Question

Book lungs are respiratory organs of
A) Mollusca
B) Mammals
C) Arachnida
D) Earthworm

Answer 1

A book lung is a form of respiratory organ that is found in joint legged invertebrate animals. It is composed of highly vascular thin plates which gives them the appearance of a book.

Complete answer:
In Arachnids which includes spiders and scorpions, atmospheric exchange of gases is carried out in the book lungs. It is a type of respiratory organ present inside an air filled cavity known as atrium. These book lungs are connected to the outside environment through spiracles or stigmata for respiration. These lungs consist of thin plates which are arranged in the form folded book. The thin plates are richly provided with blood means they are highly vascular. The air pockets and haemolymph filled tissues gives lungs an appearance of a folded book.
On the other hand, molluscs respire through ctenidia which are comb like outgrowths; mammals respire through a pair of lungs while no lungs are present in earthworm therefore, they respire through their skin. Mucus is present on the skin of earthworms and they prefer to live in some moist and humid environment.

So the correct answer is option “C” that is the book lungs are the respiratory organs of Arachnida.

Note: Arachnida belongs to phylum Arthropoda and subphylum Chelicerata. Arachnids comprises scorpions, spiders, mites, solifugae and harvestmen. Unlike insects, antennae are not present in arachnids. They have eight legs, and their bodies are distinguished into two parts namely the cephalothorax, which is present in the front and the abdomen which is present behind.