ICSE Class 10 Biology Board Exam Question Paper 2024 with Solutions

ICSE Class 10 Biology Board Exam Question Paper with Solutions

SECTION - A (40 Marks)

Attempt all questions from this Section.

Question 1. Select the correct answers to the questions from the given options. (Do not copy the questions, write the correct answer only). [15 Marks]

1.1. Duplicated chromosomes are joined at a point termed ______. [1 Mark]
1. Centrosome
2. Centromere
3. Centriole
4. Chromatid

Answer: (2) Centromere

Until they split during cell division, the centromere holds sister chromatids together.

Teacher's Note:
a) Know the distinction between centromere (joining point of chromatids), centrosome (organelle containing centrioles), and centriole (cylindrical organelle involved in spindle formation).
b) Do not confuse centromere with chromatid, which refers to the individual strands of a replicated chromosome.

1.2. The process of conversion of ADP to ATP during photosynthesis is called ______. [1 Mark]
1. Photolysis
2. Phagocytosis
3. Photophosphorylation
4. Polymerisation

Answer: (3) Photophosphorylation

Light energy drives the addition of a phosphate group to ADP, creating ATP during the light-dependent reaction.

Teacher's Note:
a) Photophosphorylation occurs in the grana (thylakoids) of chloroplasts.
b) Remember that photolysis refers to the splitting of water molecules using light energy, not ATP synthesis.

1.3. The process in which water is lost from the margins of strawberry leaves is ______. [1 Mark]
1. Osmosis
2. Imbibition
3. Diffusion
4. Guttation

Answer: (4) Guttation

Guttation is the exudation of liquid water droplets from specialized pores called hydathodes, typically at leaf margins.

Teacher's Note:
a) Guttation happens under conditions of high root pressure and low transpiration, usually in early mornings.
b) Students often confuse guttation with transpiration; note that guttation releases liquid water, whereas transpiration releases water vapor.

1.4. The hormone that affects urination is ______. [1 Mark]
1. Adrenaline
2. Vasopressin
3. Oestrogen
4. Thyroxine

Answer: (2) Vasopressin

Vasopressin, also known as Antidiuretic Hormone (ADH), promotes water reabsorption in the kidney tubules, reducing urine volume.

Teacher's Note:
a) ADH is secreted by the posterior lobe of the pituitary gland.
b) Deficiency of ADH causes diabetes insipidus, characterized by excessive urination (polyuria).

1.5. Which one of the following helps in the opening of stomata? [1 Mark]
1. Cobalt ions
2. Potassium ions
3. Magnesium ions
4. Aluminium ions

Answer: (2) Potassium ions

An influx of potassium ions into the guard cells increases their osmotic pressure, causing water to enter and the stomatal pore to open.

Teacher's Note:
a) Potassium ion concentration changes are central to the active potassium ion transport theory of stomatal movement.
b) Ensure you mention both K+ ion influx and endosmosis when explaining stomatal opening in descriptive questions.

1.6. A zygote which has Y chromosome inherited from the father will develop into a ______. [1 Mark]
1. Will depend on the chromosome inherited from the mother
2. Girl
3. Either boy or a girl
4. Boy

Answer: (4) Boy

The mother always contributes an X chromosome. Therefore, an XY combination results in a male child.

Teacher's Note:
a) Sex determination in humans is solely dependent on the sperm chromosome (X or Y) fertilizing the egg.
b) Remember that females are homogametic (XX) and males are heterogametic (XY).

1.7. The ear ossicle that transports sound vibrations to the inner ear: [1 Mark]
1. Stapes
2. Mal
3. Incus
4. Cochlea

Answer: (1) Stapes

The stapes (stirrup) is the final ear ossicle in the chain, transmitting vibrations directly to the oval window of the inner ear.

Teacher's Note:
a) The sequence of ear ossicles from outside to inside is Malleus, Incus, and Stapes.
b) Note that options like cochlea are parts of the inner ear, not ossicles.

1.8. If a person has a heart attack, what must be done immediately? [1 Mark]
P. Loosen his/her clothing
Q. Make him/her lie down in an airy room
R. Rush him/her to the hospital
S. Engage him/her in a conversation
1. P and Q
2. P and S
3. R and S
4. P, Q and R

Answer: (4) P, Q and R

Immediate first aid for a heart attack involves loosening clothes for breathing comfort, providing ventilation, and seeking urgent medical help while avoiding exertion or stressful conversations.

