Board Exam 2025
1 Mark
Q7. The valves in the human heart ensure that
:
- Oxygen-rich blood flows from left atrium to left ventricle only.
- Deoxygenated blood flows from left atrium to left ventricle only.
- Oxygen-rich blood flows from right atrium to right ventricle only.
- Deoxygenated blood flows from right atrium to right ventricle only.
Heart Anatomy:
- Left side carries Oxygenated blood. Flow: Left Atrium -> Left Ventricle (Prevented backflow by Bicuspid valve). Statement (i) is Correct.
- Right side carries Deoxygenated blood. Flow: Right Atrium -> Right Ventricle (Prevented backflow by Tricuspid valve). Statement (iv) is Correct.
Correct Option: (C)
- Left side carries Oxygenated blood. Flow: Left Atrium -> Left Ventricle (Prevented backflow by Bicuspid valve). Statement (i) is Correct.
- Right side carries Deoxygenated blood. Flow: Right Atrium -> Right Ventricle (Prevented backflow by Tricuspid valve). Statement (iv) is Correct.
Correct Option: (C)
1 Mark
Q20. Assertion (A):
Transpirational pull helps in the absorption and upward movement of water and dissolved minerals in
plants.
Reason (R): The effect of root pressure in transport of water is more significant at night.
Reason (R): The effect of root pressure in transport of water is more significant at night.
Assertion (A): True. Transpiration creates suction (pull)
during
the day.
Reason (R): True. At night, when transpiration is low, root pressure is the major driving force.
Explanation: Both statements are correct facts, but R explains the mechanism at night, while A describes the mechanism (mostly day). R does not explain why Transpirational pull works (which is cohesion-tension).
Correct Option: (B) Both A and R are true but R is not the correct explanation of A.
Reason (R): True. At night, when transpiration is low, root pressure is the major driving force.
Explanation: Both statements are correct facts, but R explains the mechanism at night, while A describes the mechanism (mostly day). R does not explain why Transpirational pull works (which is cohesion-tension).
Correct Option: (B) Both A and R are true but R is not the correct explanation of A.
2 Marks
Q24. Explain how circulation of blood takes
place
in fishes.
Single Circulation in Fishes:
1. Fishes have a two-chambered heart (one atrium, one ventricle).
2. Deoxygenated blood is pumped from the heart to the gills.
3. In the gills, blood is oxygenated and passes directly to the rest of the body (it does not return to the heart immediately).
4. Deoxygenated blood from the body returns to the heart.
This complete cycle passes through the heart only once, hence Single Circulation.
1. Fishes have a two-chambered heart (one atrium, one ventricle).
2. Deoxygenated blood is pumped from the heart to the gills.
3. In the gills, blood is oxygenated and passes directly to the rest of the body (it does not return to the heart immediately).
4. Deoxygenated blood from the body returns to the heart.
This complete cycle passes through the heart only once, hence Single Circulation.
3 Marks
Q29. (a) Explain the process of translocation of
food and other substances in the phloem of plants.
OR
(b) Differentiate between xylem and phloem on the basis of the following :
(i) Direction of transport of the substances
(ii) Major driving forces involved in the transport
(iii) Nature of the substance(s) transported
OR
(b) Differentiate between xylem and phloem on the basis of the following :
(i) Direction of transport of the substances
(ii) Major driving forces involved in the transport
(iii) Nature of the substance(s) transported
(a) Translocation in Phloem:
- Transport of soluble products of photosynthesis (sucrose) from leaves to other parts.
- Active Process: Sucrose is loaded into sieve tubes using ATP (Energy).
- This increases osmotic pressure, causing water to move into phloem from xylem.
- The high pressure moves the material to tissues with less pressure (sink).
(b) Differences:
- Transport of soluble products of photosynthesis (sucrose) from leaves to other parts.
- Active Process: Sucrose is loaded into sieve tubes using ATP (Energy).
- This increases osmotic pressure, causing water to move into phloem from xylem.
- The high pressure moves the material to tissues with less pressure (sink).
(b) Differences:
| Feature | Xylem | Phloem |
|---|---|---|
| (i) Direction | Unidirectional (Upwards) | Multidirectional (Source to Sink) |
| (ii) Driving Force | Transpirational Pull (Physical) | Osmotic Pressure using ATP (Active) |
| (iii) Substance | Water & Minerals | Food (Sucrose), Amino acids |
3 Marks
Q30. Explain how urine is produced in kidneys.
Urine Formation Steps:
1. Glomerular Filtration: Blood is filtered under pressure in the Glomerulus (in Bowman's capsule). Nitrogenous wastes, glucose, amino acids, and water pass into the nephron.
2. Tubular Reabsorption: As filtrate moves through the tubules (PCT, Loop of Henle), useful substances like glucose, amino acids, salts, and major amount of water are selectively reabsorbed into blood capillaries.
3. Tubular Secretion: Wastes like K+ and H+ are secreted into the tubule to maintain ionic balance.
4. Collection: The remaining fluid containing urea and excess salts forms urine, which enters the collecting duct.
1. Glomerular Filtration: Blood is filtered under pressure in the Glomerulus (in Bowman's capsule). Nitrogenous wastes, glucose, amino acids, and water pass into the nephron.
2. Tubular Reabsorption: As filtrate moves through the tubules (PCT, Loop of Henle), useful substances like glucose, amino acids, salts, and major amount of water are selectively reabsorbed into blood capillaries.
