Chlorophyta

Chlorophyta are microorganisms that are grouped in the kingdom called Protista. The microbes are plant-like, in that they are able to manufacture energy from sunlight. The microbes are also commonly known as green algae

Depending on the species, Chlorophyta can be single-celled, multicelled, and can associate together in colonies. The environmental diversity of Chlorophyta is vast. Many types live in marine and fresh water. Terrestrial habitats include tree trunks, moist rocks, snowbanks, and creatures including turtles, sloths and mollusks. There are some 8,000 species of chlorophytes, ranging in size from microscopic to visibly large.

There are three classes of Chlorophyta. The first class, which contains the greatest number of organisms, is called Chlorophyceae. A notable example of an organism from this class is Chlorella, which is economically important as a dietary supplement. Another member of the class is Volvox, a spherical organized community containing upwards of 60,000 cells.

The second class is called Charophyceae. Members of this class have existed since prehistoric times, as evidenced by fossil finds. An example of this class is Spirogyra, which form slimy filaments on the surface of freshwater.

The third class is called Ulvophyceae. These are marine organisms. Some become associated with sea slugs where they provide the slug with oxygen and are in turn provided with protection and nutrients. Species of a calcium-rich green algae called Halimeda form the blinding white sand beaches of the Caribbean when they wash up onshore and become bleached by the sun. Another example from this class is Ulva that grows on rocks and wharves as green, leafy-appearing clusters.

Chlorophyta contain structures that are called chloroplasts. Within the chloroplasts two pigments (chlorophyll a and chlorophyll b) are responsible for the conversion of sunlight to chemical energy. The energy is typically stored as starch, and in their cell walls, which are composed of a material called cellulose. The stored material can be used for energy as needed. This process of energy generation is similar to that which occurs in plants. There is an evolutionary basis for this similarity. Available evidence indicates that members of Chlorophyta were the precursors of plants. Chlorophyte fossils date from over one billion years ago, before the development of plants.

See also Photosynthesis

Chlorophyta (green algae) Division of algae which are typically green in colour. In common with higher land plants, green algae include chlorophylls a and b among their principal pigments, have cellulose as the main constituent of cell walls, and form food reserves of starch. Consequently it is believed that the ancestors of land plants must have belonged to this group. The organisms take many forms, ranging from unicellular to relatively complex multicellular plants. They are found today mainly in freshwater habitats and their distribution is cosmopolitan. They are known from the Precambrian onwards, and the earliest eukaryotes were probably of this division. Marine, lime-secreting green algae have contributed to algal limestone reefs since the Cambrian. Fossil genera include Palaeoporella (similar to modern Halimeda), and Coelosphaeridium (similar to modern Acetabularia). See also CHAROPHYCEAE.

green algae Large group of marine and freshwater algae (phylum Chlorophyta). They are distinct from other algae by virtue of possessing cup-shaped chloroplasts that contain chlorophyll b, and by producing cells with flagella at some stage in their lives. Green algae range in size from microscopic single-cell types to large, complex seaweeds. See also lichen

green algae The common name for algae of the division Chlorophyta. Not all members are green; e.g., members of the genera Trentepohlia and Cephaleuros may be orange.

green algae See CHLOROPHYTA.