CBSE Important Questions Class 10 Science Chapter 6

CBSE Class 10 Science Chapter 6 Question Answer – Life Processes

Science is a subject which requires deep study and understanding of the concepts covered in each chapter. Hence, one must study properly to get a clear understanding of it and have a strong command of all the topics. In this way, one can score well in the examinations.

Chapter 6 of Class 10 Science covers the topic of ‘Life Processes’. The chapter covers plant nutrition and systems like respiratory, circulatory and excretory. The students should have access to well-prepared notes so that important topics are not skipped, and the preparation is complete.

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The Important Questions Class 10 Science Chapter 6 covers all the vital points for students to get clear-cut insights over all the topics and sub-topics listed in the chapter. Solving questions would help students improve their performance, boost their confidence and score well in examinations.

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CBSE Class 10 Science Important Questions 2022-23

CBSE Class 10 Science Important Questions are also available for the following chapters:

CBSE Class 10 Science Chapter 6 Question Answer– With Solutions

The study notes of Science Class 10 Chapter 6 Important Questions on the Extramarks website are well-structured and concisely prepared for the students. This question bank saves significant time and allows students to get access to various formats of exam-oriented questions at one place.

Below are a few questions and answers from our question bank of Important Questions Class 10 Science Chapter 6.

Question 1. Why is diffusion not sufficient to meet the oxygen requirements of humans?

Answer 1: In humans, diffusion is insufficient to meet oxygen requirements. Skin is in direct contact with the environment. Diffusion is a very slow process and will take longer to reach every body cell. This process cannot meet the oxygen requirements of the body.

Question 2. What criteria can determine if something is alive or not?

Answer 2: Whether an organism is alive or not should match the following characteristics:

• Moving on its own.
• Food is required to meet energy needs and nutrition.
• Respiration
• Response to the changes taking place in the environment.
• Has growth and development.
• Removal of metabolic waste from the body.

Question 3. Mentions outside raw materials used by organisms.

Answer 3: All organisms obtain oxygen, water and food from the outside environment. These are the raw materials. Plants need raw materials such as carbon dioxide and water to prepare their food by photosynthesis.

Question 4. What processes are considered essential for maintaining life?

Answer 4: The processes essential for maintaining life are nutrition, respiration, transportation, excretion and sensitivity.

Question 5. Differentiate between autotrophic and heterotrophic nutrition?

Answer 5:

Question 6. Where do plants get raw materials for photosynthesis?

Answer 6: Plants require carbon dioxide from the atmosphere, water from groundwater and solar energy from the sun.

Question 7. Mention the role of acid in the stomach.

Answer 7: Hydrochloric acid is found in our stomach. This kills the harmful germs which enter our body via food. The acid also activates the pepsin enzyme for protein digestion.

Question 8. What is the function of digestive enzymes?

Answer 8: The digestive enzymes increase the process of breaking down complex molecules into simpler ones and absorbable molecules so that body can facilitate their absorption.

Question 9. How does the small intestine absorb digested food?

Answer 9: The innermost layer of the small intestine is the finger-like projections called villi which increase the absorption surface area. These villi also comprise the blood capillaries to aid in the absorption of simple molecules from food.

Question 10. What advantages does a terrestrial organism have over an aquatic organism in obtaining oxygen for respiration?

Answer 10: The amount of oxygen in the air is more than the amount dissolved in the water. Therefore, terrestrial organisms make less effort to get oxygen than aquatic organisms.

Question 11. What are the ways of glucose oxidation to provide energy in different organisms?

Answer 11: There are two types of respiration for oxidising glucose, i.e., aerobic and anaerobic respiration. In aerobic respiration, the complete oxidation of glucose takes place. The optimum output of energy is obtained. Oxygen is required for this process.

In anaerobic respiration, the process takes place in the absence of oxygen. The complete oxidation of glucose does not take place. Bacteria exhibit this process. In our calf muscles, sometimes anaerobic respiration takes place.

Question 12. Explain oxygen and carbon dioxide transport in human beings.

Answer 12: A gas transportation system transports oxygen and carbon dioxide in human beings. This system comprises the lungs, heart, veins and arteries.

Lungs breathe in oxygen-rich air and breathe out carbon-dioxide-rich layers.

The heart pumps deoxygenated blood to the lungs for oxygenation and distributes it to the various body parts.

Veins carry deoxygenated blood to the heart. The pulmonary vein is the exception which has oxygenated blood from the lungs to the heart.

Arteries carry oxygenated blood to various parts of the body from the heart. One exception is the pulmonary artery which carries deoxygenated blood from the heart to the lungs.

Question 13. How are the lungs designed to maximise the area for exchanging gases in humans?

Answer 13: The air passage in the lungs is divided into smaller tubes called bronchi which form bronchioles. The bronchioles terminate in balloon-like structures called alveoli. These alveoli provide maximum area for the gaseous exchange. The alveoli walls are very thin and contain an extensive network of blood vessels to facilitate the exchange of gases.

Question 14. What are the components and their function in human beings? 

Answer 14: A well-developed circulatory system is present in humans, including the heart, blood vessels and blood.

The heart is responsible for pumping and circulating blood in the whole body.

Blood vessels include arteries, veins and capillaries. The arteries have thick walls and carry oxygenated blood to different body parts.

Veins are thin-walled blood vessels carrying deoxygenated blood from all body parts back to the heart.

Capillaries are thin and narrow blood vessels in which the exchange of materials between the blood and the surrounding cells occurs.

Blood acts as connective tissue and transports food, oxygen, waste material and hormones.

Question 15. Why is the separation of oxygenated and deoxygenated blood in mammals and birds necessary?

Answer 15: Mammals and birds are warm-blooded animals. They control body temperature and do not depend on the environment to regulate body temperature. So birds and mammals need optimum oxidation of glucose which is possible with a good supply of oxygen without mixing oxygenated and deoxygenated blood.

Question 16. Name components of the transport system in organised plants.

Answer 16: The highly organised components of the transport system in plants are Xylem and phloem. Xylem contains vessels and tracheids. The phloem comprises sieve tubes and companion cells.

Question 17. How are water and minerals transported in plants?

Answer 17: The vessels and tracheids of roots, stems and leaves in xylem tissue are interconnected and form a continuous water-conducting channels.

The cells of the roots in soil contact actively take up ions, and a difference between ion concentrations is created. A steady movement of water into the root xylem from the soil creates a column of water that is pushed upwards. The plants use another strategy to move the water in the Xylem upwards to the highest point of the plant’s body.

