Previous Year Questions: Life Processes

Ans: (c) Starch into simple sugars

Saliva in the mouth contains the enzyme salivary amylase, which helps in the breakdown of starch into simple sugars. If less saliva is secreted, this conversion will be affected.

Ans: (d) Cytoplasm and Oxygen deficient muscle cells

The breakdown of glucose into pyruvate occurs in the cytoplasm. Under oxygen-deficient conditions in muscle cells, pyruvate is converted into lactic acid with the release of a small amount of energy.

Ans: (d) Amount of water in guard cells

The guard cells control the opening and closing of stomata. When they are full of water (turgid), the stomata open; when they lose water (flaccid), the stomata close.

Ans: (b) Capillaries

Capillaries are the one-cell thick blood vessels that allow exchange of materials like oxygen, carbon dioxide, nutrients, and wastes between blood and body tissues.

Ans: (a) Nitrogen

Nitrogen is an essential element required by plants for the synthesis of proteins and other important compounds like nucleic acids.

Ans: (b) B and D

Lymph contains plasma, proteins, and white blood cells (not red blood cells).
Lymph vessels carry lymph and open into larger veins, helping in the return of tissue fluid to the blood.

Ans: (c) Right atrium receives deoxygenated blood from the body and sends it to the right ventricle.

The right atrium collects deoxygenated blood from all parts of the body through veins and passes it to the right ventricle, which then pumps it to the lungs for oxygenation.

Ans: (c) Cuscuta

Cuscuta (also known as Amarbel) shows a parasitic mode of nutrition, as it obtains food from the host plant on which it climbs by absorbing nutrients through specialized structures called haustoria.

Ans: (d) A is false, but R is true.

Ans: (c) A is true, but R is false.

The xylem indeed transports water and minerals from the roots to other parts of the plant, but it is not found only in the roots - it is present throughout the plant, including the stems and leaves.

Ans: (b) Starch

Plants remove wastes such as carbon dioxide through stomata. Substances like resins and gums are stored in old xylem or dead tissues and are removed when these parts are shed. Dead cells are not excreted but are discarded by shedding of leaves, bark, or fruits.

Ans: (a) Nephron

The nephron is the basic structural and functional unit of the human kidney.
It is responsible for the filtration of blood and the formation of urine.

Ans: (b) Hydrochloric acid, Pepsin, Mucus
Gastric Glands Secretions:

• Hydrochloric acid (HCl): Creates an acidic environment (pH 1.5-3.5) to activate pepsin and kill pathogens.
• Pepsin: Digests proteins into peptides (activated from pepsinogen by HCl).
• Mucus: Protects the stomach lining from acid and pepsin damage.

Other Options:

• Bile: Secreted by the liver, stored in the gallbladder, acts in the small intestine.
• Trypsin, Lipase: Secreted by the pancreas, not gastric glands.
• Salivary amylase: Secreted in saliva, not stomach.

Ans: (c) (iii), (ii), (iv), (i), (v)

In Amoeba, nutrition occurs in this sequence:

(iii) Formation of pseudopodia (finger-like extensions) to engulf food,
(ii) Formation of a food vacuole,
(iv) Digestion of complex food into simpler substances,
(i) Absorption of nutrients into the cytoplasm,
(v) Egestion of undigested material from the cell.
Correct sequence: (iii) → (ii) → (iv) → (i) → (v)

Ans: (d) Cytoplasm and Mitochondria

In aerobic respiration, glucose is first broken down into pyruvate in the cytoplasm, and then pyruvate is further broken down into carbon dioxide and water in the mitochondria, releasing energy.

Ans: (a) It is essential to plug any leak in a blood vessel to prevent blood loss and maintain blood pressure so that oxygen and nutrients can continue to reach all parts of the body.

The component of blood that helps in this process is platelets.
Platelets release certain enzymes that help in the clotting of blood, forming a clot or scab at the site of injury, thereby sealing the wound and preventing further bleeding.

OR
(b) (i) The transport system in plants is slower than in animals because:

• Plants do not have a pumping organ like the heart.
• The movement of materials in plants depends mainly on physical processes such as diffusion, osmosis, and transpiration pull.

(ii) The phloem transports the prepared food (sucrose) from the leaves (source) to other parts of the plant (sink) like roots, fruits, and storage organs - a process known as translocation.

Ans: The main function of arteries is to carry oxygenated blood away from the heart to different parts of the body.

They have thick and elastic walls because:

• The blood pumped by the heart flows through them at high pressure, and
• The elasticity helps them withstand and maintain this high pressure without bursting.

Ans: Plants get rid of their waste materials in several ways, such as:

1. Gaseous wastes like CO₂ and O₂ are removed through stomata in leaves and lenticels in stems.
2. Excess water is lost by transpiration through stomata.
3. Resins and gums are stored in old xylem or other dead tissues and are removed from the plant when these tissues are shed.
4. Wastes may also be stored in leaves, bark, or fruits, which fall off from the plant.

Thus, plants use different methods to manage and remove their wastes efficiently.

Ans: 

(a) In aerobic respiration, the breakdown of pyruvate produces carbon dioxide and water, while in anaerobic respiration in human beings, it produces lactic acid.

(b) In respiration, carbon dioxide is released, whereas in photosynthesis, oxygen is released.

(c) In terrestrial animals, lungs are the organs of respiration, while in fishes, gills are used for respiration.

Ans: 

(a) Two nitrogenous waste products removed from the blood by human kidneys are urea and uric acid.

(b) The capillary cluster formed by a branch of the renal artery in the Bowman's capsule is called the glomerulus.

(c) Flow chart showing the path of urine:

Ans:  Blood circulation in vertebrates is called double circulation because the blood passes through the heart twice during one complete cycle - once for oxygenation and once for supplying oxygenated blood to the body.
This ensures efficient separation of oxygenated and deoxygenated blood.

Flow chart of Double circulation:

Ans:

The first step of cellular respiration is the breakdown of glucose into pyruvate, and it occurs in the cytoplasm of the cell.

(i) In the presence of oxygen (Aerobic respiration):

Pyruvate is completely broken down into carbon dioxide and water in the mitochondria, releasing energy.

(ii) Due to lack of oxygen (Anaerobic respiration):

In the absence of oxygen, pyruvate is converted into lactic acid in the muscle cells, releasing less energy.

Ans:

(i) The blood vessel that brings oxygenated blood to the heart is the pulmonary vein.
(ii) The blood vessel that brings deoxygenated blood to the heart is the vena cava (superior and inferior vena cava).

The right atrium of the heart receives deoxygenated blood from all parts of the body through the vena cava.
From the right atrium, the blood passes into the right ventricle, which then pumps the deoxygenated blood to the lungs for oxygenation through the pulmonary artery.

Ans:
(a) (i) The length of the small intestine varies in different animals according to their diet.

• In herbivores, such as cows and rabbits, the small intestine is longer because plant food (cellulose) is hard to digest, and it needs more time for complete digestion and absorption.
• In carnivores, like tigers and lions, it is shorter because animal flesh is easier to digest.

(ii) The role of the pancreas and bile juice in the digestion of food in human beings is as follows:

• The pancreas secretes pancreatic juice which contains enzymes such as trypsin (for digesting proteins) and lipase (for breaking down fats).
• The bile juice, produced by the liver and stored in the gall bladder, helps in the emulsification of fats-breaking them into smaller droplets for easier enzyme action.

(iii) The small intestine is highly adapted for absorption of digested food because:

• Its inner walls have finger-like projections called villi, which increase the surface area for absorption.
• Each villus contains blood capillaries, allowing digested nutrients to quickly enter the bloodstream and be transported to different parts of the body.

