NCERT Exemplar Chapter 6 Life Processes Class 10 Science Solutions

NCERT Exemplar Class 10 Science Chapter 6 Life Processes Solutions

NCERT Exemplar Solutions for Class 10 Science Chapter 6 Life Processes covers all the important questions and answers as well as advanced level questions. It helps in learning about the What are life processes, maintenance of functions of living organisms, single cellular organisms and multicellular organisms, Nutrition, heterotrophs, autotrophs, Respiration and human respiratory system.

The NCERT Exemplar solutions for class 10 science is very important for board exams. NCERT Exemplar Solutions for Class 10 Science Chapter 6 Life Processes is provided by our experts. They prepared the best solutions which help the students in understanding the solutions in an easy way. This chapters also covers the other topics like Transportation, Excretion, transpiration, mechanism of photosynthesis, kidneys, ureters, urinary bladder and urethra.

Chapter Name	Chapter 6 Life Processes
Book Title	NCERT Exemplar for Class 10 Science
Related Study	NCERT Solutions for Class 10 Science Chapter 6 Life Processes Revision Notes for Class 10 Science Chapter 6 Life Processes MCQ for Class 10 Science Chapter 6 Life Processes Important Questions for Class 10 Science Chapter 6 Life Processes
Topics Covered	MCQ Short Answers Questions Long Answers Questions

NCERT Exemplar Solutions for Chapter 6 Life Processes Class 10 Science

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
(c) They convert carbon dioxide and water into carbohydrates in the absence of sunlight
(d) They constitute the first trophic level in food chains

Solution

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

Autotrophs need sunlight to convert carbon dioxide and water into carbohydrates.

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
(c) Paramecium, Amoeba, Cuscuta
(d) Cuscuta, lice, tapeworm

Solution

(b) Yeast, mushroom, bread mould 

Yeast, mushroom and bread mould are saprophytes. Saprophytes break the food material outside their body and then absorb it.

3. Select the correct statement
(a) Heterotrophs do not synthesise their own food
(b) Heterotrophs utilise solar energy for photosynthesis
(c) Heterotrophs synthesise their own food
(d) Heterotrophs are capable of converting carbon dioxide and water into carbohydrates

Solution

(a) Heterotrophs do not synthesise their own food

Heterotrophs either dependent on phototrophs or other organisms for their 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
(c) Mouth → stomach → oesophagus → small intestine → large intestine
(d) Mouth → oesophagus → stomach → small intestine → large intestine

Solution

(d) Mouth → oesophagus → 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 
(c) Fats breaking down into fatty acids and glycerol 
(d) Absorption of vitamins 

Solution

(b) Starch breaking down into sugars 

Salivary Amylase enzyme present in the saliva breaks down starch into simpler sugar and helps in digesting them. Hence the breakdown of starch will be effected if salivary amylase is lacking in the saliva.

6. The inner lining of stomach is protected by one of the following from hydrochloric acid. Choose the correct one
(a) Pepsin 
(b) Mucus 
(c) Salivary amylase 
(d) Bile 

Solution

(b) Mucus

7. Which part of alimentary canal receives bile from the liver ? 
(a) Stomach 
(b) Small intestine
(c) Large intestine
(d) Oesophagus

Solution

(b) Small intestine

Bile goes to small intestine from gall bladder through hepta pancreatic duct.

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
(c) fats
(d) starch

Solution

(d) starch

Amylose and Amylo pectin make up starch. When iodine is added to starch containing water, amylose reacts with iodine to form a blue coloured complex. This solution gives blue-black colour and confirms the presence of starch in the rice water.

9. In which part of the alimentary canal food is finally digested?
(a) Stomach
(b) Mouth cavity
(c) Large intestine
(d) Small intestine

Solution

(d) Small intestine

The primary digestion process takes place in the mouth and stomach but most of the digestion process occurs in the small intestine. Then process of digestion does not take place in the large 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
(c) trypsin and lipase digest fats
(d) trypsin digests proteins and lipase emulsified fats

Solution

(d) trypsin digests proteins and lipase emulsified fats 

Trypsin breaks down proteins into polypeptides and lipase digests emulsified fat molecules into fatty acids and glycerol.

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
(c) nitrogen
(d) water vapour

Solution

(b) carbon dioxide

When carbon dioxide reacts with lime water, lime water turns milky..

12. The correct sequence of anaerobic reactions in yeast is

Solution
(d)

Glucose is breakdown in anaerobic condition in yeast cytoplasm to produce pyruvate. Pyruvate is further breakdown to ethanol and carbon dioxide.

