Algae are any of a large and diverse group of photosynthetic, eukaryotic organisms. The name is an informal term for 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 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. Algae that are carried by water are plankton, specifically phytoplankton.
A chloroplast is a type of membrane-bound organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. The photosynthetic pigment chlorophyll captures the energy from sunlight, converts it, and stores it in the energy-storage molecules ATP and NADPH while freeing oxygen from water in the cells. The ATP and NADPH is then used to make organic molecules from carbon dioxide in a process known as the Calvin cycle. Chloroplasts carry out a number of other functions, including fatty acid synthesis, amino acid synthesis, and the immune response in plants. The number of chloroplasts per cell varies from one, in unicellular algae, up to 100 in plants like Arabidopsis and wheat.
Euglena is a genus of single cell flagellate eukaryotes. It is the best known and most widely studied member of the class Euglenoidea, a diverse group containing some 54 genera and at least 200 species. Species of Euglena are found in fresh water and salt water. They are often abundant in quiet inland waters where they may bloom in numbers sufficient to color the surface of ponds and ditches green (E. viridis) or red (E. sanguinea).
Chlamydomonas is a genus of green algae consisting of about 150 species of unicellular flagellates, found in stagnant water and on damp soil, in freshwater, seawater, and even in snow as "snow algae". Chlamydomonas is used as a model organism for molecular biology, especially studies of flagellar motility and chloroplast dynamics, biogenesis, and genetics. One of the many striking features of Chlamydomonas is that it contains ion channels (channelrhodopsins) that are directly activated by light. Some regulatory systems of Chlamydomonas are more complex than their homologs in Gymnosperms, with evolutionarily related regulatory proteins being larger and containing additional domains.
Bivalvia, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class of marine and freshwater molluscs that have laterally compressed bodies enclosed by a shell consisting of two hinged parts. As a group, bivalves have no head and they lack some usual molluscan organs, like the radula and the odontophore. The class includes the clams, oysters, cockles, mussels, scallops, and numerous other families that live in saltwater, as well as a number of families that live in freshwater. The majority are filter feeders. The gills have evolved into ctenidia, specialised organs for feeding and breathing. Most bivalves bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other hard surfaces. Some bivalves, such as the scallops and file shells, can swim. Shipworms bore into wood, clay, or stone and live inside these substances.
Chlamydomonas reinhardtii is a single-cell green alga about 10 micrometres in diameter that swims with two flagella. It has a cell wall made of hydroxyproline-rich glycoproteins, a large cup-shaped chloroplast, a large pyrenoid, and an eyespot that senses light.
Sacoglossa, commonly known as the sacoglossans or the "solar-powered sea slugs", are a superorder of small sea slugs and sea snails, marine gastropod mollusks that belong to the clade Heterobranchia. Sacoglossans live by ingesting the cellular contents of algae, hence they are sometimes called "sap-sucking sea slugs".
The Archaeplastida are a major group of eukaryotes, comprising the photoautotrophic red algae (Rhodophyta), green algae, land plants, and the minor group glaucophytes. It also includes the non-photosynthetic lineage Rhodelphidia, a predatorial (eukaryotrophic) flagellate that is sister to the Rhodophyta, and probably the microscopic picozoans. The Archaeplastida have chloroplasts that are surrounded by two membranes, suggesting that they were acquired directly through a single endosymbiosis event by phagocytosis of a cyanobacterium. All other groups which have chloroplasts, besides the amoeboid genus Paulinella, have chloroplasts surrounded by three or four membranes, suggesting they were acquired secondarily from red or green algae. Unlike red and green algae, glaucophytes have never been involved in secondary endosymbiosis events.
The Unionidae are a family of freshwater mussels, the largest in the order Unionida, the bivalve molluscs sometimes known as river mussels, or simply as unionids.
Tetraselmis is a genus of phytoplankton. Tetraselmis is a green algal genus within the order Chlorodendrales, and they are characterized by their intensely-colored green chloroplast, their flagellated cell bodies, the presence of a pyrenoid within the chloroplast, and a scale-produced thecal-wall. Species within this genus are found in both marine and freshwater ecosystems across the globe; their habitat range is mainly limited by water depth due to their photosynthetic nature. Thus, they live in diverse water environments if enough nutrients and light are available for net photosynthetic activity. Tetraselmis species have proven to be useful for both research and industry. Tetraselmis species have been studied for understanding plankton growth rates, and recently a colonial species is being used to gain an understanding of multicellularity evolution. Additionally, many species are currently being examined for their use as biofuels due to their high lipid content.
