Each one of the following options has a rule regarding a certain animal group and an exception from that group written in brackets . which one is incorrect ?

Options

A. Reptiles have an incompletely four-chambered heart. (Crocodilus )
B. Amphibians have two pairs of limbs .( Icthyophis)
C. Sponges are found in marine water .(spongilla)
D. Roundworms are monoecious. (Ascaris )

Answer

To solve the question regarding the incorrect statement about animal groups and their exceptions, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: Reptiles have an incompletely four-chambered heart (Crocodilus)**
- Reptiles generally have an incompletely four-chambered heart, which means there are three chambers with some mixing of oxygenated and deoxygenated blood.
- However, the exception mentioned is Crocodilus (crocodiles), which actually possess a complete four-chambered heart.
- **Conclusion**: This statement is correct.

2. **Option B: Amphibia have two pairs of limbs (Ichthyopis)**
- Amphibians typically have two pairs of limbs.
- Ichthyopis is a type of limbless amphibian, which means it does not have the typical two pairs of limbs.
- **Conclusion**: This statement is correct.

3. **Option C: Sponges are found in marine water (Spongilla)**
- Most sponges are indeed found in marine environments.
- However, Spongilla is a genus of freshwater sponges, which makes it an exception to the general rule about sponges.
- **Conclusion**: This statement is correct.

4. **Option D: Roundworms are monoecious (Ascaris)**
- Roundworms, specifically Ascaris, are known to be dioecious, meaning they have separate male and female individuals.
- The statement that roundworms are monoecious (having both male and female reproductive organs in the same individual) is incorrect.
- **Conclusion**: This statement is incorrect.

### Final Answer:
The incorrect statement is **D. Roundworms are monoecious (Ascaris)** because roundworms are dioecious.

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