Class 10 Science Chapter 5 Previous Year Questions - Life Processes

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: Role of:
(i) Hydrochloric acid: Creates an acidic medium for facilitating the action of enzyme / kills microorganisms.
(ii) Villi: Increases the surface area for absorption of digested food.
(iii) Anal Sphincter: Exit of waste material from anus is regulated.
(iv) Lipase: Breakdown / digestion of emulsified fats or lipids

Ans: (i) Diffusion /Diffusion pressure alone cannot take care of oxygen delivery to all parts of the body.
(ii) Reasons:
(a) To ensure that the air-passage does not collapse.
(b) There is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released.
(c) Chest cavity becomes larger.  
(d) Because exchange of gases takes place in the alveoli.  

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: (i) Translocation   

(ii) Transport of soluble products or food prepared by photosynthesis, through phloem in the sieve tubes with the help of companion cells, both in upward and downward directions by utilising 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) (i) The inner lining of the stomach will not be protected from the action of acid.
(ii) Digested food will not be absorbed. / Absorption area will be 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 into glucose, and fats into fatty acids and glycerol. Therefore, the correct answer is (b) because it accurately describes the final products of these macronutrients after digestion.

Ans: When water is lost through stomata in the leaves by transpiration, it creates a suction force/transpiration pull. Due to which water is pulled up through xylem of the roots to the leaves.

Ans: (d)
This process refers to the movement of the soluble products of photosynthesis, like sugars, from the leaves where they are made to other parts of the plant where they are used or stored. Translocation is essential for distributing energy throughout the plant.

Ans: (a) (i) Formation of lactic acid in muscles causes cramps.
(ii) Aerobic respiration takes place in the presence of oxygen whereas the respiration taking place above is due to lack of oxygen. End products of aerobic respiration are CO₂ + H₂O + Energy whereas in the above case, Lactic acid + Energy is formed.
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)
 Water needed by plants is absorbed by roots. The root hair absorb water from soil by osmosis. Difference in concentration of ions is created between roots and soil which enables water to enter into roots to compensate difference in concentration.

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 pull aids in the upward movement of water from the roots to the leaves.
• A significant amount of water evaporates through the stomata on the leaf surface.
• This evaporation process generates a suction force, pulling water up through the plant from the roots.

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 longer because it will not be able to produce the oxygen required for its respiration by the process of photosynthesis. Oxygen is evolved as the byproduct of photosynthesis during the photolysis of water and helps plants to survive longer than is kept in sunlight. 

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 (in the form of ATP and NADPH) 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 the food we eat is explained with the help of activity as follows: Take two test tubes, A and B. In test tube A, put one teaspoon full of boiled rice, and in test tube B, keep one teaspoon full of boiled rice after chewing it for 3 to 5 minutes. Add 3.4 mL of water in both test tubes and add a few drops of iodine solution to each test tube. In test tube A, the colour of the rice changes because of the absence of any enzyme, while in test tube B, no colour change is observed because when rice is chewed, the amylase enzyme present in saliva breaks down the starch of rice to simple sugars.
(b) Bile juice breaks down fats into fatty acids that can be taken into the body by the digestive tract. In addition, it provides alkaline fluid in the intestine to neutralize the acidic pH of food that comes from the stomach. 

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 mechanism in which blood circulates twice through the heart in one complete cycle. Systemic circulation and pulmonary circulation are two pathways through which blood flows in double circulation.
(ii) The separation of the right and left sides of the heart helps in the separation of oxygenated and deoxygenated blood and allows the highly efficient supply of oxygen to the body. Birds and mammals are warm-blooded animals, and their metabolism is quite complex. They require a constant supply of oxygen. Without proper separation, oxygenated blood can mix with deoxygenated blood, which can cause problems in birds and mammals. Separation of the right side and left side of the heart ensures the circulation of oxygenated blood to different body parts. 

Ans: (i) Renal artery carries blood from the aorta to the kidneys for filtration.
(ii) The urethra receives urine stored in the bladder and releases it outside.
(iii) Glomerulus filters the blood passing through it and initiates urine formation.
(iv) The tubular part of the nephron allows selective reabsorption of useful substances like glucose, amino acids, salts, and water into the blood capillaries. 

Ans: Most of the carbon dioxide is released through stomata in leaves. Plants can get rid of excess water by the process of transpiration, i.e., evaporative loss of water. Many plant waste products are stored in leaves, which are excreted when shed off.