Teacher's Note:
a) Keeping the patient calm and providing adequate oxygen is critical during a cardiac emergency.
b) Conversing or panicking increases stress and heart rate, making option S incorrect.

1.9. Adjusting the focal length of the eye lens to view objects at different distances is done by ______. [1 Mark]
1. Cornea
2. Iris
3. Ciliary muscles
4. Sclera

Answer: (3) Ciliary muscles

Contraction and relaxation of the ciliary muscles alter the curvature and focal length of the crystalline lens, enabling accommodation.

Teacher's Note:
a) This process of focusing on objects at varying distances is called accommodation.
b) Do not confuse the function of ciliary muscles with the iris, which regulates the amount of light entering the eye by adjusting pupil size.

1.10. Four friends P, Q, R and S were discussing the examples of genetic disorders. The examples they quoted were as follows: [1 Mark]
P. Colour blindness and Malaria
Q. Albinism and Cholera
R. Haemophilia and Colour blindness
S. Haemophilia and Albinism
Who gave the correct examples?
1. P and Q
2. R and S
3. P and R
4. Q and S

Answer: (2) R and S

Haemophilia, colour blindness, and albinism are inherited genetic disorders, whereas malaria and cholera are infectious, acquired diseases.

Teacher's Note:
a) Genetic disorders are caused by abnormalities in genes or chromosomes.
b) Always distinguish between congenital/genetic disorders and infectious/acquired diseases.

1.11. Osmosis takes place when there is ______. [1 Mark]
1. A freely permeable membrane
2. A cell wall
3. A selectively permeable membrane
4. An impermeable membrane

Answer: (3) A selectively permeable membrane

Osmosis is the net movement of solvent molecules across a selectively permeable membrane from a region of lower solute concentration to higher solute concentration.

Teacher's Note:
a) A selectively permeable membrane permits the passage of solvent molecules while restricting certain solute particles.
b) Cell walls are freely permeable and do not regulate osmosis directly; plasma membranes act as selectively permeable boundaries.

1.12. A male gorilla has 48 chromosomes in each of its body cells. How many chromosomes will each of the sperms have? [1 Mark]
1. 24
2. 48
3. 17
4. 16

Answer: (1) 24

Sperms are haploid gametes produced by meiosis, containing half the somatic chromosome number (48 / 2 = 24).

Teacher's Note:
a) Somatic cells are diploid (2n), while gametes are haploid (n).
b) Always check whether the question asks for somatic cells or gametes before halving or doubling chromosome numbers.

1.13. Assertion (A): Sympathetic nervous system prepares the body for violent action against abnormal conditions. [1 Mark]
Reason (R): Sympathetic nervous system accelerates heartbeat.
Which of the following is correct?
1. Both A and R are True.
2. A is True, R is False.
3. A is False but R is True.
4. Both A and R are False.

Answer: (1) Both A and R are True.

The sympathetic nervous system mediates the fight-or-flight response, raising heart rate and preparing the body for stressful or emergency actions.

Teacher's Note:
a) The sympathetic system acts antagonistically to the parasympathetic nervous system.
b) Ensure you connect physiological responses like increased heart rate directly to emergency preparation.

1.14. Birth rate is the number of live births per thousand persons in ______. [1 Mark]
1. 1 year
2. 2 years
3. 10 years
4. 20 years

Answer: (1) 1 year

Birth rate (natality) is expressed as the number of live births per 1,000 individuals in a population per year.

Teacher's Note:
a) Population growth parameters like birth rate and death rate are calculated annually per thousand individuals.
b) Precise definitions of demographic terms are frequent in board exams.

1.15. Industrial melanism was observed in ______. [1 Mark]
1. Mice
2. Peppered Moth
3. House Flies
4. Crow

Answer: (2) Peppered Moth

Industrial melanism in the peppered moth (*Biston betularia*) is a classic textbook example of natural selection driven by environmental pollution.

Teacher's Note:
a) Dark-colored moths (melanic forms) survived better on soot-covered trees during the Industrial Revolution.
b) Be familiar with evolutionary examples illustrating natural selection and adaptation.

Question 2. [15 Marks]

2.1.a. Name the following: Unicellular outgrowths from the epidermis of roots. [1 Mark]

Answer: Root hair.

