The member of this phylum are terrestrial or aquatic having an organ system level organisation bilaterally symmetrical, triploblastic , segmented and eucoelomate animals ?

Options

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

Answer

To solve the question regarding the phylum that consists of terrestrial or aquatic organisms with organ system level organization, bilateral symmetry, triploblastic structure, segmentation, and being eucoelomate, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Characteristics**:
- The question describes organisms that have:
- Organ system level of organization
- Bilateral symmetry
- Triploblastic body structure (three germ layers: ectoderm, mesoderm, endoderm)
- Segmentation
- Eucoelomate (true coelom present)

2. **Analyzing the Options**:
- **Mollusca**: Generally have a soft body, often with a shell. They are not segmented and do not exhibit the characteristics mentioned.
- **Arthropoda**: These are segmented animals with jointed appendages, exhibit bilateral symmetry, are triploblastic, and have a true coelom. They can be terrestrial (like insects) or aquatic (like crabs).
- **Platyhelminthes**: These are flatworms, which are bilaterally symmetrical and triploblastic but are not segmented and are acoelomate (lack a true coelom).
- **Echinodermata**: These are marine animals (like starfish) that exhibit radial symmetry in adulthood, are not segmented, and are coelomate but do not fit the description of being bilaterally symmetrical.

3. **Identifying the Correct Phylum**:
- Based on the characteristics outlined, **Arthropoda** fits all the criteria:
- They are segmented.
- They are bilaterally symmetrical.
- They are triploblastic.
- They have a true coelom.
- They can be found in both terrestrial and aquatic environments.

4. **Conclusion**:
- Therefore, the correct answer to the question is **Arthropoda**.

### Final Answer:
The correct phylum is **Arthropoda**.