Dunaliella is a single-celled, photosynthetic green alga, that is characteristic for its ability to outcompete other organisms and thrive in hypersaline environments. It is mostly a marine organism, though there are a few freshwater species that tend to be more rare. It is a genus in which certain species can accumulate relatively large amounts of β-carotenoids and glycerol in very harsh growth conditions consisting of high light intensities, high salt concentrations, and limited oxygen and nitrogen levels, yet is still very abundant in lakes and lagoons all around the world.
Dictyochloropsis is a genus of unicellular green alga of the phylum Chlorophyta. This genus consists of free-living algae which have a reticulate (net-like) chloroplast that varies slightly in morphology between species, and that when mature always lacks a pyrenoid. Dictyochloropsis is asexual and reproduces using autospores.
Neochloris is a genus of green algae in the family Neochloridaceae. It is found in freshwater aquatic and terrestrial soil habitats.
Trebouxia is a unicellular green alga. It is a photosynthetic organism that can exist in almost all habitats found in polar, tropical, and temperate regions. It can either exist in a symbiotic relationship with fungi in the form of lichen or it can survive independently as a free-living organism alone or in colonies. Trebouxia is the most common photobiont in extant lichens. It is a primary producer of marine, freshwater and terrestrial ecosystems. It uses carotenoids and chlorophyll a and b to harvest energy from the sun and provide nutrients to various animals and insects.
Coccomyxa is a genus of green algae in the family Coccomyxaceae. This genus is defined by their small, elliptical to spherical shape, and the presence of a simple parietal chloroplast. These features, along with their occurrence in various lifestyles such as free-living, parasitic, or as photobionts, have been used to identify more than 40 species. Using additional morphological features, such as brown akinetes formation, allows for the differentiation between Coccomyxa and the genus Pseudococcomyxa, as they tend to share some morphological characteristics like the general cell shape and one-sided mucilage cap. Recent molecular analysis, however, indicates that the genus Pseudococcomyxa is contained within different Coccomyxa clades, signaling the fact that the two genera are the same. Coccomyxa has often been used as a model organism, and its genome is being completely sequenced. The genus is also an attractive candidate for biofuels.
Algae fuel, algal biofuel, or algal oil is an alternative to liquid fossil fuels that uses algae as its source of energy-rich oils. Also, algae fuels are an alternative to commonly known biofuel sources, such as corn and sugarcane. When made from seaweed (macroalgae) it can be known as seaweed fuel or seaweed oil.
Rhodomonas is a genus of cryptomonads. It is characterized by its red colour, the square-shaped plates of its inner periplast, its short furrow ending in a gullet, and a distinctly shaped chloroplast closely associated with its nucleomorph. Historically, Rhodomonas was characterized by its red chloroplast alone, but this no longer occurs as its taxonomy has become increasingly based on molecular and cellular data. Currently, there is some debate about the taxonomic validity of Rhodomonas as a genus and further research is needed to verify its taxonomic status. Rhodomonas is typically found in marine environments, although freshwater reports exist. It is commonly used as a live feed for various aquaculture species.
Nannochloropsis is a genus of algae comprising six known species. The genus in the current taxonomic classification was first termed by Hibberd (1981). The species have mostly been known from the marine environment but also occur in fresh and brackish water. All of the species are small, nonmotile spheres which do not express any distinct morphological features that can be distinguished by either light or electron microscopy. The characterisation is mostly done by rbcL gene and 18S rRNA sequence analysis.
Dinophysis is a genus of dinoflagellates common in tropical, temperate, coastal and oceanic waters. It was first described in 1839 by Christian Gottfried Ehrenberg.
Thalassiosira is a genus of centric diatoms, comprising over 100 marine and freshwater species. It is a diverse group of photosynthetic eukaryotes that make up a vital part of marine and freshwater ecosystems, in which they are key primary producers and essential for carbon cycling
