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Antoninus Liberalis, The Metamorphoses of Antoninus Liberalis translated by Francis Celoria (Routledge 1992). Online version at the Topos Text Project.
Apollodorus, Apollodorus, The Library, with an English Translation by Sir James George Frazer, F.B.A., F.R.S. in 2 Volumes. Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1921. Online version at the Perseus Digital Library.
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Apollo
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Apollonius of Rhodes, Apollonius Rhodius: the Argonautica, translated by Robert Cooper Seaton, W. Heinemann, 1912. Internet Archive.
Callimachus, Callimachus and Lycophron with an English Translation by A. W. Mair; Aratus, with an English Translation by G. R. Mair, London: W. Heinemann, New York: G. P. Putnam 1921. Online version at Harvard University Press. Internet Archive.
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Cicero, Marcus Tullius, De Natura Deorum in Cicero in Twenty-eight Volumes, XIX De Natura Deorum; Academica, with an english translation by H. Rackham, Cambridge, Massachusetts: Harvard University Press; London: William Heinemann, Ltd, 1967. Internet Archive.
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Diodorus Siculus, Library of History, Volume III: Books 4.59-8, translated by C. H. Oldfather, Loeb Classical Library No. 340. Cambridge, Massachusetts, Harvard University Press, 1939. . Online version at Harvard University Press. Online version by Bill Thayer.
Herodotus, Herodotus, with an English translation by A. D. Godley. Cambridge. Harvard University Press. 1920. Online version available at The Perseus Digital Library.
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Apollo
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Hesiod, Theogony, in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, MA., Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library.
Homeric Hymn 3 to Apollo in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, MA., Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library.
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Apollo
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Homeric Hymn 4 to Hermes, in The Homeric Hymns and Homerica with an English Translation by Hugh G. Evelyn-White, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1914. Online version at the Perseus Digital Library.
Homer, The Iliad with an English Translation by A.T. Murray, PhD in two volumes. Cambridge, MA., Harvard University Press; London, William Heinemann, Ltd. 1924. Online version at the Perseus Digital Library.
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Homer; The Odyssey with an English Translation by A.T. Murray, PH.D. in two volumes. Cambridge, MA., Harvard University Press; London, William Heinemann, Ltd. 1919. Online version at the Perseus Digital Library.
Hyginus, Gaius Julius, De Astronomica, in The Myths of Hyginus, edited and translated by Mary A. Grant, Lawrence: University of Kansas Press, 1960. Online version at ToposText.
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Apollo
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Hyginus, Gaius Julius, Fabulae, in The Myths of Hyginus, edited and translated by Mary A. Grant, Lawrence: University of Kansas Press, 1960. Online version at ToposText.
Livy, The History of Rome, Books I and II With An English Translation. Cambridge. Cambridge, Mass., Harvard University Press; London, William Heinemann, Ltd. 1919.
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Nonnus, Dionysiaca; translated by Rouse, W H D, I Books I-XV. Loeb Classical Library No. 344, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1940. Internet Archive
Nonnus, Dionysiaca; translated by Rouse, W H D, II Books XVI-XXXV. Loeb Classical Library No. 345, Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1940. Internet Archive
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Statius, Thebaid. Translated by Mozley, J H. Loeb Classical Library Volumes. Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1928.
Strabo, The Geography of Strabo. Edition by H.L. Jones. Cambridge, Mass.: Harvard University Press; London: William Heinemann, Ltd. 1924. Online version at the Perseus Digital Library.
Sophocles, Oedipus Rex
Palaephatus, On Unbelievable Tales 46. Hyacinthus (330 BCE)
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Apollo
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Ovid, Metamorphoses, Brookes More, Boston, Cornhill Publishing Co. 1922. Online version at the Perseus Digital Library. 10. 162–219 (1–8 CE)
Pausanias, Pausanias Description of Greece with an English Translation by W.H.S. Jones, Litt.D., and H.A. Ormerod, M.A., in 4 Volumes. Cambridge, MA, Harvard University Press; London, William Heinemann Ltd. 1918. Online version at the Perseus Digital Library.
