154-407: Corals are colonial marine invertebrates within the subphylum Anthozoa of the phylum Cnidaria . They typically form compact colonies of many identical individual polyps . Coral species include the important reef builders that inhabit tropical oceans and secrete calcium carbonate to form a hard skeleton. A coral "group" is a colony of very many genetically identical polyps. Each polyp
308-653: A blanket term that includes all animals apart from the vertebrate members of the chordate phylum. Invertebrates lack a vertebral column , and some have evolved a shell or a hard exoskeleton . As on land and in the air, marine invertebrates have a large variety of body plans , and have been categorised into over 30 phyla . They make up most of the macroscopic life in the oceans. The earliest animals were marine invertebrates , that is, vertebrates came later. Animals are multicellular eukaryotes , and are distinguished from plants, algae, and fungi by lacking cell walls . Marine invertebrates are animals that inhabit
462-412: A hydrostatic balance to determine the density and purity of metals and precious stones. He classified gems by what he considered their primary physical properties, such as specific gravity and hardness , rather than the common practice of the time of classifying them by colour. Biruni's main essay on political history, Kitāb al-musāmara fī aḵbār Ḵᵛārazm (" Book of nightly conversation concerning
616-508: A marine environment apart from the vertebrate members of the chordate phylum; invertebrates lack a vertebral column . Some have evolved a shell or a hard exoskeleton . The earliest animals may belong to the genus Dickinsonia , 571 million to 539 million years ago. Individual Dickinsonia typically resemble a bilaterally symmetrical ribbed oval. They kept growing until they were covered with sediment or otherwise killed, and spent most of their lives with their bodies firmly anchored to
770-457: A phylum containing over 10,000 species of animals found exclusively in aquatic (mainly marine) environments. Their bodies consist of mesoglea , a non-living jelly-like substance, sandwiched between two layers of epithelium that are mostly one cell thick . They have two basic body forms: swimming medusae and sessile polyps , both of which are radially symmetrical with mouths surrounded by tentacles that bear cnidocytes. Both forms have
924-449: A symbiotic relationship with a class of dinoflagellate algae , zooxanthellae of the genus Symbiodinium , which can form as much as 30% of the tissue of a polyp. Typically, each polyp harbors one species of alga, and coral species show a preference for Symbiodinium . Young corals are not born with zooxanthellae, but acquire the algae from the surrounding environment, including the water column and local sediment. The main benefit of
1078-487: A calcium carbonate base, with polyps that bear six stiff tentacles, and soft coral (Alcyonacea and ahermatypic coral) which are pliable and formed by a colony of polyps with eight feather-like tentacles. These two classifications arose from differentiation in gene expressions in their branch tips and bases that arose through developmental signaling pathways such as Hox , Hedgehog , Wnt , BMP etc. Scientists typically select Acropora as research models since they are
1232-472: A central axial skeleton embedded at their base in the matrix of the supporting branch. These branches are composed of a fibrous protein called gorgonin or of a calcified material. The polyps of stony corals have six-fold symmetry. In stony corals, the tentacles are cylindrical and taper to a point, but in soft corals they are pinnate with side branches known as pinnules. In some tropical species, these are reduced to mere stubs and in some, they are fused to give
1386-414: A commonly highly abundant bacterium in corals, has exhibited codiversification with its host. This hints at an intricate set of relationships between the members of the coral holobiont that have been developing as evolution of these members occurs. A study published in 2018 revealed evidence of phylosymbiosis between corals and their tissue and skeleton microbiomes. The coral skeleton, which represents
1540-454: A competitive rate to these pathogens responsible for coral bleaching, resulting in species loss. For most of their life corals are sessile animals of colonies of genetically identical polyps . Each polyp varies from millimeters to centimeters in diameter, and colonies can be formed from many millions of individual polyps. Stony coral, also known as hard coral, polyps produce a skeleton composed of calcium carbonate to strengthen and protect
1694-586: A complex digestive system using microscopic, muscle-powered hairs called cilia to exude mucus . The generalized mollusc has two paired nerve cords (three in bivalves). The brain , in species that have one, encircles the esophagus . Most molluscs have eyes and all have sensors detecting chemicals, vibrations, and touch. The simplest type of molluscan reproductive system relies on external fertilization , but more complex variations occur. All produce eggs , from which may emerge trochophore larvae , more complex veliger larvae, or miniature adults. The depiction
