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wiki20220301en000_2100	Ada	Computer science Ada (programming language), programming language based on Pascal Ada (computer virus) Air travel Ada Air, a regional airline based in Tirana, Albania Ada International Airport or Saipan International Airport, Saipan Island, Northern Mariana Islands Aerolínea de Antioquia, a Colombian airline Airline Deregulation Act, a 1978 US bill removing governmental control from commercial aviation Schools Ada, the National College for Digital Skills, a further education college in Tottenham Hale, London Ada High School (Ohio), Ada, Ohio Ada High School (Oklahoma), Ada, Oklahoma People Ada (name), a feminine given name and a surname, including a list of people and fictional characters Ada Lovelace (1815–1852), computer scientist sometimes regarded as the first computer programmer	Ada. Computer science Ada (programming language), programming language based on Pascal Ada (computer virus) Air travel Ada Air, a regional airline based in Tirana, Albania Ada International Airport or Saipan International Airport, Saipan Island, Northern Mariana Islands Aerolínea de Antioquia, a Colombian airline Airline Deregulation Act, a 1978 US bill removing governmental control from commercial aviation Schools Ada, the National College for Digital Skills, a further education college in Tottenham Hale, London Ada High School (Ohio), Ada, Ohio Ada High School (Oklahoma), Ada, Oklahoma People Ada (name), a feminine given name and a surname, including a list of people and fictional characters Ada Lovelace (1815–1852), computer scientist sometimes regarded as the first computer programmer	630
wiki20220301en000_2101	Ada	Other uses List of tropical storms named Ada Ada (food), a traditional Kerala delicacy Ada, the cryptocurrency of the Cardano blockchain platform Ada Bridge, Belgrade, Serbia , a cargo vessel built for the London and South Western Railway Ada (ship), a wooden ketch, wrecked near Newcastle, New South Wales, Australia Ada or Ardor: A Family Chronicle, novel by Vladimir Nabokov Dangme language, spoken in Ghana (ISO 639-2 and 639-3 code "ada") Ada Health GmbH, a symptom checker app See also ADA (disambiguation) Ada regulon, an Escherichia coli adaptive response protein Adah (disambiguation) Adha (disambiguation) Ada'a, a woreda in the Oromia Region of Ethiopia Ade (disambiguation) USS Little Ada (1864), a steamer captured by the Union Navy during the American Civil War	Ada. Other uses List of tropical storms named Ada Ada (food), a traditional Kerala delicacy Ada, the cryptocurrency of the Cardano blockchain platform Ada Bridge, Belgrade, Serbia , a cargo vessel built for the London and South Western Railway Ada (ship), a wooden ketch, wrecked near Newcastle, New South Wales, Australia Ada or Ardor: A Family Chronicle, novel by Vladimir Nabokov Dangme language, spoken in Ghana (ISO 639-2 and 639-3 code "ada") Ada Health GmbH, a symptom checker app See also ADA (disambiguation) Ada regulon, an Escherichia coli adaptive response protein Adah (disambiguation) Adha (disambiguation) Ada'a, a woreda in the Oromia Region of Ethiopia Ade (disambiguation) USS Little Ada (1864), a steamer captured by the Union Navy during the American Civil War	630
wiki20220301en000_2102	Aberdeen (disambiguation)	Aberdeen is a city in Scotland, United Kingdom. Aberdeen may also refer to: Places Africa Aberdeen, Sierra Leone Aberdeen, Eastern Cape, South Africa Asia Hong Kong Aberdeen, Hong Kong, an area and town on southwest Hong Kong Island Aberdeen Channel, a channel between Ap Lei Chau (Aberdeen Island) and Nam Long Shan on the Hong Kong Island in Hong Kong Aberdeen Country Park, a country park in Hong Kong Island Aberdeen floating village, at Aberdeen Harbour, containing approximately 600 junks, which house an estimated 6,000 people Aberdeen Harbour, a harbour between Aberdeen, Hong Kong and Ap Lei Chau (Aberdeen Island) Aberdeen Tunnel, a tunnel in Hong Kong Island Aberdeen Tunnel Underground Laboratory, an underground particle physics laboratory in Hong Kong Island Ap Lei Chau or Aberdeen Island, an island of Hong Kong Aberdeen (constituency), a constituency of Southern District Council India Aberdeen Bazaar, a shopping centre in Port Blair, South Andaman Island	Aberdeen (disambiguation). Aberdeen is a city in Scotland, United Kingdom. Aberdeen may also refer to: Places Africa Aberdeen, Sierra Leone Aberdeen, Eastern Cape, South Africa Asia Hong Kong Aberdeen, Hong Kong, an area and town on southwest Hong Kong Island Aberdeen Channel, a channel between Ap Lei Chau (Aberdeen Island) and Nam Long Shan on the Hong Kong Island in Hong Kong Aberdeen Country Park, a country park in Hong Kong Island Aberdeen floating village, at Aberdeen Harbour, containing approximately 600 junks, which house an estimated 6,000 people Aberdeen Harbour, a harbour between Aberdeen, Hong Kong and Ap Lei Chau (Aberdeen Island) Aberdeen Tunnel, a tunnel in Hong Kong Island Aberdeen Tunnel Underground Laboratory, an underground particle physics laboratory in Hong Kong Island Ap Lei Chau or Aberdeen Island, an island of Hong Kong Aberdeen (constituency), a constituency of Southern District Council India Aberdeen Bazaar, a shopping centre in Port Blair, South Andaman Island	632
wiki20220301en000_2103	Aberdeen (disambiguation)	India Aberdeen Bazaar, a shopping centre in Port Blair, South Andaman Island Sri Lanka Aberdeen Falls, a waterfall in Sri Lanka Australia Aberdeen, New South Wales Aberdeen, South Australia, one of the early townships that merged in 1940 to create the town of Burra Aberdeen, Tasmania, a suburb of the City of Devonport Caribbean Aberdeen, Jamaica, a town in Saint Elizabeth, Jamaica Europe Aberdeen (Parliament of Scotland constituency) Aberdeen (UK Parliament constituency) 1832-1885 Aberdeen Burghs (UK Parliament constituency) 1801-1832 Aberdeen Central (Scottish Parliament constituency) Aberdeen Central (UK Parliament constituency) Aberdeen Donside (Scottish Parliament constituency) County of Aberdeen, a historic county of Scotland whose county town was Aberdeen Old Aberdeen, a part of the city of Aberdeen in Scotland North America	Aberdeen (disambiguation). India Aberdeen Bazaar, a shopping centre in Port Blair, South Andaman Island Sri Lanka Aberdeen Falls, a waterfall in Sri Lanka Australia Aberdeen, New South Wales Aberdeen, South Australia, one of the early townships that merged in 1940 to create the town of Burra Aberdeen, Tasmania, a suburb of the City of Devonport Caribbean Aberdeen, Jamaica, a town in Saint Elizabeth, Jamaica Europe Aberdeen (Parliament of Scotland constituency) Aberdeen (UK Parliament constituency) 1832-1885 Aberdeen Burghs (UK Parliament constituency) 1801-1832 Aberdeen Central (Scottish Parliament constituency) Aberdeen Central (UK Parliament constituency) Aberdeen Donside (Scottish Parliament constituency) County of Aberdeen, a historic county of Scotland whose county town was Aberdeen Old Aberdeen, a part of the city of Aberdeen in Scotland North America	632
