Goa Board Class 7 Solutions for Science – Respiration in Organisms (English Medium)
Page No. 118:
Question 1:
Why does an athlete breathe faster and deeper than usual after finishing the race?
Solution :
During race an athlete needs more energy. To release energy, muscles need more oxygen. So to take more amount of oxygen an athlete breathes faster and deeper.
Concept insight: Energy is released by breaking down glucose in the presence of oxygen. It is called respiration.
Question 2:
List the similarities and differences between and anaerobic respiration.
Solution :
Similarity between aerobic and anaerobic respiration:
In both aerobic and anaerobic respiration, the food is broken down to release energy.
Differences between aerobic and anaerobic respiration:
Aerobic respiration | Anaerobic respiration |
i. It is the process of breakdown of food in the presence of oxygen. | i. It is the process of breakdown of food in the absence of oxygen. |
ii. Its end products are CO2 and H2O. | ii. End products of anaerobic respiration can be lactic acid (muscles) or CO2 and alcohol. |
iii. It takes longer time to release energy.
|
iii. It is a fast process as compared to aerobic respiration. |
iv. It produces large amount of energy.
|
iv. It produces less amount of energy as compared to aerobic respiration. |
Examples: It occurs in most plants and animals. | Examples: Yeast, bacteria, human muscle cells, etc. respire anaerobically. |
Concept insight: Modes of respiration – aerobic and anaerobic.
Question 3:
Why do we often sneeze when we inhale a lot of dust-laden air?
Solution :
When we inhale lots of dust-laden air, dust particles cause irritation in the upper nasal passage. So to expel them out we reflexively sneeze.
Concept insight: By sneezing body expels out the unwanted particles which enters in our nasal passage.
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?
Solution :
Test tube A will have the highest concentration of CO2. This is because test tube A contains snail. Snail is an organism that breathes in O2 and breathes out CO2, Hence, CO2 concentration increases in test tube A.
Test tube B contains a water plant, which takes in CO2 for food synthesis and gives out O2. Hence, more O2 concentration is found in test tube B.
Test tube C contains both a snail and a plant, The CO2 produced by the snail is utilized by the plant for its food synthesis and the O2 released by the plant is utilized by the snail for respiration.
Therefore, test tube A has the highest concentration of CO2.
Concept insight: CO2 is evolved during respiration as a by product along with energy and water.
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
Solution :
Question 6:
Solution :
Page No. 119:
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)
Solution :
(i) During heavy exercise the breathing rate of a person slows down. (F)
Concept insight: During exercise oxygen requirement of person increases so breathing rate increases.
(ii) Plants carry out photosynthesis only during the day and respiration only at night. (F)
Concept insight: Plants do respiration in day and night.
(iii) Frogs breathe through their skins as well as their lungs. (T)
Concept insight: Frogs breathe on land through skin and lungs and in water through skin.
(iv) The fishes have lungs for respiration. (F)
Concept insight: Fishes respire through gills.
(v) The size of the chest cavity increases during inhalation. (T)
Concept insight: Size of chest cavity increases during inhalation so that volume of lungs can increase.
Question 8:
Solution :
(i) Trachea
(ii) Ribs
(iii) Diaphragm
(iv) Stomata
(v) Spiracles
(vi) Lungs
(vii) Nostrils
(viii) Yeast
(ix) Cockroach
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.
Solution :