Mention two characteristics of algae that are similar to plants. Also, give one example of a filamentous alga and explain why it is called so?

Explanation

### Step-by-Step Solution

1. **Identify Characteristics of Algae Similar to Plants**:
- **First Characteristic**: Algae are autotrophic, meaning they can produce their own food through photosynthesis. This is similar to plants, which also use photosynthesis to convert sunlight into energy.
- **Second Characteristic**: Algae have cell walls. These cell walls provide structural support to the cells, similar to the cell walls found in many plant cells.

2. **Provide an Example of Filamentous Alga**:
- **Example**: Spirogyra is a well-known example of filamentous algae.
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