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 "central veins" are another name for the vena cava. Deoxygenated blood from the upper body and arms enter the top of the right atrium via the superior vena cava. Similarly, deoxygenated blood from the legs and abdominal cavity enter the right atrium's bottom via the inferior vena cava. 
(B) Pulmonary artery: Blood that is deprived of oxygen i.e., deoxygenated blood, is transported from the right ventricle to the lungs, where it gets oxygenated.

Ans: (A) ATP is the energy currency of the cell. During cellular respiration, the mitochondrial matrix is where the majority of ATP synthesis occurs, with each molecule of glucose oxidised producing around 32 ATP molecules. 
(B) Plants exchange gases through stomata, and the large intercellular spaces ensure that all cells are in contact with air. Carbon dioxide and oxygen are exchanged by diffusion here. 
(C) The direction of diffusion depends upon the environmental conditions and the requirements of the plant.

Ans: (b)
Saliva (i) is secreted in the mouth. Saliva contains an enzyme called salivary amylase for digestion of carbohydrates.
Liver (ii) secretes bile to emulsify fat.
The pancreas (iii) secretes pancreatic juice which contains enzyme trypsin for digestion of proteins.

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 depends on the turgidity of the guard cells. The given figure shows a closed stomatal pore which occurs when guard cells looses water and become flaccid.

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)
 Herbivores such as deer eating grass need a longer small intestine to allow the cellulose to be digested. Meat is easier to digest, hence carnivores like tigers have a shorter small intestine.

Ans: (a)
 When there is a lack of oxygen in our muscle cells, pyruvate is converted into lactic acid and energy Therefore, the correct pathway of glucose metabolism in our muscle cells during heavy exercise is:

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 flatter our diaphragm (A), and the chest cavity becomes larger as a result. Because of this, air is sucked into the lungs and fills the expanded alveoli. When our ribs and diaphragm return to their normal position and the chest cavity becomes smaller, exhalation occurs.
During breathing, the lungs always contain a residual volume of air, so that there is sufficient time for oxygen to be absorbed and for the carbon dioxide to be released. The residual volume remains unchanged in normal conditions.

Ans: (d)
 The amount of dissolved oxygen in water is fairly low as compared to the amount of oxygen in the air but the rate of breathing in aquatic organisms is much faster than that seen in terrestrial organisms because the aquatic animals have to breath rapidly to take in sufficient oxygen.

Ans:  (c)
 The mucus lining in the nasal passage helps to moisten and warm the inhaled air and also trap dust particles (i.e., helps in filtering the inhaled air).

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 have thin and moist surfaces for gaseous exchange. This characteristic is essential for both gills in fish and alveoli in humans as it allows oxygen to efficiently diffuse into the blood and carbon dioxide to diffuse out. These surfaces are specially adapted to maximize the area available for gas exchange, enhancing the efficiency of respiration in both organisms.

Ans: (c)
 When a person blows air from mouth into the test tube containing lime water, the lime water turn into a white precipitate which appears milky. This occurs because the air we exhale has more carbon dioxide.

Ans: (a)
 The right and left sides of the heart are separated by a muscular wall that prevents mixing of oxygenated with deoxygenated blood. Such separation allows a highly efficient supply of oxygen to the body.

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)
In tall trees, the driving force to move water upward is transpiration. During transpiration, as the water evaporates through the stomata in the leaves, it creates a negative pressure in the leaves and xylem tissues.

Ans: (b)
 Capillaries are tiny blood vessels which have thin walls and are one-cell thick. Exchange of materials between blood and surrounding cells takes place across these thin walled, capillaries. These also take waste products away from tissues.

Ans: (d)
 Blood vessel A represents pulmonary artery and blood vessel B represents pulmonary vein. Oxygen-rich blood from the lungs comes to the left atrium via pulmonary vein. The left atrium relaxes when it receives blood.

Ans: (b)
 The two components of phloem tissue that helps in transportation of food in plants are sieve tubes and companion cells.

Ans: (c)
 The semi-permeable lining of the tubes of haemodialyser allow the passage of waste products such as urea, creatinine, etc., from the blood to the dialysing fluid.

Ans: (c)
 Artificial kidney is not involved in the reabsorption of essential nutrients from the blood.

Ans: (a)
The used dialysing fluid/solution is rich in waste products like urea and excess salts because during the passage of patient’s blood through tubes with a semi-permeable lining, the waste products from the blood pass into the dialysing fluids by diffusion.

Ans: (c)
The function of tubules of nephron is to allow the selective reabsorption of useful substances like glucose, amino acids, salts and water into 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.
(ii) Bleeding leads to a loss of pressure, which reduces the efficiency of the pumping system. When an injury is caused, the blood platelets release certain chemicals which are called the platelet factors (e.g., thromboplastin). These platelet factors help in the clotting of blood.