wiki20220301en000_2104	Aberdeen (disambiguation)	North America Canada Aberdeen, community in the township of Champlain, Prescott and Russell County, Ontario Aberdeen, Abbotsford, a neighbourhood in the City of Abbotsford, British Columbia Aberdeen Centre, a shopping mall in Richmond, British Columbia Aberdeen, Grey County, Ontario Aberdeen, Kamloops, an area in the City of Kamloops, British Columbia Aberdeen Lake (Nunavut), a lake in Kivalliq Region, Nunavut, Canada Aberdeen, Nova Scotia, part of the Municipality of Inverness County, Nova Scotia Aberdeen Parish, New Brunswick Rural Municipality of Aberdeen No. 373, Saskatchewan Aberdeen, Saskatchewan Aberdeen Bay, a bay between southern Baffin Island and north-eastern Hector Island in the Nunavut territory Aberdeen Township, Quebec, until 1960 part of Sheen-Esher-Aberdeen-et-Malakoff, now part of Rapides-des-Joachims, Quebec Aberdeen River, a tributary of rivière aux Castors Noirs in Mauricie, Québec New Aberdeen, Nova Scotia	Aberdeen (disambiguation). North America Canada Aberdeen, community in the township of Champlain, Prescott and Russell County, Ontario Aberdeen, Abbotsford, a neighbourhood in the City of Abbotsford, British Columbia Aberdeen Centre, a shopping mall in Richmond, British Columbia Aberdeen, Grey County, Ontario Aberdeen, Kamloops, an area in the City of Kamloops, British Columbia Aberdeen Lake (Nunavut), a lake in Kivalliq Region, Nunavut, Canada Aberdeen, Nova Scotia, part of the Municipality of Inverness County, Nova Scotia Aberdeen Parish, New Brunswick Rural Municipality of Aberdeen No. 373, Saskatchewan Aberdeen, Saskatchewan Aberdeen Bay, a bay between southern Baffin Island and north-eastern Hector Island in the Nunavut territory Aberdeen Township, Quebec, until 1960 part of Sheen-Esher-Aberdeen-et-Malakoff, now part of Rapides-des-Joachims, Quebec Aberdeen River, a tributary of rivière aux Castors Noirs in Mauricie, Québec New Aberdeen, Nova Scotia	632
wiki20220301en000_2105	Aberdeen (disambiguation)	United States Aberdeen, Arkansas Aberdeen, Florida Aberdeen, Georgia Aberdeen, Idaho Aberdeen, Ohio County, Indiana Aberdeen, Porter County, Indiana Aberdeen, Kentucky Aberdeen, Maryland Aberdeen Proving Ground, a United States Army facility located near Aberdeen, Maryland Aberdeen, Massachusetts, a neighborhood of Brighton, Boston Aberdeen, Mississippi Aberdeen Lake (Mississippi), a lake in northeast Mississippi on the Tennessee-Tombigbee Waterway, close to Aberdeen, Mississippi Aberdeen Township, New Jersey Aberdeen, North Carolina Aberdeen Historic District (Aberdeen, North Carolina) Aberdeen, Ohio Aberdeen, South Dakota Aberdeen Historic District (Aberdeen, South Dakota) Aberdeen, Texas Aberdeen (Disputanta, Virginia) Aberdeen Gardens (Hampton, Virginia) Aberdeen, Washington Aberdeen Gardens, Washington Aberdeen, West Virginia Business Abrdn, formerly Standard Life Aberdeen Aberdeen Asset Management	Aberdeen (disambiguation). United States Aberdeen, Arkansas Aberdeen, Florida Aberdeen, Georgia Aberdeen, Idaho Aberdeen, Ohio County, Indiana Aberdeen, Porter County, Indiana Aberdeen, Kentucky Aberdeen, Maryland Aberdeen Proving Ground, a United States Army facility located near Aberdeen, Maryland Aberdeen, Massachusetts, a neighborhood of Brighton, Boston Aberdeen, Mississippi Aberdeen Lake (Mississippi), a lake in northeast Mississippi on the Tennessee-Tombigbee Waterway, close to Aberdeen, Mississippi Aberdeen Township, New Jersey Aberdeen, North Carolina Aberdeen Historic District (Aberdeen, North Carolina) Aberdeen, Ohio Aberdeen, South Dakota Aberdeen Historic District (Aberdeen, South Dakota) Aberdeen, Texas Aberdeen (Disputanta, Virginia) Aberdeen Gardens (Hampton, Virginia) Aberdeen, Washington Aberdeen Gardens, Washington Aberdeen, West Virginia Business Abrdn, formerly Standard Life Aberdeen Aberdeen Asset Management	632
wiki20220301en000_2106	Aberdeen (disambiguation)	Business Abrdn, formerly Standard Life Aberdeen Aberdeen Asset Management Education Aberdeen Business School Aberdeen College, formerly one of the largest further education colleges in Scotland, merged with Banff & Buchan College to form North East Scotland College Aberdeen Grammar School, Aberdeen, Scotland Aberdeen Hall, a university-preparatory school in Kelowna, British Columbia, Canada Aberdeen High School (disambiguation) King's College, Aberdeen University of Aberdeen, a public research university in the city of Aberdeen Entertainment Aberdeen (2000 film), a 2000 Norwegian-British film directed by Hans Petter Moland, starring Stellan Skarsgård and Lena Headey Aberdeen (2014 film), a 2014 Hong Kong film starring Louis Koo Aberdeen (band), an American rock band Aberdeen (song), a song by Cage The Elephant Aberdeen City (band), Boston based indie/alternative rock band	Aberdeen (disambiguation). Business Abrdn, formerly Standard Life Aberdeen Aberdeen Asset Management Education Aberdeen Business School Aberdeen College, formerly one of the largest further education colleges in Scotland, merged with Banff & Buchan College to form North East Scotland College Aberdeen Grammar School, Aberdeen, Scotland Aberdeen Hall, a university-preparatory school in Kelowna, British Columbia, Canada Aberdeen High School (disambiguation) King's College, Aberdeen University of Aberdeen, a public research university in the city of Aberdeen Entertainment Aberdeen (2000 film), a 2000 Norwegian-British film directed by Hans Petter Moland, starring Stellan Skarsgård and Lena Headey Aberdeen (2014 film), a 2014 Hong Kong film starring Louis Koo Aberdeen (band), an American rock band Aberdeen (song), a song by Cage The Elephant Aberdeen City (band), Boston based indie/alternative rock band	632
