HARVET INSTITUTE OF STUDIES

Biology
Preliminary Examination
MODEL ANSWER
Max Marks: 80

Date : 23-Sep-2024 Grade: 10th (ICSE) Time: 2 Hours

EVOLUTION -POLLUTION -A

SECTION A
(Attempt all questions from this section)
Question 1 [15]
Choose the correct answer from the options given below:
(i) The protective covering of the embryo in the uterus is________ [1]
(a) Amnion (b) Meninge (c) Pleura
Ans. (a)
(ii) A source of energy that does not cause pollution is _________ [1]
(a) Petroleum (b) Nuclear energy
(c) Solar energy (d) wood
Ans. (c)
(iii) Plasmolysis occurs when a cell is placed in [1]
(a) Hypotonic (b) Hypertonic (c) Isotonic
Ans. (b)
(iv) Auxins are abundantly produced in: [1]
(a) base of the root (b) base of the shoot
© shoot (d) meristematic region of the shoot
Ans. (d) meristematic region of the shoot
(v) Assertion (A): The sex of a child is determined by the father. [1]
Reason (R): Male have two types of sex chromosomes: XX and XY.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R is not the correct explanation of A.
(c) A is true but R is false.
(d) A is false but R is true.
Ans. (a) Both A and R are true and R is the correct explanation of A.
(vi) Exophthalmic goitre is caused due to the over activity of [1]
(a) Thymus (b) thyroid
(c) Parathyroid (d) adrenal cortex
Ans. (b)
(vii) Which of the following is the functional unit of the nervous system? [1]
(a) Neuron (b) Perikaryon (c) Axon (d) Cyton
Ans. (a) Neuron
(viii) The middle piece of sperm provides [1]
(a) energy (b) food (c) gene (d) chromosomes
Ans. (a)
(ix) Vitamin ________ is necessary for clotting. [1]
(a) D (b) K (c) A
Ans. (b)
(x) Identify the pre-human ancestor [1]
(a) Ramapithecus
(b) Australopithecus
(c) Neanderthal man
(d) Cro-Magnon
Ans. Ramapithecus
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 (xi) An example of non-biodegradable waste is: [1]
(a) Vegetable peels
(b) Sewage
(c) Livestock waste
(d) DDT
Ans. (d)
(xii) The paper used to demonstrate unequal transpiration in a dicot leaf is: [1]
(a) Filter paper (b) Litmus paper (c) Starch paper (d) Cobalt chloride paper
Ans. (d) Cobalt chloride paper
Dry cobalt chloride paper can be used to demonstrate transpiration. This turns from blue to pink when
placed on a transpiring leaf.
(xiii) Osmosis and capillarity are the same except that in osmosis there is [1]
(a) A freely permeable membrane
(b) A cell wall in between
(c) A selectively permeable membrane in between
(d) An endless inflow of water into a cell
Ans. (c)
(xiv) The theory of Natural Selection was proposed by [1]
(a) Mendel (b) Lamarck (c) Wallace (d) Darwin
Ans. Darwin
(xv) How do the daughter cells at the end of mitosis and cytokinesis compare with their parent cell when it [1]
was in G₁ of the cell cycle?
(a) The daughter cells will have half the amount of cytoplasm and half the amount of DNA.
(b) The daughter cells will have half the number of chromosomes and half the amount of DNA.
(c) The daughter cells will have the same number of chromosomes and half the amount of DNA.
(d) The daughter cells will have the same number of chromosomes and the same amount of DNA.
Ans. (d)
Question 2
(i) Name the following: [5]
(a) The blood vessel which has valves in its inner lining. [1]
Ans. Vein
(b) Storage of glucose as glycogen [1]
Ans. Insulin
(c) The biggest source of air pollution in big cities. [1]
Ans. Vehicles /automobiles
(d) The longest phase of cell cycle. [1]
Ans. Interphase
(e) Any two parts of a leaf which allow transpiration. [1]
Ans. The two parts of a leaf which allow transpiration is stomata and cuticle.
(ii) Rewrite the following in correct order: [5]
(a) Given below are five groups of terms. In each group arrange and rewrite the terms in the correct order [1]
as to be in Logical Sequence. Spongy cells, upper epidermis, stoma, palisade tissue, Substomatal space.
Ans. Upper epidermis, palisade tissue, spongy cells, Substomatal space, stoma.
(b) Cell wall, nuclear membrane, nucleolus, cytoplasm, cell membrane, nucleoplasm. [1]
Ans. Cell wall, cell membrane, cytoplasm, nuclear membrane, nucleoplasm, nucleolus.
(c) Anaphase, Telophase, Prophase, Metaphase. [1]
Ans. Prophase, Metaphase, Anaphase, Telophase.
(d) Receptor, Response, Effector, Spinal cord. [1]
Ans. Receptor, Spinal cord, Effector, Response. [As per reflex eye]
(e) Vas deferens, Epididymis, Seminiferous tubules, Urethra, Efferent ducts. [1]
Ans. Efferent ducts,Seminiferous tubules, Epididymis,Vas deferens, Urethra,
(iii) Fill in the blanks: [5]
(a) The spinal cord is the centre of _________action. [1]