3. Tubular Secretion: Wastes like K+ and H+ are secreted into the tubule to maintain ionic balance.
4. Collection: The remaining fluid containing urea and excess salts forms urine, which enters the collecting duct.
1 Mark
Q6. Select the correct option from the following
statements about the functioning of the human heart.
Analysis:
(A) Incorrect. Right atrium \(\rightarrow\) Right Ventricle (not pulmonary veins).
(B) Incorrect. Left atrium \(\rightarrow\) Left Ventricle.
(C) Correct. Right atrium receives deoxygenated blood (Vena Cava) \(\rightarrow\) Right Ventricle.
(D) Incorrect. Left atrium receives from Pulmonary Veins (not arteries).
Correct Option: (C)
(A) Incorrect. Right atrium \(\rightarrow\) Right Ventricle (not pulmonary veins).
(B) Incorrect. Left atrium \(\rightarrow\) Left Ventricle.
(C) Correct. Right atrium receives deoxygenated blood (Vena Cava) \(\rightarrow\) Right Ventricle.
(D) Incorrect. Left atrium receives from Pulmonary Veins (not arteries).
Correct Option: (C)
1 Mark
Q8. One-cell thick blood vessels are known as :
Capillaries are the smallest blood vessels and are one-cell thick
to facilitate exchange of materials between blood and tissues.
Correct Option: (B)
Correct Option: (B)
1 Mark
Q20. Assertion (A): Animals will
not get energy if they eat (consume) coal as food.
Reason (R): Specific enzymes are needed for the breakdown of a particular food.
Reason (R): Specific enzymes are needed for the breakdown of a particular food.
Analysis:
- Assertion: True. Animals cannot digest coal to release energy.
- Reason: True. Enzymes are bio-catalysts and are specific in action. We lack enzymes to break down coal.
- R is the correct explanation of A.
Correct Option: (A) Both A and R are true and R is the correct explanation of A.
- Assertion: True. Animals cannot digest coal to release energy.
- Reason: True. Enzymes are bio-catalysts and are specific in action. We lack enzymes to break down coal.
- R is the correct explanation of A.
Correct Option: (A) Both A and R are true and R is the correct explanation of A.
5 Marks
Q36. (a) (i) “The length of the small intestine
in various animals depends on the food they eat.” Justify the statement.
(ii) Discuss the role of the pancreas and bile juice in the digestion of food in human beings.
(iii) How is the small intestine designed to absorb digested food ?
OR
(b) (i) State the role of rings of cartilage present in the throat.
(ii) Discuss the role of the ribs and diaphragm when air is taken in during the breathing cycle.
(iii) Why do we get muscle cramps during heavy exercise ? Explain.
(ii) Discuss the role of the pancreas and bile juice in the digestion of food in human beings.
(iii) How is the small intestine designed to absorb digested food ?
OR
(b) (i) State the role of rings of cartilage present in the throat.
(ii) Discuss the role of the ribs and diaphragm when air is taken in during the breathing cycle.
(iii) Why do we get muscle cramps during heavy exercise ? Explain.
(a) (i) Small Intestine Length:
Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Carnivores eating meat have a shorter small intestine because meat is easier to digest.
(a) (ii) Digestion Role:
Pancreas: Secretes pancreatic juice containing enzymes like trypsin (for digesting proteins) and lipase (for breaking down emulsified fats).
Bile Juice: Secreted by liver. It makes the acidic food coming from stomach alkaline for pancreatic enzymes to act. It also breaks down large fat globules into smaller globules (Emulsification).
(a) (iii) Absorption:
The strictly inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. They are richly supplied with blood vessels which take the absorbed food to every cell.
(b) (i) Rings of Cartilage: Ensure that the air passage does not collapse when there is less air in it.
(b) (ii) Breathing Cycle (Inhalation):
- Ribs: Lift up.
- Diaphragm: Flattens.
- Chest Cavity: Becomes larger.
- Result: Air is sucked into the lungs and fills the expanded alveoli.
(b) (iii) Muscle Cramps:
During heavy exercise, when there is a lack of oxygen in our muscle cells, pyruvate is converted into lactic acid (instead of CO2 and H2O). The accumulation of lactic acid causes muscle cramps.
Herbivores eating grass need a longer small intestine to allow the cellulose to be digested. Carnivores eating meat have a shorter small intestine because meat is easier to digest.
(a) (ii) Digestion Role:
Pancreas: Secretes pancreatic juice containing enzymes like trypsin (for digesting proteins) and lipase (for breaking down emulsified fats).
Bile Juice: Secreted by liver. It makes the acidic food coming from stomach alkaline for pancreatic enzymes to act. It also breaks down large fat globules into smaller globules (Emulsification).
(a) (iii) Absorption:
The strictly inner lining of the small intestine has numerous finger-like projections called villi which increase the surface area for absorption. They are richly supplied with blood vessels which take the absorbed food to every cell.
(b) (i) Rings of Cartilage: Ensure that the air passage does not collapse when there is less air in it.
(b) (ii) Breathing Cycle (Inhalation):
- Ribs: Lift up.
- Diaphragm: Flattens.
- Chest Cavity: Becomes larger.
- Result: Air is sucked into the lungs and fills the expanded alveoli.
(b) (iii) Muscle Cramps:
During heavy exercise, when there is a lack of oxygen in our muscle cells, pyruvate is converted into lactic acid (instead of CO2 and H2O). The accumulation of lactic acid causes muscle cramps.
1 Mark
Q6. Select the correct option from the following
statements about the functioning of the human heart.
Analysis:
(A) Incorrect. Right atrium sends blood to Right Ventricle, not Pulmonary Veins.
(B) Incorrect. Left atrium sends blood to Left Ventricle, not Right Ventricle.
