Actually, algae is defined as being:
- primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leaves
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Algae is not a plant; however, it is likely a common ancestor to many plants. Scientists have difficulty agreeing on how to classify algae, but currently they are considered to be cyanobacteria (blue and green), while other algae types are considered to be of the Kingdom Protista.