Teacher's Note:
a) Root hairs significantly increase the surface area for water and mineral absorption.
b) Specify that they are unicellular extensions of epidermal cells.

2.1.b. Name the following: A defect in our eyes in which some parts of the object are in focus while the other parts are blurred. [1 Mark]

Answer: Astigmatism.

Teacher's Note:
a) Astigmatism is caused by uneven curvature of the cornea or lens.
b) It is corrected using cylindrical lenses.

2.1.c. Name the following: The tropic movement of plant parts in response to chemicals. [1 Mark]

Answer: Chemotropism.

Teacher's Note:
a) Growth of pollen tubes toward the ovule is a prime example of positive chemotropism.
b) Ensure correct spellings of biological terms like chemotropism and thigmotropism.

2.1.d. Name the following: The main nitrogenous waste formed in the body. [1 Mark]

Answer: Urea.

Teacher's Note:
a) Urea is synthesized in the liver via the ornithine cycle from excess amino acids.
b) It is excreted primarily by the kidneys through urine formation.

2.1.e. Name the following: The process of attachment of fertilized ovum to the uterine wall. [1 Mark]

Answer: Implantation.

Teacher's Note:
a) Implantation marks the beginning of pregnancy.
b) It occurs about a week after fertilization when the blastocyst embeds in the endometrium.

2.2.a. Arrange and rewrite the terms in group in correct order to be in a logical sequence, beginning with the term that is underlined: Australopithecus, Cro-Magnon, Homo erectus, Neanderthal man. [1 Mark]

Answer: Australopithecus, Homo erectus, Neanderthal man, Cro-Magnon.

Teacher's Note:
a) This sequence represents human evolutionary stages from early hominids to modern humans.
b) Always follow the starting underlined term precisely as instructed in the question.

2.2.b. Arrange and rewrite the term in group in correct order to be in a logical sequence, beginning with the term that is underlined: Pupil, Aqueous humour, Retina, Vitreous humour. [1 Mark]

Answer: Aqueous humour, Pupil, Vitreous humour, Retina.

Teacher's Note:
a) This is the pathway of light travel and the anatomical arrangement from anterior to posterior in the eyeball.
b) Check the exact starting term given in the paper.

2.2.c. Arrange and rewrite the terms in group in the correct order to be in a logical sequence, beginning with the term that is underlined: Effector, Receptor, Motor neuron, Sensory neuron. [1 Mark]

Answer: Receptor, Sensory neuron, Motor neuron, Effector.

Teacher's Note:
a) Note that the underlined term in the question paper is Effector, but the logical sequence must begin with Receptor as per reflex arc pathway.
b)

2.2.d. Arrange and rewrite the terms in group in correct order to be in a logical sequence, beginning with the term that is underlined: Loop of Henle, Distal convoluted tubule, Bowman's Capsule, Proximal convoluted tubule. [1 Mark]

Answer: Bowman's capsule, Proximal convoluted tubule, Loop of Henle, Distal convoluted tubule.

Teacher's Note:
a) This represents the sequential flow of filtrate through a nephron.
b) Students must remember the correct anatomical order regardless of the underlined term prompt.

2.2.e. Arrange and rewrite the terms in group in correct order to be in a logical sequence, beginning with the term that is underlined: Water vapour, Soil water, Leaves, Ascent of Sap. [1 Mark]

Answer: Soil water, Ascent of sap, Leaves, Water vapour.

Teacher's Note:
a) This traces the pathway of water movement through a plant from absorption to transpiration.
b) Logical sequencing questions test comprehensive process understanding.

2.3. Study the diagram given below and fill in the blanks with suitable words:
In order to prove that carbon dioxide is necessary for (a) ______, a potted plant is placed in dark for 48 hours to (b) ______ the leaves. A part of a leaf is inserted into a conical flask containing potassium hydroxide solution. This is to absorb (c) ______ from the flask. The plant is then placed in sunlight for a few hours. The experimental leaf is tested for starch. The part of the leaf that was inside the conical flask turns (d) ______, whereas the part of the left outside turns (e) ______ in colour. [5 Marks]

[Figure: Experimental setup showing a potted plant with a leaf partially inserted into a wide-mouth glass bottle/conical flask containing potassium hydroxide (KOH) solution and sealed with a split cork]

Answer:
(a) Photosynthesis
(b) destarch
(c) carbon dioxide
(d) colourless (or brown/iodine color)
(e) blue-black

Teacher's Note:
a) Potassium hydroxide (KOH) absorbs carbon dioxide, proving its necessity for starch formation during photosynthesis.
b) Iodine test turns blue-black in the presence of starch and remains brown/colourless where starch is absent.

