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In What Ways Do Green Algae Differ From Plants?

There are over 7,000 species of green algae. These organisms are part of a taxonomic group in which some but not all the members descended from a common ancestor. They are also the most diverse group of algae, according to experts at University if California, Berkeley. Once classified as plants, more recent taxonomic classifications recognize significant differences and treat some green algae separately. Because the macroscopic structure of green algae roots, stems and leaves is so different than land plants, it's tempting to distinguish them on that basis. However, for taxonomic purposes, the distinguishing characteristics are on the cellular level.

Cell Structure
- According to Professor W.P. Armstrong at Palomar College, cell structure distinguishes unicellular green algae from plants, which are multicellular. For this reason, unicellular green algae are considered protists, assigned to the Kingdom Protista, and not plants (Kingdom Plantae).
Flagella
- Researchers at the Carnegie Institute note that the possession of flagella, used for movement and the intake of food, is a distinguishing characteristic of Chlamydomonas algae that flowering plants lost in an evolutionary split about 1 billion years ago. They report research that used the genome sequence obtained for Chlamydomonas to show that "... this alga has maintained many genes that were lost during the evolution of land plants," providing further support for recent taxonomic trends that separate some green algae from plants.
Protists
- Both plants and green algae belong to the larger group of living organisms that possess eukaryotic cells (those with true nuclei). Unlike plants, however, it is possible for protists, such as euglena, to share properties with both plants and animals, making modern classification a point of debate among scholars who once classified all algae as plants.
Lack of Common Characteristics
- According to U.C. Berkeley, protists are sometimes distinguished from plants by characteristics that are absent. For example, protists lack the complexity of embryonic development that is observed in plants.
Other Living Organisms
- According to Dr. M.J. Farabee of Estrella Mountain Community College, Arizona, a distinguishing characteristic between algae and other living organisms is that while plants, animals and fungi are eukaryotic and multicellular, algae are eukaryotic and both multicellular and unicellular.

Nature