wiki20220301en000_2107	Aberdeen (disambiguation)	Other transportation Aberdeen Airport (disambiguation) Aberdeen Lock and Dam, one of four lock and dam structures on the Tennessee-Tombigbee Waterway Rail Aberdeen, Carolina and Western Railway, a short-line railroad operating in North Carolina Aberdeen and Rockfish Railroad, a short-line railroad operating in North Carolina Aberdeen Corporation Tramways Aberdeen Line (disambiguation) Aberdeen station (disambiguation) Dundee and Perth and Aberdeen Junction Railway, a later name of the Dundee and Perth Railway Shipping Aberdeen Line, a British shipping company founded in 1825 , one of several ships by that name , a sloop of the British Royal Navy that served between 1936 and 1948 , a merchant ship operated during the latter stages of World War II, later commissioned as the USS Altair	Aberdeen (disambiguation). Other transportation Aberdeen Airport (disambiguation) Aberdeen Lock and Dam, one of four lock and dam structures on the Tennessee-Tombigbee Waterway Rail Aberdeen, Carolina and Western Railway, a short-line railroad operating in North Carolina Aberdeen and Rockfish Railroad, a short-line railroad operating in North Carolina Aberdeen Corporation Tramways Aberdeen Line (disambiguation) Aberdeen station (disambiguation) Dundee and Perth and Aberdeen Junction Railway, a later name of the Dundee and Perth Railway Shipping Aberdeen Line, a British shipping company founded in 1825 , one of several ships by that name , a sloop of the British Royal Navy that served between 1936 and 1948 , a merchant ship operated during the latter stages of World War II, later commissioned as the USS Altair	632
wiki20220301en000_2108	Aberdeen (disambiguation)	Sports Aberdeen Dad Vail Regatta, the largest regular intercollegiate rowing event in the United States, named after its sponsor, Aberdeen Asset Management Aberdeen F.C. (disambiguation) Aberdeen GSFP RFC, an amateur rugby union club based in Aberdeen Aberdeen IronBirds, a minor league baseball team affiliated with the Baltimore Orioles Aberdeen L.F.C., a women's football team affiliated with Aberdeen F.C. See also Aberdeen Act Aberdeen Angus, a Scottish breed of small beef cattle Aberdeen Central (disambiguation) Aberdeen Gardens (disambiguation) Aberdeen Historic District (disambiguation) Aberdeen Hospital (disambiguation) Aberdeen Quarry, a granite quarry in Colorado Battle of Aberdeen (disambiguation) Diocese of Aberdeen and Orkney, one of the seven dioceses of the Scottish Episcopal Church Etymology of Aberdeen Marquess of Aberdeen and Temair, a title in the Peerage of the United Kingdom	Aberdeen (disambiguation). Sports Aberdeen Dad Vail Regatta, the largest regular intercollegiate rowing event in the United States, named after its sponsor, Aberdeen Asset Management Aberdeen F.C. (disambiguation) Aberdeen GSFP RFC, an amateur rugby union club based in Aberdeen Aberdeen IronBirds, a minor league baseball team affiliated with the Baltimore Orioles Aberdeen L.F.C., a women's football team affiliated with Aberdeen F.C. See also Aberdeen Act Aberdeen Angus, a Scottish breed of small beef cattle Aberdeen Central (disambiguation) Aberdeen Gardens (disambiguation) Aberdeen Historic District (disambiguation) Aberdeen Hospital (disambiguation) Aberdeen Quarry, a granite quarry in Colorado Battle of Aberdeen (disambiguation) Diocese of Aberdeen and Orkney, one of the seven dioceses of the Scottish Episcopal Church Etymology of Aberdeen Marquess of Aberdeen and Temair, a title in the Peerage of the United Kingdom	632
wiki20220301en000_2109	Algae	Algae (; singular alga ) 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 in length. Most are aquatic and autotrophic (they generate food internally) 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. Algae (; singular alga ) 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 in length. Most are aquatic and autotrophic (they generate food internally) 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.	633
wiki20220301en000_2110	Algae	No definition of algae is generally accepted. One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". Likewise, the colorless Prototheca under Chlorophyta are all devoid of any chlorophyll. Although cyanobacteria are often referred to as "blue-green algae", most authorities exclude all prokaryotes from the definition of algae. Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction.	Algae. No definition of algae is generally accepted. One definition is that algae "have chlorophyll as their primary photosynthetic pigment and lack a sterile covering of cells around their reproductive cells". Likewise, the colorless Prototheca under Chlorophyta are all devoid of any chlorophyll. Although cyanobacteria are often referred to as "blue-green algae", most authorities exclude all prokaryotes from the definition of algae. Algae constitute a polyphyletic group since they do not include a common ancestor, and although their plastids seem to have a single origin, from cyanobacteria, they were acquired in different ways. Green algae are examples of algae that have primary chloroplasts derived from endosymbiotic cyanobacteria. Diatoms and brown algae are examples of algae with secondary chloroplasts derived from an endosymbiotic red alga. Algae exhibit a wide range of reproductive strategies, from simple asexual cell division to complex forms of sexual reproduction.	633
wiki20220301en000_2111	Algae	Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytes, rhizoids of nonvascular plants, and the roots, leaves, and other organs found in tracheophytes (vascular plants). Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, such as the apicomplexans, are also derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of	Algae. Algae lack the various structures that characterize land plants, such as the phyllids (leaf-like structures) of bryophytes, rhizoids of nonvascular plants, and the roots, leaves, and other organs found in tracheophytes (vascular plants). Most are phototrophic, although some are mixotrophic, deriving energy both from photosynthesis and uptake of organic carbon either by osmotrophy, myzotrophy, or phagotrophy. Some unicellular species of green algae, many golden algae, euglenids, dinoflagellates, and other algae have become heterotrophs (also called colorless or apochlorotic algae), sometimes parasitic, relying entirely on external energy sources and have limited or no photosynthetic apparatus. Some other heterotrophic organisms, such as the apicomplexans, are also derived from cells whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of	633
wiki20220301en000_2112	Algae	whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago.	Algae. whose ancestors possessed plastids, but are not traditionally considered as algae. Algae have photosynthetic machinery ultimately derived from cyanobacteria that produce oxygen as a by-product of photosynthesis, unlike other photosynthetic bacteria such as purple and green sulfur bacteria. Fossilized filamentous algae from the Vindhya basin have been dated back to 1.6 to 1.7 billion years ago.	633
