Sea stars are

Options

A. Free living and predaceous
B. Parasites on chordates
C. Commensals with coelenterates
D. Tubicolous

Answer

**Step-by-Step Solution:**

1. **Identify the Classification of Sea Stars**: Sea stars belong to the class Asteroidea, commonly known as starfish. This classification is important to understand their biological characteristics and habits.

2. **Examine Their Physical Features**: Sea stars have specific physical features such as hard plates and spines on their bodies. They also possess tube feet, which are crucial for their movement and feeding.

3. **Understand Their Locomotion**: The presence of tube feet allows sea stars to move effectively in their marine environment. This adaptation is key to their lifestyle as free-living organisms.

4. **Analyze Their Feeding Habits**: Sea stars are predacious, meaning they hunt and kill other organisms for food. Their primary prey includes small mollusks, which they consume by using their tube feet to pry open the shells.

5. **Evaluate Other Options**:
- The second option suggests that sea stars are parasites on caudates, which is incorrect as they do not depend on other organisms for nutrition.
- The third option implies that they are commensals with cnidarians, which is also incorrect since they do not have a mutualistic relationship with cnidarians.
- The fourth option mentions that they derive nutrition from tube feet, which is not accurate as tube feet are primarily for locomotion and not for nutrient absorption.

6. **Conclude with the Correct Answer**: Based on the analysis, the correct characterization of sea stars is that they are predacious organisms that hunt and consume small mollusks.

**Final Answer**: Sea stars are predacious organisms that primarily feed on small mollusks.

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