How respiration occur in

1) cockroach 2) earthwom 3) fish

In cockroach respiration occurs by a special part called trachea. It is a tube like structure that opens out of the body through a minute hole called spiracle. There are several spiracles present on both side of the body of cockroach. Through the spiracles air enters inside the trachea where exchange of gases takes place.

Earthworm absorbs oxygen through its moist skin by the process of diffusion and gives off carbon dioxide in the same process. The body of earthworm is covered by the epidermis which continuously secretes to retain the moisture throughout the skin.

In fish respiration occurs through gills. Gills are composed of several comb like filaments that are filled with blood capillaries. When water flows over the gills oxygen dissolved in water enters inside the blood capillaries and gets dissolved with blood. Blood then carries the dissolved oxygen to the heart from where it travels in all parts of the fish’s body. At the same time the carbon dioxide that is produced in the body gets released in water from the blood capillaries of the gills.