wiki20220301en000_2113	Algae	Because of the wide range of types of algae, they have increasing different industrial and traditional applications in human society. Traditional seaweed farming practices have existed for thousands of years and have strong traditions in East Asia food cultures. More modern algaculture applications extend the food traditions for other applications include cattle feed, using algae for bioremediation or pollution control, transforming sunlight into algae fuels or other chemicals used in industrial processes, and in medical and scientific applications. A 2020 review, found that these applications of algae could play an important role in carbon sequestration in order to mitigate climate change while providing valuable value-add products for global economies.	Algae. Because of the wide range of types of algae, they have increasing different industrial and traditional applications in human society. Traditional seaweed farming practices have existed for thousands of years and have strong traditions in East Asia food cultures. More modern algaculture applications extend the food traditions for other applications include cattle feed, using algae for bioremediation or pollution control, transforming sunlight into algae fuels or other chemicals used in industrial processes, and in medical and scientific applications. A 2020 review, found that these applications of algae could play an important role in carbon sequestration in order to mitigate climate change while providing valuable value-add products for global economies.	633
wiki20220301en000_2114	Algae	Etymology and study The singular is the Latin word for 'seaweed' and retains that meaning in English. The etymology is obscure. Although some speculate that it is related to Latin , 'be cold', no reason is known to associate seaweed with temperature. A more likely source is , 'binding, entwining'. The Ancient Greek word for 'seaweed' was (), which could mean either the seaweed (probably red algae) or a red dye derived from it. The Latinization, , meant primarily the cosmetic rouge. The etymology is uncertain, but a strong candidate has long been some word related to the Biblical (), 'paint' (if not that word itself), a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean. It could be any color: black, red, green, or blue. Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name fucus appears in a number of taxa.	Algae. Etymology and study The singular is the Latin word for 'seaweed' and retains that meaning in English. The etymology is obscure. Although some speculate that it is related to Latin , 'be cold', no reason is known to associate seaweed with temperature. A more likely source is , 'binding, entwining'. The Ancient Greek word for 'seaweed' was (), which could mean either the seaweed (probably red algae) or a red dye derived from it. The Latinization, , meant primarily the cosmetic rouge. The etymology is uncertain, but a strong candidate has long been some word related to the Biblical (), 'paint' (if not that word itself), a cosmetic eye-shadow used by the ancient Egyptians and other inhabitants of the eastern Mediterranean. It could be any color: black, red, green, or blue. Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name fucus appears in a number of taxa.	633
wiki20220301en000_2115	Algae	Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name fucus appears in a number of taxa. Classifications The committee on the International Code of Botanical Nomenclature has recommended certain suffixes for use in the classification of algae. These are -phyta for division, -phyceae for class, -phycideae for subclass, -ales for order, -inales for suborder, -aceae for family, -oidease for subfamily, a Greek-based name for genus, and a Latin-based name for species. Algal characteristics basic to primary classification	Algae. Accordingly, the modern study of marine and freshwater algae is called either phycology or algology, depending on whether the Greek or Latin root is used. The name fucus appears in a number of taxa. Classifications The committee on the International Code of Botanical Nomenclature has recommended certain suffixes for use in the classification of algae. These are -phyta for division, -phyceae for class, -phycideae for subclass, -ales for order, -inales for suborder, -aceae for family, -oidease for subfamily, a Greek-based name for genus, and a Latin-based name for species. Algal characteristics basic to primary classification	633
wiki20220301en000_2116	Algae	Algal characteristics basic to primary classification The primary classification of algae is based on certain morphological features. The chief among these are (a) pigment constitution of the cell, (b) chemical nature of stored food materials, (c) kind, number, point of insertion and relative length of the flagella on the motile cell, (d) chemical composition of cell wall and (e) presence or absence of a definitely organized nucleus in the cell or any other significant details of cell structure. History of classification of algae Although Carolus Linnaeus (1754) included algae along with lichens in his 25th class Cryptogamia, he did not elaborate further on the classification of algae.	Algae. Algal characteristics basic to primary classification The primary classification of algae is based on certain morphological features. The chief among these are (a) pigment constitution of the cell, (b) chemical nature of stored food materials, (c) kind, number, point of insertion and relative length of the flagella on the motile cell, (d) chemical composition of cell wall and (e) presence or absence of a definitely organized nucleus in the cell or any other significant details of cell structure. History of classification of algae Although Carolus Linnaeus (1754) included algae along with lichens in his 25th class Cryptogamia, he did not elaborate further on the classification of algae.	633
