5. Life Processes

Class 10 Chapter 5 Life Processes

Class 10 Chapter 6 Life Processes

Multiple Choice Questions

1. Which of the following statements about the autotrophs is incorrect?

(a) They synthesise carbohydrates from carbon dioxide and water

in the presence of sunlight and chlorophyll

(b) They store carbohydrates in the form of starch

(d) They constitute the first trophic level in food chains

Answer : (c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight .

2. In which of the following groups of organisms, food material is broken down outside the body and absorbed?

(a) Mushroom, green plants, Amoeba

(b) Yeast, mushroom, bread mould

(d) Cuscuta, lice, tapeworm

Answer : (b) Yeast, mushroom, bread mould

3. Select the correct statement

(a) Heterotrophs do not synthesise their own food

(b) Heterotrophs utilise solar energy for photosynthesis

(d) Heterotrophs are capable of converting carbon dioxide and water into carbohydrates

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

4. Which is the correct sequence of parts in human alimentary canal?

(a) Mouth → stomach → small intestine → oesophagus → large intestine

(b) Mouth →oesophagus → stomach → large intestine → small intestine

(d) Mouth → oesophagus → stomach → small intestine→ large intestine

Answer : (d) Mouth → esophagus → stomach → small intestine → large intestine

5. If salivary amylase is lacking in the saliva, which of the following events in the mouth cavity will be affected?

(a) Proteins breaking down into amino acids

(b) Starch breaking down into sugars

(d) Absorption of vitamins

Answer : (b) Starch breaking down into sugars

6. The inner lining of stomach is protected by one of the following from hydrochloric acid. Choose the correct one

(a) Pepsin

(b) Mucus

(d) Bile

Answer : (b) Mucus

[ Mucus serves as a protective layer on the inner lining of the stomach, preventing it from being damaged by the acidic gastric juices, including hydrochloric acid. ]

7. Which part of alimentary canal receives bile from the liver?

(a) Stomach

(b) Small intestine

(d) Oesophagus

Answer : (b) Small intestine

8. A few drops of iodine solution were added to rice water. The solution turned blue-black in colour. This indicates that rice water contains

(a) complex proteins

(b) simple proteins

(d) starch

Answer : (d) Starch

9. In which part of the alimentary canal food is finally digested?

(a) Stomach

(b) Mouth cavity

(d) Small intestine

Answer : (d) Small intestine

10. Choose the function of the pancreatic juice from the following

(a) trypsin digests proteins and lipase carbohydrates

(b) trypsin digests emulsified fats and lipase proteins

(d) trypsin digests proteins and lipase emulsified fats

Answer : (d) Trypsin digests proteins, and lipase digests emulsified fats.

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

(a) oxygen

(b) carbon dioxide

(d) water vapour

Answer : (b) Carbon dioxide

[ Carbon dioxide reacts with lime water to form calcium carbonate, which is insoluble and gives the milky appearance.]

12. The correct sequence of anaerobic reactions in yeast is

(a) Glucose Pyruvate Ethanol + Carbondioxide

(b) Glucose Pyruvate Lactic acid

(d) Glucose Pyruvate Ethanol + Carbondioxide

Answer : (d) Glucose Pyruvate Ethanol + Carbondioxide

13. Which of the following is most appropriate for aerobic respiration?

(a) Glucose Pyruvate + Energy

(b) Glucose Pyruvate + Energy

(d) Glucose Pyruvate + Energy + Energy + Energy

Answer : (b) Glucose Pyruvate + Energy

14. Which of the following statement(s) is (are) true about respiration?

(i) During inhalation, ribs move inward and diaphragm is raised

(ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air

(iii) Haemoglobin has greater affinity for carbon dioxide than oxygen

(iv) Alveoli increase surface area for exchange of gases

(a) (i) and (iv) (b) (ii) and (iii)

Answer : (d) (ii) and (iv).

[ (i) During inhalation, ribs move inward and diaphragm is raised.

This statement is false. During inhalation, the ribs move outward and the diaphragm contracts and moves downward to increase the volume of the thoracic cavity, allowing air to flow into the lungs.

(ii) In the alveoli, exchange of gases takes place i.e., oxygen from alveolar air diffuses into blood and carbon dioxide from blood into alveolar air.

This statement is true. The primary function of the alveoli is to facilitate the exchange of gases between the air and the blood.

(iii) Haemoglobin has greater affinity for carbon dioxide than oxygen.

This statement is false. Haemoglobin has a greater affinity for oxygen than carbon dioxide. While haemoglobin does bind carbon dioxide, it does so with a lower affinity compared to oxygen. Carbon dioxide is primarily transported in the blood as bicarbonate ions.

(iv) Alveoli increase surface area for exchange of gases.

This statement is true. The alveoli provide a large surface area to maximize the efficiency of gas exchange between the air and the blood.

