Problem 136 - Objective Biology for NEET

Question

The most distinctive feature of echinoderm is (a) Gastro vascular cavity (b) Choanoctyes (c) Water vascular system/ambulacral system (d) Canal system

Step-by-Step Solution

Answer

The most distinctive feature of echinoderms is (c) Water vascular system/ambulacral system.

Step 1: Understand Echinoderm Features.

Echinoderms are a group of invertebrates that include sea stars, sea cucumbers, and urchins. They possess several unique features, such as a durable, spiny exoskeleton and the capability for regeneration. However, the most distinctive feature of echinoderms should be determined.

Step 2: Identify the Distinctive Feature.

Review the unique characteristics of echinoderms and compare them to the options: (a) Gastrovascular cavity - a basic digestive system found in some simple animal species, not specific to echinoderms. (b) Choanocytes - cells found in sponges, not echinoderms. (c) Water-vascular system, or ambulacral system - a network of water-filled canals used for locomotion, feeding, excretion, and respiration for echinoderms. (d) Canal system - a system associated with poriferans (sponges), not echinoderms.

Step 3: Select the Correct Answer

From the investigation in Step 2, it can be concluded that the water-vascular system, also known as the ambulacral system, is the most distinctive feature of echinoderms. None of the other options are specifically associated with echinoderms.

Key Concepts

Water-vascular system

Echinoderms are known for their remarkable water-vascular system. This system is like a network of pipelines that runs through their bodies. It's filled with seawater, allowing echinoderms to move and carry out essential life processes. Think of it as an internal plumbing system!

• Provides locomotion by controlling tube feet
• Aids in capturing food by coordinating movements
• Helps in respiration and excretion by moving water through the body

This system starts at a central ring canal from which radial canals extend. From radial canals, tiny tube feet protrude, acting like suction cups, enabling echinoderms to cling onto surfaces. The water-vascular system is not just distinctive; it's crucial for their survival.

Regeneration in marine invertebrates

Echinoderms have an incredible ability to regenerate. This means they can regrow lost body parts, which is quite rare among marine organisms. Imagine losing an arm and being able to grow it back!

• Sea stars can regrow entire arms, and some can regenerate their central body
• This feature aids in survival after predation or injury
• Regeneration is also thought to play a role in asexual reproduction

This ability is powered by their unique biology and cellular processes. Being able to rebirth lost parts allows echinoderms to continue thriving in diverse marine environments.

Spiny exoskeleton

One of the first things you'll notice about echinoderms is their spiny skin. These spines form part of a hard exoskeleton, which provides both protection and support.

• Made from calcium carbonate, offering strength and rigidity
• Helps deter predators due to its rough texture and sharpness
• Acts as a frame for their tubular and delicate water vascular system

The exoskeleton not only keeps echinoderms safe from predators but also gives them their unique look. This bony outer covering is what makes sea stars and sea urchins so recognizable.

Echinoderm locomotion

Echinoderms have unique ways of moving around their environments. Thanks to their water-vascular system, they can maneuver through water in ways other marine creatures cannot.

• Tube feet, which extend from radial canals, are crucial for movement
• Tubes fill with water, allowing them to push and pull along surfaces
• Movements are slow but highly controlled

By contracting muscles, echinoderms move water from one part of their water-vascular system to another. This ingenious mechanism allows them to glide across the ocean floor, even climbing over rough or vertical surfaces with ease.