wiki20220301en000_2117	Algae	Jean Pierre Étienne Vaucher (1803) was perhaps the first to propose a system of classification of algae, and he recognized three groups, Conferves, Ulves, and Tremelles. While Johann Heinrich Friedrich Link (1820) classified algae on the basis of the colour of the pigment and structure, William Henry Harvey (1836) proposed a system of classification on the basis of the habitat and the pigment. J. G. Agardh (1849–1898) divided algae into six orders: Diatomaceae, Nostochineae, Confervoideae, Ulvaceae, Floriadeae and Fucoideae. Around 1880, algae along with fungi were grouped under Thallophyta, a division created by Eichler (1836). Encouraged by this, Adolf Engler and Karl A. E. Prantl (1912) proposed a revised scheme of classification of algae and included fungi in algae as they were of opinion that fungi have been derived from algae. The scheme proposed by Engler and Prantl is summarised as follows:	Algae. Jean Pierre Étienne Vaucher (1803) was perhaps the first to propose a system of classification of algae, and he recognized three groups, Conferves, Ulves, and Tremelles. While Johann Heinrich Friedrich Link (1820) classified algae on the basis of the colour of the pigment and structure, William Henry Harvey (1836) proposed a system of classification on the basis of the habitat and the pigment. J. G. Agardh (1849–1898) divided algae into six orders: Diatomaceae, Nostochineae, Confervoideae, Ulvaceae, Floriadeae and Fucoideae. Around 1880, algae along with fungi were grouped under Thallophyta, a division created by Eichler (1836). Encouraged by this, Adolf Engler and Karl A. E. Prantl (1912) proposed a revised scheme of classification of algae and included fungi in algae as they were of opinion that fungi have been derived from algae. The scheme proposed by Engler and Prantl is summarised as follows:	633
wiki20220301en000_2118	Algae	Schizophyta Phytosarcodina Flagellata Dinoflagellata Bacillariophyta Conjugatae Chlorophyceae Charophyta Phaeophyceae Rhodophyceae Eumycetes (Fungi) The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely. Phylogeny based on plastid not nucleocytoplasmic genealogy:	Algae. Schizophyta Phytosarcodina Flagellata Dinoflagellata Bacillariophyta Conjugatae Chlorophyceae Charophyta Phaeophyceae Rhodophyceae Eumycetes (Fungi) The algae contain chloroplasts that are similar in structure to cyanobacteria. Chloroplasts contain circular DNA like that in cyanobacteria and are interpreted as representing reduced endosymbiotic cyanobacteria. However, the exact origin of the chloroplasts is different among separate lineages of algae, reflecting their acquisition during different endosymbiotic events. The table below describes the composition of the three major groups of algae. Their lineage relationships are shown in the figure in the upper right. Many of these groups contain some members that are no longer photosynthetic. Some retain plastids, but not chloroplasts, while others have lost plastids entirely. Phylogeny based on plastid not nucleocytoplasmic genealogy:	633
wiki20220301en000_2119	Algae	Phylogeny based on plastid not nucleocytoplasmic genealogy: Linnaeus, in Species Plantarum (1753), the starting point for modern botanical nomenclature, recognized 14 genera of algae, of which only four are currently considered among algae. In Systema Naturae, Linnaeus described the genera Volvox and Corallina, and a species of Acetabularia (as Madrepora), among the animals. In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves.	Algae. Phylogeny based on plastid not nucleocytoplasmic genealogy: Linnaeus, in Species Plantarum (1753), the starting point for modern botanical nomenclature, recognized 14 genera of algae, of which only four are currently considered among algae. In Systema Naturae, Linnaeus described the genera Volvox and Corallina, and a species of Acetabularia (as Madrepora), among the animals. In 1768, Samuel Gottlieb Gmelin (1744–1774) published the Historia Fucorum, the first work dedicated to marine algae and the first book on marine biology to use the then new binomial nomenclature of Linnaeus. It included elaborate illustrations of seaweed and marine algae on folded leaves.	633
wiki20220301en000_2120	Algae	W. H. Harvey (1811–1866) and Lamouroux (1813) were the first to divide macroscopic algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae (Rhodospermae), brown algae (Melanospermae), green algae (Chlorospermae), and Diatomaceae. At this time, microscopic algae were discovered and reported by a different group of workers (e.g., O. F. Müller and Ehrenberg) studying the Infusoria (microscopic organisms). Unlike macroalgae, which were clearly viewed as plants, microalgae were frequently considered animals because they are often motile. Even the nonmotile (coccoid) microalgae were sometimes merely seen as stages of the lifecycle of plants, macroalgae, or animals.	Algae. W. H. Harvey (1811–1866) and Lamouroux (1813) were the first to divide macroscopic algae into four divisions based on their pigmentation. This is the first use of a biochemical criterion in plant systematics. Harvey's four divisions are: red algae (Rhodospermae), brown algae (Melanospermae), green algae (Chlorospermae), and Diatomaceae. At this time, microscopic algae were discovered and reported by a different group of workers (e.g., O. F. Müller and Ehrenberg) studying the Infusoria (microscopic organisms). Unlike macroalgae, which were clearly viewed as plants, microalgae were frequently considered animals because they are often motile. Even the nonmotile (coccoid) microalgae were sometimes merely seen as stages of the lifecycle of plants, macroalgae, or animals.	633
wiki20220301en000_2121	Algae	Although used as a taxonomic category in some pre-Darwinian classifications, e.g., Linnaeus (1753), de Jussieu (1789), Horaninow (1843), Agassiz (1859), Wilson & Cassin (1864), in further classifications, the "algae" are seen as an artificial, polyphyletic group. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes. Later, many new groups were discovered (e.g., Bolidophyceae), and others were splintered from older groups: charophytes and glaucophytes (from chlorophytes), many heterokontophytes (e.g., synurophytes from chrysophytes, or eustigmatophytes from xanthophytes), haptophytes (from chrysophytes), and chlorarachniophytes (from xanthophytes).	Algae. Although used as a taxonomic category in some pre-Darwinian classifications, e.g., Linnaeus (1753), de Jussieu (1789), Horaninow (1843), Agassiz (1859), Wilson & Cassin (1864), in further classifications, the "algae" are seen as an artificial, polyphyletic group. Throughout the 20th century, most classifications treated the following groups as divisions or classes of algae: cyanophytes, rhodophytes, chrysophytes, xanthophytes, bacillariophytes, phaeophytes, pyrrhophytes (cryptophytes and dinophytes), euglenophytes, and chlorophytes. Later, many new groups were discovered (e.g., Bolidophyceae), and others were splintered from older groups: charophytes and glaucophytes (from chlorophytes), many heterokontophytes (e.g., synurophytes from chrysophytes, or eustigmatophytes from xanthophytes), haptophytes (from chrysophytes), and chlorarachniophytes (from xanthophytes).	633
