Why do we often sneeze when we inhale a lot of dust-laden air?

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?

Tick the correct answer:

(a) In cockroaches, air enters the body through

(i) lungs

2. gills

(iii) spiracles

(iv) skin

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

(i) carbon dioxide

2. lactic acid

2. 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

Match the items in Column I with those in Column II:

Mark ‘T’ if the statement is true and ‘F’ if it is false:

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 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

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.