Which one is not deuterostome

Options

A. Protochordata
B. Cephalchordata
C. Annelida
D. Echinodermata

Answer

To determine which option is not a deuterostome, we can follow these steps:

### Step 1: Understand the Definition of Deuterostomes
Deuterostomes are a group of animals characterized by their embryonic development, where the anus develops from the blastopore first, and the mouth develops second. This is in contrast to protostomes, where the mouth develops first.

### Step 2: Analyze the Options
We have four options to consider:
1. Protocordata
2. Cephalocordata
3. Annelida
4. Echinodermata

### Step 3: Classify Each Option
- **Protocordata**: This group includes the early chordates, which are classified as deuterostomes.
- **Cephalocordata**: This group includes lancelets, which also belong to the deuterostomes.
- **Annelida**: This phylum includes segmented worms, which are classified as protostomes, not deuterostomes.
- **Echinodermata**: This phylum includes starfish and sea urchins, which are classic examples of deuterostomes.

### Step 4: Identify the Non-Deuterostome
From the analysis:
- Protocordata: Deuterostome
- Cephalocordata: Deuterostome
- Annelida: Not a deuterostome (protostome)
- Echinodermata: Deuterostome

Thus, the option that is not a deuterostome is **Annelida**.

### Final Answer
**Annelida** is the phylum that is not a deuterostome.

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