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Ans. Reflex
(b) The direct cell division is called as ___________. [1]
Ans. Amitosis
(c) Ureter is the connecting link between_________ and ________ . [1]
Ans. kidney and urinary bladder
(d) Closing of _______ and shedding of leaves reduce ________. [1]
Ans. stomata, transpiration
(e) The brain size of Cro-Magnon was ________cc. [1]
Ans. 1350
(iv) State whether the following statements are TRUE or FALSE: [5]
(a) Hormones are the secretions of endocrine glands. [1]
Ans. True
(b) Loss of water is called bleeding. [1]
Ans. False
(c) Renal artery contains large amount of urea. [1]
Ans. True
(d) Man is the only source of environment pollution. [1]
Ans. False
(e) The fossil history of humans is complete. [1]
Ans. False: The fossil history of humans is complete Fragmentary.
(v) State the location of the following: [5]
(a) Where is heart located? [1]
Ans. Heart is located in the thoracic cavity in between the two lungs.
(b) Organ of Corti [1]
Ans. Organ of Corti - Cochlea in the inner ear.
(c) Give the exact location and one function of thylakoids [1]
Ans. Location- In chloroplasts.
Function- Light reaction of the photosynthesis.
(d) Cells that are haploid. [1]
Ans. Sperm cells in testis and ovum in ovary.
(e) Cells that secrete glucagon. [1]
Ans. Alpha cells in pancreas
SECTION B
(Attempt any four questions from this section)
Question 3
(i) Differentiate the following: Aqueous and Vitreous humor. [1]
Ans. Aqueous Humour
(i) It is a watery fluid.
(ii) It is present between the lens and cornea of the eye.

Vitreous humor.
(i) It is jelly-like fluid.
(ii) It is present between the lens and the retina of the eye.
(ii) The human female gonads are ovaries. A maturing egg in the ovary is present in a sac of cells [2]
called________(1). As the egg grows larger, the follicle enlarges and gets filled with a fluid and is now
called the_________ (2) follicle. The process of releasing the egg from the ovary is called________(3).
The ovum is picked up by the oviduct funnel and fertilization takes place in the_______ (4). In about a
week the blastocyst gets fixed in the endometrium of the uterus and this process is called______ (5).
Ans. (1) Graffian follicle (2) graffian follicle (3) ovulation
(4) oviduct (5) implantation
(iii) Give the scientific name of the organism which is cited as the classical example of "Natural Selection". [2]
Ans. A classical example of 'Natural’ Selection' is provided by peppered moth whose scientific name is
Biston bitularia.

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 (iv) List two measures each for controlling air pollution and water pollution. [2]
Ans. Air pollution -
(i) Pollutants from industries can be controlled by scrubbers and filters.
(ii) Non - polluting gases can be used in vehicles like CNG. Water Pollution-
(i) Treatment of Sewage is done before discharging them into water bodies.
(ii) Excessive use of fertilizers and pesticides should be avoided.
(v) Briefly answer the following questions: [3]
(i) State two reasons for the increase of population in India.
(ii) What is the significance of amniotic fluid?
(iii) What is the function of ear ossicles?
Ans. (i) Reasons for the increase of population in India:
• Most Indian families desire to have at least one son. Hence, a couple produces several children till a
son is born.
• Most of the rural population is still illiterate, ignorant and superstitious. Therefore, they do not make
any effort to avoid pregnancy.
(ii) Significance of amniotic fluid:
• It protects the embryo from physical damage by jerks and mechanical shocks.
• It also maintains even pressure all around the embryo.
(iii) Function of ear ossicles: Ear ossicles once set in vibrations transmit the vibration to the oval
window which sets the cochlear fluid into vibration.
Question 4
(i) Give scientific reason: Chemical fertilizers rain-washed in the lakes promote faster growth of [1]
fish/bacteria.
Ans. Bacteria.
(ii) Give the full form of the abbreviation ACTH. Which gland secretes this hormone? [2]
Ans. ACTH (Adreno Cortico’ Hormone)
It is secreted by the pituitary gland (Anterior pituitary)
(iii) A pure breeding red flower variety of pea plant (RR) is crossed with a pure breeding white flower [2]
variety of pea plant (r r).
Draw a punned square to find out the phenotypic and genotypic ratios of the progeny belonging to the
F2 generation.
Ans.

