ICSE Class 10 Biology Board Exam Question Paper 2020 with Solutions

ICSE Class 10 Biology Board Exam Question Paper with Solutions

SECTION I (40 Marks)

Question 1

(a) Name the following: [5]
(i) The process of transformation of several glucose molecules into one molecule of starch.
(ii) The point of attachment of two chromatids.
(iii) The iron containing pigment in erythrocytes.
(iv) The duct which transports urine from the kidney to the urinary bladder.
(v) The part of the brain which is concerned with memory.

Answer:
(i) Polymerisation (or Condensation)
(ii) Centromere
(iii) Haemoglobin
(iv) Ureter
(v) Cerebrum

Teacher's Note:
a) Ensure exact biological terms are used without spelling errors to secure full marks.
b) Students often confuse centromere with centrosome; remember that centromere holds sister chromatids together.

(b) Explain the following terms: [5]
(i) Allele
(ii) Diffusion
(iii) Photolysis
(iv) Phenotype
(v) Population density

Answer:
(i) Allele: Alternative forms of a gene occupying the same locus on homologous chromosomes, determining contrasting characters.
(ii) Diffusion: The free movement of molecules of a substance (gases, liquids, or solids) from a region of higher concentration to a region of lower concentration until they are evenly distributed.
(iii) Photolysis: The splitting of water molecules into hydrogen ions and oxygen in the presence of light and chloroplast during the light-dependent phase of photosynthesis.
(iv) Phenotype: The observable external physical or biochemical characteristics of an organism, determined by its genetic make-up and environmental influences.
(v) Population density: The number of individuals of a population per unit area at a given time.

Teacher's Note:
a) Definitions must include key scientific keywords such as 'alternative forms', 'higher to lower concentration', and 'splitting of water'.
b) Avoid vague descriptions; precise phrasing is essential for definitions.

(c) Given below are certain groups of terms. In each group the first pair indicates a relationship between the two terms. Rewrite and complete the second pair on a similar basis.
Example: Cytoplasm : Cytokinesis :: Nucleus : Karyokinesis. [5]
(i) Widening of hips: Oestrogen :: Deepening of voice in males : ___________.
(ii) Brain : Meninges :: Heart : ___________.
(iii) Insulin : Beta-cells :: Glucagon : ____________.
(iv) Kidney: Renal artery :: Liver : ____________.
(v) Uterus : Implantation :: Fallopian tube : __________.

Answer:
(i) Testosterone
(ii) Pericardium
(iii) Alpha-cells
(iv) Hepatic artery
(v) Fertilization

Teacher's Note:
a) Identify the exact biological relationship (hormone-function, organ-covering, hormone-secreting cell, organ-blood supply, organ-process) established by the first pair.
b) Write only the completed term clearly in the final answer.

(d) Given below are sets of five terms each. Rewrite the terms in correct order in a logical sequence beginning with the first word that is underlined: [5]
(i) Stimulus, Response, Receptor, Effector, Spinal cord.
(ii) Root hair, Endodermis, Epidermis, Xylem, Cortex.
(iii) Conjunctiva, Yellow spot, Pupil, Vitreous Humour, Aqueous Humour.
(iv) Australopithecus, Cro-Magnon Man, Homo erectus, Neanderthal Man, Homo sapiens.
(v) Artery, Capillaries, Venule, Vein, Arteriole.

Answer:
(i) Stimulus -> Receptor -> Spinal cord -> Effector -> Response
(ii) Root hair -> Epidermis -> Cortex -> Endodermis -> Xylem
(iii) Conjunctiva -> Aqueous Humour -> Pupil -> Vitreous Humour -> Yellow spot
(iv) Australopithecus -> Homo erectus -> Neanderthal Man -> Cro-Magnon Man -> Homo sapiens
(v) Artery -> Arteriole -> Capillaries -> Venule -> Vein

Teacher's Note:
a) Follow the exact pathway or evolutionary sequence starting with the underlined term.
b) Use arrows (->) to clearly indicate the sequential order.

