ICSE Class 10 Biology Board Exam Question Paper 2013 with Solutions

ICSE Board Class X Biology Board Exam Question Paper with Solutions

 

SECTION I (40 Marks)

Attempt all questions from this section.

 

Question 1

 

(a) Name the following: [5 Marks]
i. The cell body of a nerve cell.
ii. The waxy layer on the epidermis of the leaf meant to reduce transpiration.
iii. A non-biodegradable pesticide.
iv. The physical expression of genes in an individual.
v. Knot-like mass of blood capillaries inside the Bowman's capsule.

Answer:
i. Cyton / Perikaryon / Soma
ii. Cuticle
iii. DDT (Dichlorodiphenyltrichloroethane)
iv. Phenotype
v. Glomerulus

Teacher's Note:
a) This question tests basic biological terminology and definitions, which are fundamental to understanding various biological processes.
b) Students should pay attention to precise scientific terms as vague answers may not fetch full marks. For example, "cell body" for a neuron is more specifically called cyton or soma.

 

(b) State the exact location of the following: [5 Marks]
i. Chloroplast
ii. Incus
iii. Corpus callosum
iv. Guard cells
v. Pulmonary semilunar valve

Answer:
i. Mesophyll cells (palisade and spongy parenchyma) of leaves, and in the cells of young stems.
ii. Middle ear, between malleus and stapes.
iii. Beneath the cerebral cortex, connecting the two cerebral hemispheres of the brain.
iv. Epidermis of leaves, surrounding the stomatal pore.
v. At the opening of the pulmonary artery from the right ventricle.

Teacher's Note:
a) Knowing the exact location of structures is crucial for understanding their function and role in the overall biological system.
b) For structures like chloroplasts, specifying the exact cell type (mesophyll cells) is important, not just "in plants". For valves, mentioning both the origin and destination (e.g., right ventricle to pulmonary artery) provides a complete answer.

 

(c)Given below are six sets with four terms each. In each set, a term is an odd one and cannot be grouped in the same category to which the other three belong. Identify the odd one in each set and name the category to which the remaining three belong. The first one has been done as an example: [5 Marks]
Example
Odd term
Category
i.
ii.
iii.
iv.
v.
: Fructose, Sucrose, Glucose, Calcium
: Calcium
: Carbohydrates
Carbonic acid, acetic acid, benzoic acid, boric acid
Saliva, bile, sweat, tears
Cretinism, myxoedema, simple goitre, acromegaly
Sneezing, coughing, blinking, typing
Semicircular canals, cochlea, tympanum, utriculus

Answer:
i. Odd term: Boric acid
Category: Organic acids
ii. Odd term: Bile
Category: Excretory/Glandular secretions (containing water, salts, enzymes)
iii. Odd term: Acromegaly
Category: Thyroid disorders
iv. Odd term: Typing
Category: Reflex actions
v. Odd term: Tympanum
Category: Parts of the inner ear

Teacher's Note:
a) This question assesses the ability to classify biological terms based on common characteristics. Students need to identify the common category first, then the outlier.
b) For "Saliva, bile, sweat, tears", bile is primarily involved in digestion and emulsification of fats, while the others are mainly secretions for lubrication, protection, or excretion of waste. For "Cretinism, myxoedema, simple goitre, acromegaly", acromegaly is due to growth hormone excess, while the others are related to thyroid hormone deficiency or imbalance.

 

(d) Match the items in Column A with that which is most appropriate in Column B. [5 Marks]
Rewrite the matching pair.

Column A	Column B
(1) Testis	(a) Kidney
(2) Poliomyelitis	(b) Water vapour
(3) Transpiration	(c) Prostate gland
(4) Clotting of blood	(d) Iron
(5) Uriniferous tubule	(e) Uterus
	(f) Gonad
	(g) Salk's vaccine
	(h) Water droplet
	(i) Calcium
	(j) TAB vaccine

Answer:
(1) Testis - (f) Gonad
(2) Poliomyelitis - (g) Salk's vaccine
(3) Transpiration - (b) Water vapour
(4) Clotting of blood - (i) Calcium
(5) Uriniferous tubule - (a) Kidney

Teacher's Note:
a) This question tests the student's knowledge of associations between biological structures, processes, diseases, and related terms.
b) Students should carefully consider all options in Column B before making a match, as some options might seem plausible but only one is the most appropriate.