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#17327733902221848-399: A constant water flow through their bodies to obtain food and oxygen and to remove wastes. Sponges are similar to other animals in that they are multicellular , heterotrophic , lack cell walls and produce sperm cells . Unlike other animals, they lack true tissues and organs , and have no body symmetry . The shapes of their bodies are adapted for maximal efficiency of water flow through
2002-467: A cubit is not clear; with an 18-inch cubit his estimate would be 3,600 miles, whereas with a 22-inch cubit his estimate would be 4,200 miles. One significant problem with this approach is that Al-Biruni was not aware of atmospheric refraction and made no allowance for it. He used a dip angle of 34 arc minutes in his calculations, but refraction can typically alter the measured dip angle by about 1/6, making his calculation only accurate to within about 20% of
2156-807: A cultural vacuum. He was sympathetic to the Afrighids , who were overthrown by the rival dynasty of Ma'munids in 995. He left his homeland for Bukhara , then under the Samanid ruler Mansur II the son of Nuh II . There he corresponded with Avicenna , and there are extant exchanges of views between these two scholars. In 998, he went to the court of the Ziyarid amir of Tabaristan , Qabus ( r. 977–981, 997–1012 ). There he wrote his first important work, al-Athar al-Baqqiya 'an al-Qorun al-Khaliyya ("The remaining traces of past centuries", translated as "Chronology of ancient nations" or "Vestiges of
2310-546: A deep-sea plant in his Enquiries on Plants , where he also mentions large stony plants that reveal bright flowers when under water in the Gulf of Heroes . Pliny the Elder stated boldly that several sea creatures including sea nettles and sponges "are neither animals nor plants, but are possessed of a third nature ( tertia natura )". Petrus Gyllius copied Pliny, introducing the term zoophyta for this third group in his 1535 book On
2464-513: A full moon. A full moon is equivalent to four to six hours of continuous dim light exposure, which can cause light-dependent reactions in protein. Corals contain light-sensitive cryptochromes , proteins whose light-absorbing flavin structures are sensitive to different types of light. This allows corals such as Dipsastraea speciosa to detect and respond to changes in sunlight and moonlight. Moonlight itself may actually suppress coral spawning. The most immediate cue to cause spawning appears to be
2618-419: A further worm phylum with tubular digestive systems and an opening at both ends. Over 25,000 nematode species have been described, of which more than half are parasitic. It has been estimated another million remain undescribed. They are ubiquitous in marine, freshwater and terrestrial environments, where they often outnumber other animals in both individual and species counts. They are found in every part of
2772-597: A given group of people, learnt their language and studied their primary texts, presenting his findings with objectivity and neutrality using cross-cultural comparisons. Akhbar S. Ahmed concluded that Al-Biruni can be considered as the first anthropologist, others, however, have argued that he can hardly be considered an anthropologist in the conventional sense. Biruni's fame as an Indologist rests primarily on two texts. Biruni wrote an encyclopedic work on India called Taḥqīq mā li-l-Hind min maqūlah maqbūlah fī al-ʿaql aw mardhūlah (variously translated as Verifying All That
2926-436: A multi-domain marine animal symbiosis. The gammaproteobacterium Endozoicomonas is emerging as a central member of the coral's microbiome, with flexibility in its lifestyle. Given the recent mass bleaching occurring on reefs, corals will likely continue to be a useful and popular system for symbiosis and dysbiosis research. Astrangia poculata , the northern star coral, is a temperate stony coral , widely documented along
3080-505: A paddle-like appearance. Coral skeletons are biocomposites (mineral + organics) of calcium carbonate, in the form of calcite or aragonite. In scleractinian corals, "centers of calcification" and fibers are clearly distinct structures differing with respect to both morphology and chemical compositions of the crystalline units. The organic matrices extracted from diverse species are acidic, and comprise proteins, sulphated sugars and lipids; they are species specific. The soluble organic matrices of
3234-637: A pair of appendages . The rigid cuticle inhibits growth, so arthropods replace it periodically by moulting . Their versatility has enabled them to become the most species-rich members of all ecological guilds in most environments. Marine arthropods range in size from the microscopic crustacean Stygotantulus to the Japanese spider crab . Arthropods' primary internal cavity is a hemocoel , which accommodates their internal organs , and through which their haemolymph - analogue of blood - circulates; they have open circulatory systems . Like their exteriors,
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#17327733902223388-467: A refutation of astrology, in contradistinction to the legitimate science of astronomy, for which he expresses wholehearted support. Some suggest that his reasons for refuting astrology relate to the methods used by astrologers being based upon pseudoscience rather than empiricism and also to a conflict between the views of the astrologers and those of the orthodox theologians of Sunni Islam . He wrote an extensive commentary on Indian astronomy in