(e) Choose the correct answer from the four options given below: [5]
(i) The fusion of the sperm and ovum is termed as:
A. Reproduction
B. Development
C. Fertilization
D. Embryo
(ii) Agranulocytes are:
A. Lymphocytes, Monocytes
B. Lymphocytes, Basophils
C. Eosinophils, Basophils
D. Eosinophils, Monocytes
(iii) Which of the following is not a natural reflex action?
A. Knee-jerk
B. Blinking of eyes due to strong light
C. Salivation at the sight of food
D. Sneezing when any irritant enters the nose
(iv) The structural and functional units of excretion in the human kidney is the:
A. Ureter
B. Bowman’s capsule
C. Renal pelvis
D. Nephron
(v) In a human female, ovum consists of:
A. 23 pairs of autosomes
B. 22 pairs of autosomes and 1 pair of sex chromosomes
C. 22 autosomes and 1 Y-chromosome
D. 22 autosomes and 1 X-chromosome

Answer:
(i) C. Fertilization
(ii) A. Lymphocytes, Monocytes
(iii) C. Salivation at the sight of food
(iv) D. Nephron
(v) D. 22 autosomes and 1 X-chromosome

Teacher's Note:
a) Salivation at the sight of food is a conditioned reflex, whereas others are natural/unconditioned reflexes.
b) Unfertilized human ovum is a haploid gamete containing 22 autosomes and 1 X chromosome.

(f) Identify the ODD term in each set and name the CATEGORY to which the remaining three belong: [5]
(i) Auxin, Ethylene, Adrenaline, Cytokinin
(ii) Tympanum, Ear ossicles, Auditory canal, Pinna
(iii) Syringes, Soiled dressings, Discarded needles, Household detergents
(iv) Exophthalmic Goiter, Simple Goitre, Cretinism, Myxoedema
(v) Adenine, Guanine, Creatinine, Cytosine

Answer:
(i) Odd term: Adrenaline; Category: Plant hormones (Phytohormones)
(ii) Odd term: Tympanum; Category: Parts of the external ear
(iii) Odd term: Household detergents; Category: Biomedical waste
(iv) Odd term: Exophthalmic Goiter; Category: Hyposecretion disorders of the thyroid gland
(v) Odd term: Creatinine; Category: Nitrogenous bases of DNA/RNA

Teacher's Note:
a) Both the odd term and the correct common category name must be stated to earn full marks.
b) Note that Exophthalmic goiter is due to hypersecretion of thyroxine, while the other three listed are hyposecretion disorders.

(g) Match the items given in column A with the most appropriate ones in Column B and REWRITE the correct matching pairs: [5]

Answer:
(i) Biston betularia - Peppered moth
(ii) Testes - gonad
(iii) Clotting of blood - Calcium
(iv) Stroma - Light independent reaction
(v) Stomata - diffusion of gases

Teacher's Note:
a) Rewrite the matched pairs in full format as requested by the question instruction.
b) Calcium ions (Ca²⁺) play a vital role in blood coagulation.

(h) The diagram given below represents a plant movement. Answer the following questions:
A [5]

[Figure: Diagram of a carpel showing pollen grains germinating on the stigma, with a pollen tube (labeled A) growing down the style towards the ovary and ovule.]

(i) Name the tropic movement shown in the diagram.
(ii) Explain the tropic movement mentioned in (i).
(iii) Label the part marked 'A'.
(iv) What is part A attracted to?
(v) Give an example of a plant which shows Thigmotropism.

Answer:
(i) Chemotropism
(ii) Chemotropism is the directional growth movement of a plant part in response to a chemical stimulus.
(iii) Pollen tube
(iv) Chemicals secreted by the embryo sac (or ovule).
(v) Pea plant (or Passion flower / Morning glory / Cuscuta)

Teacher's Note:
a) Pollen tube growth down the style is a classic example of positive chemotropism.
b) Ensure correct spelling of 'Chemotropism' and 'Thigmotropism'.

SECTION II (40 Marks)

Attempt any four questions from this Section.

Question 2

(a) The diagram given below represents an experiment to prove the importance of a factor in photosynthesis. Answer the questions that follow:
A
KOH solution [5]

[Figure: Experimental setup showing a potted plant with one leaf enclosed in a glass flask containing potassium hydroxide (KOH) solution, with a portion of the leaf (labeled A) inside the flask and the rest outside.]

(i) Which factor is being studied here?
(ii) What is the purpose of keeping KOH in the flask?
(iii) Explain the term Photosynthesis.
(iv) What will you observe when the leaf A is tested for starch?
(v) Write a well balanced chemical equation for the process of photosynthesis.