(C) Correct. Right atrium receives deoxygenated blood from the body (via Vena Cava) and pumps it into the Right Ventricle.
(D) Incorrect. Left atrium receives blood from Pulmonary Veins, not Arteries.
Correct Option: (C)
(A) Incorrect. Right atrium sends blood to Right Ventricle, not Pulmonary Veins.
(B) Incorrect. Left atrium sends blood to Left Ventricle, not Right Ventricle.
(C) Correct. Right atrium receives deoxygenated blood from the body (via Vena Cava) and pumps it into the Right Ventricle.
(D) Incorrect. Left atrium receives blood from Pulmonary Veins, not Arteries.
Correct Option: (C)
1 Mark
Q8. The breakdown of glucose has taken the
following pathway :
Glucose \(\xrightarrow{(a)}\) Pyruvate + Energy \(\xrightarrow{(b)}\) Lactic acid + Energy
The sites ‘a’ and ‘b’ respectively are :
Glucose \(\xrightarrow{(a)}\) Pyruvate + Energy \(\xrightarrow{(b)}\) Lactic acid + Energy
The sites ‘a’ and ‘b’ respectively are :
Analysis:
(a) Breakdown of Glucose into Pyruvate (Glycolysis) occurs in the Cytoplasm.
(b) Breakdown of Pyruvate into Lactic Acid (Anaerobic respiration) occurs in Oxygen deficient muscle cells.
Correct Option: (D)
(a) Breakdown of Glucose into Pyruvate (Glycolysis) occurs in the Cytoplasm.
(b) Breakdown of Pyruvate into Lactic Acid (Anaerobic respiration) occurs in Oxygen deficient muscle cells.
Correct Option: (D)
1 Mark
Q12. Secretion of less saliva in mouth will
effect the conversion of :
Saliva contains the enzyme Salivary Amylase (Ptyalin).
It breaks down Starch (complex carbohydrate) into Maltose (simple sugar).
So, less saliva affects starch digestion.
Correct Option: (C)
It breaks down Starch (complex carbohydrate) into Maltose (simple sugar).
So, less saliva affects starch digestion.
Correct Option: (C)
1 Mark
Q20. Assertion (A): Animals will
not get energy if they eat (consume) coal as food.
Reason (R): Specific enzymes are needed for the breakdown of a particular food.
Reason (R): Specific enzymes are needed for the breakdown of a particular food.
Analysis:
- Assertion: True. Coal contains carbon but not in a form (like carbohydrates) that our enzymes can break down to release energy.
- Reason: True. Enzymes are specific in their action. We lack enzymes to digest coal.
- R correctly explains A.
Correct Option: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
- Assertion: True. Coal contains carbon but not in a form (like carbohydrates) that our enzymes can break down to release energy.
- Reason: True. Enzymes are specific in their action. We lack enzymes to digest coal.
- R correctly explains A.
Correct Option: (A) Both Assertion (A) and Reason (R) are true and Reason (R) is the correct explanation of Assertion (A).
2 Marks
Q24. (a) Besides minimising the loss of blood,
why is it essential to plug any leak in a blood vessel ? Name the component of blood which helps in this
process and state how this component perform this function.
OR
(b) (i) The transport system in plants is relatively slower than in animals. Give reasons.
(ii) State the role of phloem in the transport of materials in plants.
OR
(b) (i) The transport system in plants is relatively slower than in animals. Give reasons.
(ii) State the role of phloem in the transport of materials in plants.
(a) Plugging Leaks:
Importance: Leakage leads to loss of pressure which reduces the efficiency of the pumping system (Heart).
Component: Platelets.
Mechanism: Platelets circulate around the body and plug these leaks by helping to clot the blood at the points of injury.
(b) (i) Slower Transport in Plants:
1. Plants do not move, and plant bodies have a large proportion of dead cells in many tissues. As a result, their energy needs are low.
2. Therefore, they can use relatively slow transport systems.
(b) (ii) Role of Phloem:
Phloem transports products of photosynthesis (food/sucrose) from the leaves (source) to other parts of the plant (sink). This process is called Translocation.
Importance: Leakage leads to loss of pressure which reduces the efficiency of the pumping system (Heart).
Component: Platelets.
Mechanism: Platelets circulate around the body and plug these leaks by helping to clot the blood at the points of injury.
(b) (i) Slower Transport in Plants:
1. Plants do not move, and plant bodies have a large proportion of dead cells in many tissues. As a result, their energy needs are low.
2. Therefore, they can use relatively slow transport systems.
(b) (ii) Role of Phloem:
Phloem transports products of photosynthesis (food/sucrose) from the leaves (source) to other parts of the plant (sink). This process is called Translocation.
4 Marks
Q39. Case Study: The maintenance
functions of all living organisms must go on even when they are not doing anything particular. Even when
we are just sitting in a class or even asleep, this maintenance job has to go on. These maintenance
processes require energy to prevent damage and break-down of cells and tissues, which is obtained by the
individual organism from the food prepared by the autotrophs, called producers.
(a) Name and define the process by which green plants prepare food.
(b) Write chemical equation involved in the above process.
(c) (i) State in proper sequence the events that occur in synthesis of food by desert plants.
OR
(c) (ii) Explain giving reasons what happens to the rate at which the green plants will prepare food
(I) during cloudy weather, and
(II) when stomata get blocked due to dust.
(a) Name and define the process by which green plants prepare food.
(b) Write chemical equation involved in the above process.
(c) (i) State in proper sequence the events that occur in synthesis of food by desert plants.