3542-416: A rich cultural context. He expressed his objectives with simple eloquence: He also translated the yoga sutras of Indian sage Patanjali with the title Tarjamat ketāb Bātanjalī fi’l-ḵalāṣ men al-ertebāk : I shall not produce the arguments of our antagonists in order to refute such of them, as I believe to be in the wrong. My book is nothing but a simple historic record of facts. I shall place before
3696-559: A scientific but also a religious dimension: in Islam worship and prayer require a knowledge of the precise directions of sacred locations, which can be determined accurately only through the use of astronomical data. In carrying out his research, al-Biruni used a variety of different techniques dependent upon the particular field of study involved. His major work on astrology is primarily an astronomical and mathematical text; he states: "I have begun with Geometry and proceeded to Arithmetic and
3850-427: A single orifice and body cavity that are used for digestion and respiration . Fossil cnidarians have been found in rocks formed about 580 million years ago . Fossils of cnidarians that do not build mineralized structures are rare. Scientists currently think cnidarians, ctenophores and bilaterians are more closely related to calcareous sponges than these are to other sponges , and that anthozoans are
4004-415: A single muscular foot . Beyond that it has three further key features. Firstly, it has a muscular cloak called a mantle covering its viscera and containing a significant cavity used for breathing and excretion . A shell secreted by the mantle covers the upper surface. Secondly (apart from bivalves) it has a rasping tongue called a radula used for feeding. Thirdly, it has a nervous system including
4158-399: A single polyp and eventually develops into a juvenile and then adult by asexual budding and growth. Within a coral head, the genetically identical polyps reproduce asexually , either by budding (gemmation) or by dividing, whether longitudinally or transversely. Budding involves splitting a smaller polyp from an adult. As the new polyp grows, it forms its body parts . The distance between
4312-453: A subset of coral-associated bacteria. Many corals in the order Scleractinia are hermatypic , meaning that they are involved in building reefs. Most such corals obtain some of their energy from zooxanthellae in the genus Symbiodinium . These are symbiotic photosynthetic dinoflagellates which require sunlight; reef-forming corals are therefore found mainly in shallow water. They secrete calcium carbonate to form hard skeletons that become
4466-463: A total metamorphosis to produce the adult form. The evolutionary ancestry of arthropods dates back to the Cambrian period. The group is generally regarded as monophyletic , and many analyses support the placement of arthropods with cycloneuralians (or their constituent clades) in a superphylum Ecdysozoa . Overall however, the basal relationships of Metazoa are not yet well resolved. Likewise,
4620-409: A vast array of topics of Indian culture, including descriptions of their traditions and customs. Although he tried to stay away from political and military history, Biruni did indeed record important dates and noted actual sites of where significant battles occurred. Additionally, he chronicled stories of Indian rulers and told of how they ruled over their people with their beneficial actions and acted in
4774-444: A way of grouping organisms according to their body plan . A body plan refers to a blueprint which describes the shape or morphology of an organism, such as its symmetry , segmentation and the disposition of its appendages . The idea of body plans originated with vertebrates , which were grouped into one phylum. But the vertebrate body plan is only one of many, and invertebrates consist of many phyla or body plans. The history of
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4928-567: A wide range of chemical and mechanical sensors, mostly based on modifications of the many setae (bristles) that project through their cuticles. Arthropods' methods of reproduction and development are diverse; all terrestrial species use internal fertilization , but this is often by indirect transfer of the sperm via an appendage or the ground, rather than by direct injection. Marine species all lay eggs and use either internal or external fertilization . Arthropod hatchlings vary from miniature adults to grubs that lack jointed limbs and eventually undergo
5082-527: Is paraphyletic because the sea anemones are also in the sub-class Hexacorallia. The delineation of coral species is challenging as hypotheses based on morphological traits contradict hypotheses formed via molecular tree-based processes. As of 2020, there are 2175 identified separate coral species, 237 of which are currently endangered, making distinguishing corals to be the utmost of importance in efforts to curb extinction. Adaptation and delineation continues to occur in species of coral in order to combat
