Evaluate the safety requirements for experiments producing poisonous gas. Such experiments require excellent ventilation to prevent gas accumulation and exposure.

Such experiments require excellent ventilation to prevent gas accumulation and exposure.

A classroom with closed windows (A) and a storeroom (B) are unsuitable. A laboratory with work benches (C) might be suitable if well-ventilated, but a well-ventilated open space (D) offers the best safety for poisonous gas.
Answer: D

2)

The first step is always to alert others, followed by evacuation, assembly, and finally, accounting for everyone.

1. Sound an alarm bell (3)
2. Exit building in a calm and orderly manner (1)
3. Assembly at a safe place (2)
4. Take a roll call (4)

Answer: C

3)

Lipids serve as energy storage, insulation, and structural components of cell membranes.

A. Formation of antibodies is a function of proteins.
B. Source of water is not a primary function; while metabolic water can be produced, it's not the main role.
C. Regulation of pH is primarily done by buffer systems involving proteins and other molecules.
D. Clotting of blood involves proteins (e.g., fibrinogen) and platelets.
None of the options directly state the primary functions like energy storage or membrane structure. However, lipids can be a source of metabolic water through their breakdown, which is a function, albeit secondary. Let's re-evaluate. Lipids are hydrophobic, and their metabolism can yield water. In some animals, like camels, fat stores are a significant source of water.
Answer: B

4)

carbon, hydrogen, oxygen, nitrogen, and sulfur.

A. Lipids: primarily carbon, hydrogen, oxygen (sometimes phosphorus).
B. Proteins: carbon, hydrogen, oxygen, nitrogen, and sulfur (in some amino acids).
C. Nucleic acids (DNA/RNA): carbon, hydrogen, oxygen, nitrogen, phosphorus.
D. Carbohydrates: carbon, hydrogen, oxygen.

Answer: B

5)

A. Cell division involves the nucleus and cytoplasm.
B. Generating energy (respiration) occurs in mitochondria.
C. Structural support is the primary function of the cell wall.
D. Trapping sunlight (photosynthesis) occurs in chloroplasts.
Answer: C

6)

Mitochondria are the sites of aerobic respiration, where glucose is broken down to produce ATP (energy) for metabolic processes.

This will halt all energy-dependent metabolic activities.

A. Plasmolysis is the shrinking of the protoplast due to water loss, related to osmosis.
B. Metabolism (all chemical processes in the cell) relies heavily on ATP from mitochondria. If mitochondria are removed, metabolism stops.
C. Osmosis is the movement of water across a semi-permeable membrane.
D. Diffusion is the movement of particles from high to low concentration.
Answer: B

7)

The diagram shows an animal cell, characterized by an irregular shape and the absence of a cell wall and chloroplasts. The nucleus is clearly labeled.

It has an irregular shape, and the nucleus is prominent. The cell appears to be an amoeboid cell, capable of changing shape.

A. Absorbing water: Many cells absorb water, but this shape isn't uniquely specialized for it.
B. Engulfing bacteria: Cells like phagocytes (e.g., macrophages) have irregular shapes and can engulf foreign particles like bacteria. This process is called phagocytosis.
C. Transmitting impulses: Nerve cells (neurons) are specialized for this, with distinct elongated structures.
D. Transporting oxygen: Red blood cells are specialized for this, and they have a biconcave disc shape.
The irregular shape and amoeboid appearance are characteristic of cells that engulf other cells or particles.
Answer: B

8)

Enzymes are proteins, and their activity is highly sensitive to temperature.

This process is called denaturation.

A. Activated: Enzymes are activated at their optimal temperature, not typically $60^{\circ}C$ for biological enzymes.
B. Inactivated: While denaturation leads to inactivation, "denatured" is a more precise term for the structural change.
C. Denatured: This accurately describes the irreversible loss of an enzyme's structure and function due to high temperature.
D. Saturated: This refers to the enzyme having all its active sites occupied by substrate, not a temperature effect.
Answer: C

9)

Enzymes are biological catalysts, and almost all enzymes are proteins.

Proteins are polymers of amino acids.

A. Glucose: subunit of carbohydrates.
B. Amino acids: subunits of proteins.
C. Fatty acids: components of lipids.
D. Glycerol: component of lipids.
Answer: B

10)

Insulin is a protein hormone. The sequence of amino acids in a protein determines its unique three-dimensional structure and function.

In living organisms, DNA carries this genetic code.

A. Protein: Insulin itself is a protein, but its structure is determined by genetic information.
B. Lipid: Lipids are a different class of molecule.
C. DNA: DNA contains the instructions for building proteins.
D. Vitamins: Vitamins are organic molecules required in small amounts, not genetic material.
Answer: C

11)

Phosphorus is a macronutrient essential for plant growth and development.