Therefore, the true statements are (ii) and (iv). ]

15. Which is the correct sequence of air passage during inhalation?

(a) Nostrils → larynx → pharynx → trachea → lungs

(b) Nasal passage → trachea → pharynx → larynx → alveoli

(d) Nostrils → pharynx → larynx → trachea → alveoli

Answer : (d) Nostrils → pharynx → larynx → trachea → alveoli

16. During respiration exchange of gases take place in

(a) trachea and larynx

(b) alveoli of lungs

(d) throat and larynx

Answer : (b) Alveoli of lungs .

[ During respiration, the exchange of gases (oxygen and carbon dioxide) takes place specifically in the alveoli of the lungs. The alveoli are tiny air sacs within the lungs where oxygen from the inhaled air diffuses into the blood, and carbon dioxide from the blood diffuses into the alveolar air to be exhaled. ]

17. Which of the following statement (s) is (are) true about heart?

(i) Left atrium receives oxygenated blood from different parts of body while right atrium receives deoxygenated blood from lungs

(ii) Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs

(iii) Left atrium transfers oxygenated blood to right ventricle which sends it to different body parts

(iv) Right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body

(a) (i) (b) (ii)

Answer : (c) (ii) and (iv)

[ (i) Left atrium receives oxygenated blood from different parts of body while right atrium receives deoxygenated blood from lungs.

This statement is false. The left atrium receives oxygenated blood from the lungs via the pulmonary veins, while the right atrium receives deoxygenated blood from different parts of the body via the superior and inferior vena cava.

(ii) Left ventricle pumps oxygenated blood to different body parts while right ventricle pumps deoxygenated blood to lungs.

This statement is true. The left ventricle pumps oxygenated blood to the body through the aorta, and the right ventricle pumps deoxygenated blood to the lungs through the pulmonary artery.

(iii) Left atrium transfers oxygenated blood to right ventricle which sends it to different body parts.

This statement is false. The left atrium transfers oxygenated blood to the left ventricle, which then pumps it to the different body parts.

(iv) Right atrium receives deoxygenated blood from different parts of the body while left ventricle pumps oxygenated blood to different parts of the body.

This statement is true. The right atrium receives deoxygenated blood from the body, and the left ventricle pumps oxygenated blood to the body.

Therefore, the true statements are (ii) and (iv). ]

18. What prevents backflow of blood inside the heart during contraction?

(a) Valves in heart

(b) Thick muscular walls of ventricles

(d) All of the above

Answer : (a) Valves in the heart

[ Valves in the heart, specifically the atrioventricular (AV) valves and semilunar valves, prevent the backflow of blood during contraction. ]

19. Single circulation i.e., blood flows through the heart only once during one cycle of passage through the body, is exhibited by

(a) Labeo, Chameleon, Salamander

(b) Hippocampus, Exocoetus, Anabas

(d) Whale, Dolphin, Turtle

Answer : (b) Hippocampus, Exocoetus, Anabas

[ These organisms exhibit single circulation, where blood flows through the heart only once during one cycle of passage through the body. ]

20. In which of the following vertebrate group/groups, heart does not pump oxygenated blood to different parts of the body?

(a) Pisces and amphibians

(b) Amphibians and reptiles

(d) Pisces only

Answer : (d) Pisces only

[ In fishes (Pisces), the heart pumps oxygenated blood only to the gills for oxygenation, and then the oxygenated blood is distributed to the rest of the body.]

21. Choose the correct statement that describes arteries.

(a) They have thick elastic walls, blood flows under high pressure; collect blood from different organs and bring it back to the heart

(b) They have thin walls with valves inside, blood flows under low pressure and carry blood away from the heart to various organs of the body

(c) They have thick elastic walls, blood flows under low pressure ; carry blood from the heart to various organs of the body

(d) They have thick elastic walls without valves inside, blood flows under high pressure and carry blood away from the heart to different parts of the body.

Answer : (d) They have thick elastic walls without valves inside, blood flows under high pressure, and carry blood away from the heart to different parts of the body.

[ Arteries are vessels that carry oxygenated blood away from the heart to various parts of the body. They have thick and elastic walls, and they operate under high pressure due to the force generated by the heart's pumping action. Arteries do not have valves. ]

22. The filtration units of kidneys are called

(a) ureter

(b) urethra

(d) nephrons

Answer : (d) Nephrons

[ The filtration units of the kidneys are called nephrons ]

23. Oxygen liberated during photosynthesis comes from

(a) water

(b) chlorophyll

(d) glucose

Answer : (a) Water

[ During photosynthesis, oxygen is liberated as a byproduct, and it comes from the splitting of water molecules. ]

24. The blood leaving the tissues becomes richer in

(a) carbon dioxide

(b) water

(d) oxygen

Answer : (a) Carbon dioxide

[ The blood leaving the tissues becomes richer in carbon dioxide. This carbon dioxide is produced as a waste product of cellular respiration in the tissues.]