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Philostratus the Elder, Imagines, in Philostratus the Elder, Imagines. Philostratus the Younger, Imagines. Callistratus, Descriptions. Translated by Arthur Fairbanks. Loeb Classical Library No. 256. Cambridge, Massachusetts: Harvard University Press, 1931. . Online version at Harvard University Press. Internet Archive 1926 edition. i.24 Hyacinthus (170–245 CE)
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Philostratus the Younger, Imagines, in Philostratus the Elder, Imagines. Philostratus the Younger, Imagines. Callistratus, Descriptions. Translated by Arthur Fairbanks. Loeb Classical Library No. 256. Cambridge, Massachusetts: Harvard University Press, 1931. . Online version at Harvard University Press. Internet Archive 1926 edition. 14. Hyacinthus (170–245 CE)
Pindar, Odes, Diane Arnson Svarlien. 1990. Online version at the Perseus Digital Library.
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Apollo
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Plutarch. Lives, Volume I: Theseus and Romulus. Lycurgus and Numa. Solon and Publicola. Translated by Bernadotte Perrin. Loeb Classical Library No. 46. Cambridge, Massachusetts: Harvard University Press, 1914. . Online version at Harvard University Press. Numa at the Perseus Digital Library.
Pseudo-Plutarch, De fluviis, in Plutarch's morals, Volume V, edited and translated by William Watson Goodwin, Boston: Little, Brown & Co., 1874. Online version at the Perseus Digital Library.
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Lucian, Dialogues of the Dead. Dialogues of the Sea-Gods. Dialogues of the Gods. Dialogues of the Courtesans, translated by M. D. MacLeod, Loeb Classical Library No. 431, Cambridge, Massachusetts, Harvard University Press, 1961. . Online version at Harvard University Press. Internet Archive.
First Vatican Mythographer, 197. Thamyris et Musae
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Tzetzes, John, Chiliades, editor Gottlieb Kiessling, F.C.G. Vogel, 1826. Google Books. (English translation: Book I by Ana Untila; Books II–IV, by Gary Berkowitz; Books V–VI by Konstantino Ramiotis; Books VII–VIII by Vasiliki Dogani; Books IX–X by Jonathan Alexander; Books XII–XIII by Nikolaos Giallousis. Internet Archive).
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Valerius Flaccus, Argonautica, translated by J. H. Mozley, Loeb Classical Library No. 286. Cambridge, Massachusetts, Harvard University Press; London, William Heinemann Ltd. 1928. . Online version at Harvard University Press. Online translated text available at theoi.com.
Vergil, Aeneid. Theodore C. Williams. trans. Boston. Houghton Mifflin Co. 1910. Online version at the Perseus Digital Library.
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Secondary sources
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Apollo
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Athanassakis, Apostolos N., and Benjamin M. Wolkow, The Orphic Hymns, Johns Hopkins University Press; owlerirst Printing edition (May 29, 2013). . Google Books.
M. Bieber, 1964. Alexander the Great in Greek and Roman Art. Chicago.
Hugh Bowden, 2005. Classical Athens and the Delphic Oracle: Divination and Democracy. Cambridge University Press.
Walter Burkert, 1985. Greek Religion (Harvard University Press) III.2.5 passim
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Apollo
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Fontenrose, Joseph Eddy, Python: A Study of Delphic Myth and Its Origins, University of California Press, 1959. .
Gantz, Timothy, Early Greek Myth: A Guide to Literary and Artistic Sources, Johns Hopkins University Press, 1996, Two volumes: (Vol. 1), (Vol. 2).
Miranda J. Green, 1997. Dictionary of Celtic Myth and Legend, Thames and Hudson.
Grimal, Pierre, The Dictionary of Classical Mythology, Wiley-Blackwell, 1996. .
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Apollo
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Hard, Robin, The Routledge Handbook of Greek Mythology: Based on H.J. Rose's "Handbook of Greek Mythology", Psychology Press, 2004, . Google Books.
Karl Kerenyi, 1953. Apollon: Studien über Antiken Religion und Humanität revised edition.
Kerényi, Karl 1951, The Gods of the Greeks, Thames and Hudson, London.
Mertens, Dieter; Schutzenberger, Margareta. Città e monumenti dei Greci d'Occidente: dalla colonizzazione alla crisi di fine V secolo a.C.. Roma L'Erma di Bretschneider, 2006. .