 

(e) Choose the correct answer from the four options given below: [5 Marks]
(i) The cell component visible only during cell division is
A. Mitochondria
B. Chloroplast
C. Chromosome
D. Chromatin
(ii) Pulse wave is mainly caused by the
A. Systole of atria
B. Diastole of atria
C. Systole of the left ventricle
D. Systole of the right ventricle
(iii) The recessive gene is one which expresses itself in
A. Heterozygous condition
B. Homozygous condition
C. F2 generation
D. Y-linked inheritance
(iv) A gland which secretes both hormone and enzyme is the
A. Pituitary
B. Pancreas
C. Thyroid
D. Adrenal
(v) The ventral root ganglion of the spinal cord contains cell bodies of the
A. Motor neuron
B. Sensory neuron
C. Intermediate neuron
D. Association neuron

Answer: (i) (C) Chromosome
Answer: (ii) (C) Systole of the left ventricle
Answer: (iii) (B) Homozygous condition
Answer: (iv) (B) Pancreas
Answer: (v) (A) Motor neuron

Teacher's Note:
a) This section tests fundamental concepts across various chapters, including cell biology, circulatory system, genetics, endocrine system, and nervous system.
b) For (v), the ventral root contains motor neuron axons, and the dorsal root ganglion contains sensory neuron cell bodies. The question asks about the ventral root ganglion, which is a common point of confusion. However, typically, motor neuron cell bodies are in the ventral horn of the spinal cord grey matter, and the ventral root carries their axons. If "ventral root ganglion" is interpreted as referring to the motor component, then motor neuron is the most appropriate answer among the choices, assuming the question implies the motor pathway originating from the ventral side. (Note: True ganglia are typically sensory; motor neuron cell bodies are in the spinal cord's grey matter).

 

(f) Given below is an example of certain structures and their special functional activities. [5 Marks]
For example: Eye and vision. On a similar pattern, complete the following:
i. Neutrophils ...................................
ii. Ureter ..........................................
iii. Neurotransmitters ........................
iv. Iris of the eye ..............................
v. Placenta ......................................

Answer:
i. Neutrophils : Phagocytosis / Defence against infection
ii. Ureter : Carries urine from kidney to urinary bladder
iii. Neurotransmitters : Transmit nerve impulses across a synapse
iv. Iris of the eye : Regulates the size of the pupil / Controls the amount of light entering the eye
v. Placenta : Provides nutrition to the foetus / Exchange of gases and waste products between mother and foetus / Secretes hormones

Teacher's Note:
a) This question requires students to recall the primary function of specific biological structures or substances.
b) Students should provide concise and accurate functional activities. For placenta, multiple functions are acceptable, but focusing on its role in exchange and nutrition is key.

 

(g) The figure given below represents an experiment to demonstrate a particular aspect of photosynthesis. The letter 'A' represents a certain condition inside the flask. [5 Marks]

[Figure: A diagram showing a potted plant with one leaf (Leaf 1) partially enclosed in a flask. Inside the flask, there is a beaker containing KOH solution. Another leaf (Leaf 2) is outside the flask. The flask is sealed around the stem. The setup is exposed to light.]

i. What is the aim of the experiment?
ii. Identify the special condition inside the flask.
iii. Name an alternative chemical which can be used instead of KOH.
iv. In what manner do the leaves 1 and 2 differ at the end of the starch test?

Answer:
i. The aim of the experiment is to demonstrate that carbon dioxide is necessary for photosynthesis.
ii. The special condition inside the flask is the absence of carbon dioxide, as KOH absorbs it.
iii. An alternative chemical which can be used instead of KOH is soda lime (calcium hydroxide) or potassium hydroxide pellets.
iv. At the end of the starch test, Leaf 1 (inside the flask) will show no change or turn yellowish-brown, indicating the absence of starch. Leaf 2 (outside the flask) will turn blue-black, indicating the presence of starch.

Teacher's Note:
a) This is a classic experiment in photosynthesis. Understanding the role of each component (KOH, light, leaves) is crucial for interpreting the results.
b) Students must clearly state the aim and the expected results of the starch test for both leaves, linking them directly to the presence or absence of carbon dioxide.

