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Algal
Algae ( , ; : alga ) 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 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. Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhodophyta
Red algae, or Rhodophyta (, ; ), are one of the oldest groups of eukaryotic algae. The Rhodophyta also comprises one of the largest phyla of algae, containing over 7,000 currently recognized species with taxonomic revisions ongoing. The majority of species (6,793) are found in the Florideophyceae ( class), and mostly consist of multicellular, marine algae, including many notable seaweeds. Red algae are abundant in marine habitats but relatively rare in freshwaters. Approximately 5% of red algae species occur in freshwater environments, with greater concentrations found in warmer areas. Except for two coastal cave dwelling species in the asexual class Cyanidiophyceae, there are no terrestrial species, which may be due to an evolutionary bottleneck in which the last common ancestor lost about 25% of its core genes and much of its evolutionary plasticity. The red algae form a distinct group characterized by having eukaryotic cells without flagella and centrioles, chloroplasts th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eukaryotic
Eukaryotes () are organisms whose cells have a nucleus. All animals, plants, fungi, and many unicellular organisms, are Eukaryotes. They belong to the group of organisms Eukaryota or Eukarya, which is one of the three domains of life. Bacteria and Archaea (both prokaryotes) make up the other two domains. The eukaryotes are usually now regarded as having emerged in the Archaea or as a sister of the Asgard archaea. This implies that there are only two domains of life, Bacteria and Archaea, with eukaryotes incorporated among archaea. Eukaryotes represent a small minority of the number of organisms, but, due to their generally much larger size, their collective global biomass is estimated to be about equal to that of prokaryotes. Eukaryotes emerged approximately 2.3–1.8 billion years ago, during the Proterozoic eon, likely as flagellated phagotrophs. Their name comes from the Greek εὖ (''eu'', "well" or "good") and κάρυον (''karyon'', "nut" or "kernel"). E ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cyanobacteria
Cyanobacteria (), also known as Cyanophyta, are a phylum of gram-negative bacteria that obtain energy via photosynthesis. The name ''cyanobacteria'' refers to their color (), which similarly forms the basis of cyanobacteria's common name, blue-green algae, although they are not usually scientifically classified as algae. They appear to have originated in a freshwater or terrestrial environment. Sericytochromatia, the proposed name of the paraphyletic and most basal group, is the ancestor of both the non-photosynthetic group Melainabacteria and the photosynthetic cyanobacteria, also called Oxyphotobacteria. Cyanobacteria use photosynthetic pigments, such as carotenoids, phycobilins, and various forms of chlorophyll, which absorb energy from light. Unlike heterotrophic prokaryotes, cyanobacteria have internal membranes. These are flattened sacs called thylakoids where photosynthesis is performed. Phototrophic eukaryotes such as green plants perform photosynthesis in plasti ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cryptophyta
The cryptophyceae are a class of algae, most of which have plastids. About 220 species are known, and they are common in freshwater, and also occur in marine and brackish habitats. Each cell is around 10–50 μm in size and flattened in shape, with an anterior groove or pocket. At the edge of the pocket there are typically two slightly unequal flagella. Some exhibit mixotrophy. Characteristics Cryptophytes are distinguished by the presence of characteristic extrusomes called ejectosomes or ejectisomes, which consist of two connected spiral ribbons held under tension. If the cells are irritated either by mechanical, chemical or light stress, they discharge, propelling the cell in a zig-zag course away from the disturbance. Large ejectosomes, visible under the light microscope, are associated with the pocket; smaller ones occur underneath the periplast, the cryptophyte-specific cell surrounding. Except for '' Chilomonas'', which has leucoplasts, cryptophytes have one or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Haptophyta
The haptophytes, classified either as the Haptophyta, Haptophytina or Prymnesiophyta (named for '' Prymnesium''), are a clade of algae. The names Haptophyceae or Prymnesiophyceae are sometimes used instead. This ending implies classification at the class rank rather than as a division. Although the phylogenetics of this group has become much better understood in recent years, there remains some dispute over which rank is most appropriate. Characteristics The chloroplasts are pigmented similarly to those of the heterokonts, but the structure of the rest of the cell is different, so it may be that they are a separate line whose chloroplasts are derived from similar red algal endosymbionts. The cells typically have two slightly unequal flagella, both of which are smooth, and a unique organelle called a '' haptonema'', which is superficially similar to a flagellum but differs in the arrangement of microtubules and in its use. The name comes from the Greek ''hapsis'', touch, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Euglenid
Euglenids (euglenoids, or euglenophytes, formally Euglenida/Euglenoida, ICZN, or Euglenophyceae, ICBN) are one of the best-known groups of flagellates, which are excavate eukaryotes of the phylum Euglenophyta and their cell structure is typical of that group. They are commonly found in freshwater, especially when it is rich in organic materials, with a few marine and endosymbiotic members. Many euglenids feed by phagocytosis, or strictly by diffusion. A monophyletic group consisting of the mixotrophic Rapaza viridis (1 species) and the two groups Eutreptiales (24 species) and Euglenales (983 species) have chloroplasts and produce their own food through photosynthesis. This group is known to contain the carbohydrate paramylon. Euglenids split from other Euglenozoa more than a billion years ago. The plastids in all extant photosynthetic species is the result from secondary endosymbiosis between a phagotrophic eukaryovorous euglenid and a Pyramimonas-related green alga. Structu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorarachniophytes
