

(a) is Hypothalamus its function is to (5) Control body temperature and pituitary.

(b) is Medulla oblongata its function is to (3) Control the activities of the internal organs.

(c) is Thalamus its function is to (4) Relay pain and pressure impulse to cerebrum.

(d) is Cerebellum its function is to (2) Maintain body balance.

(e) is Cerebrum its function is the (1) Seat of intelligence.

Umbilical cord

(a) The fibres which hold the lens of the eye in position.

(b) The cells of the islets of Langerhans that secrete the hormone glucagon.

(c) The part of the chloroplast where the light independent phase occurs.

(d) Cap like structure seen around the head of the human sperm.

(e) The glands located at the upper sideward portion of the orbit of eye.

(a) Suspensory ligaments

(b) Alpha cells

(c) Stroma

(d) Acrosome

(e) Lacrimal glands

Thyroxine

The two hormones secreted by Corpus luteum are:

1. Progesterone
2. Oestrogen

Phytohormones are chemical substances produced in plants that regulate growth, development, and responses to stimuli.
Example of a growth-retarding hormone: Abscisic acid (ABA). It slows down growth and promotes dormancy in seeds and buds.

(a) Guttation

(b) Guttation is the process by which water droplets are exuded from the edges or tips of leaves through special pores called hydathodes, usually during the early morning or at night.

(c) Guttation occurs when root pressure is high and transpiration is low, especially at night, pushing out extra water through special pores called hydathodes.

Gestation is the period between fertilisation and birth during which the embryo develops inside the uterus of the mother. In humans, the gestation period is about 9 months (approximately 280 days).

(a) ACTH - Adrenocorticotropic Hormone

(b) ABA - Abscisic Acid

When rainwater flooded the godown, the dry food grains soaked up water due to imbibition and swelled.
The swollen grains pressed hard on the walls, creating high pressure, which caused the walls to crack.

(a) When Haemoglobin combines with carbon monoxide, it forms Carboxyhaemoglobin.

(b) When Haemoglobin combines with oxygen, it forms Oxyhaemoglobin.

(a) Photosynthesis performed by the trees in the Amazon rain forest absorbs carbon dioxide and releases oxygen, which helps maintain atmospheric oxygen levels. This process supports life on Earth, earning it the name ‘Lungs of the Earth’.

(b) Deforestation reduces the number of trees, leading to less carbon dioxide being absorbed and more oxygen being depleted. It causes soil erosion, loss of biodiversity, and contributes to global warming and climate change.

(c) Chlorophyll.

Ravi is suffering from Haemophilia.

(a) The odd term is Meninges.

(b) The other terms belong to parts or structures of a nerve cell (neuron).

(a) Renal arteries.

(b) Nephrons

(a) Divya boiled the leaf in water to kill the cells of the leaf and stop all chemical reactions.

(b) She then boiled the leaf in methylated spirit to remove chlorophyll, making the leaf decolorized so the starch test colour change is clearly visible.

Below diagram shows the stomatal apparatus found in the epidermis of leaves with all the different parts labelled:

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

(a) Eardrum (Tympanic membrane)

(b) Eustachian tube

(a) Lamarck proposed the theory of ‘Use and Disuse’ of organs.

(b) Meningitis is the inflammation of meninges.

(b) The child is a boy (male), because only males have XY chromosomes, and the recessive allele on the X chromosome leads to colourblindness in males.

(a) Fraternal twins

(b) Dizygotic twins

(c) Lalit (boy): XY, Leela (girl): XX

Endometrium

Two characteristic features of Neanderthal Man are:

1. Cranial Capacity — Neanderthal Man had a cranial capacity of about 1450 cm³
2. Development of Chin — Strong lower jaw with almost no chin.