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 :

An athlete needs to supply extra energy to his muscle cells which have worked hard during running. 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:
In both aerobic and anaerobic respiration, the food is broken down to release energy.
Difference:
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 cell while anaerobic respiration is caused in human cells, yeast, Bacteria etc.

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

Answer :

Sneezing expels the dust particles from the inhaled air, so that only clean air enters our body. It usually occurs because of the irritation in the upper breathing passage. This irritation happens when we inhale some unwanted particles and they get trapped in our nasal cavity. Smoke, dust, pollen, etc. are some of the unwanted particles that may cause sneezing.

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 snail will take in oxygen and gives out CO₂.

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.