 

(h) Given below are five groups of terms. In each group, arrange and rewrite the terms in the correct order so as to be in a logical sequence. For example, Question: Implantation, Parturition, Ovulation, Gestation, and Fertilisation. Answer: Ovulation, Fertilisation, Implantation, Gestation, Parturition. [5 Marks]
i. Spongy cells, Upper epidermis, Stoma, Palisade tissue, Sub-stomatal space
ii. Spinal cord, Motor neuron, Receptor, Effector, Sensory neuron
iii. Endodermis, Cortex, Soil water, Xylem, Root hair
iv. Metaphase, Telophase, Prophase, Anaphase, Cytokinesis
v. Intestine, Liver, Intestinal artery, Hepatic vein, Hepatic portal vein

Answer:
i. Upper epidermis, Palisade tissue, Spongy cells, Sub-stomatal space, Stoma
ii. Receptor, Sensory neuron, Spinal cord, Motor neuron, Effector
iii. Soil water, Root hair, Cortex, Endodermis, Xylem
iv. Prophase, Metaphase, Anaphase, Telophase, Cytokinesis
v. Intestinal artery, Intestine, Hepatic portal vein, Liver, Hepatic vein

Teacher's Note:
a) This question tests the student's understanding of the structural organization and sequential processes in various biological systems.
b) For (i), the sequence represents the layers of a leaf from top to bottom, ending with the stomatal opening. For (v), it traces the path of blood from the intestine through the liver and out.

 

SECTION II [40 Marks]

Attempt any four questions from this section

 

Question 2

 

(a) Given below is a diagram of the lateral section of the testis of a man. Study the same and answer the questions which follow:

[Figure: A diagram showing a lateral section of the human testis. Key parts are numbered: 1 points to the epididymis, 2 points to the vas deferens, 3 points to the seminiferous tubules within the testis, and 4 points to the scrotal sac.]

i. Label the parts numbered 1 to 4 in the diagram.
ii. State the functions of the parts labelled 1 and 3.
iii. What is the significance of the testes being located in the scrotal sac outside the abdomen?
iv. What is the role played by the inguinal canal?
v. What is semen? [5 Marks]

Answer:
i. 1: Epididymis
2: Vas deferens
3: Seminiferous tubules
4: Scrotal sac
ii. Function of part 1 (Epididymis): It stores sperm and allows them to mature and gain motility.
Function of part 3 (Seminiferous tubules): These are the sites of spermatogenesis (sperm formation).
iii. The testes are located in the scrotal sac outside the abdomen because spermatogenesis requires a temperature 2-3°C lower than the normal body temperature. The scrotal sac provides this cooler environment.
iv. The inguinal canal is a passage through the abdominal wall in the groin region. It allows the vas deferens, blood vessels, nerves, and lymphatic vessels to pass between the abdominal cavity and the scrotum.
v. Semen is a fluid mixture consisting of sperm (produced by the testes) and secretions from accessory glands such as the seminal vesicles, prostate gland, and bulbourethral glands. It provides a medium for sperm transport, nutrition, and protection.

Teacher's Note:
a) This question covers the anatomy and physiology of the male reproductive system, focusing on the testis and associated structures.
b) For functions, be specific. For example, for epididymis, mention both storage and maturation. For the significance of scrotal location, explicitly state the temperature requirement for spermatogenesis.

 

(b) Give the biological/technical terms for the following: [5 Marks]
i. Chemicals found in the blood which act against antigens.
ii. A constituent which causes pollution.
iii. The onset of menstruation in a young girl.
iv. Structure which connects the placenta with the foetus.
v. The fluid present between the layers of meninges.
vi. Permanently open structures seen on the bark of an old woody stem.
vii. The biological process which is the starting point of the food chain.
viii. The change in an organism resulting due to stimulus.
ix. An antiseptic substance present in tears.
x. A solution in which the relative concentration of water molecules and the solute bon either side of the cell membrane is the same.

Answer:
i. Antibodies / Immunoglobulins
ii. Pollutant
iii. Menarche
iv. Umbilical cord
v. Cerebrospinal fluid (CSF)
vi. Lenticels
vii. Photosynthesis
viii. Response
ix. Lysozyme
x. Isotonic solution

Teacher's Note:
a) This question is a comprehensive test of biological vocabulary across various topics.
b) Students should ensure they use the most precise biological term. For example, for (i), while "antibodies" is correct, "immunoglobulins" is also acceptable. For (v), "cerebrospinal fluid" is the exact term.

