Solved 2020 Question Paper ICSE Class 10 Biology

Section I (40 Marks)

Question 1(a)

Name the following:

(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) Polymerization

(ii) Centromere

(iii) Haemoglobin

(iv) Ureter

(v) Cerebrum

Question 1(b)

Explain the following terms:

(i) Allele

(ii) Diffusion

(iii) Photolysis

(iv) Phenotype

(v) Population density

Answer

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

(ii) Diffusion is the free movement of molecules of a substance from the region of their higher concentration to the region of their lower concentration when the two are in direct contact.

(iii) Photolysis is the splitting of water molecules into hydrogen ions and oxygen in the presence of light.

(iv) The observable characteristics which are genetically controlled are called as phenotype.

(v) Population density is the number of individuals per square kilometre (km²) at any given time.

Question 1(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.

(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) Widening of hips: Oestrogen :: Deepening of voice in males : Testosterone

(ii) Brain: Meninges :: Heart : Pericardium

(iii) Insulin : Beta-cells :: Glucagon : Alpha-cells

(iv) Kidney: Renal artery :: Liver : Hepatic portal vein

(v) Uterus : Implantation :: Fallopian tube : Fertilization

Question 1(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:

(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 → Pupil → Aqueous Humour → Vitreous Humour → Yellow spot

(iv) Australopithecus → Homo erectus → Neanderthal Man → Cro-Magnon Man → Homo sapiens

(v) Artery → Arteriole → Capillaries → Venule → Vein

Question 1(e-i)

The fusion of the sperm and ovum is termed as:

1. Reproduction
2. Development
3. Fertilization
4. Embryo

Answer

Fertilization

Reason — The sperm and ovum fuse together in the fallopian tube. This process is known as fertilization.

Question 1(e-ii)

Agranulocytes are:

1. Lymphocytes, Monocytes
2. Lymphocytes, Basophils
3. Eosinophils, Basophils
4. Eosinophils, Monocytes

Answer

Lymphocytes, Monocytes

Reason — Agranulocytes are a type of white blood cell that do not have visible granules in their cytoplasm when observed under a microscope. The two main types of agranulocytes are lymphocytes and monocytes.

Question 1(e-iii)

Which of the following is not a natural reflex action?

1. Knee-jerk
2. Blinking of eyes due to strong light
3. Salivation at the sight of food
4. Sneezing when any irritant enters the nose

Answer

Salivation at the sight of food

Reason — Salivation at the sight of food is a conditioned reflex as our brain already knows the taste of food.

Question 1(e-iv)

The structural and functional units of excretion in the human kidney is the:

1. Ureter
2. Bowman’s capsule
3. Renal pelvis
4. Nephron

Answer

Nephron

Reason — The structural and functional units of excretion in the human kidney is the Nephron.

Question 1(e-v)

In a human female, ovum consists of:

1. 23 pairs of autosomes
2. 22 pairs of autosomes and 1 pair of sex chromosomes
3. 22 autosomes and 1 Y-chromosome
4. 22 autosomes and 1 X-chromosome

Answer

22 autosomes and 1 X-chromosome

Reason — A somatic cell in human has 23 pairs of chromosomes out of which 22 pairs are autosomes and 1 pair is sex chromosome (XX in females and XY in males). The ovum is formed as a result of meiosis that leads to halving of chromosome numbers. Therefore, In a human female, ovum consists of 22 autosomes and 1 X-chromosome.

Question 1(f)

Identify the ODD term in each set and name the CATEGORY to which the remaining three belong:

(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
Auxin, Ethylene, Cytokinin — Plant hormone

(ii) Odd term — Pinna
Tympanum, Ear ossicles, Auditory canal — Parts of internal ear

(iii) Odd term — Household detergents
Syringes, Soiled dressings, Discarded needles — Biomedical wastes

(iv) Odd term — Exophthalmic Goiter
Simple Goitre, Cretinism, Myxoedema — Hypothyroidism

(v) Odd term — Creatinine
Adenine, Guanine, Cytosine — Nitrogenous bases

Question 1(g)

Match the items given in column A with the most appropriate ones in Column B and REWRITE the correct matching pairs:

Answer

Question 1(h)

The diagram given below represents a plant movement. Answer the following questions.

(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 plant which shows Thigmotropism.

Answer

(i) Chemotropism

(ii) Chemotropism is the phenomenon of growth or movement of a plant part towards the source of nutrients or chemicals.

(iii) A → Pollen tube

(iv) 'A' is attracted to peptones secreted by neck canal cells.

(v) Sweet Peas

Section II (40 Marks)

Question 2(a)

The diagram given below represents an experiment to prove the importance of a factor in photosynthesis. Answer the questions that follow:

(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) Factor being studied here is necessity of Carbon dioxide for photosynthesis.

(ii) KOH absorbs carbon dioxide.

(iii) Photosynthesis is the process by which living plant cells, containing chlorophyll, produce food substances (glucose and starch), from carbon dioxide and water, by using light energy and release oxygen as a by-product.

(iv) The part of leaf inside the flask will not turn blue while the part of leaf outside the flask will turn blue showing the presence of starch. This proves that photosynthesis did not occur in the leaf portion inside the flask where carbon dioxide was absent.

(v) Balanced chemical equation representing the process of photosynthesis is given below:

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

Question 2(b)

The diagram given below represents the simplified pathway of the circulation of blood. Answer the questions that follow:

(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 → Anterior vena cava
• 2 → Aorta
• 3 → Pulmonary artery
• 4 → Pulmonary vein

(ii) Coronary Artery

(iii) Blood vessel labelled as 5 is the hepatic portal vein. It serves as a critical connection between the digestive system and the liver, allowing for nutrient processing, detoxification, and regulation of various metabolic functions.