2.4.a. Select the odd one from the following: Prothrombin, Thrombin, Fibrinogen, Albumin. [1 Mark]

Answer: Albumin.

Teacher's Note:
a) Prothrombin, thrombin, and fibrinogen are blood clotting factors.
b) Albumin is a plasma protein responsible for maintaining osmotic pressure.

2.4.b. Choose the odd one out from the following terms and name the category to which the others belong: Tonsils, Glomerulus, Spleen, Lymph nodes. [1 Mark]

Answer: Glomerulus.
Category: Lymphoid organs / Lymph nodes in the human body.

Teacher's Note:
a) Glomerulus is a capillary tuft in the nephron of the kidney.
b) Tonsils, spleen, and lymph nodes are parts of the lymphatic and immune system.

2.4.c. Choose the odd one out from the following terms and name the category to which the others belong: Neutrophils, Basophils, Monocytes, Eosinophils. [1 Mark]

Answer: Monocytes.
Category: Granulocytes (white blood cells).

Teacher's Note:
a) Neutrophils, basophils, and eosinophils are granulocytes containing cytoplasmic granules.
b) Monocytes are agranulocytes.

2.4.d. Choose the odd one out from the following terms and name the category to which the others belong: Leaves, Styrofoam, Grass, Cow Dung. [1 Mark]

Answer: Styrofoam.
Category: Biodegradable substances / wastes.

Teacher's Note:
a) Styrofoam is a synthetic, non-biodegradable polymer.
b) Leaves, grass, and cow dung are natural organic waste materials that decompose easily.

2.4.e. Choose the odd one out from the following terms and name the category to which the others belong: Pulmonary artery, Renal artery, Coronary artery, Hepatic artery. [1 Mark]

Answer: Pulmonary artery.
Category: Arteries carrying oxygenated blood.

Teacher's Note:
a) The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs.
b) Renal, coronary, and hepatic arteries supply oxygenated blood to the kidneys, heart muscle, and liver respectively.

2.5. Match the items given in Column I with the most appropriate ones in Column II and rewrite the correct matching pairs: [5 Marks]

Answer:
(a) Leydig Cells - 3. Testosterone
(b) Stoma - 4. Diffusion of respiratory gases
(c) Ova - 5. Haploid cells
(d) Cranial nerve - 2. 12 pairs
(e) Cretinism - 1. Lack of thyroxine in children

Teacher's Note:
a) Match items accurately based on physiological and anatomical functions.
b) Rewrite the matched pairs clearly in the final answer script.

SECTION - B (40 Marks)

Attempt any four questions from this Section.

Question 3. [10 Marks]

3.1. Expand the abbreviation - NADP. [1 Mark]

Answer: Nicotinamide Adenine Dinucleotide Phosphate.

Teacher's Note:
a) NADP+ acts as a hydrogen acceptor in the light-dependent reactions of photosynthesis.
b) Spelling of biochemical terms must be precise for full marks.

3.2. Mention two adaptations in roots for absorption of water from the soil. [2 Marks]

Answer:
1. Presence of numerous elongated root hairs that vastly increase the surface area available for water absorption.
2. Extremely thin cell walls that facilitate the inward movement of water via osmosis.

Teacher's Note:
a) Mention surface area expansion and membrane permeability.
b) Keep answers concise and point-wise for 2-mark questions.

3.3. Differentiate between Afferent arteriole and Efferent arteriole. [3 Marks]

Answer:

Teacher's Note:
a) Differences involving diameter and pressure are critical for explaining ultrafiltration.
b) Present differences in tabular form for clarity.

3.4. Give two examples of water pollutants. [2 Marks]

Answer:
1. Chemical fertilizers and pesticides (e.g., nitrates, phosphates, DDT).
2. Industrial effluents and heavy metals (e.g., lead, mercury, oil spills).

Teacher's Note:
a) Give specific categories and examples of pollutants.
b) Avoid vague terms; name actual pollutants like heavy metals or agricultural runoffs.