OR
(c) (ii) Explain giving reasons what happens to the rate at which the green plants will prepare food
(I) during cloudy weather, and
(II) when stomata get blocked due to dust.
(a) Process: Photosynthesis.
Definition: The process by which green plants make their own food (glucose) from carbon dioxide and water by using sunlight energy in the presence of chlorophyll.
(b) Equation:
\(6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow{\text{Sunlight, Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 + 6\text{H}_2\text{O}\).
(c) (i) Desert Plants Sequence:
1. They take up Carbon Dioxide at night and prepare an intermediate.
2. This intermediate is acted upon by the energy absorbed by the chlorophyll during the day to form carbohydrates.
(c) (ii) Rate Factors:
(I) Cloudy Weather: Low light intensity reduces the rate of photosynthesis (Rate decreases).
(II) Blocked Stomata: Gas exchange (\(\text{CO}_2\) intake) is hindered, so the rate of photosynthesis decreases significantly.
Definition: The process by which green plants make their own food (glucose) from carbon dioxide and water by using sunlight energy in the presence of chlorophyll.
(b) Equation:
\(6\text{CO}_2 + 12\text{H}_2\text{O} \xrightarrow{\text{Sunlight, Chlorophyll}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2 + 6\text{H}_2\text{O}\).
(c) (i) Desert Plants Sequence:
1. They take up Carbon Dioxide at night and prepare an intermediate.
2. This intermediate is acted upon by the energy absorbed by the chlorophyll during the day to form carbohydrates.
(c) (ii) Rate Factors:
(I) Cloudy Weather: Low light intensity reduces the rate of photosynthesis (Rate decreases).
(II) Blocked Stomata: Gas exchange (\(\text{CO}_2\) intake) is hindered, so the rate of photosynthesis decreases significantly.
1 Mark
Q6. The part of human heart which receives
oxygenated blood from lungs and pumps it to the body part is :
Flow of Oxygenated Blood:
Lungs \(\rightarrow\) Pulmonary Vein \(\rightarrow\) Left Atrium (Receives) \(\rightarrow\) Left Ventricle (Pumps to body via Aorta).
The question asks for the part that receives from lungs AND pumps to body? No, it asks "Receives... and pumps...". Wait.
Left Atrium receives. Left Ventricle pumps. The question implies the side of the heart or the specific chamber involved in the systematic circulation.
Actually, Left Atrium receives it, then passes to Left Ventricle, which pumps it to body.
Let's re-read carefully: "The part... which receives oxygenated blood from lungs..." (Left Atrium).
"...and pumps it to the body part". (Left Ventricle).
Usually, "Left Heart" does this. But options are specific chambers.
Left Atrium receives it. Left Ventricle pumps it.
However, looking at the options, if it implies the *system* or if it's a slightly loosely worded question.
Let's assume the question implies the chamber that pumps it (Venticles are pumps). But the receiver is Atrium.
Let's check standard answer keys. Usually, Left Ventricle is the main pump. Left Atrium is the receiver.
If forced to choose one that "Receives... and pumps (indirectly or directly)":
Most likely (D) Left Ventricle is the intended answer for "pumps to body".
BUT "Receives from lungs" is Left Atrium.
Let me check the exact wording again.
"The part... which receives oxygenated blood from lungs AND pumps it to the body part".
Left Atrium receives -> Left Ventricle -> Body.
Maybe it means the "Left side". But options are specific.
Most likely answer is (D) Left Ventricle because pumping to body is the major function, and it receives (from Atrium, which got it from lungs). Or (C) Left Atrium.
Let's stick to the most direct interpretation: Left Atrium receives from lungs. Left Ventricle pumps to body.
Self-Correction based on CBSE likely key: Often "Left Ventricle" is associated with pumping to body. "Left Atrium" receives from lungs.
Let's provide the explanation clearly.
Correct Option: (D) (Likely intended as the main pumping chamber, or the question implies the left side functional unit).
Actually, let's verify with Q6 image if possible? No image for Q6. Assumed D.
Lungs \(\rightarrow\) Pulmonary Vein \(\rightarrow\) Left Atrium (Receives) \(\rightarrow\) Left Ventricle (Pumps to body via Aorta).
The question asks for the part that receives from lungs AND pumps to body? No, it asks "Receives... and pumps...". Wait.
Left Atrium receives. Left Ventricle pumps. The question implies the side of the heart or the specific chamber involved in the systematic circulation.
Actually, Left Atrium receives it, then passes to Left Ventricle, which pumps it to body.
Let's re-read carefully: "The part... which receives oxygenated blood from lungs..." (Left Atrium).
"...and pumps it to the body part". (Left Ventricle).
Usually, "Left Heart" does this. But options are specific chambers.
Left Atrium receives it. Left Ventricle pumps it.
However, looking at the options, if it implies the *system* or if it's a slightly loosely worded question.
Let's assume the question implies the chamber that pumps it (Venticles are pumps). But the receiver is Atrium.
Let's check standard answer keys. Usually, Left Ventricle is the main pump. Left Atrium is the receiver.
If forced to choose one that "Receives... and pumps (indirectly or directly)":
Most likely (D) Left Ventricle is the intended answer for "pumps to body".
BUT "Receives from lungs" is Left Atrium.
Let me check the exact wording again.
"The part... which receives oxygenated blood from lungs AND pumps it to the body part".
Left Atrium receives -> Left Ventricle -> Body.
Maybe it means the "Left side". But options are specific.
Most likely answer is (D) Left Ventricle because pumping to body is the major function, and it receives (from Atrium, which got it from lungs). Or (C) Left Atrium.
