NCERT Solutions for Class 7 Science Chapter 10 Respiration in Organisms

Q1. Why does an athlete breathe faster and deeper than usual after finishing the race?

Answer:

The muscles of an athlete undergo anaerobic respiration which means the oxygen is used up faster than being supplied by the blood.

Thus, to inhale more oxygen, an athlete breathes faster and deeper than usual after finishing the race.

Q2. List the similarities and differences between aerobic and anaerobic respiration.

Answer:

The similarities between aerobic and anaerobic respiration are:

(i) Carbon dioxide is produced in both reactions.

(ii) Energy is released in both reactions.

The differences between aerobic and anaerobic respiration are:

Q3. Why do we often sneeze when we inhale a lot of dust-laden air?

Answer:

Sneezing removes the foreign particle like dust particles, smoke from the air inhaled which ensures good air quality inside our body.

When we inhale, unwanted particles get trapped in the hair present in our nasal cavity. However, sometimes these particles may get past the hair causing irritation in the lining of the cavity. This causes sneezing.

Q4. T ake three test-tubes. Fill ¾th of each with water. Label them A, B and C . Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of ?

Answer:

We know,

Snail will inhale oxygen and exhale carbon dioxide whereas the plant will inhale carbon dioxide for respiration.

The test with snail and without plant will have maximum carbon dioxide concentration. Therefore, the order of test tube containing is .

Hence, test-tube A will have the highest concentration of .

Q5. Tick the correct answer:

(a) In cockroaches, air enters the body through

(i) lungs

(ii) gills

(iii) spiracles

(iv) skin

Answer:

A cockroach has small openings called spiracles on the sides of its body.

Therefore, (a) In cockroaches, air enters the body through (iii) spiracles

Q5. Tick the correct answer: (b) During heavy exercise, we get cramps in the legs due to the accumulation of

(i) carbon dioxide

(ii) lactic acid

(iii) alcohol

(iv) water

Answer:

(b) During heavy exercise, we get cramps in the legs due to the accumulation of (ii) lactic acid

During heavy exercise, muscle cells respire anaerobically because oxygen is used faster as compared to its supply by the blood. The partial breakdown of glucose produces lactic acid whose accumulation causes muscle cramps.

Q5. Tick the correct answer:

(c) Normal range of breathing rate per minute in an average adult person at rest is:

(i) 9–12

(ii) 15–18

(iii) 21–24

(iv) 30–33

Answer:

Normal range of breathing rate per minute in an average adult person at rest is (ii) 15–18

This means on an average, an adult human being breathes in and out 15–18 times in a minute.

Q5. Tick the correct answer:

(d) During exhalation, the ribs

(i) move outwards

(ii) move downwards

(iii) move upwards

(iv) do not move at all

Answer:

During exhalation, the ribs (ii) move downwards

During exhalation, ribs move down and inwards reducing the size of the chest cavity causing the air to be pushed out of the lungs.

Q6. Match the items in Column I with those in Column II:

Column I Column II
(a) Yeast (i) Earthworm
(b) Diaphragm (ii) Gills
(c) Skin (iii) Alcohol
(d) Leaves (iv) Chest cavity
(e) Fish (v) Stomata
(f) Frog (vi) Lungs and skin
(vii) Tracheae

Answer:

Q7. Mark ‘T’ if the statement is true and ‘F’ if it is false:

(i) During heavy exercise the breathing rate of a person slows down. (T/F)
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (T/F)
(iii) Frogs breathe through their skins as well as their lungs. (T/F)
(iv) The fishes have lungs for respiration. (T/F)
(v) The size of the chest cavity increases during inhalation. (T/F)

Answer:

(i) During heavy exercise the breathing rate of a person slows down. False

- During heavy exercise, we breathe faster and deeper than usual

(ii) Plants carry out photosynthesis only during the day and respiration only at night. False

- Respiration is an essential process required for the plants to live. It occurs day and night. Whereas, photosynthesis takes place only during the day.

(iii) Frogs breathe through their skins as well as their lungs. True

(iv) The fishes have lungs for respiration. False

- Fishes do not have lungs. They breathe through gills.

(v) The size of the chest cavity increases during inhalation. True

- During inhalation, ribs move up and outwards and the diaphragm moves down. This movement increases space in our chest cavity and air rushes into the lungs.

Q8. Given below is a square of letters in which are hidden different words related to respiration in organisms. These words may be present in any direction— upwards, downwards, or along the diagonals. Find the words for your respiratory system. Clues about those words are given below the square.

(i) The air tubes of insects
(ii) Skeletal structures surrounding chest cavity
(iii) Muscular floor of chest cavity
(iv) Tiny pores on the surface of leaf
(v) Small openings on the sides of the body of an insect
(vi) The respiratory organs of human beings
(vii) The openings through which we inhale
(viii) An anaerobic organism
(ix) An organism with tracheal system

Answer:

(i) The air tubes of insects - TRACHEA
(ii) Skeletal structures surrounding chest cavity - RIBS
(iii) Muscular floor of chest cavity - DIAPHRAGM
(iv) Tiny pores on the surface of leaf - STOMATA
(v) Small openings on the sides of the body of an insect - SPIRACLES
(vi) The respiratory organs of human beings - LUNGS
(vii) The openings through which we inhale - NOSTRILS
(viii) An anaerobic organism - YEAST
(ix) An organism with tracheal system - ANT

Q9. The mountaineers carry oxygen with them because:

(a) At an altitude of more than 5 km there is no air.

(b) The amount of air available to a person is less than that available on the ground.

(c) The temperature of air is higher than that on the ground.

(d) The pressure of air is higher than that on the ground.

Answer:

The mountaineers carry oxygen with them because the amount of oxygen availability to a person is less than that available on the ground. (b)

As we move higher in altitude, the density of the atmosphere lessens.