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Q1. Leaves of the plants contain tiny pores called _____.

Solution

Stomata

Q2. Which pigment carries oxygen to all the parts of the body?

• 1) Carotene
• 2) Anthocyanin
• 3) Bilirubin
• 4) Haemoglobin

Solution

The red pigment called haemoglobin present in the red blood cells carries oxygen to all the parts of the body.

Q3. Pores in leaves which continuously open and close are called

• 1) Gills
• 2) Veins
• 3) Stomata
• 4) Spiracles

Solution

Stomata in leaves continuously open and close at different time intervals to allow gaseous exchange.

Q4. Trachea is also referred to as

• 1) Bronchus
• 2) Chest cavity
• 3) Wind pipe
• 4) Larynx

Solution

Trachea allows the passage of air towards the lungs; hence it is also called wind pipe.

Q5. Which process is involved in the exchange of respiratory gases in Amoeba?

• 1) Capillary action
• 2) Diffusion
• 3) Osmosis
• 4) Reverse osmosis

Solution

Amoeba takes in oxygen and gives out carbon dioxide gas through its cell membrane by the process of diffusion.

Q6. When we breathe out, we release ________.

Solution

When we breathe out, we release carbon dioxide.

Q7. Spiracles are small openings present in the bodies of insects.

• 1) False
• 2) True

Solution

True

Q8. Which are the two processes involved in breathing?

• 1) Inhalation - Taking in air rich in oxygen, Exhalation - Giving out air rich in carbon dioxide 
• 2) Inhalation - Giving out air rich in oxygen, Exhalation - Taking in air rich in carbon dioxide
• 3) Exhalation - Taking in air rich in oxygen, Inhalation - Giving out air rich in carbon dioxide 
• 4) Inhalation - Taking in air rich in carbon dioxide, Exhalation - Giving out air rich in oxygen

Solution

Breathing involves the process of inhalation or taking in air rich in oxygen into the body and exhalation or giving out air rich in carbon dioxide out of the body

Q9. (i) How do dolphins breathe?(ii) Do snails have lungs for respiration? How do they breathe?

Solution

(i) Although the dolphins possess lungs, they breathe through their blowholes. Powerful muscles form a special plug within the blowhole which prevents water from entering the lungs when the dolphin is underwater. Dolphins have to rise to the surface of water frequently to breathe. When they are underwater, they hold their breath; when they are out of breath, they return to the surface to take in more fresh air. (ii) No, snails do not possess lungs. They respire through their skin.

Q10. Respiration in plants is a continuous process.

• 1) True
• 2) False

Solution

True

Q11. The amount of carbon dioxide present in inhaled air is approximately

• 1) 5%
• 2) 20%
• 3)  0.04%
• 4) 1%

Solution

Approximately, 0.04% of carbon dioxide is present in inhaled air.

Q12. Oxygen is taken in during ___________.

Solution

Oxygen is taken in during inhalation.

Q13. Exchange of carbon dioxide and oxygen in plants takes place through the openings called

• 1) Blowholes
• 2) Stomata
• 3) Petioles
• 4) Spiracles

Solution

During respiration, exchange of carbon dioxide and oxygen in the leaves of plants takes place through the stomata.

Q14. When do frogs use their lungs for respiration?

• 1) Under water
• 2) In air
• 3) On land
• 4) In air

Solution

Frogs use their lungs for respiration on land, while they use their skin to breathe when under water.

Q15. Which of the following is involved in the process of respiration as well as transpiration?

• 1) Midribs
• 2) Stomata
• 3) Trichomes
• 4) Leucoplasts

Solution

Stomata play a major role in respiration as well as transpiration. In respiration, they are responsible for the exchange of gases while in case of transpiration, excess water is released in the form of water vapour through the stomata.

Q16. In plants, the rate of gaseous exchange is low during

• 1) Photosynthesis
• 2) Respiration
• 3) Venation
• 4) Transpiration

Solution

In plants, each part respires independently. Therefore, there is very little transport of gases from one plant part to another.

