Which is the only phylum in the animal kingdom without any nerve cell ?

Options

A. (a) Porifera
B. (b) Coelenterata
C. (c) Annelida
D. (d) Nematoda

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the only phylum in the animal kingdom that lacks any nerve cells.

2. **Identifying the Phyla**: We need to consider the major phyla in the animal kingdom, which include Porifera, Cnidaria, Annelida, and Nematoda.

3. **Analyzing Porifera**:
- Porifera, commonly known as sponges, are the simplest form of animals.
- They are composed of a group of cells and do not have a nervous system or nerve cells.
- This suggests that Porifera could be the answer.

4. **Analyzing Cnidaria**:
- Cnidarians, such as jellyfish and corals, possess a primitive nervous system known as a nerve net.
- They have non-polar neurons, indicating the presence of nerve cells.
- Therefore, Cnidaria cannot be the answer.

5. **Analyzing Annelida**:
- Annelids, such as earthworms, have a well-developed nervous system.
- They possess a brain and a ventral nerve cord, which indicates the presence of nerve cells.
- Thus, Annelida is not the answer.

6. **Analyzing Nematoda**:
- Nematodes, or roundworms, have a more complex nervous system.
- They have ganglion cells that function similarly to brain cells and possess both dorsal and ventral nerve cords.
- Therefore, Nematoda also cannot be the answer.

7. **Conclusion**: After analyzing all the options, it is clear that the only phylum without any nerve cells is **Porifera**.

**Final Answer**: A) Porifera

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