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

Solution

(d)

Breakdown of pyruvate takes place in mitochondria in aerobic respiration. CO₂, H₂O and energy are released in the reaction.

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) 

(c) (i) and (iii) 

(d) (ii) and (iv)

Solution

(d) (ii) and (iv)

During inhalation, the ribs move outward and diaphragm is lowered. Hemoglobin has greater affinity for oxygen than CO₂.

15. Which is the correct sequence of air passage during inhalation?
(a) Nostrils → larynx → pharynx → trachea → lungs
(b) Nasal passage → trachea → pharynx → larynx → alveoli
(c) larynx → nostrils → pharynx → lungs
(d) Nostrils → pharynx → larynx → trachea → alveoli

Solution

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

Air enters the respiratory system through nostrils, passes to pharynx, larynx, trachea and then to alveoli.

16. During respiration exchange of gases take place in
(a) trachea and larynx
(b) alveoli of lungs
(c) alveoli and throat
(d) throat and larynx

Solution

(b) alveoli of lungs

Trachea and larynx provide a passage for the movement of air. Exchange of gases takes place in alveoli of lungs. From alveoli, oxygen diffuses into blood and carbon dioxide is exhaled out of blood.

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)
(c) (ii) and (iv)
(d) (i) and (iii)

Solution

(c) (ii) and (iv)

Oxygenated blood circulates through left part of the heart whereas deoxygenated blood circulates through right part of the heart. Atrium receives blood and ventricle pumps the blood out of the heart. 

18. What prevents backflow of blood inside the heart during contraction?
(a) Valves in heart
(b) Thick muscular walls of ventricles
(c) Thin walls of atria
(d) All of the above

Solution

(a) Valves in heart

Walls in the heart are responsible for pumping the blood. The valves are not responsible for

blocking the backflow of blood inside the heart 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
(c) Hyla, Rana, Draco
(d) Whale, Dolphin, Turtle

Solution

(b) Hippocampus, Exocoetus, Anabas

Reptile and amphibians have a 3 chambered hearts and show partial double circulation. All amphibians show partial double circulation. Whale is a mammal but turtle is a reptile. 

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
(c) Amphibians only
(d) Pisces only

Solution

(d) Pisces only

In single circulation, the deoxygenated blood from all part of the body is pumped into heart. From the heart, the deoxygenated blood is pumped to gills where it gets oxygenated and gets transferred to all parts of the body. Therefore, pisces do not receive oxygenated blood. 

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.

Solution

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

22. The filtration units of kidneys are called

(a) ureter
(b) urethra
(c) neurons
(d) nephrons

Solution

(d) nephrons

The functional unit of kidney is called the nephron. It helps in removing the waste products and excess substances from our body. 

23. Oxygen liberated during photosynthesis comes from:
(a) water
(b) chlorophyll

(c) carbon dioxide
(d) glucose

Solution

(a) water

Water molecule splits to produce oxygen and hydrogen ions during the process of photosynthesis. Oxygen is expelled out of plants and hydrogen is used to reduce carbon dioxide which in turn produces carbohydrates. 

24. The blood leaving the tissues becomes richer in
(a) carbon dioxide
(b) water
(c) heamoglobin
(d) oxygen

Solution

(a) carbon dioxide

Carbon dioxide gets accumulated in tissues due to respiration. Therefore, the blood leaving the tissues becomes richer in carbon dioxide. 

25. Which of the following is an incorrect statement?
(a) Organisms grow with time
(b) Organisms must repair and maintain their structure
(c) Movement of molecules does not take place among cells
(d) Energy is essential for life processes

Solution

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

Movement of molecules in cells take place in active and passive modes such as diffusion, osmosis, facilitated diffusion etc.

26. The internal (cellular) energy reserve in autotrophs is
(a) glycogen
(b) protein
(c) starch
(d) fatty acid

Solution

(c) starch

Glycogen is the stored energy in animals, plants stores energy in the form of starch.

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

(a) 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O
(b) 6CO₂ + H₂O + Sunlight→ C₆H₁₂O₆ + O₂ + 6H₂O
(c) 6CO₂ + 12H₂O + Chlorophyll + Sunlight→ C₆H₁₂O₆ + 6O₂ + 6H₂O
(d) 6CO₂ + 12H₂O + Chlorophyll + Sunlight→ C₆H₁₂O₆ + 6CO₂ + 6H₂O

Solution

(c) 6CO₂ + 12H₂O + Chlorophyll + Sunlight→ C₆H₁₂O₆ + 6O₂ + 6H₂O

Option (a) does not show the factors responsible for photosynthesis. 
Option (b) is not a balanced equation.
Option (d) is wrong as it has CO₂  in the products.

