Q1. Why does an athlete breathe faster and deeper than usual after finishing the race?
Ans:
- Athletes need a lot of energy during the race.
- For the release of this energy, they need a lot of oxygen.
- So, they breathe faster & deeper after finishing the race to restore the energy levels in the body by increase in the supply of oxygen.
Q2. List the similarities and differences between aerobic and anaerobic respiration.
Ans:
Similarities: In both aerobic & anerobic respiration:
- Food is broken down to release energy.
- It takes place in the cells.
- Produce by products.
Differences:
| Aerobic Respiration |
Anaerobic Respiration |
| It takes place in the presence of oxygen. |
It takes place in the absence of oxygen. |
| Produces more energy. |
Produces less energy. |
| By products are carbon dioxide & water. |
By products are carbon dioxide & alcohol. |
| Eg: In humans, most plants & animals |
Eg: Yeast & bacteria |
Q3. Why do we often sneeze when we inhale a lot of dust-laden air?
Ans:
- Dust laden air irritates the sensitive lining of nose.
- Sneezing is a reflexive action that helps to expel the dust & clear the airways.
- Thus, it also prevents dust from reaching the lungs.
Q4. Take three test-tubes. Fill ¾th 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?
Ans:
- Test-tube A will have the highest concentration of CO2 as it contains a snail that will release carbon dioxide through respiration.
- In both the test-tubes B & C, contain a plant which will take in CO2 & hence its concentration will decrease.
Q5. Tick the correct answer:
Ans:
(a) In cockroaches, air enters the body through (iii) spiracles.
(b) During heavy exercise, we get cramps in the legs due to the accumulation of (ii) lactic acid.
(c) Normal range of breathing rate per minute in an average adult person at rest is: (ii) 15–18.
(d) During exhalation, the ribs (ii) move downwards.
Q6. Match the items in Column I with those in Column II:
Ans:
| 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 & skin |
Q7. Mark ‘T’ if the statement is true and ‘F’ if it is false:
Ans:
(i) During heavy exercise the breathing rate of a person slows down. = F
(Explanation: During heavy exercise, the breathing rate of a person increases.)
(ii) Plants carry out photosynthesis only during the day and respiration only at night. = F
(Explanation: Plants carry out photosynthesis during the day & respiration during both day and night.)
(iii) Frogs breathe through their skins as well as their lungs. = T
(iv) The fishes have lungs for respiration. = F
(Explanation: Fishes do not have lungs; they have gills.)
(v) The size of the chest cavity increases during inhalation. = T
Q8. Given below is a square of letters in which are hidden different words related to respiration in organisms.
Ans:
(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 of leaf - stomata
(v) Small openings on the sides of the body of an insect - spiracles
(vi) The respiratory organs of human beings - lungs
(vii) The openings through which we inhale - nostrils
(viii) An anaerobic organism - yeast
(ix) An organism with tracheal system - ant
Q9. The mountaineers carry oxygen with them because:
Ans:
(b) The amount of air available to a person is less than that available on the ground.