5236-459: Is a phylum which contains only marine invertebrates. The adults are recognizable by their radial symmetry (usually five-point) and include starfish , sea urchins , sand dollars , and sea cucumbers , as well as the sea lilies . Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone . The phylum contains about 7000 living species , making it the second-largest grouping of deuterostomes (a superphylum), after
5390-515: Is a remarkable degree of similarity in the gene sequence conservation and complexity between the sea anemone and vertebrates. In particular, genes concerned in the formation of the head in vertebrates are also present in the anemone. Worms (Old English for serpent ) typically have long cylindrical tube-like bodies and no limbs . Marine worms vary in size from microscopic to over 1 metre (3.3 ft) in length for some marine polychaete worms ( bristle worms ) and up to 58 metres (190 ft) for
5544-455: Is a sac-like animal typically only a few millimeters in diameter and a few centimeters in height. A set of tentacles surround a central mouth opening. Each polyp excretes an exoskeleton near the base. Over many generations, the colony thus creates a skeleton characteristic of the species which can measure up to several meters in size. Individual colonies grow by asexual reproduction of polyps. Corals also breed sexually by spawning : polyps of
5698-405: Is coordinated by chemical communication. Corals predominantly reproduce sexually . About 25% of hermatypic corals (reef-building stony corals) form single-sex ( gonochoristic ) colonies, while the rest are hermaphroditic . It is estimated more than 67% of coral are simultaneous hermaphrodites . About 75% of all hermatypic corals "broadcast spawn" by releasing gametes — eggs and sperm —into
5852-722: Is derived from the Persian word bērūn or bīrūn ("outskirts"), as he was born in an outlying district of Kath , the capital of the Afrighid kingdom of Khwarazm . The city, now called Beruniy, is part of the autonomous republic of Karakalpakstan in northwest Uzbekistan . His name was most commonly latinized as Alberonius . Al-Biruni spent the first twenty-five years of his life in Khwarezm where he studied Islamic jurisprudence , theology, grammar, mathematics, astronomy , medicine and philosophy and dabbled not only in
6006-412: Is negatively buoyant, sinking onto the waiting egg carriers that harbor unfertilized eggs for weeks. Synchronous spawning events sometimes occur even with these species. After fertilization, the corals release planula that are ready to settle. The time from spawning to larval settlement is usually two to three days but can occur immediately or up to two months. Broadcast-spawned planula larvae develop at
6160-561: Is one, eternal, and omnipotent and eschewing all forms of idol worship. He recognizes that uneducated Hindus worshiped a multiplicity of idols yet points out that even some Muslims (such as the Jabriyah ) have adopted anthropomorphic concepts of God. Al-Biruni wrote about the peoples, customs and religions of the Indian subcontinent. According to Akbar S. Ahmed, like modern anthropologists, he engaged in extensive participant observation with
6314-403: Is rather similar to modern monoplacophorans , and some suggest it may resemble very early molluscs. Good evidence exists for the appearance of marine gastropods, cephalopods and bivalves in the Cambrian period 538.8 to 485.4 million years ago . However, the evolutionary history both of molluscs' emergence from the ancestral Lophotrochozoa and of their diversification into
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6468-512: Is reflected in the Octo in Octocorallia. Soft corals vary considerably in form, and most are colonial. A few soft corals are stolonate , but the polyps of most are connected by sheets of tissue called coenosarc, and in some species these sheets are thick and the polyps deeply embedded in them. Some soft corals encrust other sea objects or form lobes. Others are tree-like or whip-like and have
6622-459: Is still debate about the classification of these specimens, mainly because the diagnostic features which allow taxonomists to classify more recent organisms, such as similarities to living organisms, are generally absent in the Ediacarans. However, there seems little doubt that Kimberella was at least a triploblastic bilaterian animal, in other words, an animal significantly more complex than
6776-447: Is thought to have been laid down about two million years ago. Over time, corals fragment and die, sand and rubble accumulates between the corals, and the shells of clams and other molluscs decay to form a gradually evolving calcium carbonate structure. Coral reefs are extremely diverse marine ecosystems hosting over 4,000 species of fish, massive numbers of cnidarians, molluscs , crustaceans , and many other animals. At certain times in
6930-468: The Taḥqīq mā li-l-Hind mostly translation of Aryabhatta's work, in which he claims to have resolved the matter of Earth's rotation in a work on astronomy that is no longer extant, his Miftah-ilm-alhai'a (" Key to Astronomy "): [T]he rotation of the earth does in no way impair the value of astronomy, as all appearances of an astronomic character can quite as well be explained according to this theory as to