Q17. Carbon dioxide and water are released during

• 1) Alcohol production
• 2) Aerobic respiration
• 3) Anaerobic respiration
• 4) Lactic acid production

Solution

Carbon dioxide and water are products of aerobic respiration.

Q18. What do plants intake at night?

• 1) Oxygen
• 2) Carbon dioxide
• 3) Nitrogen
• 4) Water vapour

Solution

Plants take in oxygen at night for respiration. They do not perform photosynthesis at night due to unavailability of sunlight.

Q19. Our chest expands when we _______, and contracts when we _________.

Solution

Our chest expands when we inhale, and contracts when we exhale.

Q20. Few stomata are found in plants when

• 1) Carbon dioxide level is low
• 2) Oxygen level is more
• 3) Carbon dioxide level is more
• 4) Oxygen is absent

Solution

In case of high levels of carbon dioxide, fewer stomata are present on the leaves of plants. This not only allows sufficient carbon dioxide to be trapped but also reduces the loss of water by transpiration through the stomata.

Q21. Stomata are tiny pores present on the leaves.

• 1) True
• 2) False

Solution

True

Q22. Moist skin acts as the respiratory organ in 

• 1) Cockroaches
• 2) Birds
• 3) Lizards
• 4) Earthworms

Solution

Earthworms respire through their thin and moist skin.

Q23. Plants perform both respiration and photosynthesis.

• 1) True
• 2) False

Solution

True

Q24. Tracheal system in insects comprises of a number of

• 1) Air tubes
• 2) Blowholes
• 3) Fins
• 4) Gills

Solution

Tracheal system for respiration in insects consists of a number of thin air tubes called trachea and tiny holes called spiracles.

Q25. Which of the following correctly points out the difference between breathing and respiration?

• 1) Inhalation and exhalation are the two phases of respiration, whereas breathing does not involve any phases.
• 2) Breathing takes place in every cell, whereas respiration takes place in our lungs.
• 3) Respiration is a process of release of energy from food whereas breathing involves gaseous exchange.
• 4) Breathing utilises the oxygen absorbed during breathing whereas respiration removes the carbon dioxide produced during respiration.

Solution

Respiration is a process of release of energy from food whereas breathing involves gaseous exchange. There is no release of energy during breathing.

Q26. Identify A in the given figure.

• 1) Air tubes
• 2) Blow holes
• 3) Gills
• 4) Spiracles

Solution

Insects such as cockroach have spiracles on the sides of their bodies and trachea throughout inside their bodies for the process of breathing and respiration.

Q27. Earthworms breathe through their skin.

• 1) False
• 2) True

Solution

True

Q28. Why do we feel hungry after a physical activity?

Solution

After a physical activity, we take deep breathes and inhale more oxygen. As a result, more oxygen is supplied to our cells and the process of breakdown of food speeds up. Due to this, more energy is released and we tend to feel hungry.

Q29. A cockroach does not have lungs.

• 1) False
• 2) True

Solution

True

Q30. Plants mostly give out carbon dioxide during night time.

• 1) False
• 2) True

Solution

True

Q31. Inhalation means the breathing in of carbon dioxide only.

• 1) False
• 2) True

Solution

False

Q32. Where does the exchange of gases take place in the human respiratory system? Draw a neat and labelled diagram of the human respiratory system.

Solution

The exchange of gases between air and blood takes place across the walls of the alveoli. The human respiratory system:  

Q33. What is breathing?

Solution

Breathing means taking in air rich in oxygen and giving out air rich in carbon dioxide with the help of respiratory organs.

Q34. The rib cage is lifted upwards and outwards during

• 1) Exhalation
• 2) Inhalation
• 3) Digestion
• 4) Circulation

Solution

During inhalation, the muscles between the ribs contract causing the rib cage to move upwards and outwards.

Q35. Leaves have tiny pores called stomata.

• 1) True
• 2) False

Solution

True

Q36. (i) Why do we sneeze?(ii) During breathing, what changes occur in the size of the chest cavity?

