Which one of the following is a radially symmetrical, blind sac body plan and diploblastic animal?

Options

A. Spongilla
B. Euspongia
C. Asterias
D. Physalia

Answer

To solve the question "Which one of the following is a radially symmetrical, blind sac body plan and diploblastic animal?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Terms**:
- **Radially Symmetrical**: An organism is radially symmetrical if it can be divided into similar halves by multiple planes passing through the center.
- **Blind Sac Body Plan**: This refers to a body plan where there is a single opening that serves as both the mouth and the anus, leading to a gastrovascular cavity.
- **Diploblastic**: This means the organism develops from two germ layers: ectoderm and endoderm.

2. **Evaluate the Options**:
- **Option 1: Spongilla**: This is a freshwater sponge. Sponges are generally asymmetrical and do not fit the criteria of being radially symmetrical or diploblastic.
- **Option 2: Uspongia**: Similar to Spongilla, Uspongia (also known as "bath sponge") is asymmetrical and does not have a blind sac body plan.
- **Option 3: Asterias**: Asterias is a starfish, which exhibits radial symmetry. However, starfish are triploblastic (having three germ layers: ectoderm, mesoderm, and endoderm), so this option does not meet the criteria.
- **Option 4: Physalia**: Physalia, commonly known as the Portuguese man o' war, is radially symmetrical, has a blind sac body plan, and is considered diploblastic.

3. **Conclusion**:
- After evaluating all the options, the only organism that fits all the criteria of being radially symmetrical, having a blind sac body plan, and being diploblastic is **Physalia**.

### Final Answer:
The correct answer is **Option 4: Physalia**.

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