The echinoderms, hemichordates and chordates had which of the following larve as a common ancestral form?

Options

A. Tornaria
B. Trochophore
C. Dipelurula
D. Bipinnaria

Explanation

To solve the question regarding the common larval form shared by echinoderms, hemichordates, and chordates, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Groups**: First, we need to identify the three groups mentioned in the question: echinoderms, hemichordates, and chordates. These are all part of the deuterostome clade in the animal kingdom.

2. **Common Ancestral Form**: The question asks about a common ancestral larval form. In evolutionary biology, a common ancestor would imply that these groups share certain traits or developmental stages.

3. **Identifying the Larval Form**: Research and knowledge in zoology indicate that echinoderms (like starfish), hemichordates (like acorn worms), and chordates (like vertebrates) share a specific larval form called the "Diplura."

4. **Evaluating the Options**: The question provides multiple-choice answers. We need to determine which option corresponds to the Diplura larva.

5. **Conclusion**: After analyzing the information, we find that the correct answer is option number 3, which identifies the Diplura larva as the common ancestral form shared by echinoderms, hemichordates, and chordates.

### Final Answer:
The common larval form shared by echinoderms, hemichordates, and chordates is the **Diplura** larva (Option 3).

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