(iv) Write some characteristics of Homo sapiens. [2]

Ans. Some charactersticks of Homosapiens are :
(i) Large and complex brain
(ii) Ability to communicative in any language.
(iii) Ability to thinking and capable of reasoning.
(v) Briefly explain how the rate of transpiration is affected by [3]

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 (a) Intensity of light
(b) Humidity of the atmosphere.
Ans. The rate of transpiration is affected by
1. Intensity of light
(a) It has a controlling effect on the opening of the stoma through which water primarily escapes in
gaseous state.
(b) In general, transpiration rate is high during daytime, particularly when light is bright, than during
night time.
(c) The stomata are typically open during daytime, allowing the entry of CO₂ and the exit of O₂.
(d) The opening of the stomata likewise enables the escape of water as water vapor in the process of
stomatal transpiration.
(e) Except in CAM plants, the stomata are close at darkness between sunset to sunrise. In turn,
photosynthesis decreases the concentration of CO₂ in the intercellular spaces within the leaf resulting to
the opening of the stomata.
2. Humidity of the atmosphere
a) This environmental factor affects transpiration by regulating stomatal movement and
atmospheric demand. At high RH (moist air), the stoma tends to close and thus limit the exit of water
vapor from the plant.
B) Further, high RH means that the water-potential gradient from plant to the atmosphere will be
minimal compared to when RH is low.
C) In addition, at high RH the atmosphere contains more water and has low atmospheric demand,
meaning that it has limited capacity to absorb more water.
D) But as long as the stomata are open, transpiration occurs, even at saturated condition of 100%
RH. In this case the expelled water vapour readily condenses.
Question 5
(i) Define the following: Guttation [1]
Ans. Guttation is oozing of drops of water from the tip or the edges of a leaf.
(ii) Is it correct to say that the testes produce testosterone. Discuss? [2]
Ans. Yes, it is correct to say testes produce testosterone. The function of testes is to produce sperms and a
hormone, testosterone, which brings about secondary sex characteristics in boys.
(iii) Why is better to call the dark phase of photosynthesis as “light- independent phase”? [2]
Ans. The dark phase does not mean that it occurs when it is dark or at night. It only meant that the reactions
not dependent on light. That’s why, it is now better to called it “light- independent phase”
(iv) Mention two adaptations in roots for absorption of water from the soil. [2]
Ans. (i) huge surface area (ii) root hairs have thin walls
(v) Mention the three major steps involved in the production of urine. [3]
Ans. Ultra filtration, selective reabsorption and tubular secretion.
Ultra filtration: It is filtration of liquid part of the blood with great pressure created in glomerulus due
to diameter differences of afferent and efferent arteriole into Bowman's capsule. Selective reabsorption:
Selected materials like glucose, some salts, etc., only are reabsorbed in renal tubule.
Tubular secretion: In distal convoluted tubule of nephron, certain substances like K+, antibiotics are
added to filtrate from blood.
Question 6
(i) Explain the following: Destarched plant. [1]
Ans. Destarched plant : A plant is kept in dark for 24 to 72 hours in order to remove starch, to prove that
leaf starch has been formed under experimental conditions.
(ii) Mention one difference between [2]
(i) Primary and Secondary pollutants
(ii) Biodegradable and non-biodegradable pollutants.
Ans. (i) Primary pollutant remain in the environment, in the form to which they are released.
Secondary pollutants are formed by the reaction between two primary pollutant or with the
environment factors.
(ii) Biodegradable pollutants are organic in nature and decompose by bacteria and fungi.
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 Non-biodegradable pollutants are inorganic and not decompose by biological agents.
(iii) Name the three ear ossicles. How do they contribute in the mechanism of hearing? [2]
Ans. a) The three ear ossicles are malleus, incus and stapes.
b) As sound waves vibrate the tympanic membrane, it in turn moves the nearest ossicle, the
malleus, to which it is attached.
c) The malleus then transmits the vibrations, via the incus, to the stapes, and so ultimately to the
membrane of the fenestra ovalis, the opening to the vestibule of the inner ear.
(iv) Write any two major reasons for the population explosion in the world. [2]
Ans. Better health care at all age group/ fewer deaths due to better medical aids/ minimized food shortage/
Balanced and improved nutrition/ Large scale immunization.
(v) The figure given below represents the female reproductive system of a mammal: [3]