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Apollo
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Martin Nilsson, 1955. Die Geschichte der Griechische Religion, vol. I. C.H. Beck.
Parada, Carlos, Genealogical Guide to Greek Mythology, Jonsered, Paul Åströms Förlag, 1993. .
Pauly–Wissowa, Realencyclopädie der klassischen Altertumswissenschaft: II, "Apollon". The best repertory of cult sites (Burkert).
Peck, Harry Thurston, Harpers Dictionary of Classical Antiquities, New York. Harper and Brothers. 1898. Online version at the Perseus Digital Library.
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Apollo
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Pfeiff, K.A., 1943. Apollon: Wandlung seines Bildes in der griechischen Kunst. Traces the changing iconography of Apollo.
D.S.Robertson (1945) A handbook of Greek and Roman Architecture Cambridge University Press
Smith, William; Dictionary of Greek and Roman Biography and Mythology, London (1873). "Apollo"
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Apollo
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Smith, William, A Dictionary of Greek and Roman Antiquities. William Smith, LLD. William Wayte. G. E. Marindin. Albemarle Street, London. John Murray. 1890. Online version at the Perseus Digital Library.
Spivey Nigel (1997) Greek art Phaedon Press Ltd.
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External links
Apollo at the Greek Mythology Link, by Carlos Parada
The Warburg Institute Iconographic Database: ca 1650 images of Apollo
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Beauty gods
Health gods
Knowledge gods
Light deities
Maintenance deities
Music and singing gods
Oracular gods
Solar gods
Greek gods
Roman gods
Dragonslayers
Mythological Greek archers
Mythological rapists
Homosexuality and bisexuality deities
Divine twins
Deities in the Iliad
Metamorphoses characters
Characters in Greek mythology
LGBT themes in Greek mythology
Children of Zeus
Characters in the Odyssey
Characters in the Argonautica
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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
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Algae
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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.
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Algae
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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.
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Algae
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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
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Algae
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strategies, from simple asexual cell division to complex forms of sexual reproduction.
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Algae
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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
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Algae
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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
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Algae
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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.
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Algae
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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,
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Algae
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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.
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Algae
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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'.
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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.
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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.
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Algae
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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
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Algae
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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
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Algae
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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.
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Algae
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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,
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Algae
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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:
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Algae
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Schizophyta
Phytosarcodina
Flagellata
Dinoflagellata
Bacillariophyta
Conjugatae
Chlorophyceae
Charophyta
Phaeophyceae
Rhodophyceae
Eumycetes (Fungi)
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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
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Algae
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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.
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Algae
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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.
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Algae
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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.
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Algae
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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.
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Algae
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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.
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Algae
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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.
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Algae
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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
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Algae
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(e.g., synurophytes from chrysophytes, or eustigmatophytes from xanthophytes), haptophytes (from chrysophytes), and chlorarachniophytes (from xanthophytes).
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Algae
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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).
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Algae
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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
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Algae
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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.
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Algae
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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
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Algae
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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
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Algae
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'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.
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Algae
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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
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Algae
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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
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Algae
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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
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Algae
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with protective cell layers that protect the zygote and developing embryo. Hence, the land plants are referred to as the Embryophytes.
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Algae
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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:
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Algae
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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.
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Algae
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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).
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Algae
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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.
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Algae
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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
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Algae
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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
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Algae
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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
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isolated). The photobiont possibly triggers otherwise latent genes in the mycobiont.
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Algae
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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
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Algae
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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
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Algae
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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.
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Algae
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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.
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Algae
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Lifecycle
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Algae
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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
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Algae
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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
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Algae
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sexual reproduction is more costly than asexual reproduction. Meiosis has been shown to occur in many different species of algae.
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Algae
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Numbers
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Algae
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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.
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Algae
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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 ..."
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Algae
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Regional and group estimates have been made, as well:
5,000–5,500 species of red algae worldwide
"some 1,300 in Australian Seas"
400 seaweed species for the western coastline of South Africa, and 212 species from the coast of KwaZulu-Natal. Some of these are duplicates, as the range extends across both coasts, and the total recorded is probably about 500 species. Most of these are listed in List of seaweeds of South Africa. These exclude phytoplankton and crustose corallines.