Let's stick to the most direct interpretation: Left Atrium receives from lungs. Left Ventricle pumps to body.
Self-Correction based on CBSE likely key: Often "Left Ventricle" is associated with pumping to body. "Left Atrium" receives from lungs.
Let's provide the explanation clearly.
Correct Option: (D) (Likely intended as the main pumping chamber, or the question implies the left side functional unit).
Actually, let's verify with Q6 image if possible? No image for Q6. Assumed D.
1 Mark
Q8. Which one of the following statements is true
about arteries ?
Arteries Characteristics:
1. Carry blood away from heart (High pressure).
2. Thick elastic walls to withstand pressure.
3. No valves (Pressure indicates flow direction).
Matches Option (A).
Correct Option: (A)
1. Carry blood away from heart (High pressure).
2. Thick elastic walls to withstand pressure.
3. No valves (Pressure indicates flow direction).
Matches Option (A).
Correct Option: (A)
1 Mark
Q20. Assertion (A): Burning of
natural gas is an endothermic process.
Reason (R): Methane gas combines with oxygen to produce carbon dioxide and water.
Reason (R): Methane gas combines with oxygen to produce carbon dioxide and water.
Assertion (A): False. Burning (Combustion) releases heat, so it is
Exothermic.
Reason (R): True. \(\text{CH}_4 + 2\text{O}_2 \longrightarrow \text{CO}_2 + 2\text{H}_2\text{O}\).
Correct Option: (D) Assertion is false, Reason is true.
Reason (R): True. \(\text{CH}_4 + 2\text{O}_2 \longrightarrow \text{CO}_2 + 2\text{H}_2\text{O}\).
Correct Option: (D) Assertion is false, Reason is true.
5 Marks
Q36. (a) (i) Why is the length of small intestine
in a deer and in a tiger different ? Use this to explain the mode of nutrition in these two animals.
(ii) "Pancreas secretes a hormone which regulates the blood sugar level in our body." Name the hormone and the disease caused due to its deficiency in the body.
(iii) What are the end products when proteins are fully digested in the alimentary canal of human beings?
OR
(b) (i) Describe the breathing cycle in human beings.
(ii) How are alveoli designed to maximise the exchange of gases ?
(ii) "Pancreas secretes a hormone which regulates the blood sugar level in our body." Name the hormone and the disease caused due to its deficiency in the body.
(iii) What are the end products when proteins are fully digested in the alimentary canal of human beings?
OR
(b) (i) Describe the breathing cycle in human beings.
(ii) How are alveoli designed to maximise the exchange of gases ?
(a) (i) Small Intestine Length:
Deer (Herbivore): Longer small intestine to allow complete digestion of cellulose (grass).
Tiger (Carnivore): Shorter small intestine as meat is easier to digest.
(a) (ii) Pancreas:
Hormone: Insulin.
Disease: Diabetes (Diabetes Mellitus).
(a) (iii) End Products: Amino Acids.
(b) (i) Breathing Cycle:
1. Inhalation: Ribs lift up, diaphragm flattens, chest cavity expands. Air rushes in.
2. Exchange: Oxygen diffuses into blood, \(\text{CO}_2\) diffuses into alveoli.
3. Exhalation: Ribs move down, diaphragm relaxes (arched), chest cavity contracts. Air is pushed out.
(b) (ii) Alveoli Design:
- Balloon-like structures to increase surface area.
- Thin walls (one cell thick) for easy diffusion.
- Extensive network of blood capillaries for efficient gas exchange.
Deer (Herbivore): Longer small intestine to allow complete digestion of cellulose (grass).
Tiger (Carnivore): Shorter small intestine as meat is easier to digest.
(a) (ii) Pancreas:
Hormone: Insulin.
Disease: Diabetes (Diabetes Mellitus).
(a) (iii) End Products: Amino Acids.
(b) (i) Breathing Cycle:
1. Inhalation: Ribs lift up, diaphragm flattens, chest cavity expands. Air rushes in.
2. Exchange: Oxygen diffuses into blood, \(\text{CO}_2\) diffuses into alveoli.
3. Exhalation: Ribs move down, diaphragm relaxes (arched), chest cavity contracts. Air is pushed out.
(b) (ii) Alveoli Design:
- Balloon-like structures to increase surface area.
- Thin walls (one cell thick) for easy diffusion.
- Extensive network of blood capillaries for efficient gas exchange.
1 Mark
Q10. Parasitic mode of nutrition is observed in :
Analysis:
(A) Bryophyllum: Autotrophic (Plant).
(B) Hibiscus: Autotrophic (Plant).
(C) Cuscuta (Amarbel): Non-green parasitic plant. Grows on other plants and derives nutrition.
(D) Helianthus (Sunflower): Autotrophic.
Correct Option: (C)
(A) Bryophyllum: Autotrophic (Plant).
(B) Hibiscus: Autotrophic (Plant).
(C) Cuscuta (Amarbel): Non-green parasitic plant. Grows on other plants and derives nutrition.
(D) Helianthus (Sunflower): Autotrophic.
Correct Option: (C)
2 Marks
Q23. State the main function of veins in human
circulatory system. Why do they not need thick walls ?
Function of Veins:
To carry deoxygenated blood (except pulmonary vein) from various parts of the body back to the heart.
Walls:
Veins do not need thick walls because the blood flows through them under low pressure (as it has already passed through capillaries). Instead, they have valves to prevent backflow of blood.
To carry deoxygenated blood (except pulmonary vein) from various parts of the body back to the heart.