 

Question 3

 

(a) Draw a diagram of the human eye as seen in a vertical section and label the parts which suit the following descriptions relating to the [5 Marks]
i. Photosensitive layer of the eye.
ii. Structure which is responsible for holding the eye lens in its position.
iii. Structure which maintains the shape of the eye ball and the area of no vision.
iv. Anterior chamber seen in front of the eye lens.
v. Outer most transparent layer seen in front of the eye ball.

Answer:

[Figure: diagram to be added]

A well-labelled diagram of the human eye in vertical section should be drawn, showing the following parts clearly labelled according to the descriptions:
i. Retina (Photosensitive layer)
ii. Suspensory ligaments / Ciliary body (Holds the eye lens)
iii. Vitreous humour (Maintains shape of eyeball) and Blind spot (Area of no vision)
iv. Aqueous humour / Anterior chamber (Fluid in front of the eye lens)
v. Cornea (Outermost transparent layer)

Teacher's Note:
a) This question requires both drawing skills and accurate anatomical knowledge of the human eye. Students must draw a clear, neat diagram and label the parts precisely as described.
b) Ensure that the labels correspond exactly to the descriptions given. For example, "photosensitive layer" must be labelled as "Retina". For (iii), both vitreous humour and blind spot are required for full marks as they address different aspects of the description.

 

(b) Differentiate between the following pairs on the basis of what is mentioned within brackets: [5 Marks]
i. Photolysis and Photo phosphorylation (definition)
ii. Bicuspid valve and Tricuspid valve (function)
iii. Vasectomy and Tubectomy (explain)
iv. Cerebrum and Spinal cord (arrangement of nerve cells)
v. Bowman's capsule and Malpighian capsule (parts included)

Answer:

Feature	Photolysis	Photophosphorylation
Definition	It is the splitting of water molecules into protons (H+), electrons (e-), and oxygen (O2) in the presence of light during the light-dependent reactions of photosynthesis.	It is the process of synthesizing ATP from ADP and inorganic phosphate (Pi) using light energy during the light-dependent reactions of photosynthesis.

 

Feature	Bicuspid Valve	Tricuspid Valve
Function	It prevents the backflow of blood from the left ventricle into the left atrium during ventricular systole.	It prevents the backflow of blood from the right ventricle into the right atrium during ventricular systole.

 

Feature	Vasectomy	Tubectomy
Explanation	It is a surgical method of male sterilization where the vas deferens (sperm ducts) are cut and tied to prevent sperm from reaching the urethra.	It is a surgical method of female sterilization where the fallopian tubes (oviducts) are cut and tied to prevent the egg from reaching the uterus and sperm from reaching the egg.

 

Feature	Cerebrum	Spinal Cord
Arrangement of nerve cells	Grey matter (cell bodies) is on the outer surface (cerebral cortex), and white matter (axons) is on the inner side.	Grey matter (cell bodies) is on the inner side (H-shaped), and white matter (axons) is on the outer surface.

 

Feature	Bowman's Capsule	Malpighian Capsule
Parts included	It is a cup-shaped structure that encloses the glomerulus.	It includes both the Bowman's capsule and the glomerulus.

Teacher's Note:
a) Differentiating questions require clear, distinct points of comparison based on the specified criteria. Using a table format is highly recommended for clarity.
b) Ensure that the definitions/explanations are accurate and highlight the key differences. For example, in photolysis vs. photophosphorylation, one is about water splitting, the other about ATP synthesis.

 

Question 4

 

(a) Given below is a schematic diagram showing Mendel's experiment on sweet pea plants having axial flowers with round seeds (AARR) and terminal flowers with wrinkled seeds (aarr). Study the same and answer the questions which follow:

[Figure: A Punnett square diagram showing a dihybrid cross. Parent 1 is AARR (Axial round) and Parent 2 is aarr (Terminal wrinkled). Gametes for AARR are AR, and for aarr are ar. The F1 progeny shown is AaRr, resulting from the cross of AR and ar gametes.]

