CBSE Class 10 Science HOTs Life Processes Set 02

Question. Which of the following has no muscular walls?
(a) Artery
(b) Vein
(c) Arteriole
(d) Capillary
Answer: (d) Capillary

Question. Which of the following contributes most to the transport of water from the ground to the leaves of a tall tree?
(a) Root pressure
(b) Capillary rise of water in xylem
(c) Breakdown of ATP
(d) Cohesion of water and transpiration pull
Answer: (d) Cohesion of water and transpiration pull

Question. (a) Name the blood vessel that brings deoxygenated blood to the human heart. (b) Which chamber of the human heart receives deoxygenated blood? (c) Describe how deoxygenated blood from this chamber is sent to lungs for oxygenation.
Answer: (a) Vena Cava brings deoxygenated blood to the human heart.
(b) The right atrium receives deoxygenated blood from the body.
(c) When the right atrium contracts, it pours deoxygenated blood into the right ventricle. When the right ventricle contracts, the blood is pumped into the pulmonary artery, which carries it to the lungs for oxygenation.

Question. (b) What is the advantage of separate chambers in mammals and birds for oxygenated and deoxygenated blood?
Answer: The separation of chambers prevents the mixing of oxygenated and deoxygenated blood. This ensures a highly efficient supply of oxygen to the tissues, which is necessary for mammals and birds to produce the energy required to maintain a constant body temperature.

Excretion

Question. Which of the following statement is not correct?
(a) Deoxygenated blood is poured into right atrium of heart.
(b) The excretory units of flatworms are flame cells.
(c) Human kidney has about 1 million nephridia.
(d) Tracheids and vessels are non-living conducting tissues.
Answer: (c) Human kidney has about 1 million nephridia.

Question. Nitrogenous wastes are formed from the breakdown of
(a) fat
(b) water
(c) amino acids
(d) ammonia
Answer: (c) amino acids

Question. A plant gets rid of excess water through transpiration. Which is a method used by plants to get rid of solid waste products?
(a) Shortening of stem
(b) Dropping down of fruits
(c) Shedding of yellow leaves
(d) Expansion of roots into the soil
Answer: (c) Shedding of yellow leaves

Very Short Answer Type Questions

Question. Write one specific function each of the following organs in relation with excretion in human beings: (i) Renal Artery (ii) Urethra (iii) Glomerulus (iv) Tubular part of nephron
Answer: (i) Renal Artery: To carry blood from the heart to kidneys.
(ii) Urethra: To expel urine out of the body.
(iii) Glomerulus: To filter the blood passing through it and initiate urine formation.
(iv) Tubular part of nephron: Major function of tubules is reabsorption. Also, tubular secretion helps in urine formation without affecting the electrolyte balance of the body.

Question. (a) Name two excretory products other than \( O_2 \) and \( CO_2 \) in plants. (b) Why is urine yellow in colour?
Answer: (a) The two excretory products other than \( O_2 \) and \( CO_2 \) in plants are resins and gums.
(b) Urine contains pigment urochrome which imparts yellow colour.

Question. Name the substances other than water, that are reabsorbed during urine formation. What are the two parameters that decide the amount of water that is reabsorbed in the kidney?
Answer: Glucose, amino acids, and salts are selectively reabsorbed as the urine flows along the tube. The amount of water reabsorbed depends on (i) how much excess water there is in the body and (ii) how much of dissolved waste there is to be excreted.

Short Answer Type Questions

Question. Describe in brief the functions of kidneys, ureters, urinary bladder and urethra.
Answer: Functions of Kidneys: It removes the nitrogenous wastes such as urea and excess water from the blood. It regulates the osmotic pressure/water balance/pH of the blood.
Functions of Ureters: Urine formed in each kidney is carried by the long tube called ureter to the urinary bladder. Some amount of glucose, amino acid, salt and a major amount of water are reabsorbed in ureter.
Functions of Urinary bladder: It acts as a reservoir that stores urine before being discharged to the outside.
Functions of Urethra: Urine is passed out from the body through the urethra.

Question. How is urine produced?
Answer: Formation of Urine: The purpose of urine is to filter out waste products from the blood.
• The nitrogenous waste such as urea or uric acid are removed from blood in the kidneys.
• Each capillary cluster in the kidney is associated with the cup-shaped end of a tube that collects the filtered urine.
• Each kidney has large numbers of these filtration units called nephrons.
• Some substances in the initial filtrate such as glucose, amino acids, salts and a major amount of water are selectively reabsorbed as the urine flows along the tube. This depends on how much excess water is there in the body and on how much of dissolved waste there is to be excreted.
• The urine forming in each kidney enters a long tube, the ureter, which connects the kidneys with the urinary bladder.
• Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to pass out through the urethra.

