Which classes of phylum chordata are associated with organisms with streamlined bodies? What purpose does such body structure serve?

Explanation

**Step-by-Step Solution:**

1. **Identify the Phylum**: The question asks about the phylum Chordata, which includes various classes of animals.

2. **Identify the Classes with Streamlined Bodies**: Within the phylum Chordata, the two classes associated with streamlined bodies are:
- **Class Aves (Birds)**: Birds have streamlined bodies that help them fly efficiently through the air.
- **Class Pisces (Fishes)**: Fishes have streamlined bodies that enable them to swim smoothly through water.

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