Phylum Chlorophyta

The chlorophytes comprise most of the green algae. They are greenish in colour due to the abundance of chlorophyll pigments in the thylakoids. Accessory pigments, such as beta-carotene and xanthophylls, are present albeit few. Some species are single-celled whereas others are multicellular and macroscopic (e.g. Ulva sp.). Some of them form colonies, e.g. Volvox sp.. They have apical flagella that are used for locomotion. Reproduction may be asexual or sexual. Sexual reproduction in chlorophytes often involves the exchange of nuclei via the conjugation tubes. Sexual reproduction involving two identical gametes is referred to as isogamy. Oogamy, on the contrary, involves two non-identical gametes: one is small and motile whereas the other is large and non-motile. There is an alternation of generation such that the gametophyte and the sporophyte phases alternate.