Question

The _____ move about on tube feet. a. cnidarians c. annelids b. echinoderms d. flatworms

Short answer

b. echinoderms

Step-by-step solution

Understand the Question

The question asks which group of animals move using tube feet. We need to determine which of the given options use this form of locomotion.

Review Options

The options provided are (a) cnidarians, (b) echinoderms, (c) annelids, and (d) flatworms. We need to know about each group to see if they use tube feet.

Know Tube Feet

Tube feet are small, flexible, hollow appendages that are typically used by some marine animals for movement and feeding. This system is part of the water vascular system in sea creatures.

Identify Echinoderms

Echinoderms include creatures like starfish and sea urchins, which are known to possess a water vascular system with tube feet. They use tube feet for locomotion, clinging to surfaces, and feeding.

Verify Other Options

- Cnidarians (a) consist of animals like jellyfish and corals and do not have tube feet. - Annelids (c) are segmented worms and also do not have tube feet. - Flatworms (d) lack a water vascular system and tube feet.

Conclusion: Choose the Correct Answer

Based on the above steps, echinoderms, option (b), are the animals that move using tube feet.

Key concepts

Tube Feet

Tube feet are fascinating structures found in echinoderms, such as starfish, sea urchins, and sea cucumbers. These tiny, flexible appendages perform a variety of vital functions. Unlike rigid limbs, tube feet are soft and can extend and contract, allowing echinoderms to walk, cling to surfaces, and even capture food. They might look like small, fleshy tubes or sucker-like projections.

How do they move? This movement is made possible through a hydraulic mechanism powered by the echinoderm's water vascular system. When the animal wants to move, fluid within the foot is manipulated to elongate or retract it. The resulting suction created by these movements helps the animal stick to rocks or the ocean floor. This powerful suction mechanism enables starfish to pull open shellfish and is essential for their survival.

• Tube feet appear as rows on the undersides of echinoderms.
• They also serve in sensory perceiving, helping the animal feel their environment.

Water Vascular System

The water vascular system is a remarkable network of hydraulic canals that is crucial for the locomotion and feeding methods of echinoderms. This system moves water in and out of the animal's body, allowing the operation of the tube feet. Think of it as a hydraulic mechanism working throughout the echinoderm's body.

Within this system, the madreporite, a sieve-like structure on the surface of the echinoderm, acts as a gateway. It helps filter seawater into the system. This seawater travels through a series of canals, which distribute it throughout the body. The canals include the stone canal, ring canal, radial canals, and lateral canals, each channeling water to various sections.

• Water pressure within the canals is adjusted to move tube feet.
• Besides motion, the water vascular system also assists respiration and excretion in echinoderms.

Marine Locomotion

Marine locomotion among echinoderms is primarily facilitated by the interaction of the water vascular system and tube feet. These adaptations enable echinoderms to thrive in diverse marine environments. To move, echinoderms adjust the pressure within their tube feet, using the hydraulic power of the water vascular system. This adaptation is key to their movement across various underwater surfaces.

This mechanism enables echinoderms not only to roam the seabed but also to withstand currents and waves in their ocean habitats. Echinoderms are able to walk, glide, and sometimes even burrow in sands thanks to their unique structural systems.

• Locomotion is slow but allows precision and control.
• Tube feet can act in unison or individually, which aids in complex navigational tasks.