BIOLOGY (SCIENCE PAPER - 3)

Maximum Marks: 80 Time allowed: Two hours

Instructions:

• Section A is compulsory. Attempt any four questions from Section B.
• The intended marks for questions or parts of questions are given in brackets [ ].

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SECTION A (40 Marks) (Attempt all questions from this Section.)

Question 1

Choose the correct answers to the questions from the given options. [15]

(i) A patient's blood report shows a dangerously low platelet count. This condition would most directly affect: (a) Oxygen transport (b) Blood coagulation (c) Immune response (d) Nutrient distribution

(ii) In a destarched variegated leaf exposed to sunlight, the iodine test will show a positive result (blue-black) only in: (a) The parts of the leaf that were covered from light. (b) The non-green parts of the leaf. (c) The green parts of the leaf. (d) The entire leaf.

(iii) Assertion (A): The pituitary gland is known as the master gland. Reason (R): It secretes tropic hormones that control other endocrine glands. (a) (A) is true and (R) is false. (b) (A) is false and (R) is true. (c) Both (A) and (R) are true and (R) is the correct explanation of (A). (d) Both (A) and (R) are true but (R) is not the correct explanation of (A).

(iv) The part of the brain responsible for coordinating voluntary muscle movements and maintaining balance is: (a) Cerebrum (b) Cerebellum (c) Medulla Oblongata (d) Hypothalamus

(v) Which of the following is a non-biodegradable waste? (a) Paper (b) Vegetable peels (c) Plastic (d) Cotton

(vi) The law of inheritance that states that alleles for different traits are sorted independently of one another is: (a) Law of Dominance (b) Law of Segregation (c) Law of Independent Assortment (d) Law of Use and Disuse

(vii) The primary function of the loop of Henle in the nephron is: (a) Ultrafiltration (b) Selective reabsorption of glucose (c) Reabsorption of water (d) Tubular secretion

(viii) The hormone responsible for the "fight or flight" response is: (a) Insulin (b) Thyroxine (c) Adrenaline (d) Growth Hormone

(ix) The process of fusion of a male gamete with a female gamete is called: (a) Oogenesis (b) Spermatogenesis (c) Fertilization (d) Implantation

(x) Which of the following is an example of a positive tropic movement? (a) Roots growing away from light. (b) Shoots growing away from gravity. (c) A pollen tube growing towards the ovule. (d) Roots growing away from a harmful chemical.

(xi) The structure in the eye that changes shape to focus light on the retina is the: (a) Cornea (b) Iris (c) Lens (d) Pupil

(xii) The part of the ear that contains the receptors for hearing is the: (a) Pinna (b) Ossicles (c) Cochlea (d) Semicircular canals

(xiii) The main reason for the population explosion in India is: (a) High birth rate and low death rate (b) High birth rate and high death rate (c) Low birth rate and low death rate (d) Low birth rate and high death rate

(xiv) The surgical method of contraception in males is called: (a) Tubectomy (b) Vasectomy (c) Hysterectomy (d) Oophorectomy

(xv) The theory of evolution that includes the concept of "survival of the fittest" was proposed by: (a) Jean-Baptiste Lamarck (b) Charles Darwin (c) Gregor Mendel (d) Louis Pasteur

Question 2

(i) Give the biological/technical terms for the following: [5] (a) The fluid that surrounds the cells in the body. (b) The process of childbirth. (c) The functional unit of the kidney. (d) The period of pregnancy, from fertilization to birth. (e) The statistical study of human populations.

