Algae is a term used for aquatic organisms that photosynthesize like land plants yet are structurally less complex and lack vascular tissue (xylem and phloem) found in most plants. Plants that lack these specialized vessels for water transport are called
bryophytes (see
Plant Kingdom).
All algae contain chlorophyll, however groups differ in the other types of chlorophyll they posses. Algae are commonly grouped taxonomically for the type of pigment they contain; for example, there are yellow-green, golden, brown, red, and green algae.
An example of an algae is the "Green algae", which are the most diverse and familiar algae in fresh water. Green algae are considered ancestral to land plants, and share many characteristics with land plants, such as: chlorophyll, starch as the carbohydrate storage material, and cell walls made of cellulose.
Green algae exhibit a wide variety of forms from single-celled, free-swimming forms (e.g. Chlamydomonas) to motile, colonial forms of various sizes (e.g. Eudorina, Volvox), to multicellular filamentous forms (e.g. Ulothrix).