Respiration in Organisms

Science Class Seven

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NCERT Exercise questions and answer

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

Answer:

An athlete breathes faster and deeper than usual after finishing the race very fast because their body requires extra energy during heavy physical work, which requires more oxygen than normal. This forces our body to breathe fast.

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

Answer: Differences between aerobic and anaerobic respiration.

Similarities:

Both in aerobic respiration and anaerobic respiration glucose is broken down and released energy.

Both types of respirations take place inside the cell.

Differences:

Aerobic respiration take place in the presence of oxygen. While aerobic respiration takes place in the absence of oxygen.

Aerobic respiration is a slow process while anaerobic respiration is a faster process.

In aerobic respiration higher amount of energy is released while in anaerobic respiration less amount of energy is released.

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

Answer

When we inhale a lot of dust-laden air our nostril sent a message to the brain. The nasal cavity in the response starts sneezing to expel out these foreign particles. This process is a part of defense mechanism of our body.

Question (4) Take three test-tubes. Fill 3/4th 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

Test tube (A) in which only snail has been kept has highest concentration of carbon dioxide.

This is because in the test tube in which plants and snail both has been kept, some amount of carbon dioxide expelled out by snail is used in photosynthesis by the plant and has lesser concentration of carbon dioxide.

In test tube B in which only a water plant has been kept has least amount of carbon dioxide because carbon dioxide expelled out by plant in the process of respiration is used in photosynthesis.

(5) Tick the correct Answer:

(a) In cockroaches, air enters the body through

(a) Lungs

(b) gills

(d) skin

Answer (c) Spiracles

Explanation

Cockroaches have openings at the both sides of their head which is called spiracles. Cockroaches breathe through these spiracles.

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

(a) Carbon dioxide

(b) Lactic acid

(d) Water

Answer (b) Lactic acid

Explanation

During heavy exercise we need extra energy which is fulfilled by the cells by the process of respiration in the absence of oxygen. This is called anaerobic respiration.

In anaerobic respiration lactic acid is formed along with release of energy.

Due to formation lactic acid, we get cramps in the legs. Taking a rest, hot bath, or message improves the supply of oxygen to cells which breaks down the lactic acid into carbon dioxide and water, and after that we get rid of cramps.

(a) 9 -12

(b) 15-20

(d) 30-33

Answer (b) 15-20

Explanation

In the rest the breathing rate ranges from 15 to 20 per minute in an average adult.

(d) During exhalation, the ribs

(a) move outwards

(b) move downwards

(d) do not move at all

Answer(b) move downwards

Exhalation

There is a membrane present below the chest cavity which separates chest cavity and abdominal cavity. While inhalation this membrane goes down along with expansion of rib cage and provide enough space to get air in. In exhalation membrane goes up and rib cage contracts and goes down slightly, this creates high pressure zone which facilitates the expelling out carbon dioxide with ease.

Question (6) Match the items in Column 1 with those in Column 11:

Question Table
Column I	Column II
(a) Yeast	(i) Earthworm
(b) Diaphragm	(ii) Gills
(c) Skin	(iii) Alcohol
(d) Leaves	(iv) Chest cavity
(e) Fish	(v) Stomata
(f) Frog	(vi) Lungs and skin
	(vii) Trachea

Answer

Answer Table
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
	(vii) Trachea

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)

Answer: F (False)

Explanation

During heavy exercise the body of a person needs extra energy consequently needs extra oxygen to respire which is fulfilled by breathing faster.

So, given statement which says "During heavy exercise the breathing rate of a person slows down" is false.

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

Answer: (T) True

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

Answer: T (True)

(iv) The fishes have lungs for respiration.

Answer: F (False)

Explanation

Fish has gills through which it respires in the water.

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

Answer: 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.

class 7th science respiration question 8 cross words