Respiration in Organisms Question Answers: NCERT Class 7 Science

An athlete breathe faster and deeper than usual after finishing the race because he needs extra energy to his muscles which worked hard during running. For this reason, he breathes faster and deeper so that he can supply more oxygen to the cells. During running, the oxygen level of the athlete becomes less. To complete the oxygen level, he breathes faster than usual. He respires anaerobically at that time.

Similarities between Aerobic and Anaerobic Respiration

Differences between Aerobic and Anaerobic Respiration

We often sneeze when we inhale lot of dust- laden air because it expells out the foreign particles from the air that is trapped inside the nose. Sneeze happens when we inhale dust particles or contaminants present in air, they get trapped in to the hair of nose and get accumulated there. then which may can cause sneeze. 

Three test-tubes are taken and labelled A, B and C. Each test- tube is half filled with water.
(a) In test-tube A, a snail is kept,
(b) In test-tube B, a water plant is kept, and
(c) In test-tube C contains both a snail and a water plant.

(a) Test-tube A contains a snail in water. The snail will use up oxygen for respiration and produce carbon dioxide.
(b) Test-tube B contains a ‘water plant’ in water. The water plant will do photosynthesis by using carbon dioxide and water and produce oxygen. The water plant will use some of this oxygen for respiration and produce carbon dioxide will then be used by the plant in photosynthesis.
(c) Test-tube C contains both, a snail and a water plant. The carbon dioxide produced by the snail through the respiration is used by the plant for the synthesis of food and oxygen is released by the plant which is used by the snail for the respiration.

From the above, we conclude that the test-tube A containing only snail will have the highest concentration of carbon dioxide because there is no plant to use up the carbon dioxide produced during the respiration in snail.

(a) (iii) Spiracles
On the body of cockroach tiny holes are prsent on sides, these are called spiracles. Exchange of gases takes place through spiracles.

(b) (ii) Lactic acid
During heavy exercise we get cramps in the legs due to the accumulation of lactic acid because that time our muscles starts respire anaerobically. During anaerobic respiration, partial breakdown of glucose occur which forms lactic acid. When lactic acid accumulates in the muscles, causes muscle cramps.

(c) (ii) 15-18
The normal range of breathing rate per minute in a person at rest is 15- 18. Breathing rate can be determined by the number of breathes in per minute.

(d) (ii) Moves downward 
During exhalation, air comes out. In exhalation process, our ribs moves in downward and inward direction whereas diaphragm expands in size.

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              

1. Yeast: Yeast is a single- celled organism which respries anaerobically. Yeast is used to produce alcohol by fermentation process by converting glucose into alcohol. 

2. Diaphragm: The diaphragm is made up of rib cage. It is present in chest cavity. It expands inside when we inhale and during exhalation it contracts.

3. Earthworm: The earthworm respires through skin. The skin of earthworm is slipery and soft. Exchange of gases takes place through the skin. 

4. Leaves: Tiny pores present on the surface of the leaves called stomata. Stomata are the beans shaped structure which is protected by the two guard cells and helps in the exchange of gases. Transpiration of water also occurs through stomata.

5. Fish: Fish respires through gills. The breathing rate of fish is faster than the terrestrial organisms because they use dissolved oxygen in the water which is less in quantity as compared to the environment. 

6. Frog: Frogs respire through lungs as well as skin. Because frog acquires terrestrial as well as aquatic habitat. 

(i) False
During heavy excersize the breathing rate of a person is faster than as usual because of the lack of oxygen in the cells. To complete the oxygen level he breathes faster and deeper.

(ii) False
This statement is false because the process of photosynthesis is done only in the day time whereas they respire all the time. 

(iii) True
This statement is true because frog acquires both terrestrial and aquatic habitat.

(iv) False
This statement is false because they have gills which helps them to use dissolved oxygen.

(v) True                                                                                                                                                                                                                                          Lungs can be expanded by the downward and upward movement of diaphragm by intake of fresh air to expand the chest cavity. 

(i) The air tubes of insects - Trachea
(ii) Skeletal structures surrounding chest cavity - Ribs
(iii) Muscular floor of chest cavity - Diaphragm
(iv) Tiny pores on the surface on leaf - Stomata
(v) Small openings on the sides of the body of an cockroach - Spiracles
(vi) The respiratory organs of human being - Lungs
(vii) The opening through which we inhale - Nostrils                                                                                                                                                                          (viii) An anaerobic organism - Yeast
(ix) An organism with tracheal system - Ant.

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

The mountaineers carry oxygen cylinders with them because as they go higher the amount of oxygen level decreases in the air. They carry oxygen because the amount of air available to a person is less than that available on the ground.