OR

(i) The rings of cartilage present in the trachea prevent it from collapsing when there is no air inside, keeping the airway open for smooth breathing.(ii) During inhalation, the ribs move upward and outward, and the diaphragm contracts and moves downward, increasing the space in the chest cavity. This creates low pressure, allowing air to enter the lungs.
(iii) During heavy exercise, there is a lack of oxygen in the muscles. Hence, anaerobic respiration takes place, producing lactic acid. The accumulation of lactic acid causes muscle cramps and fatigue.

Ans: 

(a) The process by which green plants prepare food is called photosynthesis.
It is the process by which green plants use sunlight, carbon dioxide, and water to produce food (glucose) and release oxygen.

(b) Chemical equation of photosynthesis:

(c) (i) In desert plants, stomata remain closed during the daytime to reduce water loss and open at night to take in carbon dioxide. This helps the plant conserve water while carrying out photosynthesis.

OR

(c) (ii)
(I) During cloudy weather, sunlight is less available, so the rate of photosynthesis decreases.
(II) When stomata get blocked due to dust, CO₂ cannot enter the leaves, and hence the rate of photosynthesis decreases or may stop completely depending on blockage.

Ans: (c)

Stomata are small openings on the surface of leaves that allow gases to enter and exit the plant. They close when the plant doesn't need carbon dioxide for photosynthesis (which is when it's not producing food) and when water flows out of the guard cells (which helps the plant conserve water). Therefore, the correct answers are (ii) and (iii).

Ans: 
(i) Hydrochloric acid: Creates an acidic environment that helps enzymes work and kills harmful microorganisms.

(ii) Villi: Increases the surface area of the intestine, enhancing the absorption of nutrients.
(iii) Anal Sphincter: Controls the release of waste from the body through the anus.
(iv) Lipase: Breaks down fats into smaller molecules, aiding in their digestion.

Ans: (i) In large animals, diffusion alone cannot deliver enough oxygen throughout the body. Instead, respiratory pigments are essential because they:

• Absorb oxygen from the air in the lungs.
• Transport oxygen to tissues that need it.
• Release oxygen where it is required.

In humans, the main respiratory pigment is haemoglobin, found in red blood cells, which has a strong affinity for oxygen. Carbon dioxide is mostly carried in a dissolved form in the blood.

(ii) Reasons:
(a) Rings of cartilage in the throat prevent the air passage from collapsing.
(b) Lungs retain a residual volume of air to allow time for oxygen absorption and carbon dioxide release.
(c) When we breathe in, the diaphragm flattens and the ribs lift, making the chest cavity larger, which draws air into the lungs.
(d) The walls of alveoli contain many blood vessels to facilitate gas exchange.

Ans: (c)

• (A) is incorrect because the right atrium receives deoxygenated blood from the body through the vena cava, not oxygenated blood from the lungs. The pulmonary artery carries deoxygenated blood from the right ventricle to the lungs, not to the right atrium.
• (B) is correct because the left atrium transfers oxygenated blood to the left ventricle, which then pumps it to various parts of the body through the aorta.
• (C) is correct because the right atrium receives deoxygenated blood through the vena cava from the upper and lower parts of the body.
• (D) is incorrect because it is the left ventricle, not the left atrium, that transfers oxygenated blood to the aorta, which then sends it to different parts of the body.

Therefore, the correct answer is (c) (B) and (C).

Ans: 

• The process is translocation.
• It involves the movement of food, mainly sugars like sucrose, from the leaves (where photosynthesis occurs) to other parts of the plant through the phloem.
• This ensures all parts of the plant receive nutrients for growth, storage, and energy.

Ans: (c)
The correct statements about the human heart are (B) and (C). The left atrium does transfer oxygenated blood to the left ventricle, which then pumps it to the body. The right atrium receives deoxygenated blood from the body through the vena cava, while (A) is incorrect because the right atrium actually receives deoxygenated blood, not oxygenated, and (D) is misleading as the left atrium transfers blood to the left ventricle, not directly to the aorta.

Ans: (a) Salivary glands; Starch / Carbohydrate
(b) Stomach, Anus
(c) The consequences of specific conditions are:

(i) If mucus is not secreted by the gastric glands, the inner lining of the stomach will be unprotected from acid, leading to potential damage.

(ii) If villi are absent in the small intestine, the absorption of digested food will be significantly reduced.

OR
(c) Emulsification of fats.
Acidic medium has to be made alkaline for the pancreatic enzymes to act.  

Ans: (b)

During digestion in humans:

• Proteins are broken down into amino acids.
• Carbohydrates are converted into glucose.
• Fats are transformed into fatty acids and glycerol.

The correct answer is (b) as it accurately describes the final products of these macronutrients after digestion.

Ans: Water reaches the leaves through the xylem.

1. Roots absorb water from the soil by osmosis.
2. Water moves upward through the xylem due to transpiration pull, capillary action, and cohesion of water molecules.

This ensures water supply to the leaves for photosynthesis and other processes.

Ans: (d)

The process of transporting soluble products of photosynthesis in plants is called translocation. This involves:

• Moving substances like sugars from the leaves, where they are produced, to other parts of the plant.
• Utilising the phloem, a type of vascular tissue, for this transport.
• Delivering essential nutrients, including amino acids, to storage organs such as roots, fruits, and seeds.
• Facilitating movement in both upward and downward directions through sieve tubes and companion cells.

Translocation is vital for distributing energy throughout the plant, ensuring that all parts receive the necessary nutrients for growth and development.

Ans: (a)

i. The formation of lactic acid in muscles leads to cramps.

ii. Aerobic respiration occurs with oxygen, while cramps result from anaerobic respiration, which happens without oxygen.

iii. End products of aerobic respiration are carbon dioxide, water, and energy, whereas anaerobic respiration produces lactic acid and energy.

OR
(b) Tissue fluid / Extracellular fluid Functions:
i. Carries digested and absorbed fats from the intestine.  
ii. Drains excess fluid from extracellular space back into the blood.
iii. Fight against infections.

Ans: (a) 

• Take two healthy potted plants, A and B of nearly the same  size.
• Keep them in darkness for three days. (Destarch the plant)
• Place a watch glass containing potassium hydroxide by the side of potted plant A but not in potted plant B.
• Cover both the plants with separate bell jars and seal the bottom of the jars with Vaseline.
• Keep both the plants in sunlight for two hours.
• Pluck one leaf each from both the plants and test for the presence of starch with iodine solution.
• Observation: The leaf of the potted plant A with KOH did not turn blue-black, indicating that starch was not present. The leaf of the potted plant B turns blue.
• Conclusion: KOH absorbs CO₂ so photosynthesis did not occur in potted plant A.

OR
(b) (i) In set up (I) lime water turns milky in more time as compared to set up (II) because the air we exhaled contains high percentage of CO₂ as compared to atmospheric air.  
(ii)

Two labellings: (I) Guard Cells
(II) Chloroplast Two functions performed by stomata:
Gaseous exchange
Transpiration

Ans: (b)
The correct answer is (b) lifted ribs and flattened diaphragm. When a person breathes in, the diaphragm contracts and flattens, while the ribs are lifted upward and outward. This movement creates more space in the chest cavity, allowing air to fill the lungs.

Ans: (c)
The correct answer is (c) Assertion (A) is true, but Reason (R) is false. Aquatic organisms do breathe faster than terrestrial organisms because they need to extract enough oxygen from water, which has less oxygen available than air. Therefore, while the assertion is correct, the reason given is incorrect because it states that water has a high amount of dissolved oxygen, which is not true compared to air.