7084-740: The British Raj , were revisited. The lunar crater Al-Biruni and the asteroid 9936 Al-Biruni are named in his honour. Biruni Island in Antarctica is named after al-Biruni. In Iran, surveying engineers are celebrated on al-Biruni's birthday. In June 2009, Iran donated a pavilion to the United Nations Office in Vienna —placed in the central Memorial Plaza of the Vienna International Center . Named
7238-458: The Cambrian about 535 million years ago . Fossils are extremely rare until the Ordovician period, 100 million years later, when Heliolitida, rugose , and tabulate corals became widespread. Paleozoic corals often contained numerous endobiotic symbionts. Marine invertebrates Marine invertebrates are the invertebrates that live in marine habitats . Invertebrate is
7392-491: The Cambrian explosion , but a more nuanced understanding of animal evolution suggests a gradual development of body plans throughout the early Palaeozoic and beyond. More generally a phylum can be defined in two ways: as described above, as a group of organisms with a certain degree of morphological or developmental similarity (the phenetic definition), or a group of organisms with a certain degree of evolutionary relatedness (the phylogenetic definition). As on land and in
7546-530: The Darwin Mounds , northwest of Cape Wrath , Scotland, and others off the coast of Washington state and the Aleutian Islands . The classification of corals has been discussed for millennia, owing to having similarities to both plants and animals. Aristotle 's pupil Theophrastus described the red coral , korallion , in his book on stones, implying it was a mineral, but he described it as
7700-600: The Indian subcontinent and wrote a treatise on Indian culture entitled Tārīkh al-Hind (" The History of India "), after exploring the Hindu faith practiced in India. He was, for his time, an admirably impartial writer on the customs and creeds of various nations, his scholarly objectivity earning him the title al-Ustadh ("The Master") in recognition of his remarkable description of early 11th-century India. Al-Biruni's name
7854-710: The Islamic Golden Age . He has been called variously "Father of Comparative Religion ", "Father of modern geodesy ", Founder of Indology and the first anthropologist . Al-Biruni was well versed in physics , mathematics, astronomy , and natural sciences , and also distinguished himself as a historian, chronologist , and linguist . He studied almost all the sciences of his day and was rewarded abundantly for his tireless research in many fields of knowledge. Royalty and other powerful elements in society funded al-Biruni's research and sought him out with specific projects in mind. Influential in his own right, Al-Biruni
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#17327733902228008-599: The Mu'tazila , particularly criticising al-Jahiz and Zurqan. He also repudiated Avicenna for his views on the eternality of the universe. Of the 146 books written by al-Bīrūnī, 95 are devoted to astronomy, mathematics, and related subjects like mathematical geography. He lived during the Islamic Golden Age, when the Abbasid Caliphs promoted astronomical research, because such research possessed not only
8162-540: The Scholars Pavilion , it features the statues of four prominent Iranian scholars: Avicenna , Abu Rayhan Biruni, Zakariya Razi (Rhazes) and Omar Khayyam . A film about the life of Al-Biruni, Abu Raykhan Beruni , was released in the Soviet Union in 1974. Irrfan Khan portrayed Al-Biruni in the 1988 Doordarshan historical drama Bharat Ek Khoj . He has been portrayed by Cüneyt Uzunlar in
8316-406: The biotic desert of the deep sea , as well as shallower oceans. Most echinoderms are able to regenerate tissue, organs, limbs, and reproduce asexually ; in some cases, they can undergo complete regeneration from a single limb. Geologically, the value of echinoderms is in their ossified skeletons , which are major contributors to many limestone formations, and can provide valuable clues as to
8470-405: The chordates (which include the vertebrates , such as birds , fishes , mammals , and reptiles ). Echinoderms are unique among animals in having bilateral symmetry at the larval stage, but fivefold symmetry ( pentamerism , a special type of radial symmetry) as adults. The echinoderms are important both biologically and geologically. Biologically, there are few other groupings so abundant in
8624-599: The coral reefs that develop in tropical and subtropical waters, such as the Great Barrier Reef off the coast of Australia . These corals are increasingly at risk of bleaching events where polyps expel the zooxanthellae in response to stress such as high water temperature or toxins. Other corals do not rely on zooxanthellae and can live globally in much deeper water, such as the cold-water genus Lophelia which can survive as deep as 3,300 metres (10,800 feet; 1,800 fathoms). Some have been found as far north as
8778-412: The giant tube worm which lives in waters near underwater volcanoes and can withstand temperatures up to 90 degrees Celsius . Platyhelminthes (flatworms) form another worm phylum which includes a class Cestoda of parasitic tapeworms. The marine tapeworm Polygonoporus giganticus , found in the gut of sperm whales , can grow to over 30 m (100 ft). Nematodes (roundworms) constitute
