which one feature is common to Amphioxus , frog sea horse and crocdile

Options

A. Skeleton of cartilage and bone
B. Three chambered heart
C. Pharyngeal gill slits at least in developmental stages
D. Dorsal solid nerve cord

Answer

To determine the common feature among Amphioxus, Frog, Seahorse, and Crocodile, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Phylum**:
- All the mentioned animals (Amphioxus, Frog, Seahorse, and Crocodile) belong to the phylum Chordata. This is a crucial starting point as it indicates that they share certain characteristics typical of this phylum.

2. **List Common Features of Chordates**:
- Chordates are known for several key features, including:
- Presence of a notochord.
- Dorsal hollow nerve cord.
- Pharyngeal gill slits.
- Post-anal tail.

3. **Focus on Pharyngeal Gill Slits**:
- Among the features listed, pharyngeal gill slits are particularly significant. These structures are present during the developmental stages of all chordates, including the four animals in question.

4. **Confirm Presence in Each Animal**:
- **Amphioxus**: Known for having pharyngeal gill slits, which are used for filter feeding.
- **Frog**: As an amphibian, frogs also exhibit pharyngeal gill slits during their larval stage (tadpoles).
- **Seahorse**: Being a fish, seahorses possess gill slits for respiration.
- **Crocodile**: As a reptile, crocodiles have pharyngeal gill slits during their embryonic development.

5. **Conclusion**:
- Based on the analysis, the common feature among Amphioxus, Frog, Seahorse, and Crocodile is the presence of pharyngeal gill slits, at least during their developmental stages.

### Final Answer:
The common feature among Amphioxus, Frog, Seahorse, and Crocodile is the presence of **pharyngeal gill slits**.

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