(i) Give the phenotype of F1 progeny.
(ii) Give the phenotypes of F2 progeny produced upon by the self-pollination of F1 progeny.
(iii) Give the phenotypic ratio of F2 progeny.
(iv) Name and explain the law induced by Mendel on the basis of the above observation. [5 Marks]

Answer:
(i) The phenotype of F1 progeny is Axial flowers with Round seeds.
(ii) The phenotypes of F2 progeny produced upon self-pollination of F1 progeny are: Axial Round, Axial Wrinkled, Terminal Round, Terminal Wrinkled.
(iii) The phenotypic ratio of F2 progeny is 9 (Axial Round) : 3 (Axial Wrinkled) : 3 (Terminal Round) : 1 (Terminal Wrinkled).
(iv) The law induced by Mendel on the basis of the above observation is the Law of Independent Assortment.
Explanation: This law 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. In other words, during gamete formation, the alleles for different traits (e.g., flower position and seed shape) assort independently of each other.

Teacher's Note:
a) This question tests the understanding of Mendel's dihybrid cross and the Law of Independent Assortment.
b) Students should remember the F1 phenotype (dominant traits expressed), the four F2 phenotypes, and the classic 9:3:3:1 phenotypic ratio for a dihybrid cross. The explanation of the law must clearly state the independent segregation of different traits.

 

(b) Complete the following table by filling in the blanks from 1 to 10 with appropriate terms: [5 Marks]

Sr. No.	Gland	Secretion	Function/Effect on body
1	Thyroid	1	2
2	3	Vasopressin	4
3	5	6	Promotes glucose utilization by the body cells
4	Lacrimal gland	7	8
5	Adrenal medulla	2	10

Answer:

Sr. No.	Gland	Secretion	Function/Effect on body
1	Thyroid	1. Thyroxine	2. Regulates basal metabolic rate / Controls growth and development
2	3. Pituitary (Posterior lobe)	Vasopressin	4. Increases water reabsorption in kidney tubules / Antidiuretic hormone
3	5. Pancreas	6. Insulin	Promotes glucose utilization by the body cells
4	Lacrimal gland	7. Tears	8. Lubricates and cleanses the eye / Contains lysozyme for antiseptic action
5	Adrenal medulla	9. Adrenaline / Noradrenaline	10. Prepares body for fight or flight response / Increases heart rate, blood pressure, glucose levels

Teacher's Note:
a) This question tests knowledge of the endocrine system and other glands, including their secretions and specific functions.
b) Students should be precise with the names of hormones and their primary effects. For example, for vasopressin, mentioning its role in water reabsorption is key. For adrenal medulla, both adrenaline and noradrenaline are acceptable secretions.

 

Question 5

 

(a) The diagram given below represents the human heart in one phase of its functional activities. Study the same and answer the questions which follow:

[Figure: A diagram of the human heart. Arrows indicate blood flowing from the atria into the ventricles. The tricuspid and bicuspid valves are open, and the semilunar valves are closed. The ventricles appear relaxed and filled with blood.]

(i) Name the phase.
(ii) Label the parts 1, 2 and 3.
(iii) Which part of the heart is contracting in this phase? Give a reason to support your answer.
(iv) Draw a well-labeled diagram of part 1 and 2 to show the structural differences between them. [5 Marks]

Answer:
(i) The phase is Atrial Systole / Ventricular Diastole (or Diastole of the heart).
(ii) Based on a typical heart diagram:
1: Right Atrium
2: Left Atrium
3: Aorta (or Pulmonary Artery, depending on exact arrow placement, but Aorta is more commonly labelled as 3 in such diagrams if it's the main outflow vessel from the left ventricle). Assuming 3 points to the large vessel leaving the top of the heart.
(iii) The atria are contracting in this phase. Reason: The diagram shows blood flowing from the atria into the ventricles, and the atrioventricular valves (bicuspid and tricuspid) are open, indicating atrial contraction to push blood into the relaxed ventricles.
(iv)

[Figure: diagram to be added]

A diagram showing the right atrium (part 1) and left atrium (part 2) should be drawn. The key structural differences to highlight are:
- The wall of the left atrium (2) is slightly thicker than the right atrium (1) because it pumps blood into the left ventricle which then pumps to the entire body.
- The left atrium receives oxygenated blood from the pulmonary veins, while the right atrium receives deoxygenated blood from the vena cavae.
- The left atrium opens into the left ventricle via the bicuspid valve, while the right atrium opens into the right ventricle via the tricuspid valve.

