Problem 27 - Objective Biology for NEET

Question

Excretory and osmoregulatory structure in cockroach is (a) Flame cells (b) Green glands (c) Nephridia (d) Malpighian tubules

Step-by-Step Solution

Answer

The excretory and osmoregulatory structure in a cockroach are the Malpighian tubules.

Step 1: Identifying excretory structures

Firstly, discern that the options presented are all excretory structures, but they all belong to different species and not all to the cockroach. Flame cells are found in flatworms (Platyhelminths), green glands in crustaceans, nephridia in earthworms (Annelida).

Step 2: Recall and match the correct structure to species

Knowing that the above options are not present in cockroaches, it's clear that 'Malpighian tubules' are the remaining option which are indeed the excretory and osmoregulatory structure of a cockroach. The correct answer is then (d) Malpighian tubules.

Key Concepts

Malpighian Tubules

Malpighian tubules are fascinating excretory and osmoregulatory structures primarily found in insects, such as cockroaches. These tubular excretory organs are named after their discoverer, Marcello Malpighi. Typically, a cockroach has around 100 to 150 Malpighian tubules scattered around the junction of its midgut and hindgut. This arrangement allows the tubules to efficiently manage waste in the insect's body.

How do they work? - The tubules float in the insect's hemolymph, the insect equivalent of blood. - They collect metabolic wastes from the hemolymph and by means of diffusion, these waste materials are converted into uric acid. - Uric acid is then transported back to the digestive tract, where it is expelled from the body via the insect’s feces.

This process is particularly advantageous as uric acid is relatively non-toxic and doesn't dissolve easily in water. Thus, it allows insects to conserve water, which is crucial for their survival in various environments.

Osmoregulation in Insects

Osmoregulation is a vital process these creatures use to control the balance of water and salts in their bodies, ensuring stable internal conditions despite external changes. Insects like cockroaches face the challenge of maintaining water balance because of their small size and high surface area-to-volume ratio.

Key aspects of osmoregulation: - Malpighian tubules play a significant role in this process by reabsorbing and conserving water while excreting nitrogenous wastes as uric acid. - The structure of their cuticle also aids in reducing water loss. It acts as a waterproof barrier. - Behavioral adaptations such as seeking moist environments or minimizing movement during hot periods help them avoid dehydration.

Through these mechanisms, insects can maintain their physiological equilibrium. Despite harsh and rapidly changing environments, their efficient osmoregulatory system supports survival and proper function.

Excretion in Cockroaches

Excretion in cockroaches involves a sophisticated system that handles metabolic waste using their specialized organs, the Malpighian tubules. This system enables the cockroach to efficiently get rid of waste products while maintaining water and ion balance, which is crucial for survival in different habitats.

Cockroaches primarily excrete uric acid: - This compound is beneficial as it minimizes water loss during excretion, a process known as uricotelism. - As discussed, Malpighian tubules filter waste from the hemolymph, converting it to uric acid. - Unlike human excretion of urea, uric acid is excreted as a solid or semi-solid paste, further conserving water.

Such efficient excretory processes not only help maintain internal homeostasis but also enable cockroaches to thrive in various environments, from humid to arid conditions. Their excretory adaptations highlight their success as one of the most resilient and enduring species.