Ans: (b)
The opening and closing of stomata are indeed regulated by the movement of water in and out of guard cells. Here's a brief explanation of how it works:

Mechanism of Stomatal Movement:

Guard Cells and Stomata:

• Stomata are small openings on the surfaces of leaves and stems that allow for gas exchange (CO₂, O₂, and water vapor) between the plant and the atmosphere.
• Each stoma is flanked by a pair of guard cells, which control the opening and closing of the stoma.

Opening of Stomata:

• When guard cells take up water by osmosis, they become turgid (swollen).
• The turgidity of guard cells is primarily driven by the active transport of potassium ions (K⁺) into the guard cells. This lowers the water potential inside the guard cells, causing water to enter by osmosis.
• As the guard cells swell, they bow outward, causing the stomatal pore to open.

Closing of Stomata:

• When the guard cells lose water, they become flaccid (less swollen).
• The loss of turgor pressure in the guard cells is usually due to the active transport of potassium ions (K⁺) out of the guard cells. This raises the water potential inside the guard cells, causing water to exit by osmosis.
• As the guard cells lose turgor and shrink, the stomatal pore closes.

Ans: (c)
Assertion (A):

• This statement is true. The small intestine is lined with villi, which are small, finger-like projections rich in blood vessels. These vessels help absorb nutrients from digested food into the bloodstream.

Reason (R):

• This statement is false. While it is true that the villi increase the surface area of the small intestine, their primary role is to aid in the absorption of nutrients, not in the digestion of food. Digestion is primarily completed by enzymes within the small intestine.

Conclusion: (A) is true, but (R) is false.

Ans: (b)

• Roots absorb water from the soil through a process called osmosis.
• This process occurs because of a difference in ion concentration between the roots and the soil.
• As a result, water moves into the roots to balance this concentration difference.

Ans: (b)
 In aquatic organisms, the rate of breathing is higher.
These organisms utilize oxygen dissolved in water.
The amount of dissolved oxygen in water is relatively low compared to the oxygen available in the air.
Therefore, aquatic organisms need to breathe faster to obtain sufficient oxygen for their survival.

Ans: (b)

 Transpiration is a vital process in plants that involves the loss of water vapour from the aerial parts, primarily leaves. This process plays a crucial role in several ways:

• Water Movement: It creates a suction force that pulls water from the roots through the xylem.
• Nutrient Transport: Transpiration aids in the upward movement of water and dissolved minerals from the roots to the leaves.
• Temperature Regulation: It helps maintain optimal temperatures within the plant.

During the day, when the stomata are open, transpiration becomes the main driving force for water movement. At night, root pressure assists in this transport. Overall, transpiration is essential for maintaining the plant's hydration and nutrient supply.

Ans: (b)

• Process (X): Transpiration 
  Transpiration is the process where water is lost in the form of vapours from the aerial parts of plants, primarily through the stomata in the leaves.
• Significance (Y): Temperature Regulation 
  Transpiration helps in temperature regulation by cooling the plant. As water evaporates from the leaf surfaces, it dissipates heat, thus maintaining optimal temperature conditions for various physiological processes, including photosynthesis.

Ans: (d)
Assertion (A): The walls of atria are thicker than those of the ventricles.

• This statement is false. In reality, the walls of the ventricles are thicker than those of the atria.
• Ventricles have thicker muscular walls because they pump blood out of the heart to the lungs and the rest of the body, which requires more force (pressure).

Reason (R): Ventricles have to pump blood into various organs at high pressure.

• This statement is true. Ventricles indeed pump blood into the arteries and throughout the body at high pressure to ensure blood reaches all organs and tissues.

Therefore, while Reason (R) correctly explains the physiological need for thicker ventricular walls due to high-pressure pumping, Assertion (A) is incorrect because the ventricular walls are thicker than atrial walls, not the other way around.

Ans: The plant kept in the dark could not survive because it could not perform photosynthesis and hence could not produce food. Without food, respiration cannot continue for long, leading to the death of the plant.

Ans: The three events that occur during the process of photosynthesis are;
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates (carbon assimilation). 

Ans: (i) In Paramecium, a unicellular protozoan, the hair-like outgrowth cilia are present on the entire surface and help collect the food. They sweep the food inside the body through the oral groove.
(ii) (a) Role of hydrochloric acid: It helps to maintain the acidic pH in the stomach required for activation of the enzyme pepsin that digests proteins in the stomach.
(b) Role of trypsin in our digestion system: Trypsin breaks down protein into smaller peptides in the duodenum of the small intestine. It helps in digesting dietary protein by breaking the chain of amino acids. It also activates some proenzymes present in pancreatic juice.
(c) Role of muscular walls in the stomach in our digestive system: The muscular walls in the stomach contract periodically and thereby help in the churning and mixing of the food with the digestive enzymes and HCI. It helps in chemical digestion.
(d) Role of salivary amylase in our digestive system: Salivary amylase found in saliva breaks down the starch and converts it into the simplest sugar. 

Ans: (a)  The action of saliva on food can be demonstrated through a simple activity:

• Take two test tubes, A and B.
• In test tube A, add one teaspoon of boiled rice.
• In test tube B, add one teaspoon of boiled rice that has been chewed for 3 to 5 minutes.
• Add 3.4 mL of water to both test tubes.
• Add a few drops of iodine solution to each test tube.

Results:

• In test tube A, the rice changes colour due to the absence of enzymes.
• In test tube B, there is no colour change because the amylase enzyme in saliva breaks down the starch into simple sugars.

(b)  Bile juice emulsifies fats by breaking them into small droplets, making it easier for digestive enzymes to act on them. It also makes the medium alkaline for pancreatic enzymes.

Ans: Tissue fluid is also called lymph. The functions of tissue fluid are:
(i) It carries digested and absorbed fat from the intestine.
(ii) It drains excess fluid from extracellular space back into the blood. 

Ans: (a) If the xylem is removed, transport of water and minerals from the soil would not occur, which leads to the wilting of leaves and, ultimately, the death of the plant.
(b) In case of any injury, when bleeding occurs, platelets circulate around the body and form a mesh-like network or clot at the site of injury. 

Ans: (i)  Double circulation is a system where blood passes through the heart twice during one complete cycle. It consists of two main pathways:

• Systemic circulation: Carries oxygen-rich blood from the heart to the body.
• Pulmonary circulation: Transports deoxygenated blood from the heart to the lungs for oxygenation.

(ii) The separation of the heart into right and left sides is beneficial because:

• It prevents mixing of oxygenated and deoxygenated blood.
• This separation allows for a more efficient supply of oxygen to the body.
• Birds and mammals, being warm-blooded, have high energy needs and require a constant oxygen supply.
• Mixing blood could lead to inefficient oxygen delivery, which is critical for their complex metabolism.

In summary, the distinct sides of the heart ensure that oxygen-rich blood is effectively circulated to all body parts, supporting the energy demands of these animals.

Ans: (i) Renal artery: Carries blood from the aorta to the kidneys for filtration.
(ii) Urethra: Transports urine from the bladder to the outside of the body.

(iii) Glomerulus:  Filters blood to initiate the formation of urine.
(iv) Tubular part of nephron: Enables selective reabsorption of essential substances like glucose, amino acids, salts, and water into the blood.

Ans: Leaves of a plant assist in excretion in the following ways:

• Stomata: Most carbon dioxide is released through tiny openings called stomata in the leaves.
• Transpiration: Plants lose excess water through a process known as transpiration, which is the evaporation of water from the leaf surface.
• Waste Storage: Many waste products are stored in leaves, which are eventually shed, allowing the plant to excrete these materials.

