Members of which group are not deuterostomes?

Options

A. Chordates
B. Echinoderms
C. Arthropods
D. None of these : all are deuterostomes

Answer

To determine which group is not a deuterostome, we can analyze the given options: chordates, echinoderms, arthropods, and the statement "none of these all are deuterostomes."

### Step-by-Step Solution:

1. **Understand the Definition of Deuterostomes**:
- Deuterostomes are a group of animals characterized by their embryonic development. In these organisms, the anus develops from the blastopore, which is the first opening that forms during early embryonic development.

2. **Identify the Groups**:
- **Chordates**: This group includes vertebrates such as fish, amphibians, reptiles, birds, and mammals. Chordates are deuterostomes.
- **Echinoderms**: This group includes starfish, sea urchins, and their relatives. Echinoderms are also deuterostomes.
- **Arthropods**: This group includes insects, arachnids, and crustaceans. Arthropods are not deuterostomes; they are protostomes, meaning their mouth develops from the blastopore.

3. **Analyze the Options**:
- Since both chordates and echinoderms are deuterostomes, we focus on arthropods. The question asks for the group that is not a deuterostome.

4. **Conclusion**:
- The group that is not a deuterostome is **arthropods**.

### Final Answer:
**Arthropods are not deuterostomes.**

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