Mouth is formed as a secondary opening of alimentary canal in

Options

A. protostomes
B. schizocoelomates
C. cnidarians
D. entercoelomates

Answer

To solve the question "Mouth is formed as a secondary opening of alimentary canal in," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding the Alimentary Canal**: The alimentary canal is the digestive tract through which food passes, and it typically has openings at both ends (mouth and anus) in more complex organisms.

2. **Identifying Organism Types**: Organisms can be broadly classified into two categories based on the development of their digestive systems: protostomes and deuterostomes.

3. **Defining Protostomes**: In protostomes, the mouth develops from the blastopore (the first opening that forms during embryonic development), making it the primary opening. The anus forms later as a secondary opening.

4. **Defining Deuterostomes**: In contrast, in deuterostomes, the anus develops from the blastopore, and the mouth forms later as a secondary opening.

5. **Conclusion**: Since the question specifically asks about the mouth being a secondary opening, we conclude that the correct answer pertains to deuterostomes, where the mouth is formed as a secondary opening.

6. **Final Answer**: Therefore, the mouth is formed as a secondary opening of the alimentary canal in **deuterostomes**.