25. Which of the following is an incorrect statement?

(a) Organisms grow with time

(b) Organisms must repair and maintain their structure

(d) Energy is essential for life processes

Answer : (c) Movement of molecules does not take place among cells

[ Cells require the movement of various molecules, such as nutrients and signaling molecules, to carry out their functions and maintain cellular processes.]

26. The internal (cellular) energy reserve in autotrophic is

(a) glycogen

(b) protein

(d) fatty acid

Answer : (c) Starch

[ Starch is the primary internal (cellular) energy reserve in autotrophic . ]

27. Which of the following equations is the summary of photosynthesis?

(a)

(b)

(c)

(d)

Answer : (c)

[ This equation represents the process of photosynthesis, where carbon dioxide and water, in the presence of chlorophyll and sunlight, are converted into glucose and oxygen.]

28. Choose the event that does not occur in photosynthesis

(a) Absorption of light energy by chlorophyll

(b) Reduction of carbon dioxide to carbohydrates

(d) Conversion of light energy to chemical energy

Answer : c) Oxidation of carbon to carbon dioxide

[ In photosynthesis, carbon dioxide is reduced to carbohydrates, not oxidized to carbon dioxide. ]

29. The opening and closing of the stomatal pore depends upon

(a) oxygen

(b) temperature

(d) concentration of in stomatal

Answer : (c) Water in guard cells

[ The opening and closing of the stomata pore depend upon the turgor pressure in the guard cells, which is influenced by the uptake or loss of water by these cells.]

30. Choose the forms in which most plants absorb nitrogen

(i) Proteins

(ii) Nitrates and Nitrites

(iii) Urea

(iv) Atmospheric nitrogen

(a) (i) and (ii) (b) (ii) and (iii)

Answer : (b) (ii) and (iii)

[ Most plants absorb nitrogen in the form of nitrates and nitrites (ii) from the soil. Urea (iii) can also be a nitrogen source for some plants. ]

31. Which is the first enzyme to mix with food in the digestive tract?

(a) Pepsin

(b) Cellulase

(d) Trypsin

Answer : (c) Amylase .

[ Amylase is the first enzyme to mix with food in the digestive tract. It is responsible for the breakdown of carbohydrates into simpler sugars. ]

32. Which of the following statement(s) is (are) correct?

(i) Pyruvate can be converted into ethanol and carbon dioxide by yeast

(ii) Fermentation takes place in aerobic bacteria

(iii) Fermentation takes place in mitochondria

(iv) Fermentation is a form of anaerobic respiration

(a) (i) and (iii) (b) (ii) and (iv)

Answer : (c) (i) and (iv)

[ (i) Pyruvate can be converted into ethanol and carbon dioxide by yeast, a process known as alcoholic fermentation. (iv) Fermentation is a form of anaerobic respiration.]

33. Lack of oxygen in muscles often leads to cramps among cricketers. This results due to

(a) conversion of pyruvate to ethanol

(b) conversion of pyruvate to glucose

(d) conversion of pyruvate to lactic acid

Answer : (d) conversion of pyruvate to lactic acid .

[ Lack of oxygen in muscles often leads to cramps among cricketers due to the conversion of pyruvate to lactic acid. ]

34. Choose the correct path of urine in our body

(a) kidney → ureter → urethra → urinary bladder

(b) kidney → urinary bladder → urethra → ureter

(d) urinary bladder → kidney → ureter → urethra

Answer : (c) kidney → ureters → urinary bladder → urethra.

[ Urine is produced in the kidneys, travels through the ureters, is stored in the bladder, and exits through the urethra. ]

35. During deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in the

(a) cytoplasm

(b) chloroplast

(d) golgi body

Answer : (a) cytoplasm.

[ During the deficiency of oxygen in tissues of human beings, pyruvic acid is converted into lactic acid in the cytoplasm. ]

Short Answer Questions

36. Name the following

(a) The process in plants that links light energy with chemical energy

(b) Organisms that can prepare their own food

(d) Cells that surround a stomatal pore

(e) Organisms that cannot prepare their own food

(f) An enzyme secreted from gastric glands in stomach that acts on proteins.

Answer: (a) Photosynthesis is the process in plants that links light energy with chemical energy.

(b) Autotrophs are organisms that can prepare their own food. Examples include plants, algae, and some bacteria.

(d) Guard cells are the cells that surround a stomatal pore.

(e) Heterotrophs are organisms that cannot prepare their own food. Examples include animals, fungi, and most bacteria.

(f) Pepsin is an enzyme secreted from gastric glands in the stomach that acts on proteins.

37. “All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.

Answer : I disagree with the statement. Plants perform photosynthesis during the day, releasing oxygen and absorbing carbon dioxide. At night, in the absence of light, photosynthesis ceases, and plants respire, releasing carbon dioxide and absorbing oxygen, similar to other organisms. However, the overall oxygen release during the day exceeds the night-time carbon dioxide release.

