Question

The excretory organs found in insects are composed of a. protonephridia. b. metanephridia. c. Malpighian tubules. d. a filtration kidney. e. a secretory kidney.

Short answer

The correct answer is (c) Malpighian tubules. These are the excretory organs found in insects.

Step-by-step solution

Understanding the Terminology

Protonephridia and metanephridia are types of excretory and osmoregulatory systems found in various animals, not in insects. Filtration kidney and secretory kidney are aspects of excretion in vertebrates, particularly mammals.

Identifying the Correct Answer

The excretory organ specific to insects is known as the Malpighian tubules. These tubules filter wastes from the insect's hemolymph (a fluid equivalent of blood) and subsequently excrete them with the feces.

Key concepts

Malpighian Tubules

In the world of insects, the Malpighian tubules play a vital role in the excretory system. These tubules are long, thin structures that actively absorb waste products from the insect's hemolymph, which is a fluid similar to blood in vertebrates. Once the waste is filtered, it is mixed with digestive wastes from the gut and expelled from the body.

Malpighian tubules are uniquely adapted to the needs of insects. They are not only responsible for waste removal but also play a crucial part in maintaining water balance and ionic concentration in the body. This ability is particularly important in terrestrial insects, helping them survive in various environmental conditions.

• The system works efficiently as it combines excretion with digestion, thus conserving as much water as possible.
• The primary components excreted include nitrogenous wastes like uric acid, which is less toxic and conserves water compared to ammonia.
• Malpighian tubules adapt to the specific needs of different insect species, showing variations in number and size.

Protonephridia

Protonephridia are excretory systems found in many types of invertebrates such as flatworms. These structures consist of a network of tubules containing cells called flame cells or solenocytes. The flame cells are named so because of their flickering cilia which resemble a flame.

This system is primarily concerned with osmoregulation, meaning it helps to control the water and salt balance within the organism. It works by filtering the body fluids through a mesh-like structure and then expelling the waste out of the body via excretory pores.

• Protonephridia are adapted for organisms living in aquatic environments where maintaining fluid and salt balance is crucial.
• The flame cells create a negative pressure which helps in the movement of water and metabolites.
• These systems are generally found in simpler organisms, reflecting a more primitive form of excretion.

Metanephridia

Metanephridia are another type of excretory organ seen in more advanced invertebrates such as annelids, including earthworms. Unlike protonephridia, metanephridia have a slightly more complex structure. They consist of tubules that open internally to the body cavity through a structure called a nephrostome and externally to the environment.

These tubes collect waste directly from the body fluid and excrete it outside the organism, assisting in both waste excretion and osmoregulation. Since metanephridia open both internally and externally, they provide a more advanced filtration system than protonephridia.

• Metanephridia are efficient at dealing with larger volumes of fluid and solutes.
• These structures are well-suited to organisms that require effective regulation of internal environments.
• The waste is usually excreted in a liquid form, aiding in the maintenance of osmotic balance.