Answer:
(i) Carbon dioxide is necessary for photosynthesis.
(ii) To absorb carbon dioxide from the air inside the flask.
(iii) Photosynthesis is the process by which green plants manufacture organic food (glucose) from carbon dioxide and water in the presence of sunlight and chlorophyll, releasing oxygen as a byproduct.
(iv) Leaf part A will remain brown/yellow (tests negative for starch) because it did not receive carbon dioxide, while the part outside turns blue-black.
(v) 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6H₂O + 6O₂ (in the presence of Sunlight and Chlorophyll)

Teacher's Note:
a) KOH absorbs CO₂, creating a CO₂-free environment inside the flask.
b) Ensure balanced stoichiometry when writing the chemical equation for photosynthesis.

(b) The diagram given below represents the simplified pathway of the circulation of blood. Answer the questions that follow: [5]

[Figure: Flowchart of blood circulation showing HEAD, LUNGS, HEART, LIVER, and SMALL INTESTINE with numbered arrows 1 to 5 representing various blood vessels.]

(i) Name the blood vessels labelled 1 to 4.
(ii) Which blood vessel supplies oxygenated blood to the muscles of the heart?
(iii) What is the importance of blood vessel labelled 5?
(iv) What is the type of blood circulation that takes place between the heart and the lungs?
(v) Draw a diagram of the different blood cells as seen in a smear of human blood.

Answer:
(i) 1: Superior vena cava (or precaval), 2: Pulmonary vein, 3: Pulmonary artery, 4: Pulmonary vein (or right/left pulmonary vessels as appropriate to the diagrammatic convention; alternatively: 1-Vena cava, 2-Aorta, 3-Pulmonary artery, 4-Pulmonary vein).
(ii) Coronary artery
(iii) Hepatic portal vein transports nutrient-rich blood from the alimentary canal (small intestine) directly to the liver for processing and storage.
(iv) Pulmonary circulation
(v) [Figure: Diagram showing Red Blood Cells (biconcave discs without nucleus), White Blood Cells (Neutrophil, Monocyte, Lymphocyte, Eosinophil, Basophil with distinct nuclear shapes), and Platelets (small fragments).] First draw clean outlines and label them.

Teacher's Note:
a) The hepatic portal system is unique as it starts in capillaries of the intestine and ends in capillaries of the liver.
b) Labeling in diagrams must be clear and neat.

Question 3

(a) The diagram given below depicts a defect of the human eye which has been corrected by using a suitable lens. Answer the following questions: [5]

[Figure: Eyeball diagram showing parallel rays diverging through a concave lens before entering the eye and focusing precisely on the retina.]

(i) Name the defect that has been corrected. Which type of lens has been used for the correction?
(ii) Mention one cause for the above defect.
(iii) Where would the image have formed if the above lens was not used for correction?
(iv) Name the three concentric layers of the eyeball.
(v) Draw a neat, labelled diagram of a neuron.

Answer:
(i) Myopia (Short-sightedness); Concave lens (diverging lens).
(ii) Elongation of the eyeball from front to back OR excessive curvature of the lens / cornea.
(iii) In front of the retina.
(iv) Sclera, Choroid, Retina.
(v) [Figure: Diagram of a multipolar neuron showing cyton, dendrites, axon, myelin sheath, Schwann cell, nodes of Ranvier, and axon terminals.] Draw and label neatly.

Teacher's Note:
a) Myopia is corrected using a concave lens which diverges incoming rays so they focus correctly on the retina.
b) The three layers of the eyeball must be named from outermost to innermost: Sclera, Choroid, Retina.

(b) Give the biological reasons for the following statements: [5]
(i) It is advisable to keep green plants in an aquarium.
(ii) Water pollution is a major cause of concern in our country.
(iii) We cannot distinguish colours in dim light.
(iv) Medical discoveries such as antibiotics and vaccinations have indirectly contributed to the sharp rise in human population.
(v) Homo sapiens sapiens is the most highly evolved form of man.

Answer:
(i) Green plants release oxygen during photosynthesis which is utilized by aquatic animals for respiration, and they absorb carbon dioxide released by animals.
(ii) It causes water-borne diseases, renders water unsafe for drinking, and disrupts aquatic ecosystems.
(iii) Cone cells, which are responsible for color vision, require bright light to function, whereas rod cells (active in dim light) only perceive shades of gray.
(iv) They have drastically reduced infant mortality and death rates from infectious diseases, thereby increasing life expectancy and population growth.
(v) They possess a highly developed, large brain capacity, advanced intelligence, capacity for abstract thought, and complex speech.