Ans: (d)
(i) Rhizopus is a fungus that performs extracellular digestion. It secretes digestive enzymes outside its body to break down food material into simpler substances, which are then absorbed.
(ii) Cuscuta is a plant parasite that absorbs nutrients directly from the host plant.
(iii) Tapeworm is an animal parasite that lives inside the host's body and absorbs pre-digested nutrients.
(iv) Rhizobium is a nitrogen-fixing bacterium associated with legume roots; it does not break down food outside the body for absorption.
Therefore, (d) a fungi, Rhizopus is correct, as it digests food material outside its body and then absorbs it.

Ans: (d)
(a) This statement is correct. The length of the small intestine varies among animals depending on their diet. Herbivores generally have longer small intestines than carnivores to allow more time for digesting plant material.
(b) This statement is correct. The small intestine is the primary site for the complete digestion of food, where nutrients are broken down and absorbed.
(c) This statement is correct. The small intestine receives secretions from the liver (bile) and the pancreas (pancreatic enzymes) that aid in digestion.
(d) This statement is incorrect. The main function of the villi in the small intestine is to absorb nutrients, not water. Water absorption primarily occurs in the large intestine, not the small intestine.
Therefore, the correct answer is (d), as it is the statement that is NOT correct.

Ans: (A) Vena cava:  The vena cava consists of two main veins:

• Superior vena cava: Carries deoxygenated blood from the upper body and arms to the right atrium.
• Inferior vena cava: Transports deoxygenated blood from the legs and abdominal area to the right atrium.

(B) Pulmonary artery: 

• It carries deoxygenated blood from the right ventricle to the lungs.
• In the lungs, the blood becomes oxygenated.

Ans: (A) ATP in Cellular Respiration:

• ATP is the energy currency of cells.
• Most ATP is produced in the mitochondrial matrix during cellular respiration.
• ATP is the energy currency of the cell and stores the energy released during respiration for use in life processes.

(B) Gas Exchange in Plants:

• Plants exchange gases through stomata.
• Large intercellular spaces ensure all cells contact air.
• Carbon dioxide and oxygen are exchanged by diffusion.

(C) Conditions Affecting Gas Diffusion:

• The direction of diffusion depends on environmental conditions.
• It also relies on the needs of the plant.
• At night, carbon dioxide is mainly released; during the day, oxygen is produced.

Ans: (b)
Saliva is secreted in the mouth (i) and contains the enzyme salivary amylase, which helps digest carbohydrates. The liver (ii) secretes bile to emulsify fats, breaking them into smaller globules for easier digestion. The pancreas (iii) produces pancreatic juice, which contains enzymes like trypsin for protein digestion.

Ans: (b)
 In the given experiment, KOH (Potassium hydroxide) in the test tube absorbs carbon dioxide; thus, due to the absence of CO₂, the leaf fails to produce starch which proves that carbon dioxide is necessary for photosynthesis.

Ans: (a)
 The given experiment demonstrates the requirement of carbon dioxide for photosynthesis. When KOH absorbs the available CO₂ from the portion of leaf dipped in it, formation of sugar and starch is inhibited and the portion of leaf dipped in KOH did not show any change when dipped in iodine solution. Thus, it is proved that CO₂ is necessary for photosynthesis.

Ans: (c)
Following are the three events that occur during the process of photosynthesis
(i) Absorption of light energy by chlorophyll.
(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
(iii) Reduction of carbon dioxide to carbohydrates.

Ans: (a)
 The brown coloured iodine will turn blue-black when it reacts with starch.

Ans: (c)
 Unicellular organisms are one-celled and perform all the life processes that are essential for maintaining the life of cell or organisms like nutrition, respiration, reproduction, excretion, etc. In single-celled organisms such as Amoeba, complex substances are broken into simpler substances.

Ans: (c)
 The opening and closing of the stomatal pore depend on the turgidity of the guard cells. When guard cells lose water, they become flaccid, leading to a closed stomatal pore. Conversely, when they swell with water, the pore opens.

Ans: (b)
The correct answer is (b) Both (A) and (R) are true but (R) is not the correct explanation of (A). Nitrogen is indeed essential for plant growth, and plants absorb it mainly as inorganic nitrates or nitrites. However, while the soil is a rich source of nutrients for plants, the reason provided does not directly explain why nitrogen is taken up in that specific form, so it's not a correct explanation of the assertion.

Ans: (c)
Both potted plants should be kept in sunlight for about two hours before the starch test.

Ans: (b)
 The length of the small intestine in a deer is greater than that of a tiger due to their differing diets.

• Herbivores, like deer, consume grass, which is high in cellulose. This requires a longer small intestine for effective digestion.
• Carnivores, such as tigers, eat meat, which is easier to digest, allowing for a shorter small intestine.

The structure of the small intestine is adapted to the dietary needs of each animal, reflecting their evolutionary differences.

Ans: (a)
 During heavy exercise, when oxygen is scarce in our muscle cells, the process of anaerobic respiration occurs. Here's a simplified breakdown:

• Glucose (a six-carbon molecule) is broken down into pyruvate (a three-carbon molecule).
• This conversion leads to a build-up of lactic acid in muscles, which can cause cramps.
• In the absence of oxygen, pyruvate is converted into lactic acid and energy.

Ans: (c)
The energy released during cellular respiration is immediately used to synthesise a molecule called ATP which is energy currency of the cell and is used as fuel for cellular activities.

Ans: (a)

During inhalation, we lift our ribs and flatten our diaphragm (A), which enlarges the chest cavity. This creates a vacuum that pulls air into the lungs, filling the expanded alveoli.When we exhale, our ribs and diaphragm return to their normal positions, causing the chest cavity to shrink. This pushes air out of the lungs.

• The lungs always retain a residual volume of air, ensuring there is enough time for oxygen absorption and carbon dioxide release.
• This residual volume remains constant under normal conditions.

Ans: (d)

The rate of breathing in aquatic organisms is much slower than that seen in terrestrial organisms.The rate of breathing in aquatic organisms is actually much faster than in terrestrial organisms due to the following reasons:

• The amount of dissolved oxygen in water is relatively low compared to the oxygen available in the air.
• Aquatic animals must breathe rapidly to obtain enough oxygen from the water.
• Fish, for example, take in water through their mouths and push it past their gills, where oxygen is absorbed into their blood.

Ans:  (c)
 The mucus lining in the nasal passage serves several important functions:

• It helps to moisten the air we breathe.
• It warm the inhaled air.
• It traps dust particles and other impurities, acting as a filter.

Ans: (a)
In aerobic respiration, glucose is completely broken down to CO₂ and H₂O with the production of  a large amount of energy (ATP).

Thus, CO₂ and water are formed as a result of aerobic respiration and will not formed in the absence of oxygen (anaerobic respiration).

Ans: (b)

• Both fish and humans have respiratory structures that facilitate gas exchange.
• Both possess thin and moist surfaces for efficient gas exchange.
• In fish, this occurs in the gills, while in humans, it takes place in the alveoli.
• This structure allows for the diffusion of oxygen into the blood and the removal of carbon dioxide.

Ans: (c)

• When a person exhales into a test tube containing lime water, the following occurs:
• The lime water turns milky due to the formation of a white precipitate.
• This change indicates that the air we exhale contains a higher level of carbon dioxide.
• The reaction occurs because exhaled air has more carbon dioxide compared to inhaled air.

