Question

Choose the correct order of excretory organs in cockroach, earthworm, and rabbit respectively.
A. Skin, Malpighian tubules and kidney
B. Malpighian tubules, nephridia and kidney
C. Nephridia, Malpighian tubules and kidney
D. Nephridia, kidney and green gland

Answer 1

Hint: The excretory organ of the cockroach is malpighian tubules. This is found in the junction of midgut and hindgut. There are about 150 tubules in each insect. This system consists of branching tubules that extend from the alimentary canal which absorbs solutes, waste, and water from the surrounding hemolymph. Tubules are bathed in hemolymph and contain actin for structural protein.

Complete Answer:
- Earthworms are having slightly evolved structures known as nephridia. There is the presence of a pair of nephridia on each segment of the earthworm. They are quite similar to flame cells in that they have a tubule with cilia.
- Excreted product is carried outside through pore known as nephridiopore. They are more evolved than flame cells in that they have a system for tubular reabsorption by a network of capillaries before excretion. The excretory organ in the rabbit is a complex structure.
- The excretory organ in the case of a rabbit is the kidney as it belongs to mammals. They comprise a pair of the ureter, urinary bladder, and urethra. The major function of excretory organs are similar i.e. removal of nitrogenous waste and maintaining the salt balance in the body.

Therefore the correct order of excretory organs is Malpighian tubules, nephridia, and kidney respectively.

Note: There is the presence of malpighian tubules in all the insects and cockroaches. The earthworm is having nephridia as an excretory organ. The kidney is an excretory organ of the rabbit as it belongs to the mammal class. There is a difference in the excretory of organs but their function is similar. The excretory organ maintains the osmoregulation and removal of waste products from the body.