Problem 172 - Objective Biology for NEET

Question

Assertion: Antennal glands perform the excretory function in prawns. Reason: Malpighian tubules are present in crustacean for osmoregulation

Step-by-Step Solution

Answer

The assertion is true and the reason is false.

Step 1: Understand the Concepts

Firstly, let's understand these biological terminologies. The Antennal glands, also called Green glands, are excretory organs in prawns, which help to remove nitrogenous waste from the body and are indeed part of excretory system in crustaceans. Malpighian tubules on the other hand are excretory systems in insects for removing nitrogenous waste and are not present in crustacean. Hence, they play no role in excretion in crustaceans.

Step 2: Evaluate the Assertion and Reason

Now consider the assertion: 'Antennal glands perform the excretory function in prawns'. This statement is correct, Antennal glands, also known as Green glands, do indeed serve this function in prawns. Next, look at the reason: 'Malpighian tubules are present in crustacean for osmoregulation'. This statement is incorrect. Malpighian tubules are not present in crustacean, they are present in insects.

Step 3: Conclude

Since the assertion is true but the reason provided is incorrect and does not correctly explain the assertion, the conclusion is that the assertion is true and the reason is false.

Key Concepts

Antennal Glands

The antennal glands, often known as Green glands, are essential organs in the excretory system of crustaceans, like prawns. These glands are primarily responsible for removing nitrogenous wastes from the crustacean's body. They ensure the maintenance of internal chemical balance by filtering hemolymph, similar to how kidneys function in humans. The waste is expelled through a pore near the base of the antennae, hence their name. This efficient excretion system allows crustaceans to inhabit various aquatic environments without succumbing to the toxic buildup of waste. Key functions of antennal glands include:

• Filtration of bodily fluids
• Reabsorption of essential ions and nutrients
• Excretion of waste products

This adaptability in managing waste is crucial for crustaceans living in diverse environments, ranging from freshwater ponds to the salty oceans.

Crustacean Biology

Crustacean biology encompasses the study of numerous sea and freshwater animals like lobsters, crabs, shrimp, and prawns. This group, known as arthropods, is characterized by jointed limbs and an exoskeleton made of chitin. Crustaceans play significant ecological roles in their habitats, as they often serve as both prey and predator, maintaining the balance within their ecosystems. Crustaceans possess unique features:

• A hard, protective exoskeleton that molts as they grow
• Jointed limbs for mobility and interaction with their surroundings
• Compound eyes for enhanced vision
• Complex life cycles with various larval stages

Understanding the biology of crustaceans not only provides insights into their natural behavior and physiology but also enhances our knowledge about their role in aquatic ecosystems.

Malpighian Tubules

Unlike antennal glands, Malpighian tubules are found not in crustaceans but in insects. These tubules are specialized structures that serve as excretory and osmoregulatory organs in insects, like butterflies or beetles. Malpighian tubules extend from the junction of the midgut and hindgut and function by extracting wastes from the insect's hemolymph, aiding in maintaining ion balance and water conservation. Here's how Malpighian tubules work:

• They actively transport ions and nitrogenous waste products into the tubules, creating an osmotic gradient.
• Water follows the osmotic gradient into the tubules, allowing waste to be converted into a paste-like substance, conserving water.
• This waste is then excreted into the insect's hindgut, from where it is finally expelled from the body.

While both crustaceans and insects have distinct excretory systems adapted to their respective environments, it’s important to note that these structures, although different, are vital to each organism’s survival and ecological success.