Solution

(i) When we inhale, some unwanted particles such as dust, pollens get trapped in the hair present in our nasal cavity. However, sometimes these particles may get pass through the hair in the nasal cavity. Then they irritate the lining of the cavity, as a result of which we sneeze. Sneezing expels these foreign particles from the inhaled air and a dust -free, clean air enters our body.(ii) During inhalation, the ribs move outwards due to which the size of chest cavity increases. On the other hand, when we exhale, the size of chest cavity tends to decrease.

Q37. Fishes respire through their

• 1) Lungs
• 2) Book lungs
• 3) Spiracles
• 4) Gills

Solution

Fishes respire through gills which are projections of the skin.

Q38. Frogs can breathe through their skin.

• 1) False
• 2) True

Solution

True

Q39. How do snakes respire?

Solution

Snakes respire through the normal contraction and relaxation of muscles present between the ribs. However, they lack a diaphragm.

Q40. Earthworms breathe through the ____________.

Solution

Earthworms breathe through the moist skin.

Q41. A cockroach has small openings on the sides of its body which act as the respiratory organs.

• 1) True
• 2) False

Solution

True

Q42. State the role of stomata in plants? How do snakes respire?

Solution

Stomata are the minute openings present on the surface of leaves. They are responsible for the gaseous exchange in plants. During daytime, carbon dioxide enters through the stomata and used up for photosynthesis. Oxygen produced is given out through stomata. At night, it is vice a versa, oxygen is taken in while carbon dioxide is given out through stomata. During transpiration, the excess amount of water is also expelled out through stomata in the form of water vapour. Snakes respire through the normal contraction and relaxation of muscles present between the ribs. However, they lack a diaphragm.

Q43. Frogs tend to breathe through their skin when ____________.

Solution

Frogs tend to breathe through their skin when in water.

Q44. How is anaerobic respiration different from aerobic respiration?

Solution

During anaerobic respiration, food is broken down in the absence of oxygen while in aerobic respiration, oxygen is required for the breakdown of food to release energy.

Q45. The tracheal system in a cockroach helps in the process of 

• 1) Digestion
• 2) Respiration
• 3) Reproduction
• 4) Excretion

Solution

Cockroaches respire through their tracheal system which consists of spiracles and trachea.

Q46. Spiracles are found in

• 1) Mammals
• 2) Amphibians
• 3) Birds
• 4) Insects

Solution

Breathing in insects takes place through tiny holes called spiracles.

Q47. Breathing involves the movement of rib cage and _____________.

Solution

Breathing involves the movement of rib cage and diaphragm.

Q48. (i) Identify A and B in the given diagram.(ii) What is the composition of the air which we inhale and exhale?

Solution

(i) A is Trachea; B is Diaphragm.(ii) During inhalation, we take about 21% oxygen and 0.04% carbon dioxide in our lungs. While during exhalation, 16.4% oxygen and 4.4% carbon dioxide is taken out of the lungs.

Q49. The inhaled air passes through the nostrils into the nasal cavity.

• 1) False
• 2) True

Solution

True

Q50. We breathe out oxygen only during respiration.

• 1) True
• 2) False

Solution

False We breathe out carbon dioxide during respiration and breathe in oxygen.

Q51. (i) Explain the mechanism of breathing.(ii) What is cellular respiration?

Solution

(i) Breathing involves the movement of the diaphragm and the rib cage. During inhalation, ribs move up and outwards and diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs. The lungs get filled with air. During exhalation, ribs move down and inwards, while diaphragm moves up to its former position. This reduces the size of the chest cavity and air is pushed out of the lungs.(ii) The process of breakdown of food in the cell with the release of energy is called cellular respiration. It takes place in the cells of all organisms.

Q52. Energy is released during respiration.

• 1) False
• 2) True

Solution

True

Q53. During respiration, we breathe in

• 1) Nitrogen
• 2) Carbon dioxide
• 3) Oxygen
• 4) Water vapour

Solution

We breathe in oxygen gas present in the atmosphere during respiration.

