How important is the presence of air bladder in Pisces?

Explanation

### Step-by-Step Solution:

1. **Understanding Pisces**:
- Pisces refers to the class of fish within the phylum Chordata, which includes both cartilaginous (Chondrichthyes) and bony fish (Osteichthyes).

2. **Classification of Fish**:
- Fish are classified into two main groups:
- **Chondrichthyes**: These are cartilaginous fish, such as sharks and rays, which have a skeleton made of cartilage.
...