Teacher's Note:
a) Biological reasons require clear cause-and-effect explanations.
b) Mention rods and cones explicitly when explaining night or dim-light vision.

Question 4

(a) The figure given below shows a part of a nephron. Answer the questions that follow: [5]

[Figure: Diagram of Malpighian capsule (Renal corpuscle) showing glomerulus enclosed within Bowman's capsule, with afferent arteriole (1), efferent arteriole (2), Bowman's capsule (3), glomerulus (4), and the proximal convoluted tubule / renal tubule (X).]

(i) In which region of the kidney is the above structure present?
(ii) Label the parts numbered 1 to 4.
(iii) What is the technical term for the process that occurs in part 3?
(iv) Why is fluid X not called urine? Justify your answer.
(v) Draw a neat, labelled diagram of the urinary system of man.

Answer:
(i) Cortex (Renal cortex)
(ii) 1: Afferent arteriole, 2: Efferent arteriole, 3: Bowman's capsule, 4: Glomerulus.
(iii) Ultrafiltration
(iv) Because it is glomerular filtrate (or nephric filtrate) which still contains valuable useful substances like glucose, amino acids, and large amounts of water that are yet to be reabsorbed in the renal tubules.
(v) [Figure: Diagram of human urinary system showing kidneys, ureters, urinary bladder, and urethra.] Draw and label clearly.

Teacher's Note:
a) Ultrafiltration occurs in the glomerulus under high hydrostatic pressure.
b) Tubular reabsorption changes glomerular filtrate into urine.

(b) Differentiate between the following pairs on the basis of what is mentioned in the brackets: [5]
(i) Transpiration and Guttation (place of occurrence)
(ii) Biodegradable waste and Non-biodegradable waste (One example)
(iii) Population control and Swachh Bharat Abhiyan (One objective)
(iv) Osmosis and Active Transport (Substances undergoing movement)
(v) Metaphase and Anaphase (Position of chromosomes)

Answer:

Teacher's Note:
a) Structure differences in tabular format must strictly adhere to the parameter specified in brackets.
b) Active transport moves both ions and molecules, whereas osmosis strictly refers to solvent (water) movement.

Question 5

(a) The diagram below represents an experiment to demonstrate a certain phenomenon in a green plant: [5]

[Figure: Ganong's potometer or mercury-manometer setup showing a leafy shoot connected via stout rubber tubing to glass tubing dipping into a mercury reservoir, demonstrating suction pull due to transpiration.]

(i) Will the level of mercury in the glass tubing rise or fall? Which conducting tissue of the plant does the glass-tubing represent?
(ii) Define Transpiration.
(iii) How will the rate of the above process differ if the environment of the plant has:
1. Less humidity
2. High temperature?
(iv) State any two advantages of transpiration to the plant.
(v) Draw a neat labelled diagram of a Plasmolysed cell.

Answer:
(i) Rise; Xylem.
(ii) Transpiration is the loss of water in the form of water vapour from the aerial parts of a plant.
(iii) 1. Rate increases. 2. Rate increases.
(iv) 1. Creates a transpiration pull responsible for ascent of sap. 2. Provides cooling effect to the plant.
(v) [Figure: Diagram of a plant cell showing cell wall, contracted cytoplasm/protoplast, cell membrane, nucleus, and hypertonic solution in the vacuole/space between cell wall and plasma membrane.] Draw and label.

Teacher's Note:
a) Mercury rises due to the suction force created by rapid transpiration.
b) Both low humidity and high temperature increase the rate of transpiration by increasing the vapor pressure gradient.

(b) Give appropriate biological/ technical terms for the following: [5]
(i) The sensory organ in Cochlea.
(ii) Number of live births per 1000 people per year.
(iii) The point of contact between two neurons.
(iv) The accessory gland in human males whose secretion neutralises the acid in the vagina.
(v) Condition when blood sugar level is lowered in the blood.
(vi) Structure which helps in the adjustment of the size of the pupil.
(vii) A surgical method of fertility control in human males.
(viii) Process by which leucocytes migrate through the walls of capillaries.
(ix) A sudden inheritable change in one or more genes.
(x) A non-dividing phase of the cell cycle where more DNA is synthesised.