28. Choose the event that does not occur in photosynthesis
(a) Absorption of light energy by chlorophyll
(b) Reduction of carbon dioxide to carbohydrates
(c) Oxidation of carbon to carbon dioxide
(d) Conversion of light energy to chemical energy

Solution

(c) Oxidation of carbon to carbon dioxide.

29. The opening and closing of the stomatal pore depends upon
(a) oxygen
(b) temperature
(c) water in guard cells
(d) concentration of CO₂  in stomata

Solution

(c)  water in guard cells 

The entry of water inside guard cells facilitates its opening. The entry of water makes the guard cell turgid. Closing of guard cells is facilitated by water coming out of guard cells. Water coming out of the guard cells makes the guard cells flaccid.

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)
(c) (iii) and (iv)
(d) (i) and (iv)

Solution

(b) (ii) and (iii)

Plants cannot absorb atmospheric nitrogen. Plants can absorb the nitrogen in the form of nitrates, nitrites and urea present in the soil.

31. Which is the first enzyme to mix with food in the digestive tract?
(a) Pepsin
(b) Cellulase
(c) Amylase
(d) Trypsin

Solution

(c)  Amylase 

Amylase is secreted in mouth. It acts on the starch and converts into simpler molecules. Therefore, amylase is the first enzyme to mix with food in the digestive tract.

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) 
(c) (i) and (iv) 
(d) (ii) and (iii) 

Solution

(c) (i) and (iv) 

Anaerobes carry out fermentation in the cytoplasm.

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
(c) non conversion of glucose to pyruvate
(d) conversion of pyruvate to lactic acid

Solution

(d) conversion of pyruvate to lactic acid

In presence of oxygen breakdown of pyruvate takes place in mitochondria. This leads to the formation of lactic acid. Oxygen is used for the production of energy during workout leading to the lack of oxygen and production of lactic acid.

34. Choose the correct path of urine in our body
(a) kidney → ureter → urethra → urinary bladder
(b) kidney → urinary bladder → urethra → ureter
(c) kidney → ureters → urinary bladder → urethra
(d) urinary bladder → kidney → ureter → urethra

Solution

(c) kidney → ureters → urinary bladder → urethra

From the nephron, the urine is brought to a collecting duct of kidneys. Here the urine enters the ureters. There are 2 ureters, each opening from one kidney into the urinary bladder. The urinary bladder stores urine and increases in size as the amount of urine collected increases.

The CNS gives a voluntary message the muscles of bladder, which contracts and the bladder sphincter relaxes thereby excreting urine out 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
(c) mitochondria
(d) golgi body

Solution

(a) cytoplasm 

During deficiency of oxygen, breakdown of pyruvate takes place in cytoplasm leading to the formation of lactic acid.

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
(c) The cell organelle where photosynthesis occurs
(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.

Solution

(a) Photosynthesis
(b) Autotrophs
(c) Chloroplasts
(d) Guard cells
(e) Heterotrophs
(f) Pepsin

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

Solution

The rate of photosynthesis is more than the rate of respiration during the day time. As a result there is evolution of oxygen. At night there is no photosynthesis, so plants give out carbon dioxide due to respiration.

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

Solution

The swelling of guard cells due to absorption of water causes opening of stomatal pores while shrinking of guard cells closes the pores. Turgor changes in guard cells help in the opening and closing of stomata. When guard cells are turgid, stomatal pore is open when the guard cells are turgid while the stomatal aperture closes in flaccid conditions of the guard cells.

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.

Solution

Plant kept in continuous light will live longer, as it will be able to produce oxygen required for its respiration by the process of photosynthesis. In case of plant kept in dark CO₂ resulting in lack of oxygen and the plant will die earlier.

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.

Solution

The plant is respiring if it is releasing carbon dioxide and taking in oxygen during the day. This does not mean that there is no photosynthesis taking place in the plant. This is because photosynthesis and respiration are two independent processes..

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

Solution

Fishes respire by using the dissolved oxygen. When a fish is taken out of water, it cannot respire due to lack of dissolved oxygen and hence it dies.