8932-514: The phylum Porifera (Modern Latin for bearing pores ). They are multicellular organisms that have bodies full of pores and channels allowing water to circulate through them, consisting of jelly-like mesohyl sandwiched between two thin layers of cells . They have unspecialized cells that can transform into other types and that often migrate between the main cell layers and the mesohyl in the process. Sponges do not have nervous , digestive or circulatory systems . Instead, most rely on maintaining
9086-402: The subphylum to which they belong. Their vision relies on various combinations of compound eyes and pigment-pit ocelli : in most species the ocelli can only detect the direction from which light is coming, and the compound eyes are the main source of information, but the main eyes of spiders are ocelli that can form images and, in a few cases, can swivel to track prey. Arthropods also have
9240-417: The (French) name 'coral'." The Persian polymath Al-Biruni (d.1048) classified sponges and corals as animals, arguing that they respond to touch. Nevertheless, people believed corals to be plants until the eighteenth century when William Herschel used a microscope to establish that coral had the characteristic thin cell membranes of an animal . Presently, corals are classified as species of animals within
9394-472: The 1970s, there was already a debate about whether the emergence of the modern phyla was "explosive" or gradual but hidden by the shortage of Precambrian animal fossils. A re-analysis of fossils from the Burgess Shale lagerstätte increased interest in the issue when it revealed animals, such as Opabinia , which did not fit into any known phylum . At the time these were interpreted as evidence that
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#17327733902229548-550: The Acropora genus, colony differentiation through up-regulation and down-regulation of DEs. Systematic studies of soft coral species have faced challenges due to a lack of taxonomic knowledge. Researchers have not found enough variability within the genus to confidently delineate similar species, due to a low rate in mutation of mitochondrial DNA . Environmental factors, such as the rise of temperatures and acid levels in our oceans account for some speciation of corals in
9702-521: The Earth's lithosphere , from the top of mountains to the bottom of oceanic trenches . By count they represent 90% of all animals on the ocean floor . Their numerical dominance, often exceeding a million individuals per square meter and accounting for about 80% of all individual animals on earth, their diversity of life cycles, and their presence at various trophic levels point at an important role in many ecosystems. Echinoderms (Greek for spiny skin )
9856-670: The French and Latin Names of the Fishes of the Marseilles Region ; it is popularly but wrongly supposed that Aristotle created the term. Gyllius further noted, following Aristotle, how hard it was to define what was a plant and what was an animal. The Babylonian Talmud refers to coral among a list of types of trees, and the 11th-century French commentator Rashi describes it as "a type of tree (מין עץ) that grows underwater that goes by
10010-580: The Greek, the Arab/Muslim, and the Persian. Biruni also employed astronomy in the determination of his theories, which were complex mathematical equations and scientific calculation that allows one to convert dates and years between the different calendars. The book does not limit itself to tedious records of battle because Biruni found the social culture to be more important. The work includes research on
10164-534: The Illumina platform are of insufficient length (approximately 250 base pairs) for the design of primers and probes. In 2019, Goldsmith et al. demonstrated Sanger sequencing was capable of reproducing the biologically relevant diversity detected by deeper next-generation sequencing , while also producing longer sequences useful to the research community for probe and primer design (see diagram on right). Reef-building corals are well-studied holobionts that include
10318-628: The Indians Recount, the Reasonable and the Unreasonable , or The book confirming what pertains to India, whether rational or despicable , in which he explored nearly every aspect of Indian life. During his journey through India, military and political history were not Biruni's main focus: he decided rather to document the civilian and scholarly aspects of Hindu life, examining culture, science, and religion. He explored religion within
10472-795: The Past") on historical and scientific chronology, probably around 1000, though he later made some amendments to the book. He also visited the court of the Bavandid ruler Al-Marzuban . Accepting the definite demise of the Afrighids at the hands of the Ma'munids, he made peace with the latter who then ruled Khwarezm . Their court at Gorganj (also in Khwarezm) was gaining fame for its gathering of brilliant scientists. In 1017, Mahmud of Ghazni captured Rey. Most scholars, including al-Biruni, were taken to Ghazni,
