NCERT Class VII Science Solutions: Chapter 10-Respiration in Organisms Part 5 (For CBSE, ICSE, IAS, NET, NRA 2022)

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Question 18:

A food stall owner was preparing dough for making . He added a pinch of yeast and sugar to the dough and left it in a warm place. After few hours, the dough had risen. There was a sour smell too.

  1. Why did the dough rise?
  2. Why did the dough smell sour?
  3. Why was sugar added to the dough?
  4. What would have happened if the dough was kept in the refrigerator, soon after it was prepared?


  1. The released during respiration by the yeast results in the rise of dough.
  2. During anaerobic respiration, yeast produces alcohol resulting in sour smell.
  3. Sugar acts as food for yeast.
  4. At low temperatures, yeasts will not multiply and respire because of which the dough will not rise or become sour.

Question 19:

Observe the figures given as Figure (A) and (B) and answer the following.

  1. Which of the figures A or B indicates the process of inhalation and which the process of exhalation?
  2. In the figure label the arrows and indicate the direction of
  3. Movement of air.
  4. Movement of diaphragm.
  5. Movement of ribs.
Result for Observe the Figures Given as Figure (Q)


  1. Fig. (A) Indicates inhalation, and exhalation. Fig. (B) Indicates
Result for Observe the Figures Given as Figure (A)

Question 20:

Match the names of organisms in Column I with their organs of breathing given in Column II.

Match the Column I and Column II. (Q)
Column IColumn II
A. Butterflyi. Lungs
B. Earthwarmsii. Gills
C. Sparrowiii. Spiracles
D. Fishiv. Skin


Match the Column I and Column II. (A)
Column IColumn II
A. Butterflyiii Spiracles
B. Earthwarmsiv Skin
C. Sparrowi Lungs
D. Fishii Gills