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Respiration in Organisms

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NCERT Solutions for Class 7 Science Chapter 6

This chapter Respiration in Organisms dives into the essential process of respiration, which fuels all living things!

What is Respiration?

Respiration is the process by which cells in living organisms break down food molecules (like glucose) to release energy. This energy is crucial for all life functions, from movement and growth to maintaining body temperature.

Two Types of Respiration:

There are two main types of respiration:

  1. Aerobic Respiration: This process requires oxygen and occurs in most organisms (animals, plants, some bacteria). During aerobic respiration, glucose reacts with oxygen to produce energy, carbon dioxide, and water.
  2. Anaerobic Respiration: This process does not require oxygen and happens in some organisms (certain bacteria) or under specific conditions (like intense exercise in humans). During anaerobic respiration, glucose is broken down less efficiently, producing less energy and byproducts like lactic acid (causing muscle fatigue).

Key Points:

  • All living organisms need respiration to survive.
  • Oxygen is essential for aerobic respiration.
  • Respiration releases energy used for various life functions.
  • Plants also respire, taking in oxygen and releasing carbon dioxide (during the day through stomata in leaves).
  • Understanding respiration is important for appreciating the interconnectedness of living things.

Benefits of Knowing Respiration:

  • Explains why we need to breathe
  • Shows the link between food and energy
  • Highlights the importance of oxygen for life

NCERT Solutions for Class 7 Science Chapter 6


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

Ans : Athletes breathe heavily after a race to catch their breath

  1. Oxygen Debt: Muscles burn through oxygen during exercise. After the race, they’re “repaying” the oxygen they used up.
  2. Waste Removal: Exercise creates lactic acid, making muscles tired. Deep breaths help clear this waste and reduce fatigue.

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

Ans : 


  • Both are processes of cellular respiration: They break down food molecules (usually glucose) to release energy for the cell.
  • Both release energy: This energy is used to power various cellular functions.
  • Both involve glucose: Glucose is the primary fuel source for most organisms.


FeatureAerobic RespirationAnaerobic Respiration
Oxygen RequirementRequires oxygen (O₂)Does not require oxygen (O₂)
EfficiencyMore efficient, produces more ATP (energy)Less efficient, produces less ATP
ProductsCarbon dioxide (CO₂) and water (H₂O)Lactic acid (in animals) or ethanol and CO₂ (in some microbes)
ExamplesMost organisms (animals, plants, some bacteria)Some bacteria, yeast (during fermentation)

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

Ans : We sneeze when we inhale dust-laden air because our body has a built-in reflex to protect itself from irritants. 

  1. Dust Triggers: Tiny dust particles enter your nose when you breathe in.
  2. Irritating Signal: These particles irritate the sensitive lining inside your nose.
  3. Sneeze Reflex: The irritation triggers a message to travel to your brain.
  4. Expulsion Action: Your brain instructs your muscles to expel the irritant with a forceful burst of air (the sneeze).

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 ?

Ans : Test tube C (snail and plant) will have the most CO2! 

  • Snail: Breaths out CO2, adding it to the water.
  • Plant: Uses CO2 for food, but not as much as the snail produces.
  • Test Tube B (Plant only): Plant uses up more CO2 than in C.

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
Ans : 

(a) (iii) spiracles

(b) (ii) lactic acid 

(c) (i) 9 – 12 

(d) (ii) move downwards

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

Column IColumn II
Yeast Earthworm
LeavesChest cavity
FrogLungs and Skin

Ans : 

Column IColumn II
Yeast Alcohol
DiaphragmChest cavity
FrogLungs and Skin

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)

Ans : 

(i) False

(ii) False

(iii) True

(iv) False

(v) True

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.

NCERT Solutions Class 7 Science Chapter 10 Respiration in Animals and Plants Q8

(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

Ans : 

(i) Tracheae

(ii) Ribs

(iii) Diaphragm

(iv) Stomata

(v) Spiracles

(vi) Lungs

(vii) Nostrils 

(viii) Yeast

(ix) Insect  

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.

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

NCERT Solutions for Class 7 Science Chapter 6


How can NCERT Solutions for Class 7 Science Chapter 6 help me prepare for exams?

NCERT Solutions provide detailed explanations and answers to questions from the chapter “Respiration in Organisms.” By studying these solutions, you can strengthen your understanding of the concepts and improve your exam preparation.

Are the NCERT Solutions for Class 7 Science Chapter 6 available in different formats?

Yes, our NCERT Solutions for Class 7 Science Chapter 6 are available in various formats, including PDF downloads, online viewing, and printable versions, allowing you to choose the format that best suits your study preferences.

Can I rely solely on NCERT Solutions for Class 7 Science Chapter 6 for my science studies?

While NCERT Solutions provide comprehensive explanations for Chapter 6, it’s also beneficial to supplement your studies with additional resources such as reference books, online tutorials, and practical experiments to deepen your understanding.

How can I access NCERT Solutions for Class 7 Science Chapter 6 on your platform?

You can easily access NCERT Solutions for Chapter 6 on our platform by navigating to the Class 7 Science section and selecting Chapter 6: “Respiration in Organisms.” From there, you can view, download, or print the solutions as needed.

Are there any practice questions or exercises included in the NCERT Solutions for Chapter 6?

Yes, along with detailed solutions, the NCERT Solutions for Chapter 6 include practice questions and exercises to help reinforce your understanding of the concepts covered in “Respiration in Organisms.”

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