Bilateral symmetry, segmentation, coelom and open circulatory system characterises which of the following phyla?

Options

A. Annelida
B. Mollusca
C. Arthropoda
D. Echinodermata

Explanation

To solve the question regarding which phylum is characterized by bilateral symmetry, segmentation, coelom, and an open circulatory system, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Characteristics**:
- **Bilateral Symmetry**: This means that the organism can be divided into two identical halves along one plane.
- **Segmentation**: This refers to the division of the body into repetitive segments.
- **Coelom**: This is a fluid-filled body cavity that is completely lined by tissue derived from mesoderm.
- **Open Circulatory System**: In this system, the blood is not entirely contained within blood vessels; instead, it flows freely through cavities called hemocoels.

2. **Identify the Phyla**:
- We need to find a phylum that exhibits all these characteristics.
- Common phyla to consider include Arthropoda, Annelida, Mollusca, and others.

3. **Analyze Each Phylum**:
- **Arthropoda**: This phylum includes insects, arachnids, and crustaceans. They exhibit bilateral symmetry, segmentation, a coelom, and an open circulatory system.
- **Annelida**: This phylum includes segmented worms. They have bilateral symmetry and segmentation, but they possess a closed circulatory system.
- **Mollusca**: This phylum includes snails and octopuses. They have bilateral symmetry and a coelom but typically have a closed circulatory system (except for some).
- Other phyla do not fit all the criteria.

4. **Conclude the Correct Phylum**:
- Based on the analysis, the phylum that meets all the criteria of bilateral symmetry, segmentation, coelom, and an open circulatory system is **Arthropoda**.

5. **Final Answer**:
- Therefore, the correct answer to the question is **Arthropoda**.