The water lost through the stomata is replaced by water from the xylem vessel in the leaf. The evaporation of water molecules from the cells of a leaf creates a suction pulling water from the xylem cells of the roots.

This water loss is transpiration, allowing absorption and upward movement of water and minerals dissolved in it from roots to leaves. Transpiration is the major driving force in the movement of water in the Xylem Xylem during the day when the stomata are open. This mechanism is also called the cohesion of water theory or transpiration pull.

Question 18. How is food transported in plants?

Answer 18: The food is transported by phloem to the plant parts like roots, fruits, seeds and growing regions. This process is called translocation. In the phloem, sieve tubes are present, which, together with companion cells, translocate food in upward and downward directions. ATP is the energy provided for translocation.

Question 19. Describe the structure of the nephron with functioning.

Answer 19: Nephron is a long-coiled tubule. It’s one-end cup-shaped and called Bowman’s capsule. The other end connects to a urine collecting duct of the kidney. The glomerulus is a bundle of blood capillaries in the Bowman’s capsule.

A nephron is a functional unit of the kidney. It aids waste product removal and filters impure blood.

Question 20. How do plants get rid of excretory products?

Answer 20: Plants get rid of oxygen and carbon dioxide through diffusion. When the old branches and leaves become useless, they are shed off. Plants have a mechanism by which the roots release waste products. Raisins or gums are the waste products accumulated near the bark.

Question 21. How is the amount of urine produced regulated?

Answer 21: The kidney can reabsorb water from the filtrate. This mechanism depends upon the amount of water left in the body and the filtrate. The relative water concentration signals the brain based on whether water is reabsorbed or released. So this is how the kidneys regulate urine formation.

Question 22. Multiple choice questions.

1. The kidneys are a part of 

• Nutrition

• Respiration

• Excretion

• Transportation 

Answer 1:(c) Excretion

Explanation:

The kidneys are part of the excretory system, and nitrogenous waste like urea is removed from the blood in the kidneys.

2. The Xylem in plants are responsible for:

• Transport of water

• Transport of food

• Transport of amino acids

• Transport of oxygen.

Answer 2: (a) Transport of water

Explanation:

 The xylem is responsible for transporting water and minerals from the soil to the leaves.

3. The autotrophic mode of nutrition requires

• Carbon dioxide and water

• Chlorophyll

• Sunlight

• All of the above

Answer 3:(d) in the autotrophic mode of nutrition, carbon dioxide, water, chlorophyll and sunlight are essential for photosynthesis.

4. Autotrophic organisms include

• Bacteria and virus

• Bacteria and fungi

• Green plants and some bacteria

• Green plants and all bacteria

Answer 4: (c) Green plants and some bacteria

5. A gland which is not associated with the alimentary canal is

• Liver

• Salivary glands

• Pancreas

• Adrenal

Answer 5: (d) Adrenal

6. Which of the following is chiefly digested in the stomach?

• Carbohydrates

• Protein

• Lipids

• Fat

Answer 6: (b) Protein

7. The large intestine in humans mainly carries out

• Absorption

• Assimilation

• Digestion of fats

• Digestion of carbohydrates

Answer 7: (a) Absorption

8. The part of the digestive system where no digestion takes place is

• Ileum

• Stomach

• Mouth

• Oesophagus

Answer 8: (d) Oesophagus

9. The fermentation of glucose by Yeast normally yields

• Alcohol, CO2 and 36 ATP

• CO2, H20 and 36 ATP

• Alcohol, CO2 AND 2 ATP

• Lactic acid, CO2 and 2 ATP.

Answer 9: (c) Alcohol, CO2 AND 2 ATP

10. A large quantity of one of the following is removed from our body by the lungs:

• CO2 and H2O

• CO2 only

• H2O only

• Ammonia 

Answer 10. (a) CO2 and H2O

11. A biochemical compound combined with oxygen and distributed throughout the human body is

• Water

• Urea

• Haemoglobin

• Acetylcholine

Answer 11: ( c) Haemoglobin

12. The process in which water loss takes place in the form of water vapour through stomata is called.

• Transportation

• Transpiration

• Guttation

• Translocation 

Answer 12: (b) Transpiration

13. In a closed circulatory system, blood is completely enclosed within

• Vessels

• Heart

• Skeleton

• Sinuses

Answer 13: (b) Heart

14. Normal blood pressure (systolic/diastolic) is

• 120/80 mm of Hg

• 160/80 mm of Hg

• 120/60 mm of Hg

• 180/80 mm of Hg

Answer 14: (a) 120/80 mm of Hg

15. An instrument which measures blood pressure is called.

• Barometer

• Sphygmomanometer

• Photometer

• Manometer

Answer 15: (b) Sphygmomanometer

16. Which of the following statement is not correct?

• Deoxygenated blood is poured into the right atrium of the heart.

• The excretory units of flatworms are flame cells.

• The human kidney has about 1 million nephridia.

• Tracheids and vessels are non-living conducting tissues.

Answer 16: (c )The human kidney has about 1 million nephridia.

17. Which part of the digestive system receives bile from the liver?

• Stomach

• Small intestine

• Large intestine

• Oesophagus 

Answer 17: (b) Small intestine

18. When air is blown from the mouth into a test tube containing lime water, the lime water turns milky due to the presence of

• Oxygen

• Carbon dioxide

• Nitrogen

• Water vapour

Answer 18: (b) Carbon dioxide

19. The filtration units of kidneys are

• Ureter

• Urethra

• Neurons

• Nephrons

Answer 19: (d) Nephrons

20. Oxygen liberated during photosynthesis comes from

• Water

• Chlorophyll

• Carbon dioxide

• Glucose

Answer 20: (a) Water

21. The opening and closing of the stomatal pores depends upon

• Oxygen

• Temperature

• Water in guard cells

• The concentration of CO2 in stomata

Answer 21: (c ) Water in guard cells

 Question 23. Fill in the blanks:

• The ________ is where the respiratory and digestive passage come together.

• The conditions necessary for photosynthesis are ___________, _________, ___________ and ____________.

• The process in which the digested food passes through the intestinal wall into the bloodstream is called ___________

• The teeth covered with a sticky, yellowish layer of food particles and bacteria are called _______

• Iodine turns blue-black on reacting with ________

• The energy produced during respiration is stored in the form of ATP, which stands for ________

• Pyruvic acid is a three-carbon compound which is also known as _________

• The rate of breathing in ________ animals in much faster than in ________ animals

• The actual exchange of gases takes place in the _________of the lungs.

