What are vocal sacs? Give their function.

Explanation

### Step-by-Step Solution:

1. **Definition of Vocal Sacs**: Vocal sacs are specialized structures found in certain amphibians, primarily male frogs and toads. They are balloon-like glands located externally, specifically lining the throat area.

2. **Physical Characteristics**: These sacs appear as bulges or bags on the outside of the throat, making them easily visible from a distance. Their structure is designed to enhance sound production.

3. **Function of Vocal Sacs**: The primary function of vocal sacs is to resonate and amplify sound. When a male frog or toad calls, the vocal sac helps to increase the volume and clarity of the sound produced.

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