Question

How does exchange of gases occur in the following:

(a) fish
(b) cockroach

Answer 1

(a) Fish: The exchange of gases in fishes takes place through gills. Gills have large number of filaments supplied with thin blood capillaries. Water enters through the mouth and passes over the gills. Oxygen is absorbed by blood in the capillaries and carbon dioxide is given out through its walls.

(b) Cockroach: The exchange of gases takes place through spiracles. Oxygen-rich air enters the body through spiracles and reaches all parts of the body via trachea (respiratory tube). Trachea is further branched into tracheoles.