Anisogamous condition is seen in

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Sexual reproduction takes place through the fusion of two gametes. These gametes can be flagellated and similar in size (as in Ulothrix ) or non-flagellated (non-motile) but similar in size (as in Spirogyra ). Such reproduction is called isogamous. The fusion of two gametes dissimilar in size, as in species of Chlamydomonas is termed as anisogamous. The fusion between one large, nonmotile (static) female gamete and a smaller, motile male gamete is termed oogamous, e.g., Volvox, Fucus.