Ans: (a)

• The right side handles deoxygenated blood, sending it to the lungs for oxygen.
• The left side manages oxygenated blood, distributing it to the body.
• This separation prevents mixing of the two blood types, ensuring a more efficient supply of oxygen.
• It is particularly beneficial for animals with high energy needs, such as birds and mammals, which require constant energy to maintain their body temperature.

Ans: (a)
 In spring, new buds are formed. These buds need more energy to grow than other parts of the plant. This energy comes from the sugar stored in root or stem tissue and is transported to the buds by phloem.

Ans: (d)
The upward movement of water in tall trees is primarily driven by transpiration. This process involves:

• Water evaporating from the stomata in the leaves.
• This evaporation creates a negative pressure in the leaves and xylem tissues.
• As a result, water is pulled up from the roots through the xylem.
  In summary, transpiration not only aids in the movement of water but also helps regulate the plant's temperature.

Ans: (b)

Capillaries are tiny blood vessels with very thin walls, just one cell thick. They play a crucial role in the body by:

• Allowing the exchange of materials between blood and surrounding cells.
• Facilitating the transfer of oxygen and nutrients to tissues.
• Collecting waste products from cells for removal.

After the exchange, capillaries merge to form veins, which carry blood away from the tissues.

Ans: (d)
 Blood vessel A represents the pulmonary artery, while blood vessel B signifies the pulmonary vein.
The key functions of these blood vessels are:

• Pulmonary artery: Carries deoxygenated blood from the right ventricle of the heart to the lungs for oxygenation.
• Pulmonary vein: Transports oxygen-rich blood from the lungs to the left atrium of the heart.

Thus, oxygen-rich blood from the lungs enters the heart via the pulmonary vein, ensuring efficient oxygen supply to the body.

Ans: (b)
 The two components of phloem tissue that assist in the transportation of food in plants are:

• Sieve tubes
• Companion cells

Ans: (c) 

• The haemodialyser contains tubes with a semi-permeable lining that serve several important functions:
• They help to filter waste products like urea and creatinine from the blood.
• They allow the passage of these waste products into the dialysing fluid.
• This process mimics the kidney's function, although it does not involve re-absorption of substances.
• Finally, the purified blood is pumped back into the patient's body.

Ans: (c)

• An artificial kidney does not reabsorb essential nutrients from the blood.
• Its primary functions include:
• Removing nitrogenous wastes from the blood.
• Eliminating excess fluids from the blood.
• Filtering and purifying the blood.

Ans: (a)

• The used dialysing solution is rich in waste products.
• It contains high levels of urea and excess salts.
• During dialysis, the patient's blood flows through tubes with a semi-permeable lining.
• As blood passes through, waste products diffuse into the dialysing fluid.
• This process helps to purify the blood before it is returned to the patient.

Ans: (c)

• The tubules of the nephron are responsible for the selective reabsorption of essential substances.
•  These substances include: Glucose, Amino acids, Salts, Water
• This process allows these useful substances to return to the blood capillaries.

Ans: (i)  

• Minerals and water needed by the plants are absorbed by roots. 
•  The root hairs absorb water from the soil by the process of osmosis and take in minerals by the process of diffusion. 
•  Thus, a difference in concentration of ions is created between the roots and the soil, which enables the water to enter into the roots to compensate for the difference in concentration. 
•  This water, along with dissolved minerals from the root hairs, passes into xylem vessels through cells of the cortex, endodermis, and pericycle, and then ascent of sap takes place from the xylem of roots into the xylem of stem and finally leaf veins through vessels and tracheids.

Ans:  

•  The small intestine is the main region for the absorption of digested food. 
•  It consists of the following parts: 
•  The inner surface of the small intestine has millions of tiny finger-like projections called villi. 
•  These villi increase the surface area for efficient food absorption. 
•  Within these villi, many blood vessels are present that absorb the digested food and carry it to the bloodstream. 
•  The small intestine in human beings is the site of the complete digestion of food like carbohydrates, proteins, and fats. 
•  The absorption of digested food is necessary because an organism takes the complex organic materials by the process of absorption and then utilizes absorbed nutrients for various metabolic processes. 
•  With the help of these metabolic processes, the body uses these food nutrients for energy, growth, and cell repair. 

Ans: a - Hydrochloric acid (HCI)
b - Pepsin
c - Mucus
d - HCI makes medium acidic for the activation of an enzyme pepsin.
e - Pepsin acts in an acidic medium, which breaks down proteins into peptones.
f - The mucus protects the inner lining of the stomach from the corroding action of HCI.

Ans: (a) (i) Enzyme trypsin: This enzyme is produced by the pancreas in an inactive form called trypsinogen.
Trypsin converts the remaining proteins into peptones, and the peptones into peptides and amino acids.
(ii) Enzyme lipase: It is secreted by the pancreas and small intestine. Lipase converts fats into fatty acids and glycerol.
(b) Internally, the wall of the small intestine is provided with long finger-like projections called villi. Two functions of villi are:
(i) The villi greatly increase the absorptive surface area of the inner lining of the small intestine.
(ii) Villi are richly supplied with blood vessels that carry absorbed food to all cells of the body, where it is utilized for obtaining energy.

Ans: (a) Functions of alveoli are:
(i) They increase the surface area for the exchange of gases.
(ii) The thin walls of alveoli facilitate the rapid exchange of oxygen and carbon dioxide between alveolar air and blood.
(b) Aquatic animals like fishes obtain dissolved oxygen from water present through their gills. The amount of dissolved oxygen is quite small compared to the amount of oxygen in the air. Therefore, to obtain the required amount of oxygen from water, aquatic animals have to breathe much faster than terrestrial organisms.
(c)

Ans: (a) Since ventricles have to pump blood into various organs with high pressure, they have thicker walls than atria.
(b) The transport system in plants is slow due to:

• A less elaborate system compared to animals.
• Plants are generally less active, so their cells do not require rapid material supply.

(c) 

•  Circulation of blood in aquatic vertebrates differs from terrestrial vertebrates because: 
• Aquatic vertebrates, like fish, have gills for oxygenation and exhibit single circulation, where blood passes through the heart once per cycle. 
• Terrestrial vertebrates, like birds and humans, have lungs and use double circulation, with blood passing through the heart twice per cycle. 

(d) During the daytime, water and minerals travel faster through the xylem because the rate of transpiration is higher during the daytime.
(e) The lumen of veins has valves, which allow the blood to flow in only one direction. Thus preventing the backflow of blood.

Ans: (a) 

• Fishes have only two chambers in their heart. The blood is pumped to the gills for oxygenation, and from there, it passes directly to the rest of the body. Thus, the blood goes only once through the heart during one cycle of passage through the body. This type of circulation is termed as single circulation. 
•  In human beings, during circulation, blood travels twice through the heart in one complete cycle of the body, which is called double circulation. 
•  The pathway of blood from the heart to the lungs and back to the heart is called pulmonary circulation, and the pathway of blood from the heart to the rest of the body and back to the heart is called systemic circulation. 

• In human beings, deoxygenated blood from the body tissues is poured into the right atrium.
• Contraction of the heart forces it into the right ventricle.
• From the right ventricle, deoxygenated blood flows to the lungs through the pulmonary artery.
• Oxygenated blood from the lungs is returned to the left atrium and then into the left ventricle.
• The left ventricle forces the oxygenated blood to the whole body.
• Thus, to make one complete round or circulation circuit around all body parts, the blood passes through the heart twice.
• This is known as the double circulation of blood.