wiki20220301en000_2122	Algae	With the abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in Protista, later also abandoned in favour of Eukaryota. However, as a legacy of the older plant life scheme, some groups that were also treated as protozoans in the past still have duplicated classifications (see ambiregnal protists).	Algae. With the abandonment of plant-animal dichotomous classification, most groups of algae (sometimes all) were included in Protista, later also abandoned in favour of Eukaryota. However, as a legacy of the older plant life scheme, some groups that were also treated as protozoans in the past still have duplicated classifications (see ambiregnal protists).	633
wiki20220301en000_2123	Algae	Some parasitic algae (e.g., the green algae Prototheca and Helicosporidium, parasites of metazoans, or Cephaleuros, parasites of plants) were originally classified as fungi, sporozoans, or protistans of incertae sedis, while others (e.g., the green algae Phyllosiphon and Rhodochytrium, parasites of plants, or the red algae Pterocladiophila and Gelidiocolax mammillatus, parasites of other red algae, or the dinoflagellates Oodinium, parasites of fish) had their relationship with algae conjectured early. In other cases, some groups were originally characterized as parasitic algae (e.g., Chlorochytrium), but later were seen as endophytic algae. Some filamentous bacteria (e.g., Beggiatoa) were originally seen as algae. Furthermore, groups like the apicomplexans are also parasites derived from ancestors that possessed plastids, but are not included in any group traditionally seen as algae.	Algae. Some parasitic algae (e.g., the green algae Prototheca and Helicosporidium, parasites of metazoans, or Cephaleuros, parasites of plants) were originally classified as fungi, sporozoans, or protistans of incertae sedis, while others (e.g., the green algae Phyllosiphon and Rhodochytrium, parasites of plants, or the red algae Pterocladiophila and Gelidiocolax mammillatus, parasites of other red algae, or the dinoflagellates Oodinium, parasites of fish) had their relationship with algae conjectured early. In other cases, some groups were originally characterized as parasitic algae (e.g., Chlorochytrium), but later were seen as endophytic algae. Some filamentous bacteria (e.g., Beggiatoa) were originally seen as algae. Furthermore, groups like the apicomplexans are also parasites derived from ancestors that possessed plastids, but are not included in any group traditionally seen as algae.	633
wiki20220301en000_2124	Algae	Relationship to land plants The first land plants probably evolved from shallow freshwater charophyte algae much like Chara almost 500 million years ago. These probably had an isomorphic alternation of generations and were probably filamentous. Fossils of isolated land plant spores suggest land plants may have been around as long as 475 million years ago. Morphology	Algae. Relationship to land plants The first land plants probably evolved from shallow freshwater charophyte algae much like Chara almost 500 million years ago. These probably had an isomorphic alternation of generations and were probably filamentous. Fossils of isolated land plant spores suggest land plants may have been around as long as 475 million years ago. Morphology	633
wiki20220301en000_2125	Algae	Morphology A range of algal morphologies is exhibited, and convergence of features in unrelated groups is common. The only groups to exhibit three-dimensional multicellular thalli are the reds and browns, and some chlorophytes. Apical growth is constrained to subsets of these groups: the florideophyte reds, various browns, and the charophytes. The form of charophytes is quite different from those of reds and browns, because they have distinct nodes, separated by internode 'stems'; whorls of branches reminiscent of the horsetails occur at the nodes. Conceptacles are another polyphyletic trait; they appear in the coralline algae and the Hildenbrandiales, as well as the browns.	Algae. Morphology A range of algal morphologies is exhibited, and convergence of features in unrelated groups is common. The only groups to exhibit three-dimensional multicellular thalli are the reds and browns, and some chlorophytes. Apical growth is constrained to subsets of these groups: the florideophyte reds, various browns, and the charophytes. The form of charophytes is quite different from those of reds and browns, because they have distinct nodes, separated by internode 'stems'; whorls of branches reminiscent of the horsetails occur at the nodes. Conceptacles are another polyphyletic trait; they appear in the coralline algae and the Hildenbrandiales, as well as the browns.	633
wiki20220301en000_2126	Algae	Most of the simpler algae are unicellular flagellates or amoeboids, but colonial and nonmotile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the lifecycle of a species, are Colonial: small, regular groups of motile cells Capsoid: individual non-motile cells embedded in mucilage Coccoid: individual non-motile cells with cell walls Palmelloid: nonmotile cells embedded in mucilage Filamentous: a string of nonmotile cells connected together, sometimes branching Parenchymatous: cells forming a thallus with partial differentiation of tissues	Algae. Most of the simpler algae are unicellular flagellates or amoeboids, but colonial and nonmotile forms have developed independently among several of the groups. Some of the more common organizational levels, more than one of which may occur in the lifecycle of a species, are Colonial: small, regular groups of motile cells Capsoid: individual non-motile cells embedded in mucilage Coccoid: individual non-motile cells with cell walls Palmelloid: nonmotile cells embedded in mucilage Filamentous: a string of nonmotile cells connected together, sometimes branching Parenchymatous: cells forming a thallus with partial differentiation of tissues	633
wiki20220301en000_2127	Algae	In three lines, even higher levels of organization have been reached, with full tissue differentiation. These are the brown algae,—some of which may reach 50 m in length (kelps)—the red algae, and the green algae. The most complex forms are found among the charophyte algae (see Charales and Charophyta), in a lineage that eventually led to the higher land plants. The innovation that defines these nonalgal plants is the presence of female reproductive organs with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the Embryophytes.	Algae. In three lines, even higher levels of organization have been reached, with full tissue differentiation. These are the brown algae,—some of which may reach 50 m in length (kelps)—the red algae, and the green algae. The most complex forms are found among the charophyte algae (see Charales and Charophyta), in a lineage that eventually led to the higher land plants. The innovation that defines these nonalgal plants is the presence of female reproductive organs with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the Embryophytes.	633
