Question

Which one of the following statements is correct regarding cockroach?
A. Head is oval in shape.
B. There are 10 pair of spiracles (2 pairs of thorax and 8 pairs in abdomen)
C. Heart is differentiated into funnel shaped chambers with setae on either side
D. Each eye consists of about 1000 ommatidia.

Answer 1

Hint: Cockroaches are found in arthropoda. Eyes of cockroaches have mosaic visions due to the presence of many cells. These cells have photoreceptor cells which makes the mosaic kind of vision in cockroaches.

Complete answer:
Cockroaches are the insects found in the phylum arthropoda. They are generally found in warm conditions. These are gregarious in nature because they are generally found in the social groups.

> Cockroaches have triangular heads. Head is formed by fusion of six segments. They don’t have an oval head. That’s why option A is incorrect.

> Spiracles are involved in respiration. There are 10 pairs of spiracles. There are 20 spiracles found in the cockroach. These are divided into abdominal and thoracic regions. The abdominal spiracles are 16 in number and 4 spiracles are found in the thoracic region. That’s why ‘option B’ is incorrect.

> Their heart is differentiated into chambers which are funnel in shape. Ostia are found on either side of funnels. Setae are not found on either side of the funnel. Heart is responsible for circulating the blood across the body. That’s why ‘option C’ is incorrect.

> Cockroaches have two eyes. These are compound eyes. The eyes consist of ommatidia. Ommatidia consists of a cluster of photoreceptor cells. These are pigmented cells which are responsible for formation of complete images from the combination of several images. This is a kind of mosaic vision. That’s why the eye consists of 1000 ommatidia.

Hence, the correct answer is option (D).

Note: Cockroaches have spiracles for respiration. Their hearts are funnel shaped having ostia on either side of the funnel. The mosaic kind of vision is found in cockroaches in which several images combine to produce a complete image.