Ans: (a) Nephron is the structural and functional unit of the kidney. Its main role is to regulate the concentration of water and soluble substances like sodium and other salts by filtering the blood, reabsorbing the excess water that is needed, and excreting the rest as urine.
(b) Two factors on which the reabsorption of water from urine depends are:

• The amount of excess water which is present in the body.
• The amount of dissolved waste that needs to be excreted out of the body.

Ans: (a) The Excretory system (urinary system) in human beings consists of a pair of kidneys, a pair of ureters, a urinary bladder and a urethra.
(b) 

•  In the kidney, the wastes are converted to urine by three processes: 
• (i) Ultrafiltration: A large amount of water, along with certain harmful substances like urea, uric acid, K, ammonium salts, creatinine, etc., and certain useful substances like glucose, amino acids, Na, etc., pass through glomerular capillaries and glomerular membrane into the cavity of Bowman's capsule of nephrons under pressure. The filtrate so formed is called nephric filtrate, which is moved towards the ureter. 
• (ii) Selective reabsorption: A large amount of water and sodium, a whole of glucose and amino acids, and a small amount of urea are passed back from the nephric filtrate into the blood capillaries. It occurs either by back diffusion (i.e., water and urea) or active transport (i.e., Na, glucose, and amino acids). It generally occurs in the PCT (Proximal convoluted tubule) of nephrons. 
• (iii) Tubular secretion: Certain harmful chemicals like uric acid, creatinine, K, etc., are passed from blood capillaries surrounding the nephron into nephric filtrate by active transport. It generally occurs in the DCT (Distal convoluted tubule) of nephrons. Now, the fluid is termed as urine and is excreted out of the excretory organs. 

Ans: (a) 

• Nutrition is necessary for the human body because the human body continuously requires energy for life activities like respiration, circulation, excretion, etc.
• Energy is required even when we are sleeping because a number of biological processes keep on occurring.
• All these processes require energy, and this energy is obtained from nutrition.
• It is also needed for the growth and repair of the human body.

• The wall of the alimentary tract contains muscles that can contract and expand alternately.
• The contraction and expansion movement of the wall of the food pipe is called peristaltic movement.
• The peristaltic movement moves the partially digested food in all the digestive organs throughout the alimentary canal.

• The small intestine in herbivores is longer than in carnivores because:
• Herbivores consume plants rich in cellulose, which takes longer to digest.
• They rely on enzymes from symbiotic bacteria to break down cellulose.
• Carnivores eat flesh, which is easier to digest, resulting in a shorter small intestine.

(d) If mucus is not secreted by the gastric glands:

• The inner lining of the stomach would be exposed to hydrochloric acid and digestive enzymes.
• This could lead to erosion of the stomach lining, causing acidity and potentially ulcers.

Ans: (a) 

•  The difference in the rate of breathing between aquatic and terrestrial organisms is primarily due to their oxygen sources: 
•  Terrestrial organisms breathe in oxygen from the atmosphere, which contains about 21% oxygen. 
•  Aquatic organisms rely on oxygen that is dissolved in water, which is less than 1%. 
• Oxygen diffuses through water much slower than in air. 
•  As a result, terrestrial organisms can obtain oxygen more easily and quickly. 
•  Aquatic organisms must work harder to extract the same amount of oxygen, leading to a faster breathing rate. 

(b) The labelled diagram of the human respiratory system is as follows

Ans: (A) Journey of oxygen rich blood from lungs to various parts of the body is as follows: 
(i) The pulmonary vein brings the oxygenated blood from the lungs in the left atrium of the heart. 
(ii) The left atrium contracts and pumps blood into left ventricle through the valve. 
(iii) When the left ventricle contracts, the oxygenated blood enters the largest artery known as aorta. 
(iv) The blood travels from the aorta to larger and smaller arteries into the capillaries. 
(v) The aorta transports the blood to all the organs of the body except the lungs. 
(vi) The oxygenated blood releases oxygen, nutrients and other substances and takes away carbon dioxide and waste substances.
(vii) The deoxygenated blood enters the vena cava, which carries it to the right atrium of the heart

(B) When the system of blood vessels develop a leak, the platelets will increase, which will minimise the leakage. Whenever there is a leak in the blood vessels, the blood flows, through them. If not checked, that may cause an excessive loss of blood.

Ans: Pancreatic juice contains the digestive enzyme trypsin.

Ans:

• The movement of food in the alimentary canal is primarily due to peristalsis. This is the rhythmic contraction and relaxation of the muscles in the canal, which helps to push food downwards.
• Peristalsis occurs throughout the digestive tract.
• Food travels from the mouth to the stomach via the oesophagus.
• The stomach's muscular walls mix food with digestive juices.

Ans: (a) (i) Saliva contains salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohydrates into simpler ones).
(ii) Acid (HCI) plays an important role in the process of digestion. These are: 

• Hydrochloric acid (HCl) creates an acidic medium in the stomach, which is essential for the activation and functioning of the gastric enzyme pepsin.
• HCI kills the harmful bacteria present in the food. 
• Bile brings about the emulsification of fat (i.e., breaks fat molecules into small globules). 
• Internally, the wall of the small intestine is provided with long finger-like projections called villi. Two functions of villi are: 
• The villi greatly increase the absorptive surface area of the inner lining of the small intestine. 
• Villi are richly supplied with blood vessels that carry absorbed food to all cells of the body, where it is utilized for obtaining energy. 

(b) (i) Pepsin is a protein-digesting enzyme present in gastric juice. Pepsin gets activated in an acidic medium and splits proteins into peptones and peptides.
(ii) Lipase is secreted by the pancreas and small intestine. Lipase converts fats into fatty acids and glycerol.

Ans: The two different ways by which glucose is oxidized to provide energy in the human body are:
(i) Aerobic respiration (In the presence of oxygen): The end products in aerobic respiration are carbon dioxide, water, and energy.

(ii) Anaerobic respiration (In the lack of oxygen): The end products are lactic acid and energy.

Ans: In the absence or shortage of oxygen, glucose is oxidized in the following ways:
(i) In cytoplasm, glucose is oxidized to pyruvate and release energy.
(ii) In the muscles of humans, i.e., under anaerobic conditions, pyruvate breaks down to lactic acid and releases energy.
(iii) In yeast, i.e., during the fermentation process, pyruvate converts to ethanol while carbon dioxide releases a certain amount of energy.

Ans: (a) Differences between transport in the xylem and transport in the phloem are as follows:

(b) Significance of transpiration in plants: 
(i) The absorbed water is transported from roots to leaves through xylem vessels, which is greatly influenced by transpiration pull.
(ii) The water stream moving upwards carries dissolved minerals with it. Transpiration also helps in distributing these minerals throughout the plant.
(iii) The evaporation of water during transpiration provides a cooling effect to the leaves.

Ans: The three types of blood vessels in the human body are:
(i) Arteries are the blood vessels that carry blood from the heart to various parts of the body. They are thick-walled, elastic, and muscular, which enables them to dilate but do not rupture when the heart contracts and forces blood into them.
(ii) Veins are thin-walled blood vessels that bring blood from the body back to the heart. They are larger and hold more blood than the arteries. The lumen of veins has valves which prevent the backflow of blood.
(iii) Capillaries are thin-walled and extremely narrow blood vessels that occur at the terminals of arteries and veins. The walls of capillaries are permeable to water and dissolved substances so that the exchange of materials between the blood and body cells can take place.