(ii) Choose the odd term out from each of the following set of terms. Mention the category to which the remaining three belong: [5] (a) Cerebrum, Cerebellum, Medulla Oblongata, Neuron (b) Myopia, Hyperopia, Cataract, Astigmatism (c) Auxins, Gibberellins, Cytokinins, Adrenaline (d) Vasectomy, Tubectomy, Contraceptive pills, Surgical methods (e) Australopithecus, Homo habilis, Homo erectus, Cro-Magnon

(iii) Match the items in Column A with the most appropriate ones in Column B and rewrite the correct matching pairs: [5]

(iv) State the exact location of the following: [5] (a) Thyroid gland (b) Adrenal gland (c) Pituitary gland (d) Pancreas (e) Testes

(v) State the main function of the following: [5] (a) Red Blood Cells (b) White Blood Cells (c) Platelets (d) Plasma (e) Lymph

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SECTION B (40 Marks) (Attempt any four questions from this Section.)

Question 3

(i) Define Photosynthesis. [1] (ii) Differentiate between arteries and veins on the basis of: [2] (a) Wall thickness (b) Presence of valves (iii) Give two reasons for the population explosion in India. [2] (iv) What is the significance of the myelin sheath in a neuron? [2] (v) Draw a neat, labeled diagram of a nephron. [3]

Question 4

(i) What is a reflex arc? [1] (ii) Differentiate between biodegradable and non-biodegradable wastes with one example of each. [2] (iii) State Mendel's Law of Segregation. [2] (iv) What are the functions of the amniotic fluid? [2] (v) Explain the "fight or flight" response, mentioning the hormone involved and its effects on the body. [3]

Question 5

(i) What is meant by the term "double circulation"? [1] (ii) Mention any two objectives of the Swachh Bharat Abhiyan. [2] (iii) What is the role of the following in the human body? [2] (a) Insulin (b) Glucagon (iv) Explain the process of accommodation in the human eye. [2] (v) Describe the structure of a chromosome with a neat, labeled diagram. [3]

Question 6

(i) State the "all-or-none" principle of nerve impulse transmission. [1] (ii) What is the difference between identical and fraternal twins? [2] (iii) Give the full form of: [2] (a) ACTH (b) TSH (iv) What is the role of the placenta during pregnancy? [2] (v) Explain the mechanism of stomatal transpiration based on the Potassium Ion Exchange Theory. [3]

Question 7

(i) Define the term "natality". [1] (ii) Distinguish between phototropism and geotropism. [2] (iii) What are the problems caused by ozone layer depletion? [2] (iv) Explain the role of auxins in apical dominance. [2] (v) Draw a neat, labeled diagram of the human heart. [3]

Question 8

(i) What is the function of the cerebellum? [1] (ii) Mention two features of Homo erectus. [2] (iii) Explain why a person with blood group O is called a "universal donor". [2] (iv) What is the significance of crossing over in meiosis? [2] (v) Describe the process of urine formation in the nephron under the following headings: [3] (a) Ultrafiltration (b) Selective reabsorption (c) Tubular secretion

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Answer Key

SECTION A

Question 1 (i) (b) Blood coagulation (ii) (c) The green parts of the leaf. (iii) (c) Both (A) and (R) are true and (R) is the correct explanation of (A). (iv) (b) Cerebellum (v) (c) Plastic (vi) (c) Law of Independent Assortment (vii) (c) Reabsorption of water (viii) (c) Adrenaline (ix) (c) Fertilization (x) (c) A pollen tube growing towards the ovule. (xi) (c) Lens (xii) (c) Cochlea (xiii) (a) High birth rate and low death rate (xiv) (b) Vasectomy (xv) (b) Charles Darwin

Question 2 (i) (a) Tissue fluid / Interstitial fluid (b) Parturition (c) Nephron (d) Gestation (e) Demography

(ii) (a) Odd: Neuron, Category: Parts of the brain (b) Odd: Cataract, Category: Refractive errors of the eye (c) Odd: Adrenaline, Category: Plant hormones (d) Odd: Contraceptive pills, Category: Surgical methods of contraception (e) Odd: Cro-Magnon, Category: Early human ancestors

(iii)

1. Placenta - (d) Nourishes the fetus
2. Testes - (a) Produces sperm
3. Ovary - (c) Produces eggs
4. Fallopian tube - (b) Site of fertilization
5. Uterus - (e) Site of implantation

(iv) (a) In the neck, in front of the trachea. (b) On top of each kidney. (c) At the base of the brain. (d) Behind the stomach. (e) Within the scrotum, outside the abdominal cavity.

