LIFE PROCESSES: Long Answer Type Question for Class 10th Chapter 10 JKBOSE/NCERT
Question 1. (i) Explain how the exchange of gases occurs in plants across the surface of stems, roots and leaves.
(ii) How are water and minerals transported in plants?
Ans:
(i) Exchange of gases in plants occurs through specialized structures such as stomata, lenticels, and root hairs. In leaves, stomata are small openings present on the surface of the epidermis. Each stoma is surrounded by two specialized guard cells that control its opening and closing. During photosynthesis, carbon dioxide enters the leaf through open stomata, while oxygen and excess water vapour exit through the same openings. In stems, gases diffuse across the epidermis and the lenticels, which are small openings in the bark. In roots, gas exchange occurs through the root hairs, which are extensions of the epidermal cells.
(ii) Water and minerals are transported in plants through two main pathways: the xylem and the phloem. The xylem tissue is responsible for the transport of water and minerals from the roots to the rest of the plant. Water is absorbed by the root hairs and travels through the root cortex and endodermis to reach the xylem vessels. The movement of water in the xylem is mainly driven by transpiration, which is the loss of water vapour through the stomata in the leaves. This creates a negative pressure that pulls water up the plant.
The phloem tissue, on the other hand, transports organic nutrients, such as sugars and amino acids, from the leaves to the other parts of the plant. This process is called translocation. The movement of organic nutrients in the phloem occurs through a process called active transport, which requires energy. Phloem transport involves the loading of sugars into the sieve tube elements in the leaves, followed by their movement through the phloem sieve tubes to the sink tissues, where they are utilized or stored
Question 2. What are the components of the transport system in human beings? What are the functions of these components?
Ans: The components of the transport system in human beings are:
Heart: The heart is a muscular organ that pumps blood throughout the body. It consists of four chambers – two atria and two ventricles. The heart’s main function is to circulate oxygenated blood to the body tissues and return deoxygenated blood to the lungs for oxygenation.
Blood vessels: Blood vessels form a network of tubes that carry blood to and from different parts of the body. They include arteries, which carry oxygenated blood away from the heart; veins, which carry deoxygenated blood toward the heart; and capillaries, which are tiny, thin-walled vessels where the exchange of nutrients, gases, and waste products occurs between the blood and body tissues.
Blood: Blood is a fluid connective tissue that carries oxygen, nutrients, hormones, and waste products throughout the body. It consists of plasma, red blood cells, white blood cells, and platelets. Plasma carries dissolved substances, while red blood cells transport oxygen and carbon dioxide. White blood cells are involved in immune responses, and platelets help in blood clotting.
Question 3. List and describe in brief any five functions of blood.
(ii) Name any two parasitic plants and two parasitic animals.
Ans: (i) Functions of blood include:
Transport: Blood carries oxygen from the lungs to body tissues and carbon dioxide from tissues to the lungs. It transports nutrients, hormones, and waste products to their respective destinations in the body.
Regulation: Blood helps regulate body temperature by distributing heat and maintaining homeostasis. It also regulates pH balance and electrolyte concentrations in the body.
Protection: Blood contains white blood cells that defend the body against pathogens and foreign substances. It also contains antibodies and other immune system components that aid in immune responses. Blood clotting helps in preventing excessive bleeding from damaged blood vessels.
Maintenance of fluid balance: Blood plays a role in maintaining the balance of fluids within the body, ensuring proper hydration and preventing dehydration.
Wound healing: Blood carries platelets that help in the clotting process, sealing wounds and initiating the repair process.
(ii) Two parasitic plants: Dodder and Rafflesia. Two parasitic animals: Head lice and ticks.
Question 4. (i) Write the important function of the structural and functional unit of the kidney.
(ii) Write any one function of an artificial kidney
Ans:
(i) The structural and functional unit of the kidney is called the nephron. Its important function is to filter blood and regulate the composition of urine. Each kidney contains millions of nephrons, each consisting of a renal corpuscle (which includes the glomerulus and Bowman’s capsule) and a renal tubule.