42.  Differentiate between an autotroph and a heterotroph

Solution  

Autotrophs	Heterotrophs
They can prepare their own food.	They cannot make their own food.
Examples: Plants and certain bacteria	Examples: Animals, Fungi and protozoans

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

Solution

Nutrition provides energy for carrying out metabolic activities, hence nutrition is an absolute

necessity for the organisms.

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

Solution

Green plants are the sources of energy for all organisms. All the herbivores will die because of starvation if all the green plants disappear from the earth. This in turn will also lead to death of all the carnivores.

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

Solution

Coating Vaseline to the leaves clogs the stomata pores and stops the respiration of plants. As a result of which the plants dies.

46. How does aerobic respiration differ from anaerobic respiration ? 

Solution 

Aerobic Respiration	Anaerobic respiration
Takes place in the presence of Oxygen	Takes place in the absence of Oxygen
Carbon dioxide and water are the end products	Carbon - di – oxide and Lactic acid/ethanol are the end
More efficient in energy production	Less efficient in energy production
Takes Place in animals and plants	Takes place in unicellular organisms

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

Column A	Column B
Phloem	(i) Excretion
Nephron	(ii) Translocation of food
Veins	(iii) Clotting of blood
Platelets	(iv) Deoxygenated blood

Solution

Column A	Column B
Phloem	(ii) Translocation of food
Nephron	(i) Excretion
Veins	(iv) Deoxygenated blood
Platelets	(iii) Clotting of blood

48. Differentiate between an artery and a vein.

Solution

Artery	Vein
Artery has thick walls.	Veins have thin walls.
Valves are absent in arteries.	Valves are present in veins.
Arteries carry blood away from the heart.	Veins carry blood to the heart.
Blood flows under pressure in arteries.	Blood does no flow under pressure in veins.

49. What are the adaptations of leaf for photosynthesis ? 

Solution

Adaptation of leaf for photosynthesis are as follows 

1. In order to allow greater exposure of light, the surface of leaf is flat.
2. Presence of chlorophyll to trap sunlight
3. Presence of stomata on the lower surface for easy transpiration.

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

Solution

Digestion of cellulose takes a longer time. This is the reason why herbivores eating grass need a longer small intestine. Carnivorous animals do not have to digest cellulose and hence they have a shorter small intestine.

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

Solution

In the stomach gastric glands release hydrochloric acid, enzyme pepsin and mucus. Mucus protects the inner lining of stomach from the action of hydrochloric acid and enzyme pepsin. If the mucus is not released, it will lead to erosion of inner lining of stomach, leading to acidity and ulcers.

52. What is the significance of emulsification of fats?

Solution

The process of breakage of larger fats molecules into digestible fat globules is known as emulsification. Emulsification helps the action of enzymes on fats.

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

Solution

The process which causes the movement of food inside the alimentary canal is known as peristalsis.

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

Solution

Small intestine has specialized structures that facilitate absorption of digested food. Small intestine has number of folds that increase the area of absorption. Small intestine also has fingerlike projection called microvilli which are richly supplied by blood vessels.

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

Solution

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

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

Solution

Aquatic organisms obtain oxygen from water. Oxygen is present in dissolved state in water. As the amount of dissolved oxygen is fairly low compared to that in the air, the rate of breathing in aquatic organisms is much faster than that in terrestrial organisms.

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

Solution

The blood circulation in human heart is called double circulation. This is because the blood passes through the heart twice in one complete cycle of the body — once through the right half in the form of deoxygenated blood and once through the left half in the form of oxygenated blood.

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

Solution

Four chambered heart has the following advantages 

• Clear cut division of labors among different chambers.
• Segregation of oxygenated and deoxygenated blood.
• Efficiency of the heart will increase.

59. Mention the major events during photosynthesis

Solution

Major events of photosynthesis are 

1. Absorption of light energy by chlorophyll.
2. Conversion of light energy to chemical energy.
3. Splitting of H₂O into H₂, O₂ and e^-
4. Reduction of CO₂ 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
(c) Good manuring in the area
(d) Stomata get blocked due to dust

Solution

(a) Rate of photosynthesis decreases as the availability of sunlight decreases.

(b) Rainfall does not affect rate of photosynthesis.

(c) Manuring will not affect rate of photosynthesis.

(d) Blockage of stomata reduces the rate of photosynthesis because blockage will affect availability of carbon dioxide.

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

Solution

Adenosine triphosphate (ATP) is the energy currency produced during respiration in living organisms and also during photosynthesis in plants. It is produced in mitochondria during respiration.

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

Solution

All are parasites i.e. they derive nutrition from plants or animals without killing them.