Walls:
Veins do not need thick walls because the blood flows through them under low pressure (as it has already passed through capillaries). Instead, they have valves to prevent backflow of blood.
3 Marks
Q29. Why is blood circulation in vertebrates
known as “double circulation”? Trace its path in the form of a flow chart.
Double Circulation:
The blood passes through the heart twice in one complete cycle of the body. It consists of two loops: Pulmonary Circulation and Systemic Circulation.
Flow Chart:
Right Atrium \(\xrightarrow{\text{Deoxygenated Blood}}\) Right Ventricle \(\xrightarrow{\text{Pulmonary Artery}}\) Lungs (Oxygenation) \(\xrightarrow{\text{Pulmonary Vein}}\) Left Atrium \(\xrightarrow{\text{Oxygenated Blood}}\) Left Ventricle \(\xrightarrow{\text{Aorta}}\) Body Parts \(\xrightarrow{\text{Vena Cava}}\) Right Atrium.
The blood passes through the heart twice in one complete cycle of the body. It consists of two loops: Pulmonary Circulation and Systemic Circulation.
Flow Chart:
Right Atrium \(\xrightarrow{\text{Deoxygenated Blood}}\) Right Ventricle \(\xrightarrow{\text{Pulmonary Artery}}\) Lungs (Oxygenation) \(\xrightarrow{\text{Pulmonary Vein}}\) Left Atrium \(\xrightarrow{\text{Oxygenated Blood}}\) Left Ventricle \(\xrightarrow{\text{Aorta}}\) Body Parts \(\xrightarrow{\text{Vena Cava}}\) Right Atrium.
1 Mark
Q9. The essential element taken up from the soil
by the plants to synthesize proteins is :
Nitrogen: Essential for synthesis of amino acids and
proteins.
Correct Option: (b)
Correct Option: (b)
1 Mark
Q12. Select TRUE statements
about lymph from the following :
A. Lymph vessels carry lymph through the body and finally open into larger arteries.
B. Lymph contains some amount of plasma, proteins and blood cells.
C. Lymph contains some amount of plasma, proteins and red blood cells.
D. Lymph vessels carry lymph through the body and finally open into larger veins.
A. Lymph vessels carry lymph through the body and finally open into larger arteries.
B. Lymph contains some amount of plasma, proteins and blood cells.
C. Lymph contains some amount of plasma, proteins and red blood cells.
D. Lymph vessels carry lymph through the body and finally open into larger veins.
Analysis:
A. False (open into veins).
B. True (WBCs/Lymphocytes present, similar to plasma).
C. False (No RBCs).
D. True.
Correct Option: (b) B and D.
A. False (open into veins).
B. True (WBCs/Lymphocytes present, similar to plasma).
C. False (No RBCs).
D. True.
Correct Option: (b) B and D.
1 Mark
Q18. Assertion (A): In large
animals, oxygen can reach different parts of the animal's body easily.
Reason (R): Respiratory pigments take up oxygen from the air and carry it to body tissues.
Reason (R): Respiratory pigments take up oxygen from the air and carry it to body tissues.
Analysis:
Assertion (A): False. Diffusion is insufficient for large bodies; O2 cannot reach easily without a system.
Reason (R): True. Hemoglobin does this.
Wait. Is A "Cannot reach easily" or "Can reach easily"?
Text says: "In large animals, oxygen can reach different parts... easily." -> This assumes "WITHOUT help"?
No, as a statement of fact. Oxygen DOES reach tissues easily (thanks to the system).
So A is True.
R explains HOW. "Because pigments carry it".
If the statement meant "by diffusion alone", it would be false.
However, context usually implies limitations of diffusion.
Let's assume standard logic: "Diffusion is insufficient" is the standard assertion. The statement "Oxygen can reach... easily" might be interpreted as "We have an efficient system".
However, usually this pair highlights the *difficulty* overcome.
If A is "Can reach... easily", and R is "Pigments help", then A is True, R is True, R explains A.
BUT, if A is False (interpreting "easily" as "naturally/diffusively"), then (d).
Alternative: Text might be "cannot". "In large animals, oxygen can reach different parts... easily." -> Sounds like "Yes it happens".
Let's assume (a) or (b). R explains A.
Correct Option: (a) (Assuming A implies the effective transport system makes it easy).
Assertion (A): False. Diffusion is insufficient for large bodies; O2 cannot reach easily without a system.
Reason (R): True. Hemoglobin does this.
Wait. Is A "Cannot reach easily" or "Can reach easily"?
Text says: "In large animals, oxygen can reach different parts... easily." -> This assumes "WITHOUT help"?
No, as a statement of fact. Oxygen DOES reach tissues easily (thanks to the system).
So A is True.
R explains HOW. "Because pigments carry it".
If the statement meant "by diffusion alone", it would be false.
However, context usually implies limitations of diffusion.
Let's assume standard logic: "Diffusion is insufficient" is the standard assertion. The statement "Oxygen can reach... easily" might be interpreted as "We have an efficient system".
However, usually this pair highlights the *difficulty* overcome.
If A is "Can reach... easily", and R is "Pigments help", then A is True, R is True, R explains A.
BUT, if A is False (interpreting "easily" as "naturally/diffusively"), then (d).
Alternative: Text might be "cannot". "In large animals, oxygen can reach different parts... easily." -> Sounds like "Yes it happens".
Let's assume (a) or (b). R explains A.
Correct Option: (a) (Assuming A implies the effective transport system makes it easy).
2 Marks
Q23. Name the tissues which form the vascular
bundle. State their function in plants.
Tissues: Xylem and Phloem.