The glomerulus filters blood under high pressure, allowing water, ions, and small molecules to pass into the Bowman’s capsule. This filtrate then enters the renal tubule, where selective reabsorption and secretion take place. The renal tubule has different segments with specialized functions. Reabsorption involves the reabsorption of useful substances, such as glucose and ions, back into the bloodstream. Secretion involves the active transport of certain substances, such as drugs and excess ions, from the blood into the tubule for excretion.
(ii) An artificial kidney, such as a hemodialysis machine, performs the function of a damaged or impaired kidney. Its main function is to remove waste products and excess fluid from the blood. The machine filters the blood through a semipermeable membrane, allowing waste products, excess ions, and fluid to pass out of the blood and into a dialysis solution. The clean blood is then returned to the body. Hemodialysis helps maintain electrolyte balance, control blood pressure, and remove urea and other waste products that accumulate in the body when the kidneys are unable to perform these functions adequately.
Question 5. In the human alimentary canal, name the site of the complete digestion of various components of food. Explain the process of digestion.
Ans: The site of the complete digestion of various components of food in the human alimentary canal is the small intestine. The small intestine is divided into three parts: the duodenum, jejunum, and ileum. It is in the duodenum where the majority of digestion occurs.
The process of digestion involves the breakdown of complex food components into simpler molecules that can be absorbed by the body. In the small intestine, various enzymes and secretions are involved in digestion. These include:
Pancreatic enzymes: The pancreas secretes enzymes, such as amylases, proteases, and lipases, into the duodenum. Amylases break down carbohydrates, proteases break down proteins, and lipases break down fats.
Intestinal enzymes: The cells lining the small intestine produce enzymes like maltase, sucrase, lactase, and peptidases, which further break down complex sugars, peptides, and proteins into simpler molecules.
Bile: The liver produces bile, which is stored in the gallbladder and released into the duodenum. Bile aids in the digestion and absorption of fats by emulsifying them into smaller droplets.
Once the food components are broken down, they are absorbed through the walls of the small intestine into the bloodstream or lymphatic system for distribution to the body’s cells. The small intestine has a large surface area due to the presence of villi and microvilli, which increases the efficiency of absorption.
Question 6. Why and how does water enter continuously into the root xylem of plants?
Ans: Water enters continuously into the root xylem of plants through a process called root pressure and a phenomenon called osmosis. Root pressure is the result of the active pumping of mineral ions into the xylem by the root cells, creating a higher solute concentration in the xylem sap. This causes water to move from the soil into the root cells through osmosis.
Osmosis is the diffusion of water molecules from an area of lower solute concentration to an area of higher solute concentration across a selectively permeable membrane. The presence of mineral ions in the root cells creates a higher solute concentration, so water moves from the soil, where it is relatively dilute, into the root cells and then into the xylem.
Additionally, transpiration, the loss of water vapour from the leaves through stomata, creates a negative pressure or tension in the xylem, which pulls water upwards from the roots to replace the lost water. This process, known as the transpiration pull, also contributes to the continuous uptake of water into the root xylem.
Question 7. What are the differences between aerobic and anaerobic respiration? Name some organisms that use an anaerobic mode of respiration.
Ans: The differences between aerobic and anaerobic respiration are:
Aerobic respiration:
1. It occurs in the presence of oxygen.
2. The complete breakdown of glucose occurs, resulting in the production of carbon dioxide, water, and a large amount of energy in the form of ATP.
3. It is an efficient process that yields a high amount of ATP per glucose molecule.
4. It occurs in most eukaryotic organisms, including humans and animals.
5. Examples of organisms that use aerobic respiration are humans, plants, and many microorganisms.
Anaerobic respiration:
1. It occurs in the absence of oxygen.
2. The breakdown of glucose is incomplete, and the end products vary depending on the organism. In humans, the end product is lactic acid, while in yeast and some bacteria, the end products are alcohol and carbon dioxide.
3. It is less efficient than aerobic respiration and yields a smaller amount of ATP per glucose molecule.
4. It occurs in some bacteria, yeast, and certain muscle cells in humans during strenuous exercise when the oxygen supply is insufficient.
5. Examples of organisms that use anaerobic respiration are yeast, some bacteria, and certain muscle cells in animals.
Question 8. Discuss the major steps involved in the process of nutrition in human beings.