• ________ are long, thin, spindle-shaped cells with pits in their thick cell walls.

• The liquid part of the blood is called _______

• The expansion of an artery each time the blood is forced into it is called _______

• Gums and resins are the _________products of plants.

Answer 23:

1. The pharynx is where the respiratory and digestive passages come together.
2. The conditions for photosynthesis are sunlight, chlorophyll, carbon dioxide and water.
3. The process in which the digested food passes through the intestinal wall into the bloodstream is called absorption.
4. The teeth are covered with a sticky, yellowish layer of food particles and bacteria called plaque.
5. Iodine turns blue-black on reacting with starch.
6. The energy produced during respiration is stored in the form of ATP, which stands for Adenosine Tri-phosphate.
7. Pyruvic acid is a three-carbon compound which is also known as pyruvate.
8. The rate of breathing in aquatic animals is faster than in terrestrial animals.
9. The actual exchange of gases takes place in the alveoli of the lungs.
10. Tracheids are long, thin, spindle-shaped cells with pits in their thick cell walls.
11. The liquid part of the blood is called plasma.
12. The expansion of an artery each time the blood is forced into it is called a pulse.
13. Gums and resins are the waste products of plants.

 Question 24. Name organisms which have an anaerobic mode of respiration.

Answer 24: Bacteria and Yeast have an anaerobic mode of respiration.

Question 25. Differentiate between aerobic and anaerobic respiration.

Answer 25. 

Question 26. How does fat digestion take place in the body? Where does this process occur?

Answer 26: The digestion of fats takes place in the small intestine. The fat which enters the small intestine is in the form of large globules. The following steps are involved in the process:

• Large globules are broken down into small globules by bile salts.
• The lipase enzyme, which is present in pancreatic juice breaks emulsified fat.
• The pancreas secretes the pancreatic juice.
• The walls of the small intestine secrete enzymes that aid in breaking fats into fatty acids.

Question 27. What is the role of saliva in the digestion of food?

Answer 27: Saliva contains water, salts, mucin and salivary amylase, which breaks down starch present in the food into sugar.

Question 28. Mention the conditions necessary in autotrophic nutrition.

Answer 28: The following conditions are necessary for autotrophic nutrition:

• The presence of carbon dioxide carries out photosynthesis.
• Water
• Sunlight
• Chlorophyll.

Question 29. What are the by-products of autotrophic nutrition?

Answer 29. Oxygen is the by-product of autotrophic nutrition.

Question 30. How are the alveoli designed to maximise the exchange of gases?

Answer 30: The inner surface of the lungs has smaller tubes that terminate in the alveoli, which are balloon-like structures. The extensive network of blood vessels is present in the walls of the alveoli.

There are millions of alveoli present in the lungs. The alveolus provides a large surface area for the gaseous exchange. If all the alveoli are unfolded from the two human lungs, it will give an area of about 80 square meters.

Question 31. What are the consequences of haemoglobin deficiency?

Answer 31: Haemoglobin is the oxygen carrier, so its deficiency affects the blood supply of oxygen to tissues. Anaemia show symptoms like breathlessness and tiredness with a lack of iron.

Question 32. What is double circulation in humans? Mention its importance.

Answer 32: Humans have double circulation as the blood passes twice through the heart in one complete cycle. There are two circulations:

Pulmonary circulation begins from the right ventricle, and the blood is expelled into the pulmonary trunk. The blood reaches the vascular system of the lungs, becomes oxygenated and then returns to the heart, i.e. the left atrium through pulmonary veins.

Systemic circulation starts from the left ventricle, sending blood to the aorta. The aorta supplies the oxygenated blood to various parts of the body. The aorta divides into arteries, arterioles and then capillaries. The deoxygenated blood collected by the venules, join to form veins and vena cava finally and pour back blood into the right auricle of the heart.

The importance of deoxygenated blood is that:

• There is no mixing between the oxygenated and deoxygenated blood.
• The system ensures oxygen supply efficiently.
• Maintenance of body temperature.

Question 33. What are the differences between the transportation of materials between Xylem and phloem?

Answer 33: In Xylem, the transportation of water and minerals takes place from the roots to the leaves. The conduction takes place through xylem vessels and tracheids, which are the dead tissues.

The transportation takes place in phloem from leaves to the other parts of the plant. The process is conducted through sieve tubes and companion cells.

Question 34. Compare the alveoli and nephron functioning, including structure.

Answer 34: The alveoli are balloon-like structures which are one-celled thick and comprise an extensive network of blood capillaries. The site of gaseous exchange in the lungs is the alveoli. The exchange of oxygen and carbon dioxide occurs between the blood flowing in the capillaries of the alveoli and the gases present in the alveoli.

Nephrons are long tubular structures composed of nephrons, Bowman’s capsule and a long renal tube. The nephrons are the structural and functional unit of kidneys. Their main function is filtration and removing the nitrogenous blood in the form of urine.

Question 35. Name the cell organelle in which photosynthesis occurs.

Answer 35: Photosynthesis occurs in the chloroplast of the plant.

Question 36. In the experiment ” light is essential for photosynthesis”, why does the uncovered part of the leaf turn blue-black after contacting iodine solution?

Answer 36: Due to starch production, the uncovered part of the leaf turns blue-black after adding iodine solution.

Question 37. What do you understand by emulsification?

Answer 37: Emulsification is the breakdown of large fat globules into small fat droplets.

Question 38. Explain the process of nutrition in amoeba.

Answer 38: The steps in the nutrition of amoeba are ingestion, digestion, assimilation and egestion.

When amoeba comes in contact with the food, it sends out pseudopodia, which engulfs the food particle forming a food cup. This process is called ingestion.

When the tips of the encircling pseudopodia touch each other, there is the formation of a food vacuole, a temporary stomach that secretes digestive juices. This step is known as digestion.

The digested food gets absorbed and diffuses into the cytoplasm and then assimilates.

The egestion of the non-digested food occurs at any point on the body surface.

Question 39. When you chew chapati for a long period, it tastes sweet after some time. Mention the reason.

Answer 39: Starch is present in chapati, converted to simple sugar by the salivary enzyme amylase. The salivary glands, via the secretion of enzymes, aid in chemical digestion.

Question 40. 1 %  of starch in a test tube is added to 1 ml of saliva. After keeping the mixture for an hour, a drop of iodine solution is added. Mention the change in colour of the test tube. What does this indicate about the salivary action on starch?