INTEGRATED (MIXED) QUESTIONS

Question. (a) What is a pulse? (b) How does Paramoecium obtain its food?
Answer: (a) A pulse is the rhythmic expansion and contraction of an artery as blood is forced through it by the heart's pumping action. (b) Paramoecium has a definite shape and food is taken in at a specific spot. Food is moved to this spot by the movement of cilia which cover the entire surface of the cell.

Question. (a) “The breathing cycle is rhythmic whereas exchange of gases is a continuous process”. Justify this statement. (b) What happens if conducting tubes of circulatory system develops a leak? State in brief, how could this be avoided? (c) What is hypertension? How is it caused? What damage can it do in our body?
Answer: (a) Breathing is a mechanical process involving inhalation and exhalation, creating a rhythmic cycle. However, gas exchange at the alveolar and tissue levels occurs continuously due to the residual volume of air in the lungs, ensuring oxygen is always available for diffusion. (b) If the system develops a leak, blood pressure would drop, reducing the efficiency of the pumping system. This is avoided by platelets, which circulate in the blood and plug leaks by helping to clot the blood at the point of injury. (c) Hypertension is high blood pressure. It is caused by the constriction of arterioles, which results in increased resistance to blood flow. It can lead to the rupture of an artery and internal bleeding.

Question. How does gaseous exchange take place in Amoeba?
Answer: In Amoeba, gaseous exchange takes place through its simple cell membrane via the process of diffusion. Oxygen dissolved in the surrounding water diffuses into the cell, and carbon dioxide produced during respiration diffuses out into the water.

Question. In single celled organisms diffusion is sufficient to meet all their requirements of food, exchange of gases or removal of wastes but it is not in case of multicellular organisms. Explain the reason for this difference. 
Answer: In single-celled organisms, the entire surface of the organism is in direct contact with the environment. In contrast, in multicellular organisms, most cells are not in direct contact with the surrounding environment. Simple diffusion is too slow to cover the large distances required to transport materials to every cell in a large, complex body.

Question. Distinguish between photosynthesis and respiration.
Answer: Photosynthesis is an anabolic process where plants manufacture food using \( CO_2 \), water, and sunlight, releasing oxygen as a byproduct. Respiration is a catabolic process where food is broken down to release energy (\( ATP \)), using oxygen and releasing \( CO_2 \) as a byproduct.

Question. The leaves of a plant were covered with aluminium foil, how would it affect the physiology of the plant? 
Answer: Covering leaves with aluminium foil prevents sunlight from reaching the chlorophyll, thus stopping photosynthesis. It also blocks stomata, preventing gas exchange and transpiration. Over time, the plant will be unable to produce food and transport water/minerals, leading to its eventual death.

Question. (a) What is ATP? What is its use? (b) How does smoking affect the health of a person? (c) Describe the circulatory system on a fish.
Answer: (a) ATP (Adenosine Triphosphate) is the energy currency of the cell. It is used to drive various endothermic reactions and cellular processes like muscle contraction and protein synthesis. (b) Smoking damages the alveolar walls, reducing the surface area for gas exchange, and introduces harmful chemicals into the lungs, increasing the risk of lung cancer and respiratory diseases. (c) Fish have a two-chambered heart. Blood is pumped to the gills, where it is oxygenated, and then passes directly to the rest of the body. Blood goes through the heart only once during one cycle (single circulation).

Question. (a) Account for the following. Amphibians or many reptiles have three chambered hearts and can tolerate mixing of oxygenated and deoxygenated blood. (b) Why are the walls of ventricles thicker than the auricles? (c) State two sources from which plants obtain nitrogen for the synthesis of proteins and other compounds.
Answer: (a) Amphibians and reptiles are cold-blooded (ectotherms) and do not use energy to maintain a constant body temperature. Their energy needs are lower, so they can tolerate the partial mixing of blood. (b) Ventricles have to pump blood to various organs of the body under high pressure, whereas auricles only need to pump blood into the ventricles. (c) Plants obtain nitrogen from the soil in the form of inorganic nitrates or nitrites, and from organic compounds prepared by bacteria (like Rhizobium) from atmospheric nitrogen.

Question. (a) Write the difference between inhalation and exhalation. (b) State the roles of liver and pancreas. (c) Name the organ which performs the following functions in humans: (i) Absorption of digested food (ii) Absorption of water
Answer: (a) Inhalation involves taking in air, the diaphragm flattens, and the chest cavity expands. Exhalation involves expelling air, the diaphragm relaxes into a dome shape, and the chest cavity contracts. (b) The liver secretes bile which emulsifies fats. The pancreas secretes pancreatic juice containing enzymes like trypsin and lipase for digestion, and insulin for regulating blood sugar. (c) (i) Small intestine (villi), (ii) Large intestine.