10626-528: The Science of Numbers, then to the structure of the Universe and finally to Judicial Astrology [ sic ], for no one who is worthy of the style and title of Astrologer [ sic ] who is not thoroughly conversant with these for sciences." In these earlier chapters he lays the foundations for the final chapter, on astrological prognostication , which he criticises. In a later work, he wrote
10780-402: The abundance and performance of the microalgal symbionts, as well as calcification and physiology of the host. Studies have also suggested that resident bacteria, archaea, and fungi additionally contribute to nutrient and organic matter cycling within the coral, with viruses also possibly playing a role in structuring the composition of these members, thus providing one of the first glimpses at
10934-527: The affairs of Ḵᵛārazm ") is now known only from quotations in Bayhaqī's Tārīkh-e Masʿūdī. In addition to this various discussions of historical events and methodology are found in connection with the lists of kings in his al-Āthār al-bāqiya and in the Qānūn as well as elsewhere in the Āthār, in India, and scattered throughout his other works. Al-Biruni's Chronology of Ancient Nations attempted to accurately establish
11088-433: The air, invertebrates make up a great majority of all macroscopic life, as the vertebrates makes up a subphylum of one of over 30 known animal phyla, making the term almost meaningless for taxonomic purpose. Invertebrate sea life includes the following groups, some of which are phyla: Arthropods total about 1,113,000 described extant species, molluscs about 85,000 and chordates about 52,000. Sponges are animals of
11242-406: The algae contribute to coral coloration; some colors, however, are due to host coral pigments, such as green fluorescent proteins (GFPs). Ejection increases the polyp's chance of surviving short-term stress and if the stress subsides they can regain algae, possibly of a different species, at a later time. If the stressful conditions persist, the polyp eventually dies. Zooxanthellae are located within
11396-429: The approximately 5,000–10,000 known species feed on bacteria and other food particles in the water, some host photosynthesizing micro-organisms as endosymbionts and these alliances often produce more food and oxygen than they consume. A few species of sponge that live in food-poor environments have become carnivores that prey mainly on small crustaceans . Linnaeus mistakenly identified sponges as plants in
11550-484: The area has decreased and in some cases ceased. The area was previously considered a refuge for corals because mass bleaching events due to climate change had not been observed there. Coral restoration techniques for coral reef management are being developed to increase fertilization rates, larval development, and settlement of new corals. Brooding species are most often ahermatypic (not reef-building) in areas of high current or wave action. Brooders release only sperm, which
11704-405: The argument of Aristotle, that there is a change in the creator. He further argued that stating there is a change in the creator would mean there is a change in the effect (meaning the universe has change) and that the universe coming into being after not being is such a change (and so arguing there is no change – no beginning – means Aristotle believes the creator is negated). Al-Biruni was proud of
11858-495: The capital of the Ghaznavid dynasty. Biruni was made court astrologer and accompanied Mahmud on his invasions into India, living there for a few years. He was 44 when he went on the journeys with Mahmud of Ghazni. Biruni became acquainted with all things related to India. During this time he wrote his study of India, finishing it around 1030. Along with his writing, Al-Biruni also made sure to extend his study to science while on
12012-488: The cells of the ectoderm allow tentacles to contract to convey the food to the mouth. Similarly, circularly disposed muscular fibres formed from the endoderm permit tentacles to be protracted or thrust out once they are contracted. In both stony and soft corals, the polyps can be retracted by contracting muscle fibres, with stony corals relying on their hard skeleton and cnidocytes for defense. Soft corals generally secrete terpenoid toxins to ward off predators. In most corals,
12166-430: The central cavity, where it deposits nutrients, and leaves through a hole called the osculum . Many sponges have internal skeletons of spongin and/or spicules of calcium carbonate or silicon dioxide . All sponges are sessile aquatic animals. Although there are freshwater species, the great majority are marine (salt water) species, ranging from tidal zones to depths exceeding 8,800 m (5.5 mi). While most of
12320-689: The cnidarians. The small shelly fauna are a very mixed collection of fossils found between the Late Ediacaran and Middle Cambrian periods. The earliest, Cloudina , shows signs of successful defense against predation and may indicate the start of an evolutionary arms race . Some tiny Early Cambrian shells almost certainly belonged to molluscs, while the owners of some "armor plates," Halkieria and Microdictyon , were eventually identified when more complete specimens were found in Cambrian lagerstätten that preserved soft-bodied animals. In