Answer 40: There is no change in colour when adding the iodine solution. Saliva breaks down starch into simple sugar, which does not react with the iodine solution to produce any colour.

Question 41. How is digestion affected when the bile duct is completely blocked? Explain 

Answer 41: On blockage of the bile duct, digestion of fats is affected as the bile juice will not reach the small intestine.

Question 42. Why do the trachea walls not collapse when there is less air in them?

Answer 42: The rings of the soft cartilage bones do not allow the trachea to collapse when air is in it.

Question 43. What are enzymes?

Answer 43: Enzymes are the biological catalysts that increase the reaction rate without being used up.

Question 44. Mention the name of one digestive enzyme with its function.

Answer 44: Salivary amylase catalyses the breakdown of starch into sugar in the mouth and small intestine.

Question 45. Explain the cause of cramps after excessive physical exercise.

Answer 45: During excessive physical exercise, aerobic respiration produces energy in our muscles. Anaerobic respiration provides muscles with some extra energy required under excessive physical activity. Glucose is broken down into lactic acid due to anaerobic respiration. The accumulation of lactic acid causes muscle cramps.

Question 46. Explain the process of digestion.

Answer 46: Digestion occurs in the mouth, stomach and small intestine. The process can be explained as follows:

The digestion begins in the mouth. The saliva contains salivary amylase, which breaks down starch into sugar.

Stomach stores and mix the food with gastric juices. The gastric juice contains hydrochloric acid, mucus and pepsin. Hydrochloric acid dissolves food and creates an acidic medium for the action of pepsin. The pepsin digests protein, and the mucus protects the inner lining of the stomach from the action of hydrochloric acid.

In the small intestine, there occurs complete digestion of carbohydrates, proteins and fats. The small intestine wall contains glands which produce intestinal juice. This juice helps in the digestion of the food further. The small intestine obtains digestive juices from the liver and pancreas, which helps mix food.

The bile juice produced by the liver causes the emulsification of fats. The pancreas produces pancreatic juice for the digestion of proteins and emulsified fats. 

The digested food is absorbed through intestinal walls.

Question 47. Name the site where complete digestion of food takes place in the alimentary canal.

Answer 47: Small intestine is that part of the alimentary canal where complete digestion of food takes place.

Question 48. Explain the breakdown of glucose in a cell in the presence and absence of oxygen.

Answer 48: Glucose can be broken down in three different ways.

In the absence of oxygen, like in Yeast, pyruvate is converted to ethanol, carbon dioxide and energy. This is called fermentation.

In the case of insufficient oxygen, like in muscle cells, pyruvate converts to produce lactic acid and energy.

In the presence of oxygen, pyruvate is converted into carbon dioxide, water and energy in mitochondria.

Ethanol is a two-carbon molecule, and lactic acid is a three-carbon molecule.

The first step, glucose breakdown in both the presence and absence of oxygen, is the same. More energy is released in the presence of oxygen.

In the absence of oxygen, anaerobic respiration occurs in the muscle cells. The building of lactic acid in muscle cells causes painful muscle contraction, called cramps.

Question 49. The breathing cycle is rhythmic, whereas the gaseous exchange is a continuous process. Justify the statement.

Answer 49: The lungs always have a continuous residual air volume, so oxygen absorption and carbon dioxide release become a constant process.

Question 50. What happens when a leak is developed in the conducting tubes of the circulatory system? How can this be avoided?

Answer 50: The circulatory system loses it efficiency if it develops a leak. This could be avoided by maintaining normal blood pressure.

Question 51: What is hypertension? What causes it, and how can it cause damage to the body?

Answer 51: High blood pressure is also called hypertension. It occurs due to the constriction of very small arteries, resulting in blood flow resistance.

Hypertension could cause an artery to rupture and cause internal bleeding.

Question 52. In a single-celled organism, diffusion is sufficient to meet all the requirements of food, gas exchange and waste removal, but it is not the case in multicellular organisms. Explain the reason for this difference.

Answer 52: In single-celled organisms, there is no specific organ related to food intake, gas exchange or waste removal. This is because the entire surface of the organism is in contact with the environment.

In multicellular organisms, the skin cells directly interact with the environment. Diffusion is a slow process that takes a very long time to reach all body parts, and it is insufficient to meet oxygen requirements.

Question 53. Mention the three kinds of cells present in blood and write one function of each.

Answer 53: There are three types of cells present in the blood. They are red blood cells, white blood cells and platelets.

Red blood cells are biconvex and contain haemoglobin to transport oxygen from the lungs to body cells and take carbon dioxide from the cells to the lungs.

White blood cells are the body’s defence cells and fight against diseases and infections.

Platelets are responsible for blood clotting during injuries.

Question 54. What are the three types of blood vessels? Mention one important feature of each.

Answer 54: The human circulatory system has three types of blood vessels. These are arteries, veins and capillaries.

Arteries carry oxygenated blood from the heart to different parts of the body. They are thick-walled.

Veins carry deoxygenated blood from various organs to the heart. Veins are thin-walled.

Capillaries are responsible for exchanging material between the blood and the surrounding cells. They are thin-walled and narrow tubes which connect arteries to veins.

Question 55. Write one function of the following:

• Blood vessels

• Lymph

• Heart

Answer 55:

1. Blood vessels are all connected to form a closed circulatory system
2. The lymph is responsible for carrying digested and absorbed fat from the intestine and drains excess fluid from extracellular space back into the blood.
3. The heart is a pumping organ that receives blood from veins and pumps it into the arteries.

Question 56. What is blood pressure? Measuring it gives one point of difference between systolic and diastolic pressure.

Answer 56: Blood pressure is the force exerted against a vessel’s wall. This pressure is greater in arteries than the veins.

A sphygmomanometer measures blood pressure.

The pressure of blood inside the artery during contraction of ventricular systole is called systolic pressure, and the pressure in the artery during the relaxation, or ventricular diastole, is the diastolic pressure. The normal systolic pressure is 120 mm of Hg, and the diastolic is 80 mm of Hg.

Question 57: State the role of following in the human digestive system.

• Digestive enzymes

• Hydrochloric acid

• Villi 

Answer 57. 

1. Digestive enzymes are responsible for digesting the food we eat.
2. Hydrochloric acid creates an acidic medium to aid in the action of the pepsin enzyme.
3. Villi increase the surface area to aid in food absorption.

Question 58. Why are the walls of the ventricles thicker than the auricles?

Answer 58: Ventricles must pump blood to all the body parts during the contraction. To counteract the backward pressure exerted by the blood, it is essential to have thicker walls to prevent the heart’s bursting.