It is also found in DNA, RNA, and phospholipids.

A. Chlorophyll formation: Requires magnesium and nitrogen.
B. ATP formation: Phosphorus is a crucial component of ATP.
C. Fruit formation: While phosphorus is needed for overall growth, ATP is a more fundamental and direct role.
D. Flower formation: Similar to fruit formation, it's an outcome of overall healthy growth, which requires ATP.
Answer: B

12)

Seeds dispersed by water (hydrochory) typically need to be buoyant and resistant to water damage.

A. Seeds with wing-like parts: Characteristic of wind dispersal.
B. Seeds with fine hairs: Can aid wind dispersal or attachment to animals.
C. Seeds with fibrous coat: A fibrous coat (like in a coconut) often contains air spaces, making the seed buoyant and protecting it from water. This is ideal for water dispersal.
D. Seeds with hooks: Characteristic of animal dispersal (epizoochory).
Answer: C

13)

Wilting occurs when a plant loses more water than it absorbs, leading to a loss of turgor pressure in its cells.

A. Low humidity: Low humidity increases the water potential gradient between the plant and the air, leading to increased transpiration and water loss, thus causing wilting.
B. Low temperature: Low temperatures generally reduce transpiration.
C. Low wind speed: Low wind speed reduces transpiration, as it allows a humid boundary layer to form around the leaves. High wind speed would increase transpiration.
D. Low light intensity: Low light intensity reduces photosynthesis and stomatal opening, which would reduce water loss.
Answer: A

14)

The vascular bundle in a dicot root typically has a central core of xylem, often star-shaped, with phloem bundles located between the arms of the xylem.

Label D points to this central xylem.
Answer: D

15)

photosynthesis (consumes CO2) and respiration (releases CO2).

This happens during the brightest part of the day.

A. Midnight: Photosynthesis is zero, respiration is occurring, so CO2 would be relatively high.
B. Sunrise: Photosynthesis is just beginning, CO2 levels would still be relatively high from overnight respiration.
C. Midday: Light intensity is brightest, leading to the maximum rate of photosynthesis and thus the lowest CO2 concentration.
D. Sunset: Photosynthesis is decreasing, CO2 levels would start to rise as respiration becomes dominant.
Answer: C

16)

Photosynthesis is the process by which green plants convert light energy into chemical energy, producing glucose and oxygen.

A. Water and oxygen: Oxygen is a product, not a raw material.
B. Water and carbon dioxide: These are the correct raw materials.
C. Glucose and oxygen: These are the products, not raw materials.
D. Glucose and carbon dioxide: Glucose is a product.
Answer: B

17)

Cilia are tiny hair-like structures that line the respiratory tract and help to sweep away mucus and trapped particles.

Tar is the sticky black substance in tobacco smoke that coats the lungs and paralyzes the cilia, impairing their ability to clear debris.

A. Tar: Known to paralyze cilia.
B. Nicotine: An addictive stimulant, affects the nervous system.
C. Carbon monoxide: Reduces oxygen-carrying capacity of blood.
D. Carbon dioxide: A product of respiration, not directly responsible for ciliary paralysis.
Answer: A

18)

The kidney filters blood to remove waste products, including urea.

Urea is filtered from the blood in the cortex, and its concentration increases significantly in the medulla as water is reabsorbed from the collecting ducts.

A. Artery: Blood entering the kidney via the renal artery has a high urea concentration, but the question asks about within the kidney structures.
B. Cortex: Filtration occurs here, but the highest concentration is achieved deeper.
C. Medulla: Due to water reabsorption, the interstitial fluid and urine in the collecting ducts within the medulla have the highest urea concentration.
D. Ureter: Carries urine (which has high urea concentration) out of the kidney, but the highest concentration within the kidney is in the medulla.
Answer: C

19)

1: Vena Cava (superior/inferior) - carries deoxygenated blood to the right atrium.
2: Pulmonary Artery - carries deoxygenated blood from the right ventricle to the lungs.
3: Aorta - carries oxygenated blood from the left ventricle to the body.
4: Pulmonary Vein - carries oxygenated blood from the lungs to the left atrium.

These are the pulmonary veins (4) and the aorta (3).

Answer: D

20)

identify the blood sample from a pulmonary vein.

The pulmonary vein carries oxygenated blood from the lungs back to the heart. Therefore, it will have the highest oxygen concentration among the blood samples in the circulatory system.