Ans: (a)  

• Xylem tracheids and vessels are two water-conducting tissues present in plants that help in the rapid movement of water. 
•  In xylem tissue, vessels and tracheids of the roots, stems, and leaves are interconnected to form a continuous system of water-conducting channels reaching all parts of the plant. 
• Minerals and water needed by the plants are absorbed by root hairs from the soil by the process of osmosis and take in minerals by the process of diffusion. 
•  Thus, a difference in concentration of ions is created between the roots and the soil, which enables the water to enter into the roots to compensate for the difference in concentration. 
•  The water, along with dissolved minerals from root hairs, passes into xylem vessels through cells of the cortex, endodermis, and pericycle and then ascent of sap (i.e., upward movement of water and mineral salts from roots to the aerial parts of the plant against the gravitational force) takes place from xylem of the roots to the xylem of stem and leaves through vessels and tracheids. 
• Evaporation of water molecules from the cells of leaves creates a suction pressure that pulls the water from the xylem cells. 

Ans: The functions of the human heart include:

• Maintaining blood pressure: The heart ensures that blood is pumped throughout the body effectively.
• Pumping vital substances: It delivers essential nutrients and substances to various body parts.
• Circulating oxygen-rich blood: The heart sends oxygenated blood from the lungs to the entire body and carries carbon dioxide-rich blood back to the lungs for purification.
• Removing metabolic waste: It helps eliminate waste products, such as carbon dioxide, from body tissues.

The human heart consists of two sides: the right side and the left side. The right side receives deoxygenated blood and sends it to the lungs for purification. The left side receives oxygenated blood from the lungs and pumps it to the rest of the body. This process is known as double circulation.
Double circulation is necessary because:

• It separates oxygenated and deoxygenated blood, which is crucial for meeting the high energy demands of the body.
• This separation allows for efficient oxygen delivery to tissues, supporting the body's metabolic needs.

Ans: (a)  Excretion is a biological process that removes harmful metabolic wastes from the body. Key points include:

• It eliminates substances like nitrogenous waste, which includes urea, salts, and water.
• Accumulation of these wastes can be harmful to the body.
• The main excretory organs in humans are the kidneys.
• Kidneys filter blood to produce urine, which carries away waste.

Overall, excretion is essential for maintaining the body's health by preventing the buildup of toxic substances.

(b) A pair of kidneys are the main excretory organs in a human being. It helps excrete nitrogenous waste in the form of urea, toxins, excess salts, water-soluble vitamins, etc. and then eliminates it in the form of urine.

Ans: In the experiment in which carbon dioxide is given out during respiration, KOH (potassium hydroxide) solution or pellets are taken in a tube and placed within the conical flask. KOH absorbs the carbon dioxide, and it prevents the carbon dioxide from being utilized by the plant for the process of photosynthesis. Function of KOH
KOH: KOH solution kept in the flask absorbs carbon dioxide and creates a partial vacuum in the flask. The air present in the bent tube moves into a conical flask, and this pulls the water level up in the tube. Consequences:

1. The whole amount of CO₂ liberated gets absorbed by KOH to prevent it from being utilized by the plant for the process of photosynthesis.
2. This CO₂ absorption leads to creating a vacuum in a flask that causes an observable rise in the water level of the connected U tube.
3. Any gas produced can neither escape nor can get outside air in.
4. Germinating seed produces CO₂ via the following reactions: Aerobic respiration: C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + 38ATP

Ans: (A) X - KOH pellets 
Y - Wet germinating seeds
(B) Seeds use oxygen present in the flask and release carbon dioxide which is absorbed by potassium hydroxide. Thus, partial vacuum is created in the conical flask, as a result, water from the beaker rises in the delivery tube

Ans: (i) Saliva contains salivary amylase and is released in our mouth. It breaks down starch into sugar (complex carbohydrates into simpler ones).
(ii) Acid (HCI) plays an important role in the process of digestion. These are: 

• Hydrochloric acid (HCl) creates an acidic medium in the stomach, which is essential for the activation and functioning of the gastric enzyme pepsin.
• HCI kills the harmful bacteria present in the food. 

• The villi greatly increase the absorptive surface area of the inner lining of the small intestine. 
• Villi are richly supplied with blood vessels that carry absorbed food to all cells of the body, where it is utilized for obtaining energy. 

Ans: (A) The rate of breathing differs between aquatic and terrestrial organisms due to their environments:

• Aquatic organisms breathe faster because they extract dissolved oxygen from water.
• Water contains less oxygen than air, necessitating a quicker breathing rate.
• Terrestrial organisms breathe more slowly as they obtain oxygen from the air, which is about 21% oxygen.

(B)  Plants have lower energy needs compared to animals for several reasons:

• Plants are stationary and do not move, resulting in less energy expenditure.
• They are generally less active than animals.
• Many plant tissues contain a large amount of dead cells that provide structural support.
• As a result, plant cells do not require rapid supply of materials, leading to lower energy needs and a slower respiration rate.

Ans: (a) Two components of blood are blood plasma and blood corpuscles.
(b) Oxygenated blood from lungs → Pulmonary veins → Left atrium of heart → Left ventricle → Aorta → Arteries → Body parts
(c) When blood is pumped, valves prevent the backflow of blood between ventricles and atria. They open and allow the right amount of blood to flow from one chamber to the other.
(d) Structural difference between veins and arteries is as follows:

Ans: (a) Photosynthesis is the process where green plants show autotrophic nutrition. The raw materials required for photosynthesis are carbon dioxide water, and energy in the form of sunlight.
The equation is as follows:

(b) The three events in photosynthesis are:

• Absorption of light energy by chlorophyll.
• Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.
• Reduction of carbon dioxide to carbohydrates.

Ans: (a)

(b) Fishes breathe with the gills by diffusion.
(c) Alveoli are the balloon-like structures:

• They provide a surface for the exchange of gases.
• They contain a residual volume of air so that there is sufficient time for the exchange of gases.

(d) Haemoglobin is the respiratory pigment in humans. It transports a major part of oxygen and some amount of carbon dioxide through the blood.

Ans: (а) Blood is composed of plasma and three types of cells: red blood cells, white blood cells, and platelets.
(b) 

• Oxygenated blood from the lungs is brought to the left atrium by pulmonary veins.
• When the atrium contracts, blood is transferred to the left ventricle.
• When the ventricle contracts, blood is pushed into the aorta and through arteries to all parts of the body.

(c) The function of valves between the atria and ventricles is to:

• Prevent backflow of blood during pumping
• Ensure the correct amount of blood flows from one chamber to another

(d)

Ans:
(a) Excretion is the biological process of removal of harmful metabolic wastes from the body.
(b) Nephrons
(c) (i) Kidney, (ii) Ureter, (iii) Urinary bladder.

Excretory System of Human Beings

Ans:  Due to the higher metabolic rate and the large volume of the body, oxygen cannot diffuse into all cells of the human body quickly as oxygen will have to travel large distances to reach each and every cell. So, diffusion is insufficient to meet the oxygen demand of multicellular organisms.

Ans: The pulmonary vein carries oxygenated blood from the lungs to the left atrium of the heart.

Ans: Photosynthesis is important for a number of reasons:
(i) Food: By photosynthesis, green plants synthesize food from simple raw materials like CO₂ and H₂O. Thus, it sustains life on earth.
(ii) Oxygen: Oxygen released during the process of photosynthesis is needed by animals and humans for respiration. Oxygen also supports the combustion of fuels. The balanced chemical equation involved in the process of photosynthesis is given as:

Ans: Differences between autotrophs and heterotrophs are as follows:

Ans:

• The phloem cells transport the soluble food materials to all parts of the plant.
• The transport of food from leaves to different parts of the plant is termed translocation.
• Components of phloem are sieve tubes, companion cells, phloem parenchyma, and phloem fibres.
• The food is manufactured in the mesophyll cells (or photosynthetic cells) of a leaf.
• The manufactured food enters into sieve tubes of the phloem and is transported as a dilute aqueous solution either in an upward or downward direction.
• Food is transported to all non-green parts of the plant for their growth and metabolic activities.
• Besides food molecules, the phloem also transports amino acids, hormones synthesized in the shoot tips and root tips, and other metabolites.
• In this process, glucose is transferred to phloem tissue using energy from ATP.
• This increases the osmotic pressure of the tissue, causing the water to move into it (endosmosis).
• Soluble material is then transferred from phloem tissue to other tissues which have less pressure than in the phloem.
• Thus, according to the plant's requirement, the material is translocated from higher osmotic pressure areas to lower osmotic pressure areas.