Question 59. Write three events that occur in photosynthesis.

Answer 59: The three events are:

1. Light energy is absorbed by chlorophyll.
2. Conversion of light energy to chemical energy. There is the splitting of water into hydrogen and oxygen.
3. Reduction of carbon dioxide to carbohydrates.

Question 60. How do guard cells open and close stomatal pores?

Answer 60: The opening and closing of the stomatal pore is a function of the guard cells. There is swelling of guard cells when the water flows into them, causing the opening of the stomatal pore. The pore closes if there is shrinkage of the guard cells. There is a loss of large amounts of water through these stomata. The plant closes these pores when carbon dioxide is not required for photosynthesis.

Guard cells become turgid and flaccid based on the water entering and leaving.

Question 61. How are pH maintained in the stomach and the small intestine?

Answer 61: HCL is released by the gastric glands present on the walls of the stomach. This creates an acidic medium to facilitate the action of pepsin. Bile juice makes food alkaline in the small intestine for the pancreatic enzymes to act.

Question 62. Differentiate between inhalation and exhalation.

Answer 62: In inhalation, the diaphragm contracts and is pulled down and flattened—the volume of the thorax increases.

In exhalation, the diaphragm relaxes and is pushed back to its original position. There is a decrease in the volume of the thorax.

Question 63. What is the role of the liver and pancreas?

Answer 63: The liver secretes bile juice to break down fat into fat globules. The pancreas secretes pancreatic juice, which contains protein-digesting and starch-digesting enzymes.

Question 64. Name the organ which performs:

• Absorption of digested food.

• Absorption of water.

Answer 64:

1. The digested food is absorbed in the ileum of the small intestine.
2. The water is absorbed in the large intestine.

Question 65. Answer the following:

• Write the mechanism by which fish breathe in water.

• Name the balloon-like structures present in the lungs and mention their function.

• Name the respiratory pigment and write its role in human beings.

Answer 65:

Fishes breathe by gills through diffusion.

Alveoli are balloon-like structures. They provide a surface area for exchanging gases, and they contain a residual volume of air and sufficient time for exchanging gases.

Haemoglobin is the respiratory pigment that transports oxygen through the blood.

Question 66. List four conditions required for efficient gas exchange in an organism.

Answer 66: The required conditions are:

• Presence of extensive membrane.
• Thin membrane
• Highly vascularised membrane.

The membrane should be easily permeable to oxygen and carbon dioxide.

Question 67. Trace the movement of oxygenated blood in the body.

Answer 67: The pulmonary vein brings oxygenated blood from the lungs to the left atrium.

When the atrium contracts, the blood is transferred to the left ventricle. When the ventricles contract, blood is pushed into the aorta and through arteries to all body parts.

Question 68. Write the function of valves present in between atria and ventricles.

Answer 68: The valves present prevent the backflow of blood from the ventricles into the atria.

Question 69. Answer the following questions:

• Define excretion

• Name the basic filtration unit of kidneys.

• State the function of the bile juice.

• Mention the end products formed on complete digestion of proteins, carbohydrates and fats.

• What happens to glucose in the nephron along with the filtrate?

Answer 69:

1. Excretion is the biological process which removes harmful waste products from the body.
2. Nephrons are the basic filtration unit in the kidneys.
3. Bile juice contains bile pigments and bile salts that emulsify fat to the fatty acids. Bile juice also neutralises the acidic food in the stomach and makes it alkaline so that it can react with the enzyme of the pancreatic juice.
4. The end products formed on complete digestion of proteins, carbohydrates and fats are amino acids, glucose and fatty acid with glycerol respectively.
5. The blood capillaries surrounding the nephron reabsorb the glucose that enters the nephron.

Question 70. Name the following:

• The process in plants links light with chemical energy.

• An organism that can prepare its food.

• The cell organelles where photosynthesis occurs.

• Cells that surround a stomatal pore.

• Organisms that cannot prepare their food.

• An enzyme secreted from the gastric glands in the stomach acts on the proteins.

• What causes the movement of food into the alimentary canal?

Answer 70:

1. Photosynthesis
2. Autotrophs
3. Chloroplast
4. Guard cells
5. Heterotrophs
6. Pepsin 
7. Peristalsis 

Question 71. “All plants give out oxygen during day and carbon dioxide during night.” Give reason.

Answer 71: Yes, this is because respiration occurs throughout the day and night, but photosynthesis occurs only during the day because one of the most integral components needed for photosynthesis is sunlight. During the day, plants give out oxygen, a product of photosynthesis. Thus, plants give carbon dioxide during the nighttime, when there is no photosynthesis.

Question 72. Two green plants kept separately in oxygen-free containers, One in the dark and the other in continuous light. Which one lives longer? Give reasons.

Answer 72. The plant in continuous light will live longer because, in the presence of light, the plants will undergo photosynthesis and can convert carbon dioxide to oxygen. The plant in the dark cannot survive longer. This is because, in the absence of light, the plant cannot perform photosynthesis, and the plant will die.

Question 73. Why do fish die outside water?

Answer 73: Fishes die when taken out of water. This is due to the inability to obtain gaseous oxygen. The fish breathe through gills richly supplied with blood capillaries and readily absorb oxygen dissolved in water.

Question 74. Is nutrition a necessity for an organism? Discuss

Answer 74: Yes, nutrition is a necessity for an organism. This is because of the following reasons:

Nutrition has a role in the growth and repair of cells.

It is important to develop resistance to diseases.

Nutrition provides us with the energy for various metabolic activities of our body.

Nutrition is a source of energy to carry out the activities.

Question 75. What happens when green plants disappear from the earth?

Answer 75: If the green plants disappear from the earth, the herbivore will die of starvation, followed by carnivores and decomposers. Green plants play an important role in converting solar and chemical energy. They are the main source of energy for all heterotrophs. Plant disappearance will create a huge disbalance in the ecosystem.

Question 76. Leaves of a healthy potted plant were coated with Vaseline. Will this plant remain healthy for a long? Give a reason for your answer.

Answer 76: The Vaseline-coated plant will die soon because the layer of Vaseline will prevent the exchange of gases for respiration.

The coating will close the stomatal openings, and the plant won’t be able to get the necessary raw material for photosynthesis. Due to the clogging of stomatal pores, the plant will die due to cessation of respiration.

Question 77. What are the characteristics of a leaf for photosynthesis?