wiki20220301en000_2128	Algae	Turfs The term algal turf is commonly used but poorly defined. Algal turfs are thick, carpet-like beds of seaweed that retain sediment and compete with foundation species like corals and kelps, and they are usually less than 15 cm tall. Such a turf may consist of one or more species, and will generally cover an area in the order of a square metre or more. Some common characteristics are listed: Algae that form aggregations that have been described as turfs include diatoms, cyanobacteria, chlorophytes, phaeophytes and rhodophytes. Turfs are often composed of numerous species at a wide range of spatial scales, but monospecific turfs are frequently reported. Turfs can be morphologically highly variable over geographic scales and even within species on local scales and can be difficult to identify in terms of the constituent species.	Algae. Turfs The term algal turf is commonly used but poorly defined. Algal turfs are thick, carpet-like beds of seaweed that retain sediment and compete with foundation species like corals and kelps, and they are usually less than 15 cm tall. Such a turf may consist of one or more species, and will generally cover an area in the order of a square metre or more. Some common characteristics are listed: Algae that form aggregations that have been described as turfs include diatoms, cyanobacteria, chlorophytes, phaeophytes and rhodophytes. Turfs are often composed of numerous species at a wide range of spatial scales, but monospecific turfs are frequently reported. Turfs can be morphologically highly variable over geographic scales and even within species on local scales and can be difficult to identify in terms of the constituent species.	633
wiki20220301en000_2129	Algae	Turfs can be morphologically highly variable over geographic scales and even within species on local scales and can be difficult to identify in terms of the constituent species. Turfs have been defined as short algae, but this has been used to describe height ranges from less than 0.5 cm to more than 10 cm. In some regions, the descriptions approached heights which might be described as canopies (20 to 30 cm).	Algae. Turfs can be morphologically highly variable over geographic scales and even within species on local scales and can be difficult to identify in terms of the constituent species. Turfs have been defined as short algae, but this has been used to describe height ranges from less than 0.5 cm to more than 10 cm. In some regions, the descriptions approached heights which might be described as canopies (20 to 30 cm).	633
wiki20220301en000_2130	Algae	Physiology Many algae, particularly members of the Characeae species, have served as model experimental organisms to understand the mechanisms of the water permeability of membranes, osmoregulation, turgor regulation, salt tolerance, cytoplasmic streaming, and the generation of action potentials. Phytohormones are found not only in higher plants, but in algae, too. Symbiotic algae Some species of algae form symbiotic relationships with other organisms. In these symbioses, the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples are: Lichens	Algae. Physiology Many algae, particularly members of the Characeae species, have served as model experimental organisms to understand the mechanisms of the water permeability of membranes, osmoregulation, turgor regulation, salt tolerance, cytoplasmic streaming, and the generation of action potentials. Phytohormones are found not only in higher plants, but in algae, too. Symbiotic algae Some species of algae form symbiotic relationships with other organisms. In these symbioses, the algae supply photosynthates (organic substances) to the host organism providing protection to the algal cells. The host organism derives some or all of its energy requirements from the algae. Examples are: Lichens	633
wiki20220301en000_2131	Algae	Lichens are defined by the International Association for Lichenology to be "an association of a fungus and a photosynthetic symbiont resulting in a stable vegetative body having a specific structure". The fungi, or mycobionts, are mainly from the Ascomycota with a few from the Basidiomycota. In nature they do not occur separate from lichens. It is unknown when they began to associate. One mycobiont associates with the same phycobiont species, rarely two, from the green algae, except that alternatively, the mycobiont may associate with a species of cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associated with many different mycobionts or may live independently; accordingly, lichens are named and classified as fungal species. The association is termed a morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes	Algae. Lichens are defined by the International Association for Lichenology to be "an association of a fungus and a photosynthetic symbiont resulting in a stable vegetative body having a specific structure". The fungi, or mycobionts, are mainly from the Ascomycota with a few from the Basidiomycota. In nature they do not occur separate from lichens. It is unknown when they began to associate. One mycobiont associates with the same phycobiont species, rarely two, from the green algae, except that alternatively, the mycobiont may associate with a species of cyanobacteria (hence "photobiont" is the more accurate term). A photobiont may be associated with many different mycobionts or may live independently; accordingly, lichens are named and classified as fungal species. The association is termed a morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes	633
wiki20220301en000_2132	Algae	morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont.	Algae. morphogenesis because the lichen has a form and capabilities not possessed by the symbiont species alone (they can be experimentally isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont.	633
wiki20220301en000_2133	Algae	Trentepohlia is an example of a common green alga genus worldwide that can grow on its own or be lichenised. Lichen thus share some of the habitat and often similar appearance with specialized species of algae (aerophytes) growing on exposed surfaces such as tree trunks and rocks and sometimes discoloring them. Coral reefs	Algae. Trentepohlia is an example of a common green alga genus worldwide that can grow on its own or be lichenised. Lichen thus share some of the habitat and often similar appearance with specialized species of algae (aerophytes) growing on exposed surfaces such as tree trunks and rocks and sometimes discoloring them. Coral reefs	633