Question. (a) What are the function of lungs? (b) State the functions of the following components of transport system: (i) Blood (ii) Lymph
Answer: (a) The main function of the lungs is to facilitate gas exchange—taking in oxygen from the atmosphere into the bloodstream and releasing carbon dioxide from the bloodstream into the atmosphere. (b) (i) Blood transports nutrients, oxygen, carbon dioxide, hormones, and waste products. (ii) Lymph carries digested and absorbed fat from the intestine and drains excess fluid from extra-cellular space back into the blood.

Question. (a) Explain the mechanism of gaseous exchange between tissues and blood. (b) Describe the mechanism of blood clotting. (c) How is carbon dioxide obtained by (i) aquatic plants and (ii) terrestrial plants?
Answer: (a) Gaseous exchange occurs via diffusion. Blood arriving at tissues has a high concentration of \( O_2 \) and low \( CO_2 \), while tissues have low \( O_2 \) and high \( CO_2 \). Oxygen diffuses from blood into tissues, and carbon dioxide diffuses from tissues into blood. (b) When a blood vessel is injured, platelets release thromboplastin. This triggers a series of reactions that convert prothrombin into thrombin. Thrombin then converts soluble fibrinogen into insoluble fibrin threads, which form a mesh (clot) to stop bleeding. (c) (i) Aquatic plants take in \( CO_2 \) dissolved in water through their general body surface. (ii) Terrestrial plants take in atmospheric \( CO_2 \) through stomata present on the surface of leaves.

ASSERTION AND REASON QUESTIONS

In the following Questions, the Assertion and Reason have been put forward. Read the statements carefully and choose the correct alternative from the following:
(a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.
(b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.
(c) Assertion is true but the Reason is false.
(d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: When air is blown through lime water, lime water turns milky.
Reason: Air contains 78% nitrogen and 21% oxygen.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: Veins have thin walls to collect blood from different organs.
Reason: Blood in veins are not under pressure.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Human being has a complex respiratory system.
Reason: Human skin is impermeable to gases.
Answer: (b) Both the Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: All proteins in our food are digested in small intestine only.
Reason: The protein digesting enzymes are released into small intestine and stomach.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Nitrogen is an essential element for plant growth and is taken up by plants in the form of inorganic nitrates or nitrites.
Reason: The soil is the nearest and richest source of raw materials like nitrogen, phosphorus and other minerals for the plants. 
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Aerobic respiration release less energy as compared to anaerobic respiration.
Reason: Mitochondria is the power house of the cell. 
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Energy is required to carry out different life processes.
Reason: Energy is obtained in the form of ATP in the mitochondria. 
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Molecular movements help in repair and maintenance of cell organelles, cells and tissues.
Reason: Molecular movements are involved in removal of catabolic products like \( CO_2 \) and \( NH_3 \).
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: In parasitic nutrition, an organism lives on or inside another living organism and derives its food.
Reason: Parasites obtain predigested or partially digested food from their host.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: The stomata are present in the leaves and green stems of a plant.
Reason: The gaseous exchange in plants takes place only through the stomata in leaves.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: Chloroplasts are the organelles in the cells of green plants which contain chlorophyll.
Reason: The site of photosynthesis in cell of the leaf is chlorophyll.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: The process of obtaining food by Amoeba is phagocytosis.
Reason: Amoeba ingests the food particles by forming finger like projections called pseudopodia around it
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: Due to the presence of hydrochloric acid, the gastric juice is acidic in nature.
Reason: In acidic medium, the enzyme pepsin begins the digestion of proteins present in food the form smaller molecules in small intestine.
Answer: (c) Assertion is true but the Reason is false.

Question. Assertion: The digested food which is not used by our body immediately is stored in the liver in the form of a carbohydrate starch.
Reason: The stored food can be used as a source of energy by the body as and when required.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: The act of expelling the undigested food from the large intestine is called excretion.
Reason: The exit of undigested food is controlled by anal sphincter.
Answer: (d) The statement of the Assertion is false but the Reason is true.

Question. Assertion: Plants use oxygen of air for respiration and release carbon dioxide.
Reason: Oxygen and carbon dioxide are called respiratory gases.
Answer: (b) The Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.

Question. Assertion: The build up of lactic acid in our muscles during sudden activity causes cramps.
Reason: The anaerobic respiration in animal muscle tissue produces lactic acid as the end produce.
Answer: (a) Both the Assertion and the Reason are correct and the Reason is the correct explanation of the Assertion.

Question. Assertion: The inner walls of the small intestine have finger like projections called villi which are rich in blood.
Reason: These villi have a large surface area to help the small intestine in completing the digestion of food. 
Answer: (b) Both the Assertion and the Reason are correct but the Reason is not the correct explanation of the Assertion.