1. Why does an athlete breathe faster and deeper than usual after finishing the race?
Answer:
An athlete breathes faster and deeper after finishing a race because their body needs more oxygen to produce extra energy. During the race, the muscles use more energy, and the oxygen supply to the muscles is less. Therefore, the body tries to take in more oxygen by breathing faster and deeper to help break down food and release energy.
2. List the similarities and differences between aerobic and anaerobic respiration.
Answer:
Similarities:
- Both processes release energy from food.
- Both processes occur in the cells.
Differences:
- Aerobic respiration uses oxygen, while anaerobic respiration does not.
- Aerobic respiration produces more energy compared to anaerobic respiration.
- Aerobic respiration results in carbon dioxide and water, while anaerobic respiration results in lactic acid or alcohol.
3. Why do we often sneeze when we inhale a lot of dust-laden air?
Answer:
We sneeze when we inhale a lot of dust-laden air because the dust particles irritate the lining of the nasal cavity. Sneezing helps to expel these particles from our nose, preventing them from entering our respiratory system.
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, which contains the snail, will have the highest concentration of CO₂ because the snail releases carbon dioxide during respiration. In test tube B, the plant will use the CO₂ for photosynthesis. In test tube C, the plant will absorb the CO₂ released by the snail for photosynthesis, reducing the overall CO₂ concentration.
5. Tick the correct answer:
(a) In cockroaches, air enters the body through
(i) lungs
(ii) gills
(iii) spiracles
(iv) skin
Answer: (iii) spiracles
(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
Answer: (ii) lactic acid
(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
Answer: (ii) 15 – 18
(d) During exhalation, the ribs
(i) move outwards
(ii) move downwards
(iii) move upwards
(iv) do not move at all
Answer: (ii) move downwards
6. Match the items in Column I with those in Column II:
Column I
(a) Yeast
(b) Diaphragm
(c) Skin
(d) Leaves
(e) Fish
(f) Frog
Column II
(i) Earthworm
(ii) Gills
(iii) Alcohol
(iv) Chest cavity
(v) Stomata
(vi) Lungs and skin
(vii) Tracheae
Answer:
(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
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.
Answer: False
(ii) Plants carry out photosynthesis only during the day and respiration only at night.
Answer: False
(iii) Frogs breathe through their skins as well as their lungs.
Answer: True
(iv) The fishes have lungs for respiration.
Answer: False
(v) The size of the chest cavity increases during inhalation.
Answer: 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.
(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 the 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
Answer:
(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.
Answer: (b) The amount of air available to a person is less than that available on the ground.