NCERT Solutions Class 7 Science Chapter 10 Respiration in Organisms

NCERT Solutions for Class 7 Science for chapter 10 Respiration in Organisms

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

Answer. 1 An athlete breathes faster and deeper than usual after finishing the race because running requires large amount of energy. This energy is derived from rapid and quick breakdown of food by oxygen. Fast breathing supplies large amounts of oxygen to produce the required energy.

Glucose + O₂  -> carbon dioxide + water + energy

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

Answer. 2

Similarities between aerobic and anaerobic modes of respiration are as follows:

1. Both aerobic and anaerobic modes of respiration involve breakdown of glucose and production of energy.
2. Both the modes are found in both higher and lower organisms.

Differences between aerobic and anaerobic modes of respiration are as follows:

1. Aerobic respiration takes place in sufficient supply of oxygen while anaerobic respiration takes place in either deficiency or absence of oxyge
2. Aerobic respiration produces larger amount of energy than anaerobic respiration.
3. The end-products of aerobic respiration are carbon dioxide and water while the end-products of anaerobic respiration are carbondioxide and alcohol or lactic acid.

Glucose + O2 carbon dioxide + water + energy

Glucose (without oxygen) ---> lactic acid + energy (in muscles)

4. Aerobic respiration is the primary mode of respiration in higher organisms whereas anaerobic respiration is the primary mode of respiration in lower organisms.

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

Answer.3 We often sneeze on inhaling dust-laden air because dust particles get entangled in the hair present in the nostrils which irritate the nasal membrane and cause sneezing. Hair found in the nostrils prevents entry of dust particles into lungs and sneezing expels them from the nose, allowing only clean air to enter the lungs.

Question.4 Take 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 CO₂?

Answer. 4 All the organisms produce carbon dioxide and water as the final products of respiration. Test tube A will have the highest concentration of CO2 because the snail kept in it produces carbon dioxide in the process of respiration. On the other hand, test tube B will have the least concentration of carbon dioxide among the three because the water plant performs photosynthesis during which carbon dioxide is utilised and oxygen is produced. In the test tube C, carbon dioxide produced by the snail and by the plant is used up in the process of photosynthesis performed by the plant.

Question.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.5

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

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

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

(d) During exhalation, the ribs (ii) move downwards

Question. 6. Match the items in Column I with those in

Column II:

Answer. 6 The correctly matched contents of Column I with Column II are as follows:

Question.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. 7

(i) False (ii) False (iii) True (iv) False (v) True

Question.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. 8

(i) Trachea

(ii) Ribs

(iii) Diaphragm

(iv) Stomata

(v) Spiracles

(vi) Lungs

(vii) Nostrils

(viii) Yeast

(ix) Ant

Question.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.9 The mountaineers carry oxygen with them because: (b) The amount of air available to a person is less than that available on the ground.