38. How do the guard cells regulate opening and closing of stomatal pores?

Answer : The guard cells regulate the opening and closing of stomatal pores to control water loss and gas exchange. When the plant does not need carbon dioxide for photosynthesis, it closes these pores. Guard cells swell when water flows into them, causing the stomatal pore to open. Conversely, the pore closes when the guard cells shrink as water exits them. This regulation helps balance water retention and carbon dioxide intake.

39. Two green plants are kept separately in oxygen free containers, one in the dark and the other in continuous light. Which one will live longer? Give reasons.

Answer : The plant kept in continuous light will live longer. In light, the plant can perform photosynthesis, producing oxygen and glucose needed for survival. The plant in the dark cannot photosynthesize and will exhaust its stored energy and oxygen quickly, leading to its demise.

40. If a plant is releasing carbon dioxide and taking in oxygen during the day, does it mean that there is no photosynthesis occurring? Justify your answer.

Answer : No, it does not necessarily mean that there is no photosynthesis occurring. If a plant is releasing carbon dioxide and taking in oxygen during the day, it indicates that the rate of cellular respiration is higher than the rate of photosynthesis. Photosynthesis may still be happening, but the plant's energy needs for respiration might exceed the oxygen produced by photosynthesis, leading to a net intake of oxygen and release of carbon dioxide.

41. Why do fishes die when taken out of water?

Answer : Fish die when taken out of water because they rely on gills to extract oxygen from water. Gills are specialized organs that allow fish to absorb dissolved oxygen from water, which has a higher oxygen content in a form they can use. When out of water, their gills collapse and cannot efficiently extract oxygen from the air, leading to suffocation and eventual death due to lack of oxygen.

42. Differentiate between an autotroph and a heterotroph.

Answer : Autotrophs and heterotrophs are distinguished by their methods of obtaining energy and nutrients:

Autotrophs:

(i) Organisms that produce their own food from inorganic substances. Examples: Plants, algae, and certain bacteria.

Heterotrophs:

(i) Organisms that cannot produce their own food and must consume other organisms for energy and nutrients. Examples: Animals, fungi, and most bacteria.

43. Is ‘nutrition’ a necessity for an organism? Discuss.

Answer : Yes, nutrition is essential for organisms. It provides the energy and nutrients required for growth, repair, and maintenance of bodily functions. Without adequate nutrition, organisms cannot sustain life processes, resulting in poor health or death. Nutrients support metabolic activities and overall well-being.

44. What would happen if green plants disappear from earth?

Answer : If green plants disappeared from Earth, oxygen production would drastically decline, leading to a severe reduction in atmospheric oxygen. Additionally, the absence of plants would disrupt food chains, causing widespread extinction of herbivores and subsequently carnivores. Ecosystems would collapse, affecting climate stability and biodiversity.

45. Leaves of a healthy potted plant were coated with vaseline. Will this plant remain healthy for long? Give reasons for your answer.

Answer : No, the plant will not remain healthy for long. Coating leaves with Vaseline blocks stomatal pores, which are essential for gas exchange. This prevents the plant from taking in carbon dioxide for photosynthesis and releasing oxygen and water vapor. Over time, the lack of essential gases and inability to transpire will lead to the plant's decline.

46. How does aerobic respiration differ from anaerobic respiration?

Answer : Aerobic respiration requires oxygen and produces more energy (ATP), carbon dioxide, and water as byproducts. It occurs in the mitochondria. Anaerobic respiration does not require oxygen, produces less energy (ATP), and results in byproducts like lactic acid (in animals) or ethanol and carbon dioxide (in yeast). It occurs in the cytoplasm.

47. Match the words of Column (A) with that of Column (B)

Column (A)	Column (B)
(a) Phloem	(i)Excretion
(b) Nephron	(ii) Translocation of Food
(c) Veins	(iii) Clotting of Blood
(d) Platelets	(iv) Deoxygenated blood

Answer : (a) Phloem --- (ii) Translocation of food

(b) Nephron --- (i) Excretion

(d) Platelets (iii) Clotting of Blood

48. Differentiate between an artery and a vein.

Answer : Arteries and veins differ in their structure and function:

Arteries:

Function: Carry blood away from the heart.

Structure: Thick, elastic walls to withstand high pressure.

Blood: Usually oxygenated (except pulmonary arteries).

Veins:

Function: Carry blood toward the heart.

Structure: Thinner walls, contain valves to prevent backflow.

Blood: Usually deoxygenated (except pulmonary veins).

49. What are the adaptations of leaf for photosynthesis?

Answer : Leaves are adapted for photosynthesis with a large surface area for maximum light absorption, thin structure for efficient gas exchange, chloroplasts containing chlorophyll to capture light, stomata for gas exchange, and a network of veins to transport water and nutrients.

50. Why is small intestine in herbivores longer than in carnivores?

Answer : The small intestine in herbivores is longer than in carnivores because herbivores consume plant-based diets that are harder to digest and require more time and surface area for nutrient absorption. The longer intestine allows for efficient breakdown and absorption of cellulose and other plant materials.

