Which of the following represents the correct physiological sequence of steps involved in the process of nitrogenous waste excretion and water conservation in an insect, starting from the body cavity to final expulsion?
- 1Active transport of potassium ions and soluble urates from the hemolymph into the lumen of the Malpighian tubules
- 2Flow of the fluid mixture along the tubules into the junction of the midgut and hindgut
- 3Selective reabsorption of water, essential salts, and ions by specialized rectal glands
- 4Precipitation of soluble urates into insoluble solid uric acid crystals due to acidification of rectal contents
- 5Elimination of dry uric acid pellets from the body through the anus along with digestive fecal matter
Answer
The correct physiological sequence begins with active transport of wastes into Malpighian tubules, movement of fluid into the hindgut, reabsorption of water and ions by rectal glands, precipitation of uric acid crystals in the acidic rectum, and final elimination through the anus.
The correct ordering outlines uricotelic excretion in insects: secretion from hemolymph into Malpighian tubules, drainage into the hindgut, active reabsorption of water and salts by rectal glands, precipitation of uric acid into solid crystals, and egestion through the anus.
Step-by-Step Solution
Key Concept
Excretion via Malpighian tubules and rectal water conservation in insects (Uricotelism)