An animal was observed as bilaterally symmetrical, metamerically segmented and triploblastic in nature. It was identified as an arthropod.
Which character should have been identified first to call it an arthropod ?

Options

A. Presence of coelom
B. Presence of gills
C. Jointed appendages
D. Compound eyes

Answer

To determine which character should have been identified first to classify the animal as an arthropod, let's analyze the characteristics mentioned in the question and the key features of arthropods.

### Step-by-Step Solution:

1. **Understanding the Characteristics**:
- The animal is bilaterally symmetrical, which means it can be divided into two identical halves.
- It is metamerically segmented, indicating that its body is divided into repeated segments.
- It is triploblastic, meaning it has three germ layers: ectoderm, mesoderm, and endoderm.

2. **Identifying Arthropods**:
- Arthropods are characterized by having an exoskeleton made of chitin, jointed appendages, and segmented bodies.
- The presence of jointed appendages is a defining feature of arthropods.

3. **Analyzing the Options**:
- **Option 1: Presence of Coelom**: While arthropods are coelomates, this characteristic is not exclusive to them, as other groups like annelids and mollusks also possess a coelom.
- **Option 2: Presence of Gills**: Gills are specific to certain arthropods (like crustaceans) and cannot be used to classify all arthropods.
- **Option 3: Jointed Appendages**: This is the most significant characteristic that defines arthropods. If an organism has jointed appendages, it can be classified as an arthropod.
- **Option 4: Compound Eyes**: While many arthropods have compound eyes, this feature is not exclusive to them and can also be found in some annelids.

4. **Conclusion**:
- The most definitive characteristic that should have been identified first to classify the animal as an arthropod is the presence of **jointed appendages**.

### Final Answer:
The character that should have been identified first to call it an arthropod is **jointed appendages**.

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