AIIMS 2019 Zoology Cockroach MCQ Question

Explanation of Periplaneta americana (American Cockroach)

Correct Answer: D) It is nocturnal and present in damp places.

Periplaneta americana, commonly known as the American cockroach, is an insect belonging to the order Blattodea and is widely recognized for its adaptability to various environments. Let’s explore why option D is the correct statement and clarify the inaccuracies of the other options.

Why Option D is Correct:

• Nocturnal Behavior: The American cockroach is primarily active at night (nocturnal), which provides it with a survival advantage by avoiding predators and human activity during the day.
• Habitat Preference: These cockroaches thrive in warm, moist environments, and are often found in places such as kitchens, basements, and sewers. Their preference for damp places is due to their need for moisture, which is crucial for their survival and reproduction.

Why Other Options are Incorrect:

A) It has 6 muscular hearts

• This statement is incorrect because Periplaneta americana does not have hearts in the same way vertebrates do. Instead, cockroaches have a dorsal vessel that functions as a heart, and it is a long tube-like structure that pumps hemolymph (the insect equivalent of blood) throughout their open circulatory system. The structure does not consist of six separate muscular hearts.

B) It has 10 thoracic segments

• This option is misleading because the American cockroach has three thoracic segments: the prothorax, mesothorax, and metathorax. Each of these segments typically bears one pair of legs, adding to the total of six legs overall, which is characteristic of insects. Therefore, this statement is incorrect.

C) Anal style is present in both male and female

• The "anal style" refers to a specific structure found in certain insect species, particularly in males. In the case of Periplaneta americana, males have a distinct structure called the "anal style" that is not present in females. Therefore, stating that it is present in both sexes is inaccurate.

Summary

In conclusion, the correct answer is option D because it accurately describes the nocturnal nature and habitat preferences of Periplaneta americana. The incorrect options either misrepresent the anatomical features or biological characteristics of this species. Understanding these distinctions is crucial for studying the biology and ecology of cockroaches and other arthropods.