Answer 77: The adaptation is given below:

• Leaf has a large surface area to aid in maximum absorption of light.
• Arrangement of leaves to absorb the optimum amount of light.
• A greater number of veins are important for providing mechanical support.
• Veins participate in quickly transporting substances to and from the mesophyll cells.
• The leaf is the site of transpiration and cools the leaf surface for optimum photosynthesis.
• Numerous stomata are present, which are beneficial in gaseous exchange.
• A large number of chloroplasts are present on the upper surface of leaves.

Question 78. Why do herbivores have longer small intestines than carnivores?

Answer 78: Cellulose is difficult to digest and takes longer for complete digestion, so herbivores need a long small intestine. Meat is easier to digest; hence, carnivores like tigers have a shorter small intestine.

Question 79. What happens when the gastric glands do not secrete mucus?

Answer 79: If the gastric glands do not secrete mucus, there will be corrosion of the inner lining of the stomach, thereby causing acidity, ulceration and extreme discomfort. This is because mucus protects the stomach’s inner lining from the action of hydrochloric acid and the enzyme pepsin.

Question 81. Why does absorption of digested food occur in the small intestine?

Answer 81: This is because of the following reasons:

1. The digestion of food is completed in the small intestine.
2. The small intestine’s inner lining has villi, which are finger-like projections, and increase the surface area in absorption.
3. The intestine wall has blood vessels that carry the absorbed food to various parts of the body.

Question 82. Why is the breathing rate in aquatic organisms much faster than in terrestrial organisms?

Answer 82: This is because the amount of oxygen dissolved in water is low compared to the amount of oxygen present in the air. Aquatic animals take water through their mouth and pass it to the gills, where the blood takes up the dissolved oxygen.

Question 83. What is the advantage of a four-chambered heart?

Answer 83: The advantage of a four-chambered heart is that it prevents the oxygenated and deoxygenated blood from being mixed. The left side of the four-chambered heart is completely separated from the right side of the heart by septa. This mechanism is useful for animals with high energy needs, like birds and mammals. This mechanism also ensures the efficient supply of oxygenated blood to all body parts.

Question 84. In each of the following situations, what happens to the rate of photosynthesis?

• Cloudy days

• No rainfall in the area

• Good manuring in the area

• Stomata get blocked due to duct

Answer 84: 

1. Photosynthesis is reduced due to the low intensity of the light.
2. The rate of photosynthesis is not affected in the case of no rainfall.
3. When manuring is done, soil fertility is increased, but the rate of photosynthesis is not affected.
4. When the stomata are blocked, the rate of photosynthesis is reduced. This affects carbon dioxide availability.

Question 85. Name the energy currency in the living organisms and where it is produced.

Answer 85: Adenosine Triphosphate (ATP) is the energy currency of living organisms. It is produced during respiration and also during photosynthesis. The site of ATP production is mitochondria during the process of respiration.

Question 86. What is common in Cuscuta, ticks and leeches?

Answer 86: They all are parasites and derive their nutrition from the host by harming them but without killing them.

Question 87. What are the functions of the gastric glands present in the walls of the stomach?

Answer 87: The functions of gastric glands are as follows:

• Secrete mucus to protect the stomach.
• Secretion of hydrochloric acid to make the food soft and acidified allows pepsin to act upon the food.
• Secretion of the enzyme pepsin that digests proteins.
• Hydrochloric acid kills the germs present in the food.
• Hydrochloric acid reduces the stomach pH to make the environment suitable for the digestive glands to act.

Question 88. Plants have low energy needs as compared to animals. Explain.

Answer 88: Plants have low energy requirements because they do not move, and most of the body is made up of dead cells like sclerenchyma. Animals require energy because they move in search of food and shelter.

Question 89. Water enters continuously into the root xylem. Explain

Answer 89: The root cells are in contact with the soil, so they are active in taking up the ions. These ions pass inward, increasing osmotic concentrations of Xylem. Because of this, the water continuously passes into the root xylem from the soil. Water is responsible for photosynthesis, and its continuous flow is related to the transpiration pull.

Question 90. How do the leaves of plants help in the process of excretion?

Answer 90: The waste material in leaves is present in the vacuoles of mesophyll and epidermal cells. When old leaves fall, the waste material goes along with the leaves. Secondly, the transpiration of gases via stomata helps remove gaseous waste products of respiration and photosynthesis.

Question 91. Why is soil important for plant growth?

Answer 91: The importance of soil for the growth of plants is:

• Anchorage
• The base for plant growth and allows root penetration.
• Source of organic material, which is essential for plant growth.
• Soil provides water and minerals for plants.
• It establishes symbiotic associations with microbes.
• Aids in the respiration of root cells due to the availability of oxygen in food materials.

Question 92. Describe the alimentary canal of man.

Answer 92: The length of alimentary canals is 9 meters. It consists of:

• Mouth
• Pharynx
• Oesophagus
• Stomach
• Small intestine
• Large intestine
• The mouth leads to the buccal cavity. The tongue has taste buds. Teeth are present in both jaws. The four types of teeth present are incisors, canines, premolars and molars. There is a total of 32 teeth in number.
• The pharynx is a short and conical region.
• The Oesophagus is a narrow, long, muscular tube leading to the stomach.
• The small intestine is a convoluted tube, and it has three regions. The first part is the stomach which is curved and C-shaped. The jejunum is longer and coiled. The last part is the ileum, whose inner surface is folded to form villi which absorb the products of digestion.

The large intestine is short and wide. It has three regions: caecum, colon and rectum. The caecum is a small and rounded blind sac which gives rise to the vermiform appendix, the colon is inverted U-shaped, and the rectum opens exteriorly through the anus.

Question 93: Multiple choice questions:

1. Which statement about autotrophs is incorrect?

• They synthesise carbohydrates from carbon dioxide and water in the presence of sunlight and chlorophyll.

• They store carbohydrates in starch form.

• They convert carbon dioxide and water into carbohydrates in the absence of sunlight.

• They are the first trophic level in food chains.

Answer: (c) convert carbon dioxide and water without sunlight into carbohydrates.

Explanation: 

This is because autotrophs need sunlight to convert carbohydrates without sunlight.

2. 2. In which of the following groups of organisms are food materials broken down outside the body and absorbed?

• Mushroom, green plants, amoeba

• Yeast, mushroom, bread mould

• Paramecium, amoeba, Cuscuta

• Cuscuta, lice, tapeworm

Answer: (b) Yeast, mushroom and bread mould.