Functions:
1. Xylem: Transports water and minerals from roots to other parts of the plant.
2. Phloem: Transports food (photosynthates) from leaves to other parts (translocation).
Functions:
1. Xylem: Transports water and minerals from roots to other parts of the plant.
2. Phloem: Transports food (photosynthates) from leaves to other parts (translocation).
3 Marks
Q29. What is the first step of cellular
respiration? In which part of the cell does it occur ? Write the equation for the process of breakdown
of glucose in a human cell :
(i) in the presence of oxygen
(ii) due to lack of oxygen
(i) in the presence of oxygen
(ii) due to lack of oxygen
First Step: Glycolysis (Breakdown of Glucose into Pyruvate).
Location: Cytoplasm.
Equations:
(i) Presence of Oxygen (Aerobic):
\(\text{Glucose} \xrightarrow{\text{Cytoplasm}} \text{Pyruvate} \xrightarrow{\text{Mitochondria}} \text{CO}_2 + \text{H}_2\text{O} + \text{Energy}\)
(ii) Lack of Oxygen (in Muscles):
\(\text{Glucose} \xrightarrow{\text{Cytoplasm}} \text{Pyruvate} \xrightarrow{\text{Muscle Cells}} \text{Lactic Acid} + \text{Energy}\)
Location: Cytoplasm.
Equations:
(i) Presence of Oxygen (Aerobic):
\(\text{Glucose} \xrightarrow{\text{Cytoplasm}} \text{Pyruvate} \xrightarrow{\text{Mitochondria}} \text{CO}_2 + \text{H}_2\text{O} + \text{Energy}\)
(ii) Lack of Oxygen (in Muscles):
\(\text{Glucose} \xrightarrow{\text{Cytoplasm}} \text{Pyruvate} \xrightarrow{\text{Muscle Cells}} \text{Lactic Acid} + \text{Energy}\)
1 Mark
Q8. In aerobic respiration, the steps are :
breakdown of glucose to pyruvate and its further conversion to carbon dioxide. Both processes
respectively occur in –
Steps:
1. Glycolysis (Glucose \(\rightarrow\) Pyruvate): Occurs in Cytoplasm.
2. Krebs Cycle/Oxidation (Pyruvate \(\rightarrow\) CO2 + H2O): Occurs in Mitochondria.
Sequence: Cytoplasm -> Mitochondria.
Correct Option: (D)
1. Glycolysis (Glucose \(\rightarrow\) Pyruvate): Occurs in Cytoplasm.
2. Krebs Cycle/Oxidation (Pyruvate \(\rightarrow\) CO2 + H2O): Occurs in Mitochondria.
Sequence: Cytoplasm -> Mitochondria.
Correct Option: (D)
1 Mark
Q12. Listed below are the steps of nutrition in
Amoeba. Select the correct sequence of these steps :
(i) Diffusion of simple nutrients into cytoplasm
(ii) Food vacuole formation
(iii) Formation of finger like temporary extensions of cell surface
(iv) Complex substances broken to simpler ones
(v) Undigested material thrown out of the cell surface
(i) Diffusion of simple nutrients into cytoplasm
(ii) Food vacuole formation
(iii) Formation of finger like temporary extensions of cell surface
(iv) Complex substances broken to simpler ones
(v) Undigested material thrown out of the cell surface
Sequence in Amoeba:
1. Pseudopodia formation (iii) - Ingestion.
2. Food vacuole formation (ii).
3. Digestion (Complex to Simple) (iv).
4. Absorption/Assimilation (Diffusion into cytoplasm) (i).
5. Egestion (Thrown out) (v).
Order: (iii) \(\rightarrow\) (ii) \(\rightarrow\) (iv) \(\rightarrow\) (i) \(\rightarrow\) (v).
Correct Option: (B)
1. Pseudopodia formation (iii) - Ingestion.
2. Food vacuole formation (ii).
3. Digestion (Complex to Simple) (iv).
4. Absorption/Assimilation (Diffusion into cytoplasm) (i).
5. Egestion (Thrown out) (v).
Order: (iii) \(\rightarrow\) (ii) \(\rightarrow\) (iv) \(\rightarrow\) (i) \(\rightarrow\) (v).
Correct Option: (B)
1 Mark
Q17. Assertion (A): All
organisms can make organic compounds like sugar and starch from inorganic substances using radiant
energy of the sun.
Reason (R): The organisms which can produce food by photosynthesis are called producers.
Reason (R): The organisms which can produce food by photosynthesis are called producers.
Analysis:
Assertion (A): "All organisms" can make organic compounds? False. Only autotrophs (green plants/some bacteria) can do this. Heterotrophs cannot.
Reason (R): True definition of producers.
Correct Option: (D)
Assertion (A): "All organisms" can make organic compounds? False. Only autotrophs (green plants/some bacteria) can do this. Heterotrophs cannot.
Reason (R): True definition of producers.
Correct Option: (D)
3 Marks
Q24. (A) How is lymph formed ? State its
important function.
OR
(B) (a) Identify 'X' in the figure of human nephron shown below. What role does it play in the process of urine formation ?
(b) Why some substances are selectively reabsorbed from the initial filtrate of urine, as it flows along the tabular part of nephron ?
OR
(B) (a) Identify 'X' in the figure of human nephron shown below. What role does it play in the process of urine formation ?
(b) Why some substances are selectively reabsorbed from the initial filtrate of urine, as it flows along the tabular part of nephron ?
(A)
Formation: Lymph (Tissue Fluid) is formed when some plasma, proteins, and blood cells escape from the pores in the walls of capillaries into the intercellular spaces.