51. What will happen if mucus is not secreted by the gastric glands?

Answer : If mucus is not secreted by the gastric glands, the stomach lining would be exposed to the acidic gastric juices and digestive enzymes. This could lead to damage of the stomach tissue, resulting in ulcers, inflammation, and potential bleeding. Mucus is essential for protecting the stomach lining from the harsh acidic environment.

52. What is the significance of emulsification of fats?

Answer : Emulsification of fats is significant because it breaks down large fat droplets into smaller ones, increasing the surface area for lipase enzymes to act. This process enhances the efficiency of fat digestion and absorption in the small intestine, allowing for better nutrient utilization and energy extraction.

53. What causes movement of food inside the alimentary canal?

Answer : Movement of food inside the alimentary canal is primarily caused by peristalsis, a series of wave-like muscle contractions. These contractions push food through the digestive tract, from the esophagus to the intestines. Additionally, segmentation in the intestines mixes food with digestive enzymes and aids in nutrient absorption.

54. Why does absorption of digested food occur mainly in the small intestine?

Answer : Absorption of digested food occurs mainly in the small intestine due to its extensive surface area, provided by villi . This structure maximizes nutrient absorption. The small intestine also has a highly specialized lining with transport mechanisms that effectively absorb nutrients, vitamins, and minerals into the bloodstream.

55. Match Group (A) with Group (B)

Group (A)	Group(B)
(a) Autotrophic nutrition	(i) Leech
(b) Heterotrophic nutrition	(ii) Paramecium
(c) Parasitic nutrition	(iii) Deer
(d) Digestion in food vacuoles	(iv) Green plant

Answer : (a) Autotrophic nutrition (iv) Green plant

(b) Heterotrophic nutrition (iii) Deer

(d) Digestion in food vacuoles (ii) Paramecium

56. Why is the rate of breathing in aquatic organisms much faster than in terrestrial organisms?

Answer : Aquatic organisms often have a faster rate of breathing than terrestrial organisms because water contains less dissolved oxygen compared to air. To meet their oxygen needs, aquatic organisms must continuously move water over their gills, requiring rapid and frequent breathing. In contrast, air has a higher oxygen content, allowing terrestrial organisms to breathe more slowly.

57. Why is blood circulation in human heart called double circulation?

Answer : Blood circulation in the human heart is called double circulation because it involves two separate pathways: the pulmonary circulation and the systemic circulation.

Pulmonary Circulation: Blood is pumped from the right side of the heart to the lungs to receive oxygen and release carbon dioxide.

Systemic Circulation: Oxygenated blood returns to the left side of the heart, which then pumps it to the rest of the body.

This dual circuit ensures efficient oxygen delivery and carbon dioxide removal, enhancing overall circulatory efficiency.

58. What is the advantage of having four chambered heart?

Answer : The advantage of having a four-chambered heart is the complete separation of oxygenated and deoxygenated blood. This design ensures that oxygen-rich blood from the lungs is pumped directly to the body, while oxygen-poor blood is directed to the lungs for reoxygenation. This separation enhances the efficiency of oxygen delivery and carbon dioxide removal, supporting higher metabolic rates and more effective circulation.

59. Mention the major events during photosynthesis.

Answer : The major events during photosynthesis are :

(i) Absorption of light energy by chlorophyll.

(ii) Conversion of light energy to chemical energy and splitting of water molecules into hydrogen and oxygen.

(iii) Reduction of carbon dioxide to carbohydrates.

60. In each of the following situations what happens to the rate of photosynthesis?

(a) Cloudy days

(b) No rainfall in the area

(d) Stomata get blocked due to dust.

Answer: The rate of photosynthesis are :

(a) Cloudy Days: The rate of photosynthesis decreases due to reduced sunlight, which lowers the energy available for light-dependent reactions.

(b) No Rainfall in the Area: The rate of photosynthesis decreases as a lack of water limits the availability of raw materials for the process, affecting the plant's ability to perform photosynthesis.

(c) Good Manuring in the Area: The rate of photosynthesis increases due to improved nutrient availability, which enhances plant growth and efficiency in capturing sunlight and processing nutrients.

(d) Stomata Get Blocked Due to Dust: The rate of photosynthesis decreases as blocked stomata hinder gas exchange, reducing the intake of carbon dioxide and the release of oxygen.

61. Name the energy currency in the living organisms. When and where is it produced?

Answer : The energy currency in living organisms is adenosine triphosphate (ATP). It is produced during cellular respiration:

In the Mitochondria: ATP is generated primarily through oxidative phosphorylation in the mitochondria during aerobic respiration.

In the Cytoplasm: ATP is also produced during glycolysis in the cytoplasm.

ATP is used by cells to perform various energy-requiring processes.

62. What is common for cuscuta, ticks and leeches?

Answer : Cuscuta, ticks, and leeches are all parasitic organisms that derive nutrients from other living hosts, often causing harm to their hosts in the process.