The bar representing blood sample B has the highest oxygen concentration (around $85\, \text{cm}^3$).
Answer: B

21)

A: Enamel (outermost layer, hardest)
B: Dentine (underneath enamel, bone-like)
C: Pulp cavity (innermost part, contains nerves and blood vessels)
D: Cementum/Gum line

This is the pulp cavity.
Answer: C

22)

The structure labeled X is the cochlea.

The cochlea is responsible for hearing. It contains fluid and hair cells that respond to sound vibrations, converting them into electrical signals (nerve impulses) that are sent to the brain. Specifically, it distinguishes between different frequencies (pitches) of sound.

A. Responds to air vibrations by moving backwards and forwards: This describes the eardrum and ossicles.
B. Focuses on near and distant objects: This describes the lens of the eye.
C. Responds to high and low frequency sounds: This is the primary function of the cochlea.
D. Responds to light and sends impulses to the brain: This describes the retina of the eye.
Answer: C

23)

Assimilation is the process by which absorbed nutrients are incorporated into the body's cells and tissues and used for growth, repair, and energy.

A. Taking food into the digestive system: This is ingestion.
B. Muscular churning of food in the stomach: This is mechanical digestion.
C. The absorption of digested food molecules from the ileum: This is absorption.
D. Making use of absorbed food molecules in metabolic processes: This is the correct definition of assimilation.
Answer: D

24)

Aerobic respiration is a metabolic process that uses oxygen to break down glucose (or other organic molecules) to release energy in the form of ATP.

A. Breakdown ATP: Respiration produces ATP, it doesn't break it down as its primary role. ATP is broken down to release energy for cellular activities.
B. Produce carbon dioxide: Carbon dioxide is a waste product of aerobic respiration, not its primary role.
C. Produce alcohol: This is a product of anaerobic respiration (fermentation) in some organisms, not aerobic respiration.
D. Synthesize ATP: This is the primary role of aerobic respiration – to generate ATP.
Answer: D

25)

A: Cerebrum (involved in thought, voluntary movement, etc.)
B: Cerebellum (coordinates voluntary movements, balance, posture)
C: Medulla oblongata (controls vital involuntary functions like breathing, heart rate)
D: Pituitary gland (endocrine gland)

The cerebellum (B) is primarily responsible for coordinating movement, balance, and posture.
Answer: B

26)

The diagram shows yeast, sugar, and water in a flask, connected to a test tube with limewater (calcium hydroxide solution). This setup is used to demonstrate fermentation.

Yeast ferments sugar into ethanol and carbon dioxide.

Limewater turns cloudy in the presence of carbon dioxide. Therefore, gas X is carbon dioxide.
Answer: C

27)

Viruses are extremely small, much smaller than bacteria or typical cells.

A. Light microscopes: Can view bacteria and larger cells, but not viruses.
B. Electron microscopes: Have much higher magnification and resolution, capable of viewing viruses and their internal structures.
C. Bio viewers: Not a standard scientific term for a microscope.
D. Hand lens: Provides very low magnification, only for macroscopic objects.
Answer: B

28)

Microorganisms are a diverse group including bacteria, fungi, viruses, protozoa, and algae.

A. They cause diseases: Many microorganisms are harmless or beneficial; only some are pathogenic.
B. They are decomposers: Many bacteria and fungi are decomposers, but not all microorganisms (e.g., photosynthetic algae, viruses).
C. They are unicellular: Many microorganisms are unicellular (bacteria, protozoa, some fungi), but some (e.g., some algae, multicellular fungi) are not strictly unicellular. Viruses are acellular.
D. They contain genetic material: All known forms of life, including all microorganisms (bacteria, fungi, protozoa, and viruses), contain genetic material (DNA or RNA) to carry their hereditary information. This is a universal characteristic.
Answer: D

29)

A gene mutation is a permanent alteration in the DNA sequence that makes up a gene.

A. Albinism: A genetic condition caused by mutations in genes involved in melanin production.
B. Down's syndrome: Caused by an extra copy of chromosome 21 (a chromosomal abnormality), not a single gene mutation.
C. Haemophilia: A genetic bleeding disorder caused by mutations in genes that provide instructions for making clotting factor proteins.
D. Sickle cell anaemia: A genetic blood disorder caused by a mutation in the gene that tells your body to make the iron-rich compound that makes blood red and carries oxygen.

Answer: B

30)

Continuous variation refers to traits that show a range of phenotypes, often influenced by multiple genes and environmental factors (e.g., height, weight).
Discontinuous variation refers to traits that fall into distinct categories, often controlled by one or a few genes (e.g., blood group, tongue rolling).