Answer:
(i) Organ of Corti
(ii) Birth rate (Natality)
(iii) Synapse
(iv) Cowper's gland (Bulbourethral gland) / Prostate gland
(v) Hypoglycemia
(vi) Iris
(vii) Vasectomy
(viii) Diapedesis
(ix) Mutation
(x) Interphase (specifically Synthesis / S-phase)

Teacher's Note:
a) Ensure technical terms are spelled accurately (e.g., Organ of Corti, Diapedesis).
b) S-phase is the correct sub-phase of interphase where DNA replication occurs.

Question 6

(a) State two functions of: [5]
(i) Ear
(ii) Ethylene
(iii) Tears
(iv) Testis
(v) Cerebellum

Answer:
(i) Ear: Hearing and maintenance of body balance (equilibrium).
(ii) Ethylene: Promotes fruit ripening and stimulates abscission of leaves/flowers.
(iii) Tears: Lubricate the cornea and wash away dust particles / contain lysozyme to kill bacteria.
(iv) Testis: Produce sperms (male gametes) and secrete the male sex hormone testosterone.
(v) Cerebellum: Coordinates voluntary muscular movements and maintains body balance/equilibrium.

Teacher's Note:
a) Two distinct functions must be clearly stated for each item.
b) Lysozyme in tears provides antiseptic action.

(b) Complete the table: [5]

Answer:
(i) Insulin
(ii) Pancreas
(iii) Pituitary gland
(iv) Promotes general body growth / skeletal growth
(v) Thyroxine
(vi) Regulates basal metabolism / rate of tissue oxidation
(vii) Adrenaline
(viii) Adrenal gland (Adrenal medulla)
(ix) Pituitary gland (Posterior pituitary)
(x) Uterine contractions during child birth / milk ejection

Teacher's Note:
a) Every blank in the table must be matched correctly with its corresponding hormone, gland, or function.
b) Ensure precise gland names are provided (e.g., Islets of Langerhans / Pancreas).

Question 7

(a) A homozygous dominant tall pea plant bearing red flowers (TTRR) is crossed with a homozygous recessive dwarf pea plant bearing white flowers (ttrr). [5]
(i) What is the phenotype and genotype of F₁ individuals?
(ii) Write the possible combination of gametes that are obtained when two F₁ hybrid plants are crossed.
(iii) Mention the phenotypic ratio of the F₂ generation.
(iv) State Mendel’s Law of Independent Assortment.
(v) Name two X-linked disorders found in humans.

Answer:
(i) Phenotype: Tall with red flowers; Genotype: TtRr.
(ii) TR, Tr, tR, tr.
(iii) 9 : 3 : 3 : 1 (Tall red : Tall white : Dwarf red : Dwarf white).
(iv) Mendel's Law of Independent Assortment states that when two pairs of traits are combined in a hybrid, segregation of one pair of characters is independent of the other pair of characters.
(v) Haemophilia and Colour blindness (or Duchenne muscular dystrophy).

Teacher's Note:
a) Dihybrid cross produces a phenotypic ratio of 9:3:3:1 in the F₂ generation.
b) Gametes produced by heterozygous F₁ (TtRr) are TR, Tr, tR, and tr in equal proportions.

(b) The diagram given below is that of a developing human foetus. Answer the questions that follow: [5]

[Figure: Diagram of a developing foetus inside the uterus showing umbilical cord (1), placenta (2), and amniotic sac/fluid (3).]

(i) Label the parts numbered 1 to 3 in the diagram.
(ii) Mention any two functions of the part labelled 2 in the diagram.
(iii) Explain the significance of the part numbered 3 in the diagram.
(iv) Define the term 'Gestation'. What is the normal gestational period of the developing embryo?
(v) Mention the sex chromosomes in a male and female embryo.

Answer:
(i) 1: Umbilical cord, 2: Placenta, 3: Amniotic cavity / Amniotic fluid.
(ii) Placenta functions: 1. Supplies oxygen and nutrients from mother to foetus. 2. Removes carbon dioxide and nitrogenous wastes from foetus to mother.
(iii) Amniotic fluid acts as a shock absorber to protect the foetus from mechanical injury and prevents desiccation.
(iv) Gestation: The period of complete intra-uterine development of the embryo/foetus from conception to birth. Normal gestational period is about 280 days (or 9 months / 40 weeks).
(v) Male embryo: XY; Female embryo: XX.

Teacher's Note:
a) Placenta is the structural and metabolic bridge between mother and foetus.
b) Amniotic fluid provides a uniform pressure and cushioning environment for the growing foetus.