Which of the following systems do the cnidaria and comb jellies have that sponges lack?

Options

A. Respiratory
B. Nervous
C. Excretory
D. Reproductive

Explanation

To answer the question "Which of the following systems do the cnidaria and comb jellies have that sponges lack?" we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Organisms**:
- We are comparing three groups: sponges, cnidarians, and comb jellies.

2. **Understand the Characteristics of Sponges**:
- Sponges are multicellular organisms that lack true tissues and organs. They do not have a nervous system, respiratory system, or excretory system.

3. **Examine Cnidarians and Comb Jellies**:
- Cnidarians (like jellyfish, corals, and sea anemones) and comb jellies (like the sea gooseberry) are more complex than sponges. They possess a simple nervous system known as a nerve net, which allows them to respond to stimuli.

4. **Analyze the Options**:
- **Respiratory System**: Both sponges and cnidarians/comb jellies do not have a specialized respiratory system. They rely on diffusion for gas exchange.
- **Nervous System**: Cnidarians and comb jellies have a nerve net, while sponges lack any nerve cells.
- **Excretory System**: Neither sponges nor cnidarians/comb jellies have a true excretory system; they also rely on diffusion for waste removal.
- **Reproductive System**: All three groups have reproductive systems, but they differ in complexity and method.

5. **Conclude the Answer**:
- The only system that cnidarians and comb jellies possess, which sponges lack, is the **nervous system** (specifically, the nerve net in cnidarians and comb jellies).

### Final Answer:
The system that cnidaria and comb jellies have that sponges lack is the **nervous system**.

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