Ans: The major steps involved in the process of nutrition in human beings are:
Ingestion: The intake of food through the mouth.
Digestion: The mechanical and chemical breakdown of food into simpler molecules. It begins in the mouth with chewing and the action of saliva-containing enzymes (e.g., amylase) on carbohydrates. In the stomach, gastric juice containing enzymes (e.g., pepsin) further digests proteins. The small intestine is where most digestion occurs, with enzymes from the pancreas and intestinal wall breaking down carbohydrates, proteins, and fats.
Absorption: The uptake of digested food molecules and nutrients into the bloodstream or lymphatic system. This occurs mainly in the small intestine, where the inner lining is highly folded and has villi and microvilli to increase the surface area for absorption.
Assimilation: The utilization and incorporation of absorbed nutrients by cells for energy production, growth, and repair.
Egestion: The elimination of undigested waste material, mainly in the form of faeces, through the rectum and anus.
Question 9. Explain the process of nutrition in Amoeba.
Ans: In Amoeba, nutrition occurs through a process called phagocytosis. Amoeba is a unicellular organism that engulfs its food using pseudopodia, which are temporary extensions of its cell membrane and cytoplasm.
The process of nutrition in Amoeba involves the following steps:
Detection: Amoeba senses the presence of food particles in its environment through chemical signals.
Engulfment: Once a food particle, such as a microscopic organism or organic matter, is detected, Amoeba extends pseudopodia around it, forming a food vacuole. The food vacuole is internalized and separated from the external environment.
Digestion: Enzymes, such as proteases and lipases, are secreted into the food vacuole to break down the ingested food into simpler molecules.
Absorption: The digested nutrients, including sugars, amino acids, and fatty acids, are absorbed from the food vacuole into the cytoplasm of Amoeba.
Assimilation: The absorbed nutrients are utilized by Amoeba for energy production, growth, and maintenance of cellular functions.
Egestion: Undigested waste material is expelled from the cell through the process of exocytosis.
Question 10. Describe the structure and functioning of the nephron.
Ans: The nephron is the structural and functional unit of the kidney. Each kidney contains millions of nephrons, and they play a vital role in the filtration and regulation of blood and the formation of urine.
Structure of a nephron:
Renal corpuscle: It consists of the glomerulus, a network of capillaries, and Bowman’s capsule, a cup-shaped structure that surrounds the glomerulus. The glomerulus filters blood, and the filtrate is collected in Bowman’s capsule.
Renal tubule: It starts from the Bowman’s capsule and consists of several segments – the proximal convoluted tubule, the loop of Henle, and the distal convoluted tubule. The renal tubule is responsible for the reabsorption and secretion of substances.
Functioning of a nephron:
Filtration: Blood enters the glomerulus under high pressure, and small molecules such as water, ions, glucose, and waste products are filtered out of the blood and into the Bowman’s capsule. This forms the initial filtrate.
Reabsorption: As the filtrate passes through the renal tubule, essential substances like glucose, amino acids, and water are selectively reabsorbed back into the blood through the walls of the tubule. Reabsorption occurs mainly in the proximal convoluted tubule and the loop of Henle.
Secretion: Certain substances, such as excess ions and waste products like urea and drugs, are actively transported from the blood into the renal tubule. This process occurs mainly in the distal convoluted tubule.
Concentration and Dilution: The loop of Henle plays a crucial role in creating a concentration gradient in the surrounding tissues. It allows the kidney to produce concentrated urine or dilute the urine, depending on the body’s hydration needs.
Formation of Urine: After passing through the renal tubule, the filtrate, now called urine, collects in the collecting ducts, which further concentrate or dilute the urine depending on hormonal signals. Finally, the urine flows into the renal pelvis and is eliminated from the body through the ureter, bladder, and urethra.
Question 11. What are the various modes of excretion in plants?
Ans: Plants excrete waste products through various modes, including:
Stomatal excretion: Some waste products, such as water vapour, oxygen, and small amounts of carbon dioxide, are excreted through the stomata present on the leaves and stems during transpiration.