wiki20220301en000_2134	Algae	Coral reefs Coral reefs are accumulated from the calcareous exoskeletons of marine invertebrates of the order Scleractinia (stony corals). These animals metabolize sugar and oxygen to obtain energy for their cell-building processes, including secretion of the exoskeleton, with water and carbon dioxide as byproducts. Dinoflagellates (algal protists) are often endosymbionts in the cells of the coral-forming marine invertebrates, where they accelerate host-cell metabolism by generating sugar and oxygen immediately available through photosynthesis using incident light and the carbon dioxide produced by the host. Reef-building stony corals (hermatypic corals) require endosymbiotic algae from the genus Symbiodinium to be in a healthy condition. The loss of Symbiodinium from the host is known as coral bleaching, a condition which leads to the deterioration of a reef. Sea sponges	Algae. Coral reefs Coral reefs are accumulated from the calcareous exoskeletons of marine invertebrates of the order Scleractinia (stony corals). These animals metabolize sugar and oxygen to obtain energy for their cell-building processes, including secretion of the exoskeleton, with water and carbon dioxide as byproducts. Dinoflagellates (algal protists) are often endosymbionts in the cells of the coral-forming marine invertebrates, where they accelerate host-cell metabolism by generating sugar and oxygen immediately available through photosynthesis using incident light and the carbon dioxide produced by the host. Reef-building stony corals (hermatypic corals) require endosymbiotic algae from the genus Symbiodinium to be in a healthy condition. The loss of Symbiodinium from the host is known as coral bleaching, a condition which leads to the deterioration of a reef. Sea sponges	633
wiki20220301en000_2135	Algae	Sea sponges Endosymbiontic green algae live close to the surface of some sponges, for example, breadcrumb sponges (Halichondria panicea). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species.	Algae. Sea sponges Endosymbiontic green algae live close to the surface of some sponges, for example, breadcrumb sponges (Halichondria panicea). The alga is thus protected from predators; the sponge is provided with oxygen and sugars which can account for 50 to 80% of sponge growth in some species.	633
wiki20220301en000_2136	Algae	Lifecycle	Algae. Lifecycle	633
wiki20220301en000_2137	Algae	Rhodophyta, Chlorophyta, and Heterokontophyta, the three main algal divisions, have lifecycles which show considerable variation and complexity. In general, an asexual phase exists where the seaweed's cells are diploid, a sexual phase where the cells are haploid, followed by fusion of the male and female gametes. Asexual reproduction permits efficient population increases, but less variation is possible. Commonly, in sexual reproduction of unicellular and colonial algae, two specialized, sexually compatible, haploid gametes make physical contact and fuse to form a zygote. To ensure a successful mating, the development and release of gametes is highly synchronized and regulated; pheromones may play a key role in these processes. Sexual reproduction allows for more variation and provides the benefit of efficient recombinational repair of DNA damages during meiosis, a key stage of the sexual cycle. However, sexual reproduction is more costly than asexual reproduction. Meiosis has been	Algae. Rhodophyta, Chlorophyta, and Heterokontophyta, the three main algal divisions, have lifecycles which show considerable variation and complexity. In general, an asexual phase exists where the seaweed's cells are diploid, a sexual phase where the cells are haploid, followed by fusion of the male and female gametes. Asexual reproduction permits efficient population increases, but less variation is possible. Commonly, in sexual reproduction of unicellular and colonial algae, two specialized, sexually compatible, haploid gametes make physical contact and fuse to form a zygote. To ensure a successful mating, the development and release of gametes is highly synchronized and regulated; pheromones may play a key role in these processes. Sexual reproduction allows for more variation and provides the benefit of efficient recombinational repair of DNA damages during meiosis, a key stage of the sexual cycle. However, sexual reproduction is more costly than asexual reproduction. Meiosis has been	633
wiki20220301en000_2138	Algae	benefit of efficient recombinational repair of DNA damages during meiosis, a key stage of the sexual cycle. However, sexual reproduction is more costly than asexual reproduction. Meiosis has been shown to occur in many different species of algae.	Algae. benefit of efficient recombinational repair of DNA damages during meiosis, a key stage of the sexual cycle. However, sexual reproduction is more costly than asexual reproduction. Meiosis has been shown to occur in many different species of algae.	633
wiki20220301en000_2139	Algae	Numbers The Algal Collection of the US National Herbarium (located in the National Museum of Natural History) consists of approximately 320,500 dried specimens, which, although not exhaustive (no exhaustive collection exists), gives an idea of the order of magnitude of the number of algal species (that number remains unknown). Estimates vary widely. For example, according to one standard textbook, in the British Isles the UK Biodiversity Steering Group Report estimated there to be 20,000 algal species in the UK. Another checklist reports only about 5,000 species. Regarding the difference of about 15,000 species, the text concludes: "It will require many detailed field surveys before it is possible to provide a reliable estimate of the total number of species ..."	Algae. Numbers The Algal Collection of the US National Herbarium (located in the National Museum of Natural History) consists of approximately 320,500 dried specimens, which, although not exhaustive (no exhaustive collection exists), gives an idea of the order of magnitude of the number of algal species (that number remains unknown). Estimates vary widely. For example, according to one standard textbook, in the British Isles the UK Biodiversity Steering Group Report estimated there to be 20,000 algal species in the UK. Another checklist reports only about 5,000 species. Regarding the difference of about 15,000 species, the text concludes: "It will require many detailed field surveys before it is possible to provide a reliable estimate of the total number of species ..."	633