63. Explain the role of mouth in digestion of food.

Answer : The mouth plays a crucial role in digestion by mechanically and chemically processing food. Teeth crush and grind food into smaller particles, while saliva, secreted by salivary glands, moistens the food to ease its passage and contains the enzyme salivary amylase to begin breaking down starches into simpler sugars. The tongue helps mix food with saliva and move it around the mouth, facilitating thorough digestion. This pre-digested food is then moved down the digestive tract through rhythmic peristaltic movements, ensuring it is properly processed as it progresses through the alimentary canal.

64. What are the functions of gastric glands present in the wall of the stomach?

Answer : The gastric glands in the stomach wall perform essential functions by releasing hydrochloric acid, pepsin, and mucus. Hydrochloric acid creates an acidic environment that activates pepsin for protein digestion . Mucus protects the stomach lining from damage by acid and digestive enzymes, ensuring the stomach's integrity and proper function.

65. Match the terms in Column (A) with those in Column (B)

Column (A)	Group (B)
(a) Trypsin	(i) Pancreas
(b) Amylase	(ii) Liver
(c) Bile	(iii) Gastric glands
(d) Pepsin	(iv) Saliva

Answer : (a) Trypsin ---- (i) Pancreas

(b) Amylase ---- (iv) Saliva

(d) Pepsin ---- (iii) Gastric glands .

66. Name the correct substrates for the following enzymes

(a) Trypsin (b) Amylase

Answer : (a) Trypsin: Proteins (it breaks down proteins into smaller peptides).

(b) Amylase: Starch (it breaks down starch into simpler sugars like maltose).

(d) Lipase: Lipids (it breaks down fats into fatty acids and glycerol).

67. Why do veins have thin walls as compared to arteries?

Answer : Veins have thinner walls compared to arteries because they carry blood at lower pressure. Arteries need thick, elastic walls to withstand and maintain high pressure from the heart's pumping action. In contrast, veins operate under lower pressure and have less need for such thick walls, relying instead on valves and surrounding muscle contraction to help return blood to the heart.

68. What will happen if platelets were absent in the blood?

Answer : If platelets were absent in the blood, blood clotting would be severely impaired. Platelets are crucial for forming blood clots to stop bleeding by aggregating at injury sites and aiding in clot formation. Without them, even minor injuries could lead to excessive bleeding and difficulty in healing wounds.

69. Plants have low energy needs as compared to animals. Explain.

Answer : Plants have low energy needs compared to animals because they are autotrophs, producing their own food through photosynthesis. This process converts sunlight into chemical energy, which plants use to synthesize carbohydrates from carbon dioxide and water. Unlike animals, which need to consume other organisms to obtain energy, plants rely on solar energy, which is abundant and free. Additionally, plants do not require energy for complex movements or high metabolic rates, further reducing their overall energy demands.

70. Why and how does water enter continuously into the root xylem?

Answer : Water enters continuously into the root xylem due to osmosis, driven by the higher concentration of solutes in the root cells compared to the soil. This osmotic pressure draws water from the soil into the root cells, creating a positive root pressure that pushes water upward through the xylem to the rest of the plant.

71. Why is transpiration important for plants?

Answer : Transpiration is crucial for plants as it aids in the absorption and upward movement of water and dissolved minerals from roots to leaves. This process also helps in temperature regulation. At night, root pressure aids in water transport, but during the day, when stomata are open, the transpiration pull becomes the major driving force for moving water through the xylem.

72. How do leaves of plants help in excretion?

Answer : Leaves help in plant excretion by shedding waste products through transpiration and guttation. They release excess water, oxygen, and other waste gases via stomata. Additionally, during leaf fall, plants get rid of accumulated waste substances stored in leaves, effectively removing them from the plant system.

Long Answer Questions

73. Explain the process of nutrition in Amoeba.

Answer: The process of nutrition in Amoeba :

Amoeba, a single-celled organism, acquires nutrition through a process called phagocytosis. It begins by extending its pseudopodia, which are temporary projections of its cell membrane. These pseudopodia surround and engulf food particles, such as bacteria or smaller microorganisms, forming a food vacuole within the cell. Once the food is enclosed, the vacuole merges with lysosomes, which contain digestive enzymes.

The enzymes break down the food into simpler, absorbable nutrients. These nutrients then diffuse into the cytoplasm of the amoeba, where they are used for energy and growth. The indigestible waste materials are eventually expelled from the cell through a process called egestion, where the food vacuole moves to the cell membrane and releases the waste outside the cell. This method allows amoebas to obtain their nutrients in an environment where they cannot use traditional methods of ingestion and digestion.

74. Describe the alimentary canal of man.

Answer : The alimentary canal in humans is a complex system designed to process food efficiently. The process begins in the mouth, where food is crushed by the teeth and mixed with saliva, a fluid that not only wets the food for easier passage but also contains the enzyme salivary amylase, which begins breaking down starch into simple sugars. The food is then moved by the tongue and pushed down the esophagus through rhythmic contractions called peristalsis.