Lenticular excretion: Plants with lenticels, such as woody stems and roots, excrete gases, including oxygen and carbon dioxide, through these small openings.
Root excretion: Plants excrete organic acids, ions, and other waste products into the soil through the root system. This helps in maintaining proper pH levels and removing toxic substances.
Guttation: Guttation is the excretion of excess water from the tips of leaves in the form of droplets. It occurs when root pressure is high and the rate of transpiration is low.
Bark exfoliation: Some plants shed their bark periodically, which helps in removing accumulated waste substances
Question 12. (i) The upward movement of water normally requires a pump in our houses, but in tall trees, the water rises without any external support. Explain the mechanism.
(ii) State three points of difference between the transport of materials in the xylem and phloem tissues.
Ans: (i) The upward movement of water in tall trees occurs through a process called the transpiration-cohesion-tension mechanism. Transpiration is the loss of water vapour through the stomata in leaves. As water evaporates from the leaf surfaces, it creates a negative pressure or tension that pulls water from the roots to the leaves.
This tension is possible due to the cohesion and adhesion properties of water molecules. Water molecules are cohesive, meaning they stick together, and adhere to the walls of the xylem vessels. This creates a continuous column of water in the xylem from the roots to the leaves. As water molecules evaporate from the leaves, they pull up the entire column of water due to cohesion and adhesion.
(ii) Three points of difference between the transport of materials in the xylem and phloem tissues are:
Composition: The xylem transports water and mineral salts from the roots to the aerial parts of the plant. It is a non-living tissue consisting of specialized cells called vessel elements and tracheids. Phloem, on the other hand, transports organic nutrients, such as sugars, amino acids, and hormones, from the leaves to other parts of the plant. It is a living tissue composed of sieve tube elements and companion cells.
The direction of flow: The flow of materials in the xylem is unidirectional, moving upwards from the roots to the shoots. In contrast, the flow in the phloem can be bidirectional, as it carries nutrients both upwards and downwards, depending on the metabolic needs of the plant.
Mechanism of transport: In the xylem, the movement of water and minerals is mainly driven by transpiration, which creates a negative pressure or tension. The movement occurs passively through the process of cohesion and adhesion. In the phloem, the transport of organic nutrients occurs through active mechanisms, including loading at the source (site of production) and unloading at the sink (site of utilization or storage). Energy in the form of ATP is required for these active transport processes.
The four major glands associated with the digestive system of humans are:
Salivary glands: These glands, located in the mouth, secrete saliva. Saliva contains enzymes, such as amylase, that begin the digestion of carbohydrates. It also lubricates food for easier swallowing.
Gastric glands: Found in the stomach lining, gastric glands secrete gastric juice. Gastric juice contains hydrochloric acid, enzymes like pepsin, and mucus. Hydrochloric acid helps in the breakdown of food and creates an acidic environment for enzyme activity. Pepsin begins the digestion of proteins.
Pancreas: The pancreas is located behind the stomach and produces pancreatic juice. Pancreatic juice contains enzymes, such as amylases, proteases, and lipases, that further break down carbohydrates, proteins, and fats. It also neutralizes the acidic chyme from the stomach.
Liver: Although not a gland, the liver plays a crucial role in digestion. It produces bile, which is stored in the gallbladder and released into the small intestine. Bile aids in the digestion and absorption of fats by emulsifying them into smaller droplets.
Question 14. (i) Explain the process of digestion of proteins in the stomach and small intestine.
(ii) How is the small intestine designed to absorb digested food?
Ans: (i) The process of digestion of proteins in the stomach and small intestine involves the following steps:
Stomach: In the stomach, proteins are partially digested by the enzyme pepsin, which is secreted by the gastric glands. Pepsin works best in an acidic environment created by hydrochloric acid. It breaks down proteins into smaller polypeptides.
Small intestine: The partially digested proteins, along with other partially digested food, enter the small intestine. Here, pancreatic enzymes, such as trypsin and chymotrypsin, are released into the small intestine. These enzymes further break down the polypeptides into smaller peptides. Enzymes produced by the intestinal lining, including peptidases, complete the breakdown of peptides into amino acids, which are the building blocks of proteins. These amino acids are then absorbed through the intestinal lining into the bloodstream.