3.5. Ali has some pea plants in his garden which need a support to grow as seen in the picture given below:
a. Name the phenomenon depicted by the shoot in the given figure.
b. Define the above phenomenon.
c. Write the name of the part marked X. [2 Marks]

[Figure: A potted pea plant with a climbing tendril coiling around a vertical support stick, with a label X pointing to the leaf tendril]

Answer:
a. Thigmotropism.
b. Thigmotropism is the directional growth movement of plant organs in response to contact or touch with a solid object.
c. Leaf tendril.

Teacher's Note:
a) Tendrils exhibit positive thigmotropism by coiling around supports.
b) Ensure all sub-parts (a, b, c) are answered separately and clearly.

Question 4. [10 Marks]

4.1. Give the biological term for the surgical method of contraception in human females. [1 Mark]

Answer: Tubectomy.

Teacher's Note:
a) Tubectomy involves ligating or cutting the fallopian tubes to prevent eggs from meeting sperm.
b) The corresponding male surgical method is vasectomy.

4.2. State two harmful effects of acid rain on the environment. [2 Marks]

Answer:
1. It lowers the pH of soil and water bodies, damaging aquatic life and killing vegetation.
2. It causes corrosion and weathering of metal structures, historical buildings, and marble monuments (stone leprosy).

Teacher's Note:
a) Mention impacts on both living organisms (aquatic/flora) and non-living infrastructure.
b) Sulfur dioxide and nitrogen oxides are the primary precursors of acid rain.

4.3. Enlist different advantages of transpiration. [3 Marks]

Answer:
1. It creates a transpirational pull that aids in the ascent of sap and passive absorption of water and minerals.
2. It provides a cooling effect, preventing leaves from overheating in intense sunlight.
3. It helps maintain cell turgidity and facilitates gaseous exchange through open stomata.

Teacher's Note:
a) Transpiration is often described as a 'necessary evil', but its upward pull and cooling functions are vital.
b) List at least three distinct physiological benefits.

4.4. Write any two objectives of Swachh Bharat Abhiyan. [2 Marks]

Answer:
1. To eliminate open defecation across rural and urban areas by constructing household and community toilets.
2. To improve overall public health and personal hygiene through proper solid and liquid waste management.

Teacher's Note:
a) Swachh Bharat Abhiyan emphasizes sanitation, waste management, and behavioral change.
b) Keep answers focused on sanitation and health objectives.

4.5. Mohan is fond of playing basketball. His concentration is on shooting the ball into the opponent's basket as given in the picture.
a. Which part of the brain helps Mohan to concentrate in putting the ball into the basket?
b. Name the sense organ that helps to gauge the distance between the ball and the basket.
c. Name the part of the brain that co-ordinates all the voluntary muscular movements of his body. [2 Marks]

[Figure: A basketball player jumping and aiming to shoot the ball into a hoop]

Answer:
a. Cerebrum.
b. Eye.
c. Cerebellum.

Teacher's Note:
a) Cerebrum is the center of concentration, memory, and voluntary thought.
b) Cerebellum coordinates voluntary muscular activity and maintains body balance.

Question 5. [10 Marks]

5.1. Name the type of nerve which has the fibres of both sensory and motor neurons. [1 Mark]

Answer: Mixed nerve.

Teacher's Note:
a) Spinal nerves are typical examples of mixed nerves containing both afferent and efferent fibers.
b) Sensory nerves carry impulses to the CNS, while motor nerves carry impulses away.

5.2. Differentiate between Australopithecus and Modern man based on body hair. [2 Marks]

Answer:

Teacher's Note:
a) Evolution led to a reduction in body hair as humans developed clothing and shelter.
b) Restrict the comparison strictly to body hair as requested by the prompt.

5.3. Give suitable biological reasons for the following statement: The birth rate in India is very high. [2 Marks]

Answer:
1. Widespread illiteracy and lack of awareness regarding reproductive health and contraception.
2. Socio-cultural factors such as traditional preferences for male children and early marriages.

Teacher's Note:
a) Population explosion factors include social customs, poverty, and inadequate family planning access.
b) State at least two valid socio-biological reasons.

5.4. Give the exact location of the pericardium. [2 Marks]

Answer:
The pericardium is a double-layered membranous sac that encloses the heart, located within the thoracic cavity between the lungs (in the mediastinum).

