Sexual reproduction in algae are of three type:
1. Isogamy: Fusion of morphologically and Physiologically similar gametes
E.g. Ulothrix.
2. Anisogamy: Fusion of either morphologically or physiologically dissimilar gametes
E.g. Pandorina
3. Oogamy: Fusion of both morphologically and physiologically dissimilar gametes.
E.g. Sargassum.
The life cycle shows distinct alternation of generation.