In the stomach, the food is mixed with gastric juices, including hydrochloric acid and the enzyme pepsin, which aid in protein digestion. The stomach's mucus lining protects it from acid damage. Food is then gradually released into the small intestine, where it undergoes further digestion with the help of bile from the liver and enzymes from the pancreas. Bile emulsifies fats, making them easier to digest, while pancreatic enzymes continue the breakdown of proteins, carbohydrates, and fats.

The small intestine, with its villi-lined walls, is the main site for nutrient absorption. The villi increase the surface area for absorption, allowing nutrients to enter the bloodstream. The remaining undigested food moves to the large intestine, where water is absorbed, and the leftover material is excreted through the anus, regulated by the anal sphincter .

75. Explain the process of breathing in man.

Answer : The process of breathing in humans, also known as respiration, involves two main phases: inhalation (inspiration) and exhalation (expiration).

Inhalation (Inspiration):

During inhalation, the diaphragm, a dome-shaped muscle located below the lungs, contracts and flattens, while the intercostal muscles between the ribs contract to lift the ribcage upwards and outwards. This increases the volume of the thoracic cavity (chest), causing a decrease in pressure inside the lungs compared to the external environment. As a result, air rushes into the lungs through the nose or mouth, passing down the trachea and into the bronchi, which divide into smaller bronchioles that lead to the alveoli (tiny air sacs). In the alveoli, oxygen from the inhaled air diffuses into the bloodstream.

Exhalation (Expiration):

During exhalation, the diaphragm and intercostal muscles relax, returning to their original positions. This reduces the volume of the thoracic cavity and increases the pressure inside the lungs. As a result, air is pushed out of the lungs through the bronchi, trachea, and exits through the nose or mouth. In the alveoli, carbon dioxide—a waste product of cellular respiration—diffuses out of the blood and is expelled during exhalation.

This cyclic process ensures that oxygen is constantly supplied to the body's cells for energy production, while carbon dioxide is removed as a waste product.

76. Explain the importance of soil for plant growth.

Answer : Soil is crucial for plant growth because it provides essential nutrients, water, and support. It supplies plants with minerals such as nitrogen, phosphorus, and potassium, which are vital for growth and development. Soil also retains moisture and facilitates the uptake of water through the roots. Additionally, soil anchors plants, stabilizing them and allowing for proper root expansion.

77. Draw the diagram of alimentary canal of man and label the following parts.

Mouth, Oesophagus, Stomach, Intestine

Answer : The diagram of alimentary canal of man :

78. How do carbohydrates, proteins and fats get digested in human beings?

Answer : In human beings, carbohydrates, proteins, and fats undergo digestion through a series of processes in the digestive system:

Carbohydrates: Digestion begins in the mouth, where salivary amylase starts breaking down starches into simpler sugars. In the stomach, carbohydrate digestion continues minimally, but the major digestion occurs in the small intestine. Pancreatic amylase further breaks down starches into maltose and other disaccharides. Enzymes on the intestinal lining, such as maltase and lactase, then convert these disaccharides into monosaccharides (glucose, fructose, and galactose), which are absorbed into the bloodstream.

Proteins: Protein digestion starts in the stomach, where pepsin, an enzyme activated by stomach acid, begins breaking proteins into smaller peptides. In the small intestine, pancreatic proteases (trypsin, chymotrypsin) further break these peptides into even smaller peptides and amino acids. Peptidases on the intestinal lining then convert these peptides into individual amino acids, which are absorbed into the bloodstream.

Fats: Fat digestion starts in the small intestine. Bile, produced by the liver and stored in the gallbladder, emulsifies fats, breaking them into smaller droplets to increase the surface area for enzymatic action. Pancreatic lipase then breaks down these droplets into fatty acids and glycerol. These products are absorbed into the intestinal cells, reassembled into triglycerides, and then transported through the lymphatic system before entering the bloodstream.

79. Explain the mechanism of photosynthesis.

Answer : Photosynthesis is the process by which autotrophic organisms, primarily plants, convert light energy into chemical energy, fulfilling their carbon and energy requirements. This process takes place in the chloroplasts of plant cells in the presence of sunlight and the green pigment chlorophyll. The following steps of the mechanism of photosynthesis:

(i) Absorption of Light Energy by Chlorophyll: Chlorophyll, present in the chloroplasts, captures sunlight, which initiates the process of photosynthesis.

(ii) Conversion of Light Energy into Chemical Energy and Splitting of Water Molecules: The absorbed light energy is converted into chemical energy, which is used to split water molecules (H₂O) into hydrogen (H) and oxygen (O₂). This splitting process is known as photolysis, and the oxygen produced is released into the atmosphere as a byproduct.

(iii) Reduction of Carbon Dioxide into Carbohydrates: Carbon dioxide (CO₂) from the atmosphere is taken up by the plant and reduced to form carbohydrates (such as glucose) using the hydrogen generated from the splitting of water. This reduction process is powered by the chemical energy produced during the light-dependent reactions.