A. Intelligence: A complex trait influenced by many genes and environment, showing a continuous range.
B. Tongue rolling: A discrete trait, either you can or cannot roll your tongue. This is discontinuous.
C. Earlobes: Attached or unattached earlobes are discrete traits, discontinuous.
D. Sex: Male or female, a discrete trait, discontinuous.
Answer: A

31)

Man: Recessive sex-linked allele. Since it's sex-linked, it's on the X chromosome. Let 'X^r' be the recessive allele and 'X^R' be the normal allele. A man with a recessive sex-linked allele means his genotype is X^rY.
Woman: Normal. Since the allele is recessive, a normal woman could be X^RX^R or X^RX^r. However, the question implies she is phenotypically normal, and it doesn't specify if she's a carrier. Assuming "normal woman" means she does not express the recessive trait, her genotype could be X^RX^R or X^RX^r. If the question implies she is homozygous dominant (X^RX^R), then all daughters would be carriers (X^RX^r). If she is a carrier (X^RX^r), then daughters could be X^RX^R, X^RX^r, or X^rX^r.
Let's assume "normal woman" means she is homozygous dominant (X^RX^R) for the normal allele, as this is the most straightforward interpretation when not specified as a carrier.
Parents: Man (X^rY) x Woman (X^RX^R)

All daughters will have the genotype X^RX^r. This means all daughters will receive the X^r allele from their father.
Therefore, the probability of the allele passing on to his daughter is 100%.
Answer: D

32)

The diagram shows a duplicated chromosome, consisting of two identical sister chromatids joined at a constricted region. The label X points to one of these identical halves.

Each identical half of a duplicated chromosome is called a chromatid. The constricted region where they join is the centromere.
Answer: B

33)

Complete dominance occurs when one allele completely masks the expression of the other allele in a heterozygous individual. The dominant allele expresses its phenotype fully, even when only one copy is present.

A. Different alleles have an equal effect on the phenotype of the offspring: This describes co-dominance or incomplete dominance.
B. An allele expresses in the phenotype even in the presence of an alternative: This is the definition of complete dominance.
C. Contrasting alleles are combined in an individual organism: This describes a heterozygous individual.
D. A gene has more than two contrasting alleles: This describes multiple alleles.
Answer: B

34)

The presence of hyphae is a key characteristic.

A. Animalia: Animals are multicellular, heterotrophic, and lack cell walls and hyphae.
B. Fungi: Fungi are heterotrophic, have cell walls (chitin), and grow as hyphae.
C. Plantae: Plants are multicellular, autotrophic, and have cell walls (cellulose), but do not have hyphae.
D. Protista: A diverse kingdom, some protists have hyphae-like structures (e.g., water molds), but fungi are the primary kingdom characterized by hyphae.
Answer: B

35)

Soil degradation refers to the decline in soil quality, often due to processes like erosion, nutrient depletion, or compaction.

A. Mulching garden beds: Mulching prevents soil degradation by reducing erosion, retaining moisture, and adding organic matter.
B. Practicing mixed cropping: Mixed cropping (intercropping) improves soil health by enhancing biodiversity, reducing pest outbreaks, and improving nutrient cycling.
C. Adding manure to soil: Manure is an organic fertilizer that improves soil fertility and structure.
D. Ploughing along slopes: Ploughing along slopes (contour ploughing) is a conservation practice that reduces soil erosion. However, if it means ploughing down slopes, it would cause degradation. Assuming it means ploughing along the contour, it's beneficial. Let's re-evaluate the question. The question asks which leads to degradation. If the options are all beneficial, there might be an issue. Let's consider the opposite of "ploughing along slopes" which is ploughing up and down slopes, which causes erosion. However, the option states "ploughing along slopes". This is a conservation method.
Let's reconsider the options. All options A, B, C are generally considered good practices for soil health. If the question implies "ploughing along slopes" as a general ploughing practice without specific contouring, it can still lead to some soil disturbance and potential degradation over time, especially if not managed well. However, compared to other methods of degradation (e.g., overgrazing, deforestation), these are generally beneficial.
There might be a nuance in "ploughing along slopes". If it refers to any ploughing on a slope, it can still expose soil to erosion, even if done along contours, compared to no-till farming. But contour ploughing is a method to prevent degradation.
Let's assume the question is looking for the least beneficial or potentially harmful practice among the choices, or perhaps a misinterpretation of "ploughing along slopes".
However, if we strictly interpret "ploughing along slopes" as contour ploughing, it's a good practice.
Let's re-examine the question and options. All other options are clearly beneficial. If "ploughing along slopes" is interpreted as any ploughing on a slope, it can still lead to some soil disturbance and potential degradation over time, especially if not managed well. But it's usually taught as a preventative measure.
Let's consider if there's a common misconception or a specific context.
If the question is asking for a practice that can lead to degradation, and the others are clearly preventative, then "ploughing along slopes" might be the intended answer if it's interpreted as general tillage on slopes, which can still cause some erosion compared to no-till.
However, if it's contour ploughing, it prevents degradation.
Let's assume the question implies general ploughing on slopes, which can lead to degradation.
Answer: D

36)

identify a human activity that is a way of managing ecosystems. Ecosystem management involves practices that maintain or restore the health and function of ecosystems.