The chlorarachniophytes are a small group of exclusively marine algae widely distributed in tropical and temperate waters. They are typically mixotrophic, ingesting bacteria and smaller protists as well as conducting photosynthesis. Normally they have the form of small amoebae, with branching cytoplasmic extensions that capture prey and connect the cells together, forming a net. They may also form flagellate zoospores, which characteristically have a single subapical flagellum that spirals backwards around the cell body, and walled coccoid cells. The chloroplasts were presumably acquired by ingesting some green alga. They are surrounded by four membranes, the outermost of which is continuous with the endoplasmic reticulum, and contain a small nucleomorph between the middle two, which is a remnant of the alga's nucleus. This contains a small amount of DNA and divides without forming a mitotic spindle. The origin of the chloroplasts from green algae is supported by their ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Glaucophyta
The glaucophytes, also known as glaucocystophytes or glaucocystids, are a small group of unicellular algae found in freshwater and moist terrestrial environments, less common today than they were during the Proterozoic. The stated number of species in the group varies from about 14 to 26. Together with the red algae (Rhodophyta) and the green algae plus land plants ( Viridiplantae or Chloroplastida), they form the Archaeplastida. However, the relationships among the red algae, green algae and glaucophytes are unclear, in large part due to limited study of the glaucophytes. The glaucophytes are of interest to biologists studying the development of chloroplasts because some studies suggest they may be similar to the original algal type that led to green plants and red algae in that glaucophytes may be basal Archaeplastida. Unlike red and green algae, glaucophytes only have asexual reproduction. Characteristics The plastids of glaucophytes are known as 'muroplasts', 'cyanoplas ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Microalgae
Microalgae or microphytes are microscopic algae invisible to the naked eye. They are phytoplankton typically found in freshwater and marine systems, living in both the water column and sediment. They are unicellular species which exist individually, or in chains or groups. Depending on the species, their sizes can range from a few micrometers (μm) to a few hundred micrometers. Unlike higher plants, microalgae do not have roots, stems, or leaves. They are specially adapted to an environment dominated by viscous forces. Microalgae, capable of performing photosynthesis, are important for life on earth; they produce approximately half of the atmospheric oxygen and use the greenhouse gas carbon dioxide to grow photoautotrophically. "Marine photosynthesis is dominated by microalgae, which together with cyanobacteria, are collectively called phytoplankton." Microalgae, together with bacteria, form the base of the food web and provide energy for all the trophic levels above them. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Archaeplastida
The Archaeplastida (or kingdom Plantae '' sensu lato'' "in a broad sense"; pronounced /ɑːrkɪ'plastɪdə/) 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 feeding on 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 cells of the Archaeplastida typically lack centri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chlorophyta
Chlorophyta or Prasinophyta is a taxon of green algae informally called chlorophytes. The name is used in two very different senses, so care is needed to determine the use by a particular author. In older classification systems, it refers to a highly paraphyletic group of ''all'' the green algae within the green plants (Viridiplantae) and thus includes about 7,000 species of mostly aquatic photosynthetic eukaryotic organisms. In newer classifications, it refers to the sister clade of the streptophytes/ charophytes. The clade Streptophyta consists of the Charophyta in which the Embryophyta (land plants) emerged. In this latter sense the Chlorophyta includes only about 4,300 species. About 90% of all known species live in freshwater. Like the land plants ( embryophytes: bryophytes and tracheophytes), green algae (chlorophytes and charophytes besides embryophytes) contain chlorophyll a and chlorophyll b and store food as starch in their plastids. With the exception of Palm ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phaeophyceae
Brown algae (singular: alga), comprising the class Phaeophyceae, are a large group of multicellular algae, including many seaweeds located in colder waters within the Northern Hemisphere. Brown algae are the major seaweeds of the temperate and polar regions. They are dominant on rocky shores throughout cooler areas of the world. Most brown algae live in marine environments, where they play an important role both as food and as a potential habitat. For instance, ''Macrocystis'', a kelp of the order Laminariales, may reach in length and forms prominent underwater kelp forests. Kelp forests like these contain a high level of biodiversity. Another example is ''Sargassum'', which creates unique floating mats of seaweed in the tropical waters of the Sargasso Sea that serve as the habitats for many species. Many brown algae, such as members of the order Fucales, commonly grow along rocky seashores. Some members of the class, such as kelps, are used by humans as food. Between 1,500 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
