NCERT Solutions for Class 7 Science Chapter 10 Respiration In Organisms

Q.1 Why does an athlete breathe faster and deeper than usual after finishing the race?

Answer :

(1) During the run, the energy demand is high, but the oxygen supply to produce energy is limited.
Therefore, anaerobic respiration takes place in the muscle cells to fulfill the energy demand.

(2) An athlete needs to supply extra energy to his muscle cells which have worked hard during running.

(3) For this, he breathes faster and deeper so that more oxygen is supplied to the cells.
This speeds up the breakdown of food and as a result, more energy is released.

Q.2 List the similarities and differences between aerobic and anaerobic respiration.

Answer :

Similarities:


(1) In both aerobic and anaerobic respiration, the food is broken down to release energy.

(2) Both occur inside the cells.

(3) Both supply by-products.

(4) Both use glucose as the starting molecule. This is called the substrate.

(5) Both respiration produce ATP.

(6) Food is oxidized in both cases and energy is released.

Differences:

(1) Aerobic respiration takes place in the presence of oxygen while anaerobic respiration takes place in the absence of oxygen.

(2) Aerobic respiration's products are CO₂ and H₂O while anaerobic respiration's products are CO₂ and alcohol.

(3) Aerobic is a slow process while anaerobic is a fast process.

(4) Aerobic respiration is caused in animals and plant cells while anaerobic respiration is caused in human cells, yeast, bacteria, etc.

(5) Aerobic respiration releases more energy than anaerobic respiration.

Q.3 Why do we often sneeze when we inhale a lot of dust-laden air?

Answer :

(1) Sneezing expels the dust particles from the inhaled air so that only clean air enters our body.

(2) When we inhale dust-laden air, the dust irritates the nose; as a reflexive action, dust is thrown out through sneezing.

(3) When we inhale air containing dust particles, the particles get trapped in the hair present in nostrils.

(4) Sometimes, these particles may pass through the hair and enter the nasal cavity. They irritate the mucus lining of the nasal cavity, and as a result we sneeze.

Q.4 Take three test-tubes. Fill each of them 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 CO₂ ?

Answer :

Test-tube A will have the highest concentration of CO₂ because :

(1) Test-tube A will have a snail that expels out CO₂ into the tube. Living organisms use oxygen and release CO₂ during respiration.

(2) Since a plant is present in both test tubes B and C, the plant will inhale CO₂ to decrease CO₂ concentration.

(3) Thus, there will be less concentration of CO₂ in B and C test tubes.

Q.5 Tick the correct answer:
(a) In cockroaches, air enters the body through
(i) lungs
(ii) gills
(iii) spiracles
(iv) skin
(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
(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
(d) During exhalation, the ribs
(i) move outwards (ii) move downwards (iii) move upwards (iv) do not move at all

Answer :

a) (iii) spiracles

b) (ii) lactic acid

c) (ii) 15–18

d) (ii) move downwards

Q.6 Match the items in Column I with those in Column II:
Column I
(a) Yeast
(b) Diaphragm
(c) Skin
(d) Leaves
(e) Fish
(f) Frog
Column II
(i) Earthworm
(ii) Gills
(iii) Alcohol
(iv) Chest cavity
(v) Stomata
(vi) Lungs and skin
(vii) Trachae

Answer :

Column I $?$ Column II

(a) Yeast $?$ (iii) Alcohol

(b) Diaphragm $?$ (iv) Chest cavity

(c) Skin $?$ (i) Earthworm

(d) Leaves $?$ (v) Stomata

(e) Fish $?$ (ii) Gills

(f) Frog $?$ (vi) Lungs and skin

Q.7 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. (F)

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

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

(iv) The fishes have lungs for respiration. (F)

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

Q.8 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) Trachea

(ii) Ribs

(iii) Diaphragm

(iv) Stomata

(v) Spiracles

(vi) Lungs

(vii) Nostrils

(viii) Yeast

(ix) Ant

Q.9 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 :

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