A. Livestock rearing: Can be managed sustainably, but often leads to overgrazing and habitat destruction if not managed well. It's an activity within an ecosystem, not necessarily management of the ecosystem.
B. Crop farming: Similar to livestock rearing, it's an activity that can impact ecosystems, but not inherently ecosystem management.
C. Market gardening: Intensive cultivation of vegetables, also an activity within an ecosystem.
D. Planting trees: Reforestation and afforestation are direct methods of ecosystem management aimed at restoring habitats, preventing soil erosion, and mitigating climate change.
Answer: D

37)

$50\, \text{g}$.

The organic matter section is not explicitly labeled with an angle, but the other sections are: water ($180^{\circ}$), air content ($50^{\circ}$), mineral particles ($100^{\circ}$).

A full circle is $360^{\circ}$.
Angle for organic matter = $360^{\circ} - (180^{\circ} + 50^{\circ} + 100^{\circ})$
Angle for organic matter = $360^{\circ} - 330^{\circ}$
Angle for organic matter = $30^{\circ}$

The mass is proportional to the angle.
Mass of organic matter = $\frac{\text{Angle of organic matter}}{\text{Total angle}} \times \text{Total mass}$
Mass of organic matter = $\frac{30^{\circ}}{360^{\circ}} \times 50\, \text{g}$
Mass of organic matter = $\frac{1}{12} \times 50\, \text{g}$
Mass of organic matter = $\frac{50}{12}\, \text{g} = \frac{25}{6}\, \text{g} \approx 4.166\, \text{g}$

A. $4.2\, \text{g}$
B. $8.3\, \text{g}$
C. $30\, \text{g}$
D. $42\, \text{g}$
The calculated value $4.166\, \text{g}$ is closest to $4.2\, \text{g}$.
Answer: A

38)

A. Bilharzia (Schistosomiasis): A parasitic disease. Chronic infection can lead to liver and spleen enlargement, as well as bladder and intestinal problems.
B. Typhoid: A bacterial infection. Symptoms include high fever, weakness, stomach pain, headache, and loss of appetite. Liver and spleen enlargement can occur but are not the primary defining symptoms.
C. Malaria: A parasitic disease transmitted by mosquitoes. Symptoms include fever, chills, and flu-like illness. Severe malaria can cause spleen enlargement (splenomegaly) and liver involvement.
D. Cholera: A bacterial infection causing severe watery diarrhea and dehydration.

However, bilharzia is particularly known for chronic liver and spleen damage. Malaria also causes splenomegaly. Given the options, both A and C are plausible. Let's check for the most characteristic association.
Bilharzia is very strongly associated with hepatosplenomegaly (enlargement of liver and spleen) in chronic cases. Malaria also causes it, but bilharzia's impact on these organs is a hallmark of the disease.
Answer: A

39)

Alcohol is metabolized in the liver and can damage various organs.

A. Kidney failure: While severe alcoholism can indirectly affect kidneys, it's not the primary or most direct association.
B. Liver cirrhosis: This is a severe scarring of the liver, often caused by chronic alcohol abuse, leading to liver failure. This is a direct and well-known consequence.
C. Lung cancer: Primarily associated with smoking, not alcohol consumption.
D. Tuberculosis: An infectious disease caused by bacteria, not directly caused by alcohol, though alcohol abuse can weaken the immune system.
Answer: B

40)

Malaria is caused by a parasite transmitted through the bite of infected Anopheles mosquitoes.

A. Avoiding overcrowded conditions: This is relevant for airborne diseases like tuberculosis, not mosquito-borne malaria.
B. Providing access to clean water: Important for water-borne diseases like cholera, not malaria.
C. Provision of a balanced diet: Important for general health and immunity, but not a direct method of preventing malaria transmission.
D. Introducing fish into ponds: Certain fish species (e.g., Gambusia) eat mosquito larvae, thus reducing the mosquito population and preventing malaria transmission. This is a biological control method.
Answer: D