(iv) Pulmonary circulation

(v) Below diagram shows the different blood cells as seen in a smear of human blood:

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:

(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 is the defect that has been corrected. Concave lens has been used.

(ii) Lens is too curved.

(iii) The image would have been formed in front of retina if the above lens was not used for correction.

(iv)

1. Outer- Sclera
2. Middle- Choroid
3. Inner - Retina

(v) Diagram of a neuron with the parts labelled is shown below:

Question 3(b)

Give the biological reasons for the following statements:

(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 which dissolves in the water. This oxygen is used by fish in the aquarium. Therefore, to maintain the oxygen level in the water it is advisable to keep green plants in an aquarium.

(ii) India has the world's largest population but has only 4% of the world's freshwater resources. Pollution of water bodies, such as rivers, lakes, and groundwater is rapidly depleting these limited reserves leading to an acute shortage of clean water for domestic, agricultural, and industrial use.

(iii) We cannot distinguish colours in dim light because the cone cells, responsible for vision of colours are sensitive only to bright light.

(iv) Medical discoveries such as antibiotics and vaccinations have lowered death rate by treatment and prevention of deadly diseases, thus, indirectly contributing to the sharp rise in human population.

(v) Homo sapiens sapiens is the most highly evolved form of man as they possess the following main characteristics:

1. Bipedal locomotion.
2. Cranial capacity ranging from 1450 to 1600 cm³ and a much enlarged cerebrum.
3. Prominent chin, snout disappeared.
4. Highly reduced body hair.

Question 4(a)

The figure given below shows a part of a nephron.
Answer the questions that follow:

(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

(ii) Parts numbered 1 to 4 are:

• 1 → Afferent arteriole
• 2 → Efferent arteriole
• 3 → Glomerulus
• 4 → Bowman's capsule

(iii) Ultrafiltration

(iv) Fluid X is called glomerular filtrate and not urine because it contains almost all the liquid part of the blood i.e., plasma along with most of its organic and inorganic substances including urea, glucose, amino acids, etc. These substances, along with water, are reabsorbed before urine is formed.

(v) Labelled diagram of the urinary system is shown below:

Question 4(b)

Differentiate between the following pairs on the basis of what is mentioned in the brackets:

(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

(i) Transpiration occurs through the stomata from leaves while guttation occurs through hydathodes from leaf tip.

(ii) Leaves are biodegradable waste while plastic is non-biodegradable waste.

(iii) Population control aims at lowering the growth rate of population and Swachh Bharat Abhiyan aims at cleanliness in surrounding.

(iv) In osmosis, there is movement of solvent or water but in active transport there is movement of ions or salt particles.

(v) In metaphase, the chromosomes are arranged in equatorial plane while in anaphase the chromosomes are moved toward poles.

Question 5(a)

The diagram below represents an experiment to demonstrate a certain phenomenon in a green plant:

(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) The level of mercury in the glass tubing will rise. The glass-tubing represents xylem.

(ii) Transpiration is the loss of water in the form of vapour from the aerial parts of the plant.

(iii)

1. Less humidity increases the rate of transpiration.
2. High temperature increases the rate of transpiration.

(iv) Two advantages of transpiration to the plants are:

1. Cooling effect.
2. Creation of suction force for ascent of sap.

(v) Labelled diagram of a plasmolysed cell is given below :

Question 5(b)

Give appropriate biological technical terms for the following:

(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

(iii) Synapse

(iv) Prostate gland

(v) Hypoglycemia

(vi) Iris

(vii) Vasectomy

(viii) Diapedasis

(ix) Mutation

(x) Synthesis Phase (S)

Question 6(a)

State two functions of:

(i) Ear

(ii) Ethylene

(iii) Tears

(iv) Testis

(v) Cerebellum

Answer

(i) Two functions of Ear:

1. Hearing
2. Balancing

(ii) Two functions of Ethylene:

1. Acceleration of senesence
2. Ripening of fruits

(iii) Two functions of Tears:

1. Lubrication
2. Antibacterial due to presence of lysozyme

(iv) Two functions of Testis:

1. Sperm formation (spermatogenesis)
2. Production of Testosterone

(v) Two functions of Cerebellum:

1. Maintain balance of the body.
2. Coordinate muscular activity.

Question 6(b)

Complete the table:

Answer

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).

(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 - All plants will be Tall and will bear red flowers.
Genotype - TtRr

(ii) TR, Tr, tR, tr

(iii) 9:3:3:1

(iv) Law of Independent Assortment, states that when there are two pairs of contrasting characters, the distribution of the members of one pair into the gametes is independent of the distribution of the other pair.

(v) Colour-blindness and Haemophilia

Question 7(b)

The diagram given below is that of a developing human foetus. Answer the questions that follow:

(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) Parts numbered 1 to 3 are:

• 1 → Umbilical cord
• 2 → Placenta
• 3 → Amniotic fluid

(ii) Function of placenta are:

1. Passes nutrients and respiratory gases to foetus from mother.
2. Acts as endocrine gland, secretes oestrogen and progesterone.

(iii) Amniotic fluid protects the embryo from physical damage by jerk. It keeps an even pressure all around the foetus. It also permits restricted movement to foetus.

(iv) The full term of the development of the embryo in the uterus is called gestation. The normal gestational period of the developing embryo is 280 days.

(v) Male — XY.
     Female — XX.