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

Solution

Role of mouth in digestion of food:

• Food is crushed into small pieces by the teeth.
• Food mixes with saliva present in the mouth and the enzyme amylase (found in saliva)
• breaks down starch into sugars.
• Tongue mixes the food with saliva.
• Ingestion of food 
• Breakage of food by Mastication 
• Saliva aids easy swallowing of food 
• Salivary amylase breaks starch into simpler carbohydrates. 
  

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

Solution

The functions of the gastric glands present in the wall of the stomach are as follows:

• Production of pepsin enzyme which helps in the digestion of proteins.
• Secretion of mucus which protects the inner lining of stomach.

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

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

Solution 

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

66. Name the correct substrates for the following enzymes
(a) Trypsin
(b) Amylase
(c) Pepsin
(d) Lipase

Solution 

(a)  Protein 

(b) Starch 

(c) Protein 

(d) Lipid 

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

Solution

Arteries have thick and elastic walls as they carry blood from the heart to various organs of the body under high pressure. Veins collect the blood from different organs and bring it back to the heart. In this process the blood is no longer under pressure. This is the reason why the walls of veins are thin. Veins also have valves to ensure that blood flows only in one direction.

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

Solution

Platelets help in the clotting of blood. In the absence of platelets blood will not clot. Thus, in case of injuries blood flow cannot be stopped without clotting and this may prove fatal for the person.

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

Solution

Plants stand still at one place and they do not travel in search of food. Most of the transport in plants occurs through passive transport which does not require energy. This is the reason why plants require low energy compared to animals.

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

Solution

Cells of root being in close contact with soil actively take up ions. This increases the ion-concentration inside the root and thereby increasing the osmotic pressure. This results in the movement of water from the soil into the root.

71. Why is transpiration important for plants?

Solution

Transpiration is important for plants because of the following reasons.

(a) It helps in absorption and upward movement of water and minerals from roots to leaves.

(b) It prevents the plant parts from heating up.

72. How do leaves of plants help in excretion?

Solution

Many plants store waste materials in the vacuoles of mesophyll cells and epidermal cells. When old leaves fall, the waste materials are excreted along with the leaves.

Long Answer Questions 

73. Explain the process of nutrition in Amoeba.

Solution

Amoeba shows holozoic mode of nutrition which comprises of ingestion, digestion, absorption, assimilation and egestion.

• Ingestion: Fingerlike projections called as pseudopodia, help amoeba to trap the food particles. Pseudopodia present outside amoeba’s body help in taking food along with water.
• Digestion: After ingesting the food, food vacuoles are made. Enzymes are released in the food vacuole for digestion.
• Absorption: The nutrients enter the cytoplasm through osmosis after digestion.
• Assimilation: Nutrients are utilized by the cell for various purposes.
• Egestion: To empty its contents outside the cell, the food vacuole goes near the cell membrane. This results in expulsion of waste materials from the cell.

74. Describe the alimentary canal of man. 

Solution

Human Ailmentary canal has the following parts 

• Buccal Cavity: Buccal cavity is generally called as mouth. It consists of tongue, teeth and salivary gland. It is the entry site for the food to digestive system. Food is breakdown into simpler molecules in the buccal cavity. The salivary amylase breaks the starch into simpler carbohydrates.
• Oesophagus: Buccal cavity is connected to long tube like structure called the oesophagus. Oesophagus connects the buccal cavity to the stomach. This assists the flow of food towards the stomach. Oesophagus has a valve like structure to prevent backflow of food particles.
• Stomach: Stomach is a J Shaped organ which has gastric glands in it. Gastric glands secrets hydrochloric acid, pepsin and mucus which help in the digestion of food.
• Small Intestine: Small intestine is highly coiled long structure. Major food absorption takes place in the small intestine. Specialized structures facilitate absorption of digested food in the small intestine. Large number of folds in the small intestine increases the area of absorption. Small intestine also has fingerlike projection called microvilli which are richly supplied by blood vessels.
• Large Intestine: Large intestine is shorter than the small intestine but its lumen is larger than that of small intestine. The major function of the large intestine is to absorb water from the remaining indigestible food matter and transmit the useless waste material from the body.
• Rectum: Large intestine opens into the rectum. It stores the waste materials and undigested food.
• Anus: It is the opening at the end of alimentary canal. Solid waste materials leave the body through the anus.