Teacher's Note:
a) Mention that it is a double-walled membrane protecting the heart against friction and mechanical shock.
b) Precise anatomical location scores full marks.

5.5. Given below is a schematic representation of the inheritance of the shape of the seeds of garden peas. Answer the questions that follow:
a. Which is the dominant and recessive allele of the trait?
b. What does the ratio 3 : 1 in the F2 generation represent?
c. State Mendel's Law of Dominance. [3 Marks]

[Figure: Monohybrid cross schematic showing Parent round seeds crossed with wrinkled seeds, producing F1 round seeds, and F2 generation showing a 3:1 ratio of round to wrinkled seeds]

Answer:
a. Dominant allele: R (round seeds); Recessive allele: r (wrinkled seeds).
b. The 3:1 ratio represents the phenotypic ratio in the F2 generation, where 75% of offspring exhibit the dominant trait (round) and 25% exhibit the recessive trait (wrinkled).
c. Mendel's Law of Dominance states that in a heterozygous organism, the allele that is expressed in the phenotype is dominant, while the allele that is masked is recessive.

Teacher's Note:
a) Understand the difference between phenotypic (3:1) and genotypic (1:2:1) ratios.
b) State Mendel's law clearly using standard genetic terminology.

Question 6. [10 Marks]

6.1. Define the following terms: Diapedesis. [1 Mark]

Answer: Diapedesis is the outward squeezing of white blood cells (leucocytes) through the thin walls of blood capillaries into surrounding tissues to fight infection.

Teacher's Note:
a) This process is crucial for the immune defense mechanism against pathogens.
b) Use keywords like capillary walls and WBC migration.

6.2. Distinguish between Diabetes mellitus and Diabetes insipidus (endocrine gland concerned). [3 Marks]

Answer:

Teacher's Note:
a) Distinguish clearly between pancreatic endocrine dysfunction (mellitus) and pituitary hormone deficiency (insipidus).
b) Tabular format ensures all comparative points are clearly visible.

6.3. Give a scientific reason: Carbon monoxide is highly dangerous when inhaled. [2 Marks]

Answer:
Carbon monoxide binds irreversibly with hemoglobin in the blood to form carboxyhemoglobin, which drastically reduces the oxygen-carrying capacity of the blood and can lead to suffocation and death.

Teacher's Note:
a) Emphasize the stable, irreversible nature of carboxyhemoglobin.
b) Mention oxygen transport impairment.

6.4. The diagram given below shows a section of the human ovary.
a. Name the process for the release of the part labelled 1.
b. Write the name of the structure marked 2. [2 Marks]

[Figure: Section of human ovary showing developing ovarian follicles and corpus luteum, with label 1 pointing to the released ovum/secondary oocyte during ovulation and label 2 pointing to the corpus luteum]

Answer:
a. Ovulation.
b. Corpus luteum.

Teacher's Note:
a) Ovulation is triggered by the LH surge midway through the menstrual cycle.
b) Corpus luteum secretes progesterone to maintain the uterine lining during pregnancy.

6.5. Draw a neat, labelled diagram of a chloroplast. [2 Marks]

Answer:
[Figure: Diagram of a chloroplast showing outer membrane, inner membrane, grana (stacks of thylakoids), stroma (ground fluid), and intergral lamellae/frets]

Teacher's Note:
a) Ensure key parts like granum, stroma, and double membrane envelope are clearly labeled.
b) Neat pencil diagrams with clear straight pointer lines are essential in biology exams.

Question 7. [10 Marks]

7.1. Define the following: Hormone. [1 Mark]

Answer: Hormones are non-nutrient chemical messengers secreted directly into the bloodstream by endocrine glands to regulate specific physiological target organs and metabolic activities.

Teacher's Note:
a) Highlight that hormones are secreted by ductless glands and transported via blood.
b) Mention target specificity.

7.2.a. Which part of the human ear gives 'Static balance' to the body? [1 Mark]

Answer: Utricle and saccule (vestibular apparatus / vestibule of the inner ear).

Teacher's Note:
a) Static balance refers to the orientation of the head relative to gravity when stationary.
b) Distinguish between static balance organs (utricle and saccule) and dynamic balance organs (semicircular canals).

7.2.b. Which part of the human ear gives 'Dynamic balance' to the body? [1 Mark]

Answer: Semicircular canals.