(v) (a) Transport of oxygen. (b) Fight infection / Provide immunity. (c) Help in blood clotting. (d) Transport of nutrients, hormones, and waste products. (e) Transports white blood cells and returns tissue fluid to the blood.

SECTION B (Brief Answers)

Question 3 (i) The process by which green plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. (ii) (a) Arteries have thick, muscular walls; veins have thin walls. (b) Arteries do not have valves (except at the base of the aorta and pulmonary artery); veins have valves to prevent backflow of blood. (iii) High birth rate and low death rate. (iv) It insulates the axon and allows for saltatory conduction, which greatly increases the speed of nerve impulse transmission. (v) Diagram of a nephron should include Bowman's capsule, glomerulus, PCT, Loop of Henle, DCT, and collecting duct.

Question 4 (i) The neural pathway that mediates a reflex action, typically including a receptor, sensory neuron, interneuron, motor neuron, and effector. (ii) Biodegradable wastes can be decomposed by microorganisms (e.g., paper), while non-biodegradable wastes cannot (e.g., plastic). (iii) During gamete formation, the two alleles for a heritable character separate from each other, so that each gamete ends up with only one allele for that character. (iv) It cushions and protects the fetus from mechanical shock and maintains a constant temperature. (v) The "fight or flight" response is triggered by the hormone adrenaline from the adrenal medulla. It increases heart rate, blood pressure, and blood glucose levels, preparing the body for emergency situations.

Question 5 (i) The blood passes through the heart twice for each complete circuit of the body (pulmonary and systemic circulation). (ii) To eliminate open defecation and to implement modern and scientific municipal solid waste management. (iii) (a) Insulin lowers blood glucose levels. (b) Glucagon raises blood glucose levels. (iv) The process by which the eye changes the shape of its lens (using ciliary muscles) to focus on objects at different distances. (v) Diagram of a chromosome should show two sister chromatids joined at a centromere.

Question 6 (i) A neuron will fire an action potential with the same intensity once the stimulus threshold is reached, regardless of the strength of the stimulus above the threshold. (ii) Identical twins develop from one fertilized egg that splits, so they are genetically identical. Fraternal twins develop from two separate eggs fertilized by two different sperm, so they are genetically like siblings. (iii) (a) Adrenocorticotropic Hormone (b) Thyroid-Stimulating Hormone (iv) It provides nutrition, facilitates gas exchange, removes waste, and produces hormones to maintain the pregnancy. (v) In light, K+ ions are pumped into guard cells, lowering their water potential. Water enters by osmosis, making the cells turgid and opening the stoma. In darkness, K+ ions leave, water exits, and the guard cells become flaccid, closing the stoma.

Question 7 (i) The number of live births per thousand people in a population in a given year. (ii) Phototropism is the growth response to light, while geotropism is the growth response to gravity. (iii) Increased UV radiation reaching Earth, which can cause skin cancer, cataracts, and damage to ecosystems. (iv) Auxins produced by the apical bud inhibit the growth of lateral buds, causing the plant to grow taller with a single main stem. (v) Diagram of the human heart should show the four chambers, major blood vessels, and valves.

Question 8 (i) To coordinate voluntary muscle movements, posture, and balance. (ii) Larger cranial capacity than Homo habilis and was efficiently bipedal. (iii) Because their red blood cells have no A or B antigens, so their blood can be transfused to people with any blood type without causing an immune reaction. (iv) It is the exchange of genetic material between homologous chromosomes, which creates new combinations of alleles and increases genetic variation. (v) (a) High pressure forces water and small solutes from the blood into Bowman's capsule. (b) Essential substances like glucose, water, and ions are reabsorbed from the filtrate back into the blood. (c) Waste products and excess ions are actively transported from the blood into the filtrate.