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Algae
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669 marine species from California (US)
642 in the check-list of Britain and Ireland
and so on, but lacking any scientific basis or reliable sources, these numbers have no more credibility than the British ones mentioned above. Most estimates also omit microscopic algae, such as phytoplankton.
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Algae
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The most recent estimate suggests 72,500 algal species worldwide.
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Algae
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Distribution
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Algae
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The distribution of algal species has been fairly well studied since the founding of phytogeography in the mid-19th century. Algae spread mainly by the dispersal of spores analogously to the dispersal of Plantae by seeds and spores. This dispersal can be accomplished by air, water, or other organisms. Due to this, spores can be found in a variety of environments: fresh and marine waters, air, soil, and in or on other organisms. Whether a spore is to grow into an organism depends on the combination of the
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Algae
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an organism depends on the combination of the species and the environmental conditions where the spore lands.
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Algae
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The spores of freshwater algae are dispersed mainly by running water and wind, as well as by living carriers. However, not all bodies of water can carry all species of algae, as the chemical composition of certain water bodies limits the algae that can survive within them. Marine spores are often spread by ocean currents. Ocean water presents many vastly different habitats based on temperature and nutrient availability, resulting in phytogeographic zones, regions, and provinces.
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Algae
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To some degree, the distribution of algae is subject to floristic discontinuities caused by geographical features, such as Antarctica, long distances of ocean or general land masses. It is, therefore, possible to identify species occurring by locality, such as "Pacific algae" or "North Sea algae". When they occur out of their localities, hypothesizing a transport mechanism is usually possible, such as the hulls of ships. For example, Ulva reticulata and U. fasciata travelled from the mainland to Hawaii in
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Algae
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fasciata travelled from the mainland to Hawaii in this manner.
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Algae
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Mapping is possible for select species only: "there are many valid examples of confined distribution patterns." For example, Clathromorphum is an arctic genus and is not mapped far south of there. However, scientists regard the overall data as insufficient due to the "difficulties of undertaking such studies."
Ecology
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Algae
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Algae are prominent in bodies of water, common in terrestrial environments, and are found in unusual environments, such as on snow and ice. Seaweeds grow mostly in shallow marine waters, under deep; however, some such as Navicula pennata have been recorded to a depth of . A type of algae, Ancylonema nordenskioeldii, was found in Greenland in areas known as the 'Dark Zone', which caused an increase in the rate of melting ice sheet. Same algae was found in the Italian Alps, after pink ice appeared on parts
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Algae
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Italian Alps, after pink ice appeared on parts of the Presena glacier.
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Algae
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The various sorts of algae play significant roles in aquatic ecology. Microscopic forms that live suspended in the water column (phytoplankton) provide the food base for most marine food chains. In very high densities (algal blooms), these algae may discolor the water and outcompete, poison, or asphyxiate other life forms.
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Algae
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Algae can be used as indicator organisms to monitor pollution in various aquatic systems. In many cases, algal metabolism is sensitive to various pollutants. Due to this, the species composition of algal populations may shift in the presence of chemical pollutants. To detect these changes, algae can be sampled from the environment and maintained in laboratories with relative ease.
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Algae
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On the basis of their habitat, algae can be categorized as: aquatic (planktonic, benthic, marine, freshwater, lentic, lotic), terrestrial, aerial (subaerial), lithophytic, halophytic (or euryhaline), psammon, thermophilic, cryophilic, epibiont (epiphytic, epizoic), endosymbiont (endophytic, endozoic), parasitic, calcifilic or lichenic (phycobiont).
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Algae
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Cultural associations
In classical Chinese, the word is used both for "algae" and (in the modest tradition of the imperial scholars) for "literary talent". The third island in Kunming Lake beside the Summer Palace in Beijing is known as the Zaojian Tang Dao, which thus simultaneously means "Island of the Algae-Viewing Hall" and "Island of the Hall for Reflecting on Literary Talent".
Cultivation
Seaweed farming
Bioreactors
Uses
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Algae
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Cultivation
Seaweed farming
Bioreactors
Uses
Agar
Agar, a gelatinous substance derived from red algae, has a number of commercial uses. It is a good medium on which to grow bacteria and fungi, as most microorganisms cannot digest agar.
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Algae
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