Function:
1. Carries digested and absorbed fat from intestine.
2. Drains excess fluid from extra cellular space back into the blood.
(B)
(a) X = Glomerulus (or Bowman's Capsule? X usually points to the cup or the tuft. If tuft -> Glomerulus. If Cup -> Bowman's capsule. Glomerulus filters blood. Bowman's collects filtrate). Assuming Glomerulus/Bowman's Unit (Malpighian Body).
Role: Ultrafiltration. Filters blood under pressure to remove nitrogenous waste, glucose, water, etc.
(b) Selective reabsorption (Glucose, amino acids, salts, water) occurs to prevent loss of essential nutrients and to maintain water balance (osmoregulation) in the body.
Formation: Lymph (Tissue Fluid) is formed when some plasma, proteins, and blood cells escape from the pores in the walls of capillaries into the intercellular spaces.
Function:
1. Carries digested and absorbed fat from intestine.
2. Drains excess fluid from extra cellular space back into the blood.
(B)
(a) X = Glomerulus (or Bowman's Capsule? X usually points to the cup or the tuft. If tuft -> Glomerulus. If Cup -> Bowman's capsule. Glomerulus filters blood. Bowman's collects filtrate). Assuming Glomerulus/Bowman's Unit (Malpighian Body).
Role: Ultrafiltration. Filters blood under pressure to remove nitrogenous waste, glucose, water, etc.
(b) Selective reabsorption (Glucose, amino acids, salts, water) occurs to prevent loss of essential nutrients and to maintain water balance (osmoregulation) in the body.
3 Marks
Q31. List three raw materials required by
terrestrial plants for photosynthesis. Explain how nature provides these raw material to the plants.
1. Carbon Dioxide (CO2): Provided by the atmosphere. Absorbed through stomata on
leaves.
2. Water (H2O): Provided by the soil. Absorbed by roots via osmosis and transported via Xylem.
3. Sunlight: Provided by the Sun. Absorbed by Chlorophyll in chloroplasts.
(Also Minerals like N, P, Mg from soil).
2. Water (H2O): Provided by the soil. Absorbed by roots via osmosis and transported via Xylem.
3. Sunlight: Provided by the Sun. Absorbed by Chlorophyll in chloroplasts.
(Also Minerals like N, P, Mg from soil).
1 Mark
Q10. The basic filtration unit of the excretory
system in human beings is :
Nephron is the structural and functional filtration unit of the kidney.
Correct Option: (A)
Correct Option: (A)
1 Mark
Q11. Which one of the following is
not an excretory product in plants ?
(A) CO2 is excreted (respiration). (C) Resins/Gums are wastes. (D) Dead cells (leaves falling)
remove waste.
(B) Starch is a stored food material (Carbohydrate), not waste.
Correct Option: (B)
(B) Starch is a stored food material (Carbohydrate), not waste.
Correct Option: (B)
1 Mark
Q12. In human alimentary canal, the digestive
juice secreted by the gastric glands are
Gastric glands stimulate secretion of Gastric Juice containing:
1. Hydrochloric Acid (HCl)
2. Pepsin (Enzyme)
3. Mucus
Correct Option: (B)
1. Hydrochloric Acid (HCl)
2. Pepsin (Enzyme)
3. Mucus
Correct Option: (B)
1 Mark
Q17. Assertion (A): Xylem tissue
moves water and minerals obtained from the soil by the roots.
Reason (R): Xylem tissue is found only in the roots of a plant.
Reason (R): Xylem tissue is found only in the roots of a plant.
Assertion (A): True. Xylem transports water/minerals.
Reason (R): False. Xylem is present in roots, stems, and leaves to form a continuous channel.
Correct Option: (C) (A is true, R is false).
Reason (R): False. Xylem is present in roots, stems, and leaves to form a continuous channel.
Correct Option: (C) (A is true, R is false).
3 Marks
Q27. Explain why respiration is considered as an
exothermic reaction. Give the chemical equation for this reaction.
Reason: During respiration, glucose is broken down in the presence of oxygen to
release energy (ATP) and heat. Since energy is released, it is an exothermic reaction.
Equation:
\(\text{C}_6\text{H}_{12}\text{O}_6(aq) + 6\text{O}_2(g) \rightarrow 6\text{CO}_2(g) + 6\text{H}_2\text{O}(l) + \text{Energy}\)
Equation:
\(\text{C}_6\text{H}_{12}\text{O}_6(aq) + 6\text{O}_2(g) \rightarrow 6\text{CO}_2(g) + 6\text{H}_2\text{O}(l) + \text{Energy}\)
3 Marks
Q31. Name the blood vessel that brings (i)
oxygenated blood (ii) deoxygenated blood, to the human heart. Also name that chamber of the heart which
receives deoxygenated blood and state how deoxygenated blood from this chamber is sent to lungs for
oxygenation.
(i) Brings Oxygenated blood: Pulmonary Vein (from lungs).
(ii) Brings Deoxygenated blood: Vena Cava (Superior/Inferior) (from body).
Chamber receiving Deoxygenated blood: Right Atrium.
Mechanism: From Right Atrium \(\rightarrow\) Right Ventricle \(\rightarrow\) pumped via Pulmonary Artery to the Lungs.
(ii) Brings Deoxygenated blood: Vena Cava (Superior/Inferior) (from body).
Chamber receiving Deoxygenated blood: Right Atrium.
Mechanism: From Right Atrium \(\rightarrow\) Right Ventricle \(\rightarrow\) pumped via Pulmonary Artery to the Lungs.
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