Explanation:

Saprophytes break down the food outside the body, so the correct answer is Yeast, mushroom and bread mould as they are the saprophytes.

3.Select the correct statement.

• Heterotrophs do not synthesise their food.

• Heterotrophs utilise solar energy for photosynthesis.

• Heterotrophs synthesise their food.

• Heterotrophs convert carbon dioxide and water into carbohydrates.

Answer: (a)  Heterotrophs do not synthesise their food.

Explanation:

The heterotrophs depend on phototrophs or other organisms to obtain their food.

• If salivary amylase is absent in saliva, this affects which event in the oral cavity?
• Protein breaks down into amino acid

• Starch breaking down into sugar

• Fats breaking down into fatty acids and glycerol

• Absorption of vitamins

Answer: (b) starch breaking down into sugar.

Explanation:

Salivary amylase plays an important role in digestion. It breaks down starch into sugar. This digestive function would be affected in the absence of salivary amylase.

• A few drops of iodine solution added to rice water turned the solution into a blue-black colour. What does this indicate that rice water contains:
• Complex proteins

• Simple proteins

• Fats

• Starch

Answer: (d) Starch

Explanation:

Amylose and amylopectin are present in starch. When iodine is added to starch, a blue colour is produced because the amylose component of starch reacts with iodine. This colour complex indicates that starch is present in the rice water.

• Where does the final digestion of food take place?
• Stomach

• Mouth cavity

• Large intestine

• Small intestine

Answer: (d) small intestine

Explanation:

The digestion starts in the mouth. In the small intestine, complete digestion takes place, and in the large intestine, digestion does not occur.

• What is the function of pancreatic juice? Choose from the following:
• Lipase digest carbohydrates, and the proteins are digested by trypsin.

• Trypsin is responsible for digesting emulsified fats and lipase proteins.

• Fats are digested by trypsin and lipase.

• Trypsin digests proteins and lipase-emulsified fats.

Answer: (d) trypsin digests proteins and lipase-emulsified fats.

Explanation:

Trypsin digests protein by breaking it down into proteins and polypeptides. Fatty acids and glycerol are produced on fat emulsification by lipase.

• When is air blown from the mouth into a test tube which contains lime water, due to the presence of which the following, lime water turns milky?
• Water vapour

• Carbon dioxide

• Oxygen

• Nitrogen 

Answer 8: (b) carbon dioxide

Explanation:

When carbon dioxide and water react, it turns milky.

• Which of the following statements about respiration are true?
• Ribs move inward, and the diaphragm is raised in inhalation.

• The gaseous exchange occurs in the alveoli. The oxygen from the alveolar air diffuses into the blood, and carbon dioxide from the blood into the alveolar air.

• Haemoglobin has a greater affinity for carbon dioxide compared to oxygen.

• The surface area of the alveoli increases for gaseous exchange.

• i and iv

• ii and iii

• i and iii

• ii and iv

Answer: (d) ii and iv are correct.

Statement i is wrong due to the outward movement of ribs and lowered diaphragm movement during inhalation. Option iii is wrong as haemoglobin has more affinity for oxygen than carbon dioxide.

• Where does the exchange of gases take place during respiration?
• Throat and larynx

• Alveoli of lungs

• Trachea

• Trachea and larynx

Answer: (b) alveoli of lungs

Explanation:

Alveoli are responsible for the exchange of gases during respiration. From the alveoli, there is the diffusion of oxygen into the blood. The larynx and trachea are passages for air movement.

• What prevents the backflow of blood inside the heart during contraction?
• Valves in heart

• Wall of ventricles

• Wall of atria

• All of these

Answer (a) valves of the heart

Explanation:

The thick walls of ventricles and thin walls of atria are responsible for blood pumping. They have no role in preventing the backflow of blood inside the heart during contraction.

• Single circulation, i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by which of the following groups?
• Labeo, Chameleon, Salamander

• Hippocampus, Exocoetus, Anabas

• Hyla, Rana, Draco

• Whale, Dolphin, Turtle

Answer 12: (b) Hippocampus, Exocoetus, Anabas

Explanation:

Partial double circulation is present in reptiles and amphibians, which have three-chambered hearts in options a and c. In option d, the whale is a mammal, and the turtle is a reptile, so it is incorrect.

• In which of the following is oxygenated blood not pumped to different body parts?
• Pisces and amphibians

• Amphibians and reptiles

• Amphibians only

• Pisces only.

Answer: (d) Pisces only.

Explanation:

Deoxygenated blood from all body parts is pumped into the heart through single circulation. The heart pumps this blood into the gills, where it gets oxygenated. 

Question 94. Mention the adaptation of leaves to carry out photosynthesis.

Answer 94: The leaf surface is flat to increase light exposure. To trap sunlight, chlorophyll is present. Transpiration takes place through stomata.

Question 95. What will happen if the platelets are absent in the blood?

Answer 95: Platelets are responsible for the clotting of blood. In the absence of platelets, the blood will not clot. This will increase the severity in cases of injury and may prove to be life-threatening.

Question 96. Mention the importance of transpiration in plants.

Answer 96: The transpiration carries the following:

To facilitate the ascent of sap, transpiration pull is created.

The rise of sap is important to ensure water availability in photosynthesis.

Plants get rid of excess water due to transpiration.

Question 97. Explain the breathing process in human beings.

Answer 97: There are two processes of breathing in human beings:

• Inhalation
• Exhalation

Inhalation is the process in which oxygen is taken in. Ribs come out in this process. The diaphragm moves down. There is an increase in the volume of the lungs and a decrease in pressure. Due to this, the air moves towards the lungs.

Exhalation is the process in which carbon dioxide is given out. The ribs go down, and there is an upward movement of the diaphragm: the pressure increases, and the volume of the lungs decreases. As a result of this, the air moves out of the lungs.

98. Explain the functions of:

• Blood

• Lymph

• Lungs

Answer 98:

1.The functions of blood are:

• Transportation of oxygen to the tissues of the body.
• Transports absorbed nutrients.
• Carries nitrogenous waste to the kidneys
• Regulation of body temperature
• Maintenance of body pH.
• Maintains water balance.
• Lymphocytes produce antibodies to protect and fight against diseases.
• Blood allows the healing of wounds as it contains platelets.

2.The functions of lymph are:

• It carries digested and absorbed fat from the intestine.
• Drainage of excess fluid from extracellular space into the blood.
• Kills germs and protects the body.

3.The functions of the lungs are:

• Take in oxygen and give out carbon dioxide.
• Purification of blood as they remove carbon dioxide from it.