Parts indicated by guidelines A to D are as follows:

A - Uterus, B - Fallopian tube, C - Ovary. D - Vagina
Give appropriate terms for each of the following:
(a) The onset of reproductive phase in a young female.
(b) Rupture of follicle and release of ovum from the ovary.
(c) Monthly discharge of blood and disintegrated tissues in human female.
Ans. (a) Menarche
(b) Ovulation
(c) Menstruation
Question 7
(i) Differentiate the following: Osmosis and Plasmolysis [1]
Ans. Osmosis
It is the movement of water from its region of higher concentration to its region of lower concentration
through a semipermeable membrane.

Plasmolysis
It is the shrinkage of protoplasm when a cell is placed in a hypertonic solution.
(ii) What is Ganong's Potometer used for? Write any two limitations of this apparatus. [2]
Ans. Ganong's Potometer is used to measure the rate of transpiration.
Its two limitations are given below :
(a) The introduction of air bubble is not easy.
(b) The plant uses some water for photosynthesis, etc., therefore the rate cannot be measured.
(iii) Given below is a diagrammatic representation of certain types of blood vessels in human body. [2]

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 (a) Identify the types of blood vessels numbered 1 to 5.
(b) Where can such an arrangement be found as an example — in lungs or in heart walls?
Ans. (a) 1. areteries, 2.capillaries, 3.arterioles ,4.veins 5.venules,
(b) in heart walls
(iv) What are the advantages of IUD? [2]
Ans. 1. IUD is easy to use and very effective.
2. IUD is very effective in birth control.
3. It is mainly suitable for those who want to practise small family norms after having one or two
children.
(v) The figure given represents an experiment set-up to study a physiological process in plants [3]

(i) Name the physiological process being studied.

(ii) Explain the process.
(iii) What is the aim of the experiment?
Ans. (i) Photosynthesis.
(ii) It is a physiological process by which chlorophyll bearing cells of the plant prepare glucose in the
presence of sunlight using CO₂ and water. O₂ released during this process.
(iii) To prove that oxygen is released during photosynthesis.
Question 8
(i) Explain the following: The raisins swell up when kept in water. [1]
Ans. Water being hypotonic solution, enters into the raisins when they are kept in water due to endosmosis.
(ii) Explain the theory of use and disuse by giving an example. [2]
Ans. 1. Lamarck proposed the theory of use and disuse.
2. He theorised that organism loose characteristics they do not require and developed
characteristics that are useful, e.g. The neck of giraffe was long because it stretched to reach leaves on
high trees.
(iii) Two pairs (A & B) of rabbits were crossed as given below. [2]
(a) Can you tell which coat colour (black or white) is dominant?
(b) Is the coat colour sex-linked?

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Ans. (a) Black coat colour is dominant.
(b) Yes, the coat colour is sex-linked.
(iv) Mention two advantages of Transpiration. [2]
Ans. Cooling effect, suction force, distribution Of water and minerals salts.
(v) Describe an experiment to prove that sunlight is necessary for photosynthesis. [3]
Ans. a) Take a potted plant.
B) Destarch it for 48 hours
c) Select one leaf and fit it with a Ganong's light: screen. Place the plant in sunlight.
d) After 2-3 hours pick up the leaf under screen and test n for starch.
e) The part of the leaf which is covered by light screen does not show any starch test No
photosynthesis has taken place there .
f) The part which is uncovered turns blue black showing that photosynthesis has taken place
there.

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