Algae is an informal term for a large and diverse group of photosynthetic eukaryotic organisms. It is a polyphyletic grouping that includes species from multiple distinct clades. Included organisms range from unicellular microalgae, such as Chlorella,Prototheca and the diatoms, to multicellular forms, such as the giant kelp, a large brown alga which may grow up to 50 metres (160 ft) in length. Most are aquatic and autotrophic and lack many of the distinct cell and tissue types, such as stomata, xylem and phloem that are found in land plants. The largest and most complex marine algae are called seaweeds, while the most complex freshwater forms are the Charophyta, a division of green algae which includes, for example, Spirogyra and stoneworts.
Alternation of generations is the type of life cycle that occurs in those plants and algae in the Archaeplastida and the Heterokontophyta that have distinct haploid sexual and diploid asexual stages. In these groups, a multicellular haploid gametophyte with n chromosomes alternates with a multicellular diploid sporophyte with 2n chromosomes, made up of n pairs. A mature sporophyte produces haploid spores by meiosis, a process which reduces the number of chromosomes to half, from 2n to n.
Fucus is a genus of brown algae found in the intertidal zones of rocky seashores almost throughout the world.
Ulva lactuca, also known by the common name sea lettuce, is an edible green alga in the family Ulvaceae. It is the type species of the genus Ulva. A synonym is U. fenestrata, referring to its "windowed" or "holed" appearance.
Macrocystis is a monospecific genus of kelp. This genus contains the largest of all the phaeophyceae or brown algae. Macrocystis has pneumatocysts at the base of its blades. Sporophytes are perennial and the individual may live for up to three years; stipes/fronds within a whole individual undergo senescence, where each frond may persist for approximately 100 days. The genus is found widely in subtropical, temperate, and sub-Antarctic oceans of the Southern Hemisphere and in the northeast Pacific from Baja California to Sitka, Alaska. Macrocystis is often a major component of temperate kelp forests.
Codium is a genus of seaweed in the Chlorophyta of the order Bryopsidales. Paul Silva was an expert on the genus Codium taxonomy at the University of California at Berkeley. There are about 50 species worldwide.
The history of phycology is the history of the scientific study of algae. Human interest in plants as food goes back into the origins of the species and knowledge of algae can be traced back more than two thousand years. However, only in the last three hundred years has that knowledge evolved into a rapidly developing science.
Phyllospadix scouleri, or Scouler's surfgrass, is a flowering marine plant in the family Zosteraceae. It is native to the coastline of western North America from the Alaskan panhandle to Baja California.
Polysiphonia is a genus of filamentous red algae with about 19 species on the coasts of the British Isles and about 200 species worldwide, including Crete in Greece, Antarctica and Greenland. Its members are known by a number of common names. It is in the order Ceramiales and family Rhodomelaceae.
Arnoldiella is a genus of green algae in the family Pithophoraceae.
Boodlea is a genus of green algae in the family Boodleaceae.
Bornetella is a genus of green algae in the family Dasycladaceae.
Dangemannia is a genus of green algae in the family Oltmannsiellopsidaceae.
Pabia is a genus of green algae in the order Trebouxiales.
Trentepohlia is a genus of filamentous chlorophyte green algae in the family Trentepohliaceae, living free on terrestrial supports such as tree trunks and wet rocks or symbiotically in lichens. The filaments of Trentepohlia have a strong orange colour caused by the presence of large quantities of carotenoid pigments which mask the green of the chlorophyll.
Calkinsia is a monotypic genus of excavates comprising the single species Calkinsia aureus. It lives in low-oxygen seafloor environments. It is not classified in any of the three well-known groups of the Euglenozoa, but is placed in its own group, the Symbiontida. Some authors have classified Calkinsia alongside Postgaardi, but Postgaardi has not been studied well enough to test this hypothesis.
Cutleria is a genus of brown algae, one of 2–6 genera in the order Cutleriales. AlgaeBase recognises 11 species in the genus.
Braarudosphaera bigelowii is a coastal coccolithophore in the fossil record going back 100 million years. The family Braarudosphaeraceae are single-celled coastal phytoplanktonic algae with calcareous scales with five-fold symmetry, called pentaliths. With 12 sides, it has a regular dodecahedral structure, approximately 10 micrometers across.
Crouania is a genus of red algae (Rhodophyta) in the Callithamniaceae family. The name of the genus honours the French born Crouan brothers, Pierre-Louis Crouan and Hippolyte-Marie Crouan. It was first described by Jacob Georg Agardh in 1842, and the type species is Crouania attenuata.
Champia is a genus of red algae in the family Champiaceae, first described in 1809 by Nicaise Auguste Desvaux