The carbohydrates produced during photosynthesis serve as an immediate energy source for the plant. Any surplus is stored as starch, an internal energy reserve, for future use. This stored starch can be converted back into sugars when the plant requires energy.

80. Explain the three pathways of breakdown in living organisms.

Answer : In living organisms, the breakdown of food materials to release energy occurs through three primary pathways:

(i) Aerobic Respiration: This process occurs in the presence of oxygen and is the most efficient way to extract energy from glucose. It begins with the breakdown of glucose (a six-carbon molecule) into pyruvate (a three-carbon molecule) in the cytoplasm. The pyruvate then enters the mitochondria, where it is further broken down into carbon dioxide and water. This pathway releases a large amount of energy, which is used to synthesize ATP (adenosine triphosphate), the energy currency of the cell. This process is predominant in most multicellular organisms, including humans.

i.e. , Glucose (6-carbon molecules) Pyruvate (3-carbon molecules) + Energy Carbon dioxide + Water + Energy

(ii) Anaerobic Respiration (Fermentation): In the absence of oxygen, cells can still produce energy through anaerobic respiration. In this process, pyruvate is converted into ethanol and carbon dioxide in organisms like yeast. This occurs in the cytoplasm and is known as fermentation. Since no oxygen is involved, the energy yield is much lower than in aerobic respiration. Anaerobic respiration is common in certain bacteria and yeast.

i.e. , Glucose (6-carbon molecules) Pyruvate (3-carbon molecules) + Energy Ethanol + Carbon dioxide + Energy

(iii) Lactic Acid Fermentation: This pathway occurs in the muscle cells of animals when oxygen levels are insufficient, such as during intense physical activity. Here, pyruvate is converted into lactic acid, which is also a three-carbon molecule. The accumulation of lactic acid in muscles can cause cramps. Like other forms of anaerobic respiration, this process yields less energy compared to aerobic respiration.

i.e. , Glucose (6-carbon molecules) Pyruvate (3-carbon molecules) + Energy Lactic acid + Energy

In all these pathways, the energy released from the breakdown of glucose is used to synthesize ATP, which then powers various cellular activities.

81. Describe the flow of blood through the heart of human beings.

Answer : The heart is a muscular organ with four chambers designed to separate oxygen-rich blood from oxygen-poor blood and efficiently direct blood flow through the body and lungs.

Oxygen-Rich Blood Flow:

Oxygen-rich blood from the lungs returns to the heart and enters the left atrium through the pulmonary veins. As the left atrium relaxes, it fills with this oxygenated blood. When the left atrium contracts, it sends blood into the left ventricle. The left ventricle, with its thick muscular walls, then contracts powerfully to pump the oxygen-rich blood through the aortic valve into the aorta. From the aorta, the blood travels through the arteries to various tissues and organs of the body.

De-Oxygenated Blood Flow:

Deoxygenated blood, which has returned from the body, enters the heart through the right atrium via the superior and inferior vena cavae. As the right atrium fills with blood, it relaxes. When it contracts, the blood flows into the right ventricle. The right ventricle, which also has a muscular wall, then contracts to push the deoxygenated blood through the pulmonary valve into the pulmonary arteries, leading to the lungs for oxygenation.

Valves in the heart - specifically the tricuspid valve (between the right atrium and right ventricle), the pulmonary valve (between the right ventricle and pulmonary artery), the mitral valve (between the left atrium and left ventricle), and the aortic valve (between the left ventricle and aorta) - prevent the backflow of blood and ensure unidirectional flow.

This efficient flow of blood through the heart and lungs ensures that oxygenated blood reaches the tissues while deoxygenated blood is sent to the lungs for reoxygenation.

82. Describe the process of urine formation in kidneys.

Answer : The process of urine formation in the kidneys involves several key steps that efficiently filter and process blood to remove waste products.

The kidneys, located on either side of the backbone in the abdomen, are essential organs in the excretory system. Each kidney contains millions of tiny filtration units called nephrons. A nephron comprises a cluster of very thin-walled blood capillaries known as the glomerulus, encased in a cup-shaped structure called Bowman’s capsule.

The filtration process begins in the glomerulus, where blood pressure forces water and small molecules like glucose, amino acids, salts, and urea from the blood into Bowman’s capsule. This filtrate is collected and then flows through a coiled tube where selective reabsorption occurs. As the filtrate moves along the tubule, essential substances such as glucose, amino acids, and a significant amount of water are reabsorbed back into the bloodstream. The reabsorption of water is regulated based on the body's needs, influenced by the amount of excess water and dissolved waste present.

The remaining filtrate, now concentrated and containing primarily waste products, becomes urine. This urine then travels through the ureters, long tubes that connect each kidney to the urinary bladder. The bladder serves as a storage organ where urine accumulates until it reaches a certain volume. When the bladder is full, its muscular walls contract, signaling the urge to urinate. The urine is then expelled from the bladder through the urethra, completing the process of waste removal from the body.