Question

Spiracles of Cockroach which are larger and always kept open are
A. First and second pairs
B. First and third pairs
C. First and tenth pairs
D. Second and third pairs

Answer 1

Hint:The process of respiration In Cockroach takes place through spiracles. These are the small openings on the sides of its body. Through spiracles, oxygen-rich air enters into the body of the Cockroach and moves into the tracheal tubes therefore, diffuse into various tissues and cells of the body.

Complete answer:
To answer this question at first, we should know what are spiracles in Cockroach and why are they used. The respiration in Cockroach occurs through spiracles. When air enters through external openings, into its respiratory system, spiracles provide a way to the internal respiratory system. The respiratory organ of Cockroach is known as tracheae. In Cockroach there are in total 10 pairs of spiracles which are found in the body of an adult Cockroach. These are located along the length of the body, but are majorly found at the down sides of the abdomen. As, they are dedicated to take in oxygen, while others are used to expel carbon dioxide. The first and third pairs of spiracles are larger and remain open all times. Thoracic spiracles are used externally for closing lids which are attached to the muscles. The first thoracic spiracle is the largest spiracle on the cockroach. Most of the abdominal spiracles possess similarity in size, except the last abdominal spiracle. It has a D-shaped opening and is larger and shaped differently.
In the given options, as from the above explanation It is concluded that the first and third pairs of spiracles of Cockroach are larger and are always kept open.

Thus, the correct answer is option B, i.e., first and third pairs of spiracles of Cockroach.

Note:By looking at Cockroach anatomy it reveals that Cockroaches carry 10 pairs of spiracles, which the most an insect can have and these spiracles are used in respiration. Some of the spiracles are found on the thorax between the dorsal parts of the legs while, others run along the sides of the abdominal segments or between them.