Teacher's Note:
a) Semicircular canals detect rotational and angular movements of the head.
b) Crista ampullaris receptors within the canals respond to fluid movement during acceleration.

7.3. Describe the structural differences between an artery and a vein. [3 Marks]

Answer:

Teacher's Note:
a) Structural adaptations reflect the high pressure of arterial blood versus low pressure in venous blood.
b) Tabulate differences across wall thickness, valves, and lumen size.

7.4. Write any two limitations of using a Ganong's potometer to demonstrate the uptake of water. [2 Marks]

Answer:
1. Setting up the potometer without introducing air bubbles in the capillary tube is extremely difficult.
2. Ambient temperature and humidity changes can easily alter transpiration rates, affecting accuracy.

Teacher's Note:
a) Remember that a potometer measures water uptake, which is approximately equal to water lost via transpiration.
b) Mention experimental sensitivities like temperature fluctuations or air bubbles.

7.5. A teacher drew the diagram of the heart on the blackboard and told the students to copy it in their notebooks. Mahesh couldn't see the diagram clearly as it appeared blurred to him.
a. Name the defect of the eye Mahesh is suffering from.
b. Where is the image formed in this defect?
c. Mahesh consults an eye doctor and is prescribed suitable lenses to correct the defect. Which type of lens do his spectacles have? [2 Marks]

Answer:
a. Myopia (near-sightedness).
b. In front of the retina.
c. Concave lens (diverging lens).

Teacher's Note:
a) Myopia makes distant objects appear blurred because light focuses in front of the retina.
b) A concave lens diverges incoming light rays to focus them correctly on the retina.

Question 8. [10 Marks]

8.1. Define the following term: Ultrafiltration. [1 Mark]

Answer: Ultrafiltration is the high-pressure filtration of blood through the glomerulus into Bowman's capsule, where small solutes and water pass through while blood cells and large proteins are retained.

Teacher's Note:
a) Ultrafiltration occurs due to the pressure difference between the wider afferent arteriole and narrower efferent arteriole.
b) Mention selective retention of large molecules and cells.

8.2.a. Name the mineral elements required for the clotting of blood. [1 Mark]

Answer: Calcium ions (Ca²⁺).

Teacher's Note:
a) Calcium acts as an essential cofactor in multiple steps of the blood clotting cascade.
b) Ensure mineral name and ionic form are specified correctly.

8.2.b. Name the mineral element required for the synthesis of thyroxine. [1 Mark]

Answer: Iodine.

Teacher's Note:
a) Iodine is an indispensable component of thyroid hormones.
b) Iodine deficiency leads to goitre.

8.3. State any two harmful effects of noise pollution on human health. [2 Marks]

Answer:
1. Prolonged exposure can cause hearing impairment or permanent deafness.
2. It induces chronic stress, anxiety, high blood pressure (hypertension), and sleep disturbances.

Teacher's Note:
a) Include both auditory (hearing loss) and non-auditory (hypertension, stress) health effects.
b) Keep answers direct and well-structured.

8.4. Why are RBCs efficient in their functions though they lack nucleus and mitochondria? [3 Marks]

Answer:
1. Absence of a nucleus increases surface-area-to-volume ratio and creates more internal space to pack maximum hemoglobin for oxygen transport.
2. Lack of mitochondria ensures that red blood cells do not consume the oxygen they transport, carrying it efficiently to body tissues.
3. Their biconcave shape and flexible structure allow them to squeeze easily through narrow capillaries.

Teacher's Note:
a) The lack of organelles in mammalian RBCs is a specialized evolutionary adaptation for gas transport.
b) Explain both hemoglobin accommodation and lack of oxygen consumption.

8.5. The diagram given below represents a stage in mitosis.
a. Identify the stage given above.
b. Give one reason to support your answer in (a).
c. Mention the number of chromosomes given in the diagram. [2 Marks]

[Figure: Diagram of a cell in anaphase showing sister chromatids pulled apart toward opposite poles by spindle fibers]

Answer:
a. Anaphase.
b. Centromeres split and sister chromatids are pulled apart toward opposite poles.
c. 8 chromosomes (or 4 pairs moving toward opposite poles).

Teacher's Note:
a) Anaphase is distinguished by the separation of sister chromatids moving to opposite poles.
b) Count the separating chromatids/chromosomes carefully from the provided diagram.