Question

Which of the following phylums has book lungs as the respiratory organs?
A. Protozoa
B. Cnidarians
C. Arthropods
D. Amphibians

Answer 1

Hint: The process of respiration requires various kinds of organs, in humans, lungs help in the process of respiration whereas in some animals book lungs help in the process of respiration. They are seen as small openings in the abdomen of the organism.

Complete Answer:
We will find out about the respiratory system of various phylums in order to find the correct answer.

Option A: Protozoa is a single celled organism which does not have any specialised structure for respiration. They generally respire with the help of the plasma membrane which is the outermost layer of the cell. Therefore, this is the incorrect option.

Option B: Even Cnidarians do not have any specialised organs like the lungs or the heart which is used in the process of respiration. Their internal cavity is generally used for the process of respiration.

Option C: In Arthropods, specialised organs like gills and trachea are seen. The aquatic arthropods respire via the gills and the terrestrial forms rely on diffusion via tiny tubes known as trachea. Respiratory organs like book gills and book lungs are also seen.
As arthropods have a cutaneous skeleton, cutaneous respiration is not possible thus the respiration majorly happens via the respiratory organs.

Option D: Amphibians have well developed organs for respiration like lungs. They even breathe via the skin and this is known as cutaneous respiration. Some aquatic amphibians and tadpoles have gills for breathing.

Thus, the correct option is C) Arthropods.

Note: In humans, the process of respiration involves taking up oxygen and exhaling carbon dioxide from the body. The process of inhalation or taking up of oxygen is a passive process and the process of exhalation is an active process as it requires energy.