(ii) The small intestine is designed to absorb digested food efficiently. It has specialized adaptations that maximize the surface area available for absorption, including:
Villi: The inner lining of the small intestine has finger-like projections called villi, which increase the surface area. Each villus contains a network of blood capillaries and a lacteal, a small lymphatic vessel. These blood vessels and lacteals absorb nutrients from the digested food.
Microvilli: The surface of the cells lining the villi has microscopic projections called microvilli, often referred to as the “brush border.” Microvilli further increase the surface area for absorption.
Thin walls: The walls of the small intestine are thin, allowing for efficient diffusion of nutrients from the lumen of the intestine into the bloodstream and lacteals.
Rich blood supply: The villi and microvilli are well-supplied with blood vessels, ensuring that absorbed nutrients are quickly transported away for utilization by the body.
Question 15. What is lymph? How is the composition of lymph different from blood plasma? What is the direction of its flow? List two functions of the lymphatic system.
Ans: Lymph is a fluid that circulates throughout the lymphatic system. It is derived from the interstitial fluid that surrounds the body’s cells. Lymph is similar in composition to blood plasma but lacks red blood cells and platelets.
The composition of lymph differs from blood plasma in that it contains a higher concentration of lymphocytes (a type of white blood cell) and a lower concentration of proteins. Lymph also contains fatty acids and absorbed fat-soluble vitamins from the small intestine.
The flow of lymph is generally unidirectional, moving from the lymphatic capillaries to successively larger lymphatic vessels, eventually draining into the thoracic duct or the right lymphatic duct. From there, lymph enters the bloodstream at the junctions of the internal jugular and subclavian veins.
Two functions of the lymphatic system are:
Immune defence: Lymph nodes, which are present along lymphatic vessels, contain lymphocytes that help in immune responses. They filter and trap foreign substances, such as pathogens or cancer cells, and initiate an immune response to eliminate them.
Fluid balance: The lymphatic system helps maintain fluid balance by returning excess interstitial fluid, not reabsorbed by capillaries, back to the bloodstream. This prevents the accumulation of fluid and helps in the regulation of blood volume and pressure.
Question 16. (i) How many times the blood goes through the heart during one cycle in fish and why?
(ii) List the respiratory pigment present in our body. Where is it present?
(iii) Why are valves present in the heart and veins?
Ans: (i) In fish, blood goes through the heart only once during one cycle because fish have a single circulation system known as single circulation. The blood is pumped by the heart to the gills, where it is oxygenated. Oxygenated blood then travels to the rest of the body before returning to the heart. This single circuit through the heart allows for efficient oxygenation of blood in the gills before it is distributed to the body.
(ii) The respiratory pigment present in our body is haemoglobin. It is present in red blood cells (erythrocytes). Haemoglobin binds to oxygen in the lungs and carries it to tissues throughout the body, facilitating oxygen transport and exchange.
(iii) Valves are present in the heart and veins to prevent the backflow of blood. In the heart, valves ensure that blood flows in one direction, from the atria to the ventricles and then out to the arteries. In veins, valves prevent the backward flow of blood as it moves toward the heart. Valves help maintain the unidirectional flow of blood and prevent the pooling of blood in the lower extremities.
Question: Which processes would you consider essential for maintaining life? Several processes are considered essential for maintaining life, including:
Ans: Respiration: The process of obtaining energy from organic molecules through cellular respiration.
Nutrition: The intake of nutrients, such as carbohydrates, proteins, fats, vitamins, and minerals, for growth, energy production, and repair.
Circulation: The transport of oxygen, nutrients, hormones, and waste products throughout the body via the circulatory system.
Excretion: The removal of metabolic waste products, such as carbon dioxide and nitrogenous wastes, from the body.
Reproduction: The process of producing offspring to ensure the survival of the species.
Growth and development: The increase in size and complexity of an organism over time.
Homeostasis: The maintenance of a stable internal environment, including temperature, pH, and ion concentration, to support optimal bodily functions.
Response to stimuli: The ability to perceive and respond to changes in the environment.
DNA replication and cell division: The processes by which genetic material is replicated and passed on during cell division.