Teacher's Note:
a) This question requires a thorough understanding of the cardiac cycle and the anatomy of the human heart.
b) For (i), both "Atrial Systole" and "Ventricular Diastole" describe the state shown. For (iii), the reason must directly relate to the visual evidence in the diagram. For (iv), the drawing should clearly depict the relative wall thickness and the connections to major vessels and valves, even if simplified.

 

(b) Give biological reasons for the following: [5 Marks]
(i) The wall of the ventricle is thicker than the auricle.
(ii) The renal cortex has a dotted appearance.
(iii) Wooden frames of doors get jammed during the monsoon season.
(iv) Throat infections can lead to ear infections.
(v) The hand automatically shows the direction to turn a cycle without thinking.

Answer:
(i) The wall of the ventricle is thicker than the auricle (atrium) because ventricles have to pump blood to greater distances and against higher pressure. The right ventricle pumps blood to the lungs, and the left ventricle pumps blood to the entire body, requiring stronger contractions and thus thicker muscular walls.
(ii) The renal cortex has a dotted appearance due to the presence of numerous Malpighian capsules (renal corpuscles) and convoluted tubules (proximal and distal convoluted tubules) of the nephrons, which are densely packed in this region.
(iii) Wooden frames of doors get jammed during the monsoon season due to the phenomenon of imbibition. Wood, being a hydrophilic colloid, absorbs water from the humid atmosphere, causing it to swell and increase in volume, leading to jamming.
(iv) Throat infections can lead to ear infections because the middle ear is connected to the pharynx (throat) by the Eustachian tube. Pathogens from a throat infection can travel up this tube to the middle ear, causing an infection (otitis media).
(v) The hand automatically shows the direction to turn a cycle without thinking because it is a conditioned reflex action. Through repeated practice and learning, the brain has established a neural pathway for this action, allowing it to be performed subconsciously without conscious thought.

Teacher's Note:
a) This question requires students to provide scientific explanations for various biological and everyday phenomena.
b) Each reason should be concise and directly address the "why" of the statement. For example, for (i), link thickness to the need for pumping blood over long distances and against pressure.

 

Question 6

 

(a) The figure given below shows the epidermal cells of an onion bulb. This cell was then transferred to a drop of sugar solution.

[Figure: A diagram showing a rectangular plant cell (onion epidermal cell) with a cell wall, cell membrane, cytoplasm, and a large central vacuole.]

(i) Draw a well-labelled diagram of the epidermal cell as it would appear after immersion in a strong sugar solution.
(ii) What scientific term is used for the changes as shown in (i)?
(iii) What should be done to restore the cell back to its original condition?
(iv) Give the scientific term for the recovery of the cell as a result of the step taken in (iii) Above.
(v) Define the term osmosis. [5 Marks]

Answer:
(i)

[Figure: diagram to be added]

The diagram should show an onion epidermal cell where the cell wall remains intact, but the cell membrane has shrunk inwards, pulling away from the cell wall. The cytoplasm and vacuole would appear shrunken and concentrated in the center of the cell. Labels should include: Cell wall, Shrunken protoplast, Cell membrane, Vacuole.
(ii) The scientific term used for the changes as shown in (i) is Plasmolysis.
(iii) To restore the cell back to its original condition, it should be transferred to a hypotonic solution (e.g., distilled water).
(iv) The scientific term for the recovery of the cell as a result of the step taken in (iii) is Deplasmolysis.
(v) Osmosis is the movement of water molecules from a region of higher water concentration (lower solute concentration) to a region of lower water concentration (higher solute concentration) across a semi-permeable membrane.

Teacher's Note:
a) This question focuses on the concepts of osmosis, plasmolysis, and deplasmolysis in plant cells.
b) For the diagram, it's crucial to show the protoplast shrinking away from the cell wall, while the cell wall itself retains its shape. The definition of osmosis must include the movement of water, concentration gradient, and the semi-permeable membrane.