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 less elaborate than in animals, as plants are less active, so their cells do not need to be supplied with materials quickly.
(c) The aquatic vertebrates, like fish, have gills to oxygenate blood. The flow of blood in a fish is single circulation because the blood passes through the heart only once in one complete cycle of the body. Terrestrial vertebrates, like birds and humans, have double circulation as the blood travels to the heart twice in one complete cycle of blood, and they have lungs for oxygenation of blood.
(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.
(b) 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.
(b) 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 j the partially digested food in all the digestive organs throughout the alimentary canal.
(c) The small intestine in herbivores is longer than in carnivores because herbivores eat plants, rich in cellulose, which takes longer time for complete digestion by the enzymes present in symbiotic bacteria. Therefore, they have longer small intestines. Carnivores feed on flesh, which is easier to digest and does not contain cellulose. Therefore, they have shorter intestines for the digestion of food eaten by them.
(d) Gastric glands secrete HCI, mucus, renin, and pepsin enzymes. The mucus protects the inner lining of the stomach from the action of acidic HCI and enzymes. In the absence of mucus, there would be erosion of the inner lining of the stomach, leading to acidity and ulcers.

Ans: (a) Terrestrial organisms inspire atmospheric oxygen, while aquatic organisms thrive on the dissolved oxygen present in water. Air contains about 21% oxygen, while water has less than 1% oxygen in a dissolved state. Oxygen diffuses through water at a much slower rate than in air. A terrestrial organism has the advantage of utilizing greater amounts of oxygen at a faster rate with lesser effort, whereas aquatic organisms have to put more effort into obtaining the same amount of oxygen; therefore, breathing in aquatic organisms is much faster than the terrestrial organisms.
(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 within the alimentary canal is mostly caused by peristalsis. Peristalsis is the rhythmic contraction and relaxation of muscles of the alimentary canal to push the food downward.

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.
(b) Plants are autotrophic and do not have to move from one place to another in search of their food. Movements in a plant occur at the cellular level, and hence, they require less energy. Animals are heterotrophic and move in search of food and other activities; hence, they require a higher amount of energy than plants.

Ans: The functions of the human heart are as follows:
(i) The heart maintains the blood pressure.
(ii) The heart pumps vital substances and nutrients to different body parts.
(iii) The heart pumps the oxygen-rich blood to the whole body and CO₂-rich blood to the lungs for purification.
(iv) The heart is responsible for removing metabolic waste, such as CO_2, from all the tissues of the body. The heart of human beings consists of two sides - right and left. The right side of the heart receives deoxygenated blood and sends it further for purification to the lungs. The left side of the heart receives oxygenated blood from the lungs, which is pumped further and sent to all the parts of the body through blood vessels. This is called double circulation. The energy demands of human beings are too high and hence the separation of oxygenated and deoxygenated blood is necessary to meet high energy demands.

Ans: (a) Excretion is a biological process by which harmful metabolic wastes like nitrogenous substances are removed from the body. Metabolic activities produce waste products like water, salts, CO₂, uric acid, and urea. Accumulation of these excretory wastes beyond a certain limit inside the body is harmful to the body.
(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) Rate of breathing is faster in aquatic organisms because they take in dissolved oxygen from water. The amount of dissolved oxygen in water is lower as compared to the amount of oxygen in air. Rate of breathing is slow in terrestrial organisms as they take oxygen from the air which is 21% in the air.
(B) Plants are fixed at a place and do not show any locomotion. Plants are less active. Plants have a large portion of dead cells in many tissues which supply mechanical support to the plants. Their cells do not need to be supplied with materials so quickly. Therefore, plants have low energy needs and respire at a slow 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 valves prevent the backflow of blood from ventricles into the atria.

(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: The transport of food prepared in the leaves, by the process of photosynthesis, to various parts (roots, stems, branches, etc.) of the plant is called translocation.

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) Venacava: 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: It occurs through phagocytosis. It capture food by pseudopodia (ingestion) ingested food, enclosed in cell membrane is called food vacuole. The food is broken with enzymes present in cytoplasm and undigested food ‘is thrown out through cell membrane.
Nutrition in Paramoecium: The cell has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia present on the entire surface of the cell.

Ans: There are fine hair and mucus gland in the inner lining of nose which filter the incoming air of germs and dust. Moreover the air attains the optimum temperature before reaching the lungs.

Ans: Transpiration is the process of removal of water vapours from the aerial parts of a plant, mainly through stomata in the leaves. Evaporation of water molecules from the cells of a leaf creates a suction force which pulls water from the xylem cells. This transpiration helps in upward movement of water from roots to leaves.