Q54. Why do muscle cramps arise after a heavy exercise?

Solution

The cramps occur when muscle cells respire anaerobically. The partial breakdown of glucose produces lactic acid. The accumulation of lactic acid causes muscle cramps.

Q55. (i) Why do frogs use their lungs as well as skin for breathing? (ii) How do plant roots take in oxygen?

Solution

(i) On land, frogs use their lungs to breathe, but there are no ribs or diaphragm to support breathing. The skin of a frog is permeable to oxygen, carbon dioxide and water. There are a number of blood vessels near the surface of the skin. So, when a frog is underwater, oxygen is transmitted through the skin directly into the bloodstream.(ii) Roots take up air from the air spaces present between the soil particles.

Q56. The skin of an earthworm feels ____________.

Solution

Moist

Q57. Breathing is a part of respiration.

• 1) True
• 2) False

Solution

True

Q58. How do earthworms breathe?

Solution

Earthworms breathe through their skin. The skin of an earthworm is moist and slimy and gases can easily pass through it.

Q59. Woody stems take in air through the openings called

• 1) Guard cells
• 2) Lenticels
• 3) Stomata
• 4) Epidermis

Solution

Woody stems take in air through the openings called lenticels.

Q60. Explain the process of aerobic respiration.

Solution

When breakdown of glucose occurs with the use of oxygen, it is called aerobic respiration. In the cell, glucose is broken down into carbon dioxide and water by using oxygen.

Q61. How is energy released during anaerobic respiration?

Solution

In the absence of oxygen, glucose breaks down into alcohol and carbon dioxide, with the release of energy.

Q62. Stomata are not involved in gaseous exchange.

• 1) False
• 2) True

Solution

False

Q63. Insects have a network of air tubes called tracheae for gas exchange.

• 1) True
• 2) False

Solution

True

Q64. Stomata take part in exchange of_________.

Solution

Gases

Q65. What are anaerobes? Give one example.

Solution

The organisms that can survive in the absence of air are called anaerobes. They get energy through anaerobic respiration. For example, yeast.

Q66. (i) What is breathing?(ii) Differentiate between aerobic and anaerobic respiration.

Solution

(i) Breathing is the process by which air rich in oxygen is taken inside the body of an organism and air rich in carbon dioxide is expelled from the body with the help of breathing organs. (ii) Difference between aerobic and anaerobic respiration: Aerobic respiration Anaerobic respiration 1. Aerobic respiration takes place in the presence of oxygen. 2. Complete breakdown of food occurs in aerobic respiration. 3. The end products in aerobic respiration are carbon dioxide and water. 4. Aerobic respiration produces a considerable amount of energy. 1. Anaerobic respiration takes place in the absence of oxygen. 2. Partial breakdown of food occurs in anaerobic respiration. 3. The end products in anaerobic respiration may be alcohol and carbon dioxide (as in yeast), or lactic acid (as in muscles) 4. Much less energy is produced in anaerobic respiration.

Q67. Both inhalation and exhalation take place during  ____.

Solution

Both inhalation and exhalation take place during breathing.

Q68. ________ and water are released during respiration.

Solution

Carbon dioxide and water are released during respiration.

Q69. Leaves take in oxygen from the air with the help of _____.

Solution

Stomata

Q70. Explain the breathing mechanism in insects.

Solution

Insects have a network of air tubes called tracheae for gas exchange. Oxygen rich air rushes through spiracles (or small openings) into the tracheal tubes, diffuses into the body tissue, and reaches every cell of the body. Similarly, carbon dioxide from the cells goes into the tracheal tubes and moves out through spiracles. These air tubes or tracheae are found only in insects.

Q71. Give two similarities between aerobic and anaerobic respiration.

Solution

a.During both processes, energy is released by the breakdown of food. b.Carbon dioxide and water are also released during these processes.

Q72. _____ are small openings present in an insect's body.

Solution

Spiracles

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