 

(b) Briefly explain the following terms. [5 Marks]
(i) Genes
(ii) Cytokinesis in plant cells
(iii) Guttation
(iv) Diabetes insipidus
(v) Disinfectants

Answer:
(i) Genes: Genes are specific sequences of DNA (or RNA in some viruses) that carry genetic information and determine specific traits or characteristics of an organism. They are the basic units of heredity, located on chromosomes.
(ii) Cytokinesis in plant cells: Cytokinesis in plant cells is the division of the cytoplasm following nuclear division (mitosis or meiosis). It involves the formation of a cell plate in the center of the cell, which grows outwards to form a new cell wall, dividing the parent cell into two daughter cells.
(iii) Guttation: Guttation is the exudation of xylem sap (water droplets) from the margins or tips of leaves of some plants, especially herbaceous ones, during the night or early morning when transpiration is low and root pressure is high.
(iv) Diabetes insipidus: Diabetes insipidus is a condition characterized by excessive thirst and the excretion of large amounts of dilute urine. It is caused by a deficiency of antidiuretic hormone (ADH) or the kidneys' inability to respond to ADH.
(v) Disinfectants: Disinfectants are chemical agents applied to inanimate objects or surfaces to destroy or inhibit the growth of harmful microorganisms. They are generally too strong to be applied to living tissues.

Teacher's Note:
a) This question tests the student's ability to define and explain key biological terms accurately and concisely.
b) For each term, provide a clear and complete explanation, highlighting its essential characteristics. For example, for cytokinesis in plant cells, mention the cell plate formation, which is distinct from animal cell cytokinesis.

 

Question 7

 

(a)
(i) Draw a well-labeled diagram to show the anaphase stage of mitosis in a plant cell having four chromosomes.
(ii) State any two harmful effects of acid rain.
(iii) Expand the following biological abbreviations:
(1) NADP
(2) ACT [5 Marks]

Answer:
(i)

[Figure: diagram to be added]

A well-labelled diagram of anaphase in a plant cell with four chromosomes should be drawn. Key features to include:
- A rectangular cell wall.
- Sister chromatids separating and moving towards opposite poles of the cell.
- Each pole receiving four distinct chromosomes (each now considered a full chromosome).
- Spindle fibers (kinetochore microtubules) pulling the chromosomes.
- Elongation of the cell.
- Absence of centrioles (characteristic of plant cells).
Labels: Cell wall, Separating chromatids (now chromosomes), Spindle fibers, Pole.
(ii) Two harmful effects of acid rain are:
1. It damages buildings, monuments, and statues, especially those made of marble (e.g., Taj Mahal), by corroding them.
2. It acidifies lakes and rivers, harming aquatic life (fish, amphibians) by altering their habitat's pH.
(iii) Expansions:
(1) NADP: Nicotinamide Adenine Dinucleotide Phosphate
(2) ACT: Adrenocorticotrophic Hormone

Teacher's Note:
a) This question combines drawing, general knowledge, and abbreviation expansion, covering cell division, environmental science, and biochemistry/endocrinology.
b) For the anaphase diagram, ensure that the chromosomes are clearly shown moving to opposite poles and that the cell wall is present. For acid rain, provide distinct and significant harmful effects. For abbreviations, spell out the full names correctly.

 

(b)
(i) List any two major activities of the Red Cross.
(ii) Write any two major reasons for the population explosion in the world.
(iii) Write the names of four nitrogenous bases in a DNA molecule. [5 Marks]

Answer:
(i) Two major activities of the Red Cross are:
1. Providing humanitarian aid and disaster relief during emergencies, conflicts, and natural calamities.
2. Promoting health services, blood donation, and first aid training.
(ii) Two major reasons for the population explosion in the world are:
1. Decline in death rates due to advancements in medicine, sanitation, and disease control, leading to increased life expectancy.
2. High birth rates, often influenced by lack of education, traditional beliefs, and limited access to family planning methods in many developing regions.
(iii) The names of four nitrogenous bases in a DNA molecule are:
1. Adenine (A)
2. Guanine (G)
3. Cytosine (C)
4. Thymine (T)

Teacher's Note:
a) This question covers general awareness, environmental science, and molecular biology.
b) For Red Cross activities, focus on its core humanitarian mission. For population explosion, ensure the reasons are distinct and significant, addressing both reduced mortality and sustained high fertility. For DNA bases, list all four correctly.