Ans: The diagram of the human excretory system is as follows:

Ans:  (a) Glucose breaks down anaerobically i.e., in the absence of O₂; in yeast in the following manner:

(b) Since fishes are aquatic, they take in O₂ dissolved in water. They take water through their mouth, which goes to their gills, where the dissolved oxygen is taken up by the blood and transported. The CO₂ is given out through the same passage.

(c) The balloon-like structures in our lungs are the alveoli.
Their functions are:

• They are very thin-walled and hence help in gaseous exchange.
• They contain an extensive network of blood vessels that help in the transport of respiratory gases.
•  They increase the surface area for the absorption of gases.

(d) The respiratory pigment is Haemoglobin.
Its role is:

• It has an affinity for oxygen and hence helps in the transport of oxygen from alveoli to body tissues.
• It also has an affinity for CO₂ and hence helps in the transport of CO₂ from body tissues to alveoli.

Ans: (a) The process of nutrition in green plants is Photosynthesis. The type of nutrition is autotrophic nutrition. Autotrophic nutrition requires sunlight, chlorophyll, water, and carbon dioxide.
Plants prepare their own food in the form of glucose, which gets converted to starch. This is done using CO₂ and H₂O, which are fixed using energy from sunlight from the chlorophyll molecules present in green plants.
Equation - 

(b) The three events involved are:

• The absorption of sunlight occurs through chlorophyll.
• Conversion of this light energy into chemical energy and splitting of water into H⁺ and OH^- using this energy.
• Reduction of CO₂ to carbohydrate by using H⁺ produced due to splitting of water.

Ans: (a) Various components of the transport system and their functions:

(b) If there is a leak in the blood vessels due to injury, then the blood platelets help plug these leaks. The platelets make the clot by forming a mesh-like structure over the leak in which other blood cells get entangled, ultimately plugging the leak.

Ans: Translocation is the process by which plants transport the products of photosynthesis from the leaves to various parts of the plant, including:

• Roots
• Stems
• Branches

This transport occurs through the phloem, a type of vascular tissue, and involves:

• Movement of sucrose and other nutrients.
• Delivery to storage organs like roots, fruits, and seeds.
• Support for growing organs.

Translocation is an energy-dependent process, using ATP to increase osmotic pressure, which facilitates the movement of substances in the phloem.

This allows the plant to distribute nutrients according to its needs, such as transporting stored sugars to new buds in spring.

Ans: Raw materials required for photosynthesis are carbon dioxide (CO₂), water, light, and chloroplast.

Ans: Differences between breathing and respiration are as follows:

Ans: Glucose is first broken down in the cell cytoplasm into a three-carbon molecule called pyruvate. Pyruvate is further broken down in the following ways to provide energy.

Ans: (i) Mouth, (ii) Gall Bladder, (iii) Pancreas, (iv) Large Intestine, (v) Small intestine.

Ans: 
(a) 
(i) As starch in fruits/storage roots tubers etc.
(ii) As glycogen.
(b) Amoeba is a unicellular eukaryotic organism that exhibits a holozoic mode of nutrition.
Five steps are involved in this mode of nutrition:

• Ingestion: Amoeba feeds on microscopic organisms. It takes in food using finger-like projections called pseudopodia. It encircles the food and engulfs or ingests it by a process called phagocytosis. The food comes to lie in a vesicle called a phagosome or food vacuole.
• Digestion: A lysosome fuses with a phagosome, and complex substances are broken down into simpler ones. Such a type of digestion that occurs within a cell is referred to as Intracellular digestion. The digested food then diffuses into the cytoplasm.
• Absorption and Assimilation: The digested food that has diffused into the cytoplasm is quickly absorbed by the organism and converted into various constituents of protoplasm.
• Egestion: The undigested food material reaches the rear end of the organism and is thrown out by the process of exocytosis. The membrane of the vesicle fuses with the surface membrane.
  
  

Ans: (i) Fine hair and mucus are present in the nasal passage so that any dust particles, pathogens, etc., can be trapped in here, and only clean air will enter the lungs. This is one of the defence mechanisms of our body.
(ii) Rings of cartilage are present in the throat so that the trachea does not collapse on respiration.

Ans: Parasites are organisms that obtain nutrients from the bodies of other living organisms and harm them as a result.
(i) Plant parasite - cuscuta
(ii) Animal parasite - Tapeworm
Organisms that break down food outside the body and then absorb it are saprophytes.
Example: fungi, bacteria.

Ans: 
Material transported by:
(i) Xylem: Water and minerals.
(ii) Phloem: Organic molecules like sucrose.
(iii) Pulmonary vein: Oxygenated blood from lungs to heart.
(iv) Vena cava: Impure and deoxygenated blood from the body to the heart.
(v) Pulmonary artery: Deoxygenated blood from the heart to the lungs.
(vi) Aorta: Oxygenated blood from the heart to body parts.

Ans: In the case of a single-celled organism, the entire surface of the organism is in contact with the environment, and hence, no specific organ for taking in food, exchanging gases, or removing waste may be needed. In multicellular organisms, only the cells of the skin are in direct contact with the environment. Diffusion is a very slow process, and it will take a very long time to reach all the cells of the body parts. Diffusion is insufficient to melt oxygen requirements.

Ans: (a) Digestive enzymes digest the food we eat.
(b) Hydrochloric acid creates an acidic medium to facilitate the action of the enzyme pepsin.
(c) Villi increases the surface area inside the small intestine to facilitate the absorption of food.

Ans: Gastric glands are present in the wall of the stomach. They secrete gastric juices containing mucus, protein-digesting enzymes pepsin, rennin, and hydrochloric acid (HCI).

Ans: Nutrition in amoeba: 

• Nutrition occurs through phagocytosis.
• Amoeba captures food using pseudopodia, which are temporary extensions of the cell.
• The ingested food is enclosed in a food vacuole.
• Inside the food vacuole, enzymes break down the food into simpler substances.
• Undigested food is expelled through the cell membrane.

Nutrition in Paramoecium:

• Paramoecium has a definite shape and takes in food at a specific location.
• Food is directed to this location by the movement of cilia that cover the cell's surface.

Ans: Breathing through the nose is advisable for several reasons:

• The inner lining of the nose contains fine hairs and mucus glands that filter incoming air, trapping germs and dust.
• This process helps to warm and humidify the air before it reaches the lungs.
• Breathing through the nose also promotes better oxygen absorption in the body.

Ans: Transpiration is the process through which water vapour is lost from the aerial parts of a plant, primarily via the stomata in the leaves.

This process plays a crucial role in the upward movement of water from the roots to the leaves:

• As water evaporates from the leaf cells, it creates a suction force.
• This suction pulls water from the xylem cells in the roots.
• Transpiration helps in the absorption of water and minerals, facilitating their movement to the leaves.
• It also aids in regulating the plant's temperature.

During the day, when the stomata are open, the transpiration pull is the main driving force for water movement in the xylem.