Question 99. Explain heterotrophic nutrition. What are the types of heterotrophic nutrition? Explain with examples.

Answer 99: Heterotrophic nutrition is a type of nutrition where an organism derives its food from another living organism. 

There are three types of heterotrophic nutrition:

In saprophytic nutrition, nutrients are obtained from dead and decaying organic matter. Examples are fungi, Yeast and bacteria.

In parasitic nutrition, the mode of obtaining food is synthesised by the others. The parasite is the organism which obtains food. This type of nutrition is seen in fungi, bacteria, plants like Cuscuta and animals like roundworms and plasmodium.

Holozoic nutrition is seen in amoeba, frogs and human beings. In this, complex organic matter in the form of solid food is ingested, digested and absorbed into the cells utilised by the body.

Question 100. Name the sources from which plants obtain nitrogen to synthesise proteins and other compounds.

Answer 100: The two sources are inorganic nitrates or nitrites and organic compounds prepared by bacteria from atmospheric nitrogen.

Question 101. Amphibians or many reptiles have three-chambered hearts and can tolerate mixing oxygenated and deoxygenated blood. Why?

Answer 101: The body temperature of cold-blooded animals depends upon the environment’s temperature. They do not require much energy as they do not maintain their body temperature. The energy produced is less when oxygenated and deoxygenated blood is mixed. This is seen in amphibians and reptiles.

Question 102. What is the function of the ureter, urinary bladder and urethra?

Answer 102: Urine formation is carried by the ureter to the urinary bladder in each kidney. The glucose, amino acid, salt and water is reabsorbed in the ureter.

The urinary bladder store urine, so it is a reservoir. The urine passes out from the body through the urethra.

Question 103. What is ATP, and what is its use?

Answer 103: ATP is a nitrogenous compound used as a fuel in various cell activities.

Question 104. What are the functions of the large intestine?

Answer 104: The functions of the large intestine are as follows:

The large intestine walls absorb water and electrolytes from undigested food.

Formation and storage of faeces.

Question 105. How do unicellular organisms remove waste?

Answer 105: The waste is removed by diffusion in unicellular organisms.

Question 106. Why is the colour of urine yellow?

Answer 106: Urine is yellow due to urea, uric acid and ammoniacal salts.

Question 107. Answer the following questions:

• What is the importance of systemic circulation in organisms?

• Where is the heart located?

• What does heartbeat mean?

• What is the largest artery of the body?

• Give one synonym for high blood pressure.

• Which is the liquid part of the blood.

• Which component of blood is responsible for clot formation?

• What is transpiration?

• What is translocation?

• Which tissue transports soluble products of photosynthesis in a plant?

• Which tissue transports water and mineral in a plant.

• Name the excretory products in plants.

• What do you mean by artificial kidney?

• In which part of the alimentary canal does digestion not occur?

• Where does the digestion of fats take place in the body?

Answer 107:

1. The systemic circulation circulates oxygen and removes waste materials from the body.
2. The heart is located in the thoracic cavity above the diaphragm between the two lungs.
3. Heartbeat refers to the rhythmic expansion and contraction of the heart.
4. The largest artery is the aorta.
5. High blood pressure is also called hypertension.
6. Plasma is the liquid part of the blood.
7. Platelets are responsible for clot formation.
8. Transpiration means water loss in the form of water vapour from the aerial parts of the plant.
9. Translocation is food transport from the leaves to other parts of the plant.
10. Phloem transports soluble products of photosynthesis.
11. Xylem transports water and minerals in a plant.
12. Resins and gums are the excretory products of the plant.
13. An artificial kidney is a device which removes the nitrogenous waste products from the blood of a person whose kidneys are damaged with a process called dialysis.
14. Digestion does not occur in the large intestine of the alimentary canal.
15. The small intestine is the site where the digestion of fat occurs.

Question 108. State whether true or false:

• The glomerulus acts as a dialysis bag.

• Bowman’s capsule is found in the heart.

• The peristaltic movement occurs in the mouth to push food into the alimentary canal.

• The release of energy in aerobic respiration is less when compared to the anaerobic process.

• Before testing the presence of starch, chlorophyll removal must be done from the leaf because it interferes due to its green colour.

• When the absorbed food is taken in by the body cells and used for growth and repair is called egestion.

• The cytoplasm is the site for aerobic respiration.

• Plant respiration is a faster process compared to the slow process in animals.

• Carbohydrates are digested by enzymes present in both saliva and pancreatic juice.

• The  small intestine length  in a human adult is about 3.5 m

Answer 108:

1. True.
2. False. Bowman’s capsule is present in the kidneys.
3. False. Peristaltic movement bring food down the pipe into the stomach.
4. False. The energy released in aerobic respiration is more than in anaerobic respiration.
5. True.
6. False 
7. False. The site for aerobic respiration is mitochondria.
8. False. The rate of respiration is fast in animals compared to plants.
9. True
10. False.The small intestine is long when compared to large intestine. The length is about 6.5meters in a human adult.

Question 109: What are stomata?

Answer 109: Stomata are the tiny pores or opening present on the surface of the leaf. They are responsible for exchanging gases between plants and the atmosphere.

Question 110. Why is anaerobic respiration inefficient?

Answer 110: There is an incomplete breakdown of glucose in anaerobic respiration, so less energy is produced. Therefore it is less efficient.

Question 111. What are the consequences of the diaphragm rupture of a person in an accident?

Answer 111: This will lead to immediate death due to respiratory failure.

Question 112. Why is smoking harmful?

Answer 112: Cilia are tiny hair-like structures present in the upper part of the respiratory system. They remove dust and other particles which enter the body via inhalation. These cilia are damaged by smoking. Due to this, harmful substances like smoke, dust and chemicals enter the lungs and cause cough and respiratory infections. Smoking causes lung cancer. In lung cancer, the lungs erode faster and fail to perform their normal functions.

Question 113. Describe the circulatory system of fish.

Answer 113: The heart of fish contains one atrium and one ventricle. Gills carry out the function of oxygenation. The heart supplies blood to the gills, where the blood gets oxygenated and is provided to the rest of the parts of the body.

Question 114. How does paramoecium obtain food?

Answer 114: Paramoecium, a unicellular organism, has a definite shape. The food particle moves into the mouth by moving thin hair-like structures called cilia on the entire surface of the paramecium cell.

Question 124: What are peristaltic movements?

Answer 124: This is defined as the contraction and relaxation of muscles in the food pipe. This brings food pipe food down into the stomach.

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