75. Explain the process of breathing in man 

Solution

Breathing in humans has two processes

1. Inhalation
2. Exhalation

• Inhalation: The process of taking oxygen in is known as inhalation. During this process, the ribs come out and diaphragm moves down. This increases the volume of the lungs and decreases the pressure. As a result of which air moves towards the lungs.
• Exhalation: The process of throwing out carbon-dioxide is known as exhalation. During this process, ribs move downwards and diaphragm moves upwards. This decreases the volume of the lungs and increases the pressure. As a result air moves out of the lungs.

76 . Explain the importance of soil for plant growth.

Solution

Soil is very important for the growth of the plant for the following reasons.

1. Soil provides a platform for the penetration of roots thus provide a base for the growth of the plants.
2. Soil also acts as a reservoir of the water.
3. Soil provides the essential minerals necessary for the growth of the plant.
4. Soil also has organic materials necessary for the plant growth.
5. Soil has microorganisms that have symbiotic relationship with the plant and as a result these microbes assist plant growth and their life processes.

77. Draw the diagram of alimentary canal of man and label the following parts. Mouth, Oesophagus, Stomach, Intestine

Solution

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

Solution

• Carbohydrate Digestion: Digestion of cabohydrates starts in the buccal cavity. In the buccal cavity, salivary enzymes break down the starch into simple sugar molecules. Other sugar molecules are breakdown to glucose in small intestine.
• Protein Digestion: The pepsin secreted by gastric glands present in the stomach partially help in the digestion of proteins. Trypsin and chymotrypsin enzymes secreted by the pancreatic juice in small intestine further complete the digestion of proteins.
• Fat Digestion: Fats are digested in small intestine. Bile juice present in the liver emulsifies the fat and breaks it down to small globules. Lipase enzyme converts these small fat globules into glycerol and fatty acids.

79. Explain the mechanism of photosynthesis 

Solution

The process by which plants produce their own food by utilizing sunlight, CO₂ and water is known as photosynthesis.

CO₂ and water are converted to carbohydrates with the evolution of oxygen.

Photosynthesis reaction can be given by following reaction.

Process of Photosynthesis is divided into 4 processes

1. Absorption of light energy by chlorophyll
2. Conversion of light energy into chemical energy
3. Splitting of water molecules into Hydrogen and Oxygen
4. Reduction of CO₂ to produce carbohydrates

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

Solution

Glucose is first broken down to pyruvate which is a 3 carbon molecule. This process takes place in the cytoplasm of all organisms.

Pyruvate is further broken down by the flowing steps.

• In yeast: Pyruvate is broken down in the absence of oxygen and this process is called anaerobic respiration. In yeasts, CO₂ and ethanol are produced by the breakdown of pyruvate.
• In Muscle Cells: The energy demand of our muscles cells increases rapidly during rigorous physical activity. This is compensated by anaerobic respiration in muscle cells. In muscle cells pyruvate breaks down into lactic acid.
• In Mitochondria: Pyruvate is broken down by aerobic respiration (in presence of oxygen) in mitochondria. H₂O and CO₂ are produced by the breakdown of pyruvate. Aerobic respiration is most common in most of the organisms.

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

Solution

The path of blood flow through human heart is as follows:

1. Deoxygenated blood from different organs of the body enters the right atrium through the vena cava.
2. Blood goes to the right ventricle from the right atrium. The tricuspid valve between the right atrium and right ventricle prevents the backflow of blood.
3. The blood goes to the lungs from the right ventricle through the pulmonary artery.
4. Carbon dioxide is removed from the blood and oxygen enters the blood inside the lungs.
5. From the lungs, blood goes to the left atrium through the pulmonary vein.
6. From the left atrium, the blood goes to the left ventricle.
7. The blood is pumped into the aorta from the left ventricle so that it can be supplied to different organs.

82. Describe the process of urine formation in kidneys

Solution

A cluster of very thin-walled blood capillaries form the basic filtration unit in the kidneys. Each capillary cluster in the kidney is associated with the cup-shaped end of a coiled tube called Bowman’s capsule that collects the filtrate (Fig. 6.14).

A large numbers of these filtration units called nephrons packed close together in each kidney.

As the urine flows along the tube, some substances in the initial filtrate, such as glucose, amino acids, salts and a major amount of water, are selectively re-absorbed. The urine formed in each kidney eventually enters a long tube called the ureter, which connects the kidneys to the urinary bladder.

Urine is stored in the urinary bladder until the pressure of the expanded bladder leads to the urge to pass it out through the urethra. As the bladder is muscular, it is under nervous control.