12474-439: The colony during storms or other disruptions. The separated individuals can start new colonies. Corals are one of the more common examples of an animal host whose symbiosis with microalgae can turn to dysbiosis , and is visibly detected as bleaching. Coral microbiomes have been examined in a variety of studies, which demonstrate how oceanic environmental variations, most notably temperature, light, and inorganic nutrients, affect
12628-794: The coral cytoplasm and due to the algae's photosynthetic activity the internal pH of the coral can be raised; this behavior indicates that the zooxanthellae are responsible to some extent for the metabolism of their host corals. Stony Coral Tissue Loss Disease has been associated with the breakdown of host-zooxanthellae physiology. Moreover, Vibrio bacterium are known to have virulence traits used for host coral tissue damage and photoinhibition of algal symbionts. Therefore, both coral and their symbiotic microorganisms could have evolved to harbour traits resistant to disease and transmission. Corals can be both gonochoristic (unisexual) and hermaphroditic , each of which can reproduce sexually and asexually. Reproduction also allows coral to settle in new areas. Reproduction
12782-588: The coral itself together with its symbiont zooxanthellae (photosynthetic dinoflagellates), as well as its associated bacteria and viruses. Co-evolutionary patterns exist for coral microbial communities and coral phylogeny. It is known that the coral's microbiome and symbiont influence host health, however, the historic influence of each member on others is not well understood. Scleractinian corals have been diversifying for longer than many other symbiotic systems, and their microbiomes are known to be partially species-specific. It has been suggested that Endozoicomonas ,
12936-574: The dangers posed by the climate crisis. Corals are colonial modular organisms formed by asexually produced and genetically identical modules called polyps. Polyps are connected by living tissue to produce the full organism. The living tissue allows for inter module communication (interaction between each polyp), which appears in colony morphologies produced by corals, and is one of the main identifying characteristics for a species of coral. There are two main classifications for corals: hard coral (scleractinian and stony coral) which form reefs by
13090-432: The dark portion of the night between sunset and moonrise. Over the lunar cycle, moonrise shifts progressively later, occurring after sunset on the day of the full moon. The resulting dark period between day-light and night-light removes the suppressive effect of moonlight and enables coral to spawn. The spawning event can be visually dramatic, clouding the usually clear water with gametes. Once released, gametes fertilize at
13244-466: The difference in daylight hours by latitude, seasons and Earth's relative positions with Moon and stars. At the same time, Biruni was also critical of Indian scribes, who he believed carelessly corrupted Indian documents while making copies of older documents. He also criticized the Hindus on what he saw them do and not do, for example finding them deficient in curiosity about history and religion. One of
13398-577: The discovery of body plans can be seen as a movement from a worldview centred on vertebrates, to seeing the vertebrates as one body plan among many. Among the pioneering zoologists , Linnaeus identified two body plans outside the vertebrates; Cuvier identified three; and Haeckel had four, as well as the Protista with eight more, for a total of twelve. For comparison, the number of phyla recognised by modern zoologists has risen to 35 . Historically body plans were thought of as having evolved in rapidly during
13552-483: The eastern coast of the United States. The coral can live with and without zooxanthellae (algal symbionts), making it an ideal model organism to study microbial community interactions associated with symbiotic state. However, the ability to develop primers and probes to more specifically target key microbial groups has been hindered by the lack of full-length 16S rRNA sequences, since sequences produced by
13706-704: The ectoderm. The sac-like body built up in this way is attached to a hard surface, which in hard corals are cup-shaped depressions in the skeleton known as corallites . At the center of the upper end of the sac lies the only opening called the mouth, surrounded by a circle of tentacles which resemble glove fingers. The tentacles are organs which serve both for tactile sense and for the capture of food. Polyps extend their tentacles, particularly at night, often containing coiled stinging cells ( cnidocytes ) which pierce, poison and firmly hold living prey paralyzing or killing them. Polyp prey includes plankton such as copepods and fish larvae. Longitudinal muscular fibers formed from
13860-404: The evolutionary "aunts" or "sisters" of other cnidarians, and the most closely related to bilaterians. Cnidarians are the simplest animals in which the cells are organised into tissues. The starlet sea anemone is used as a model organism in research. It is easy to care for in the laboratory and a protocol has been developed which can yield large numbers of embryos on a daily basis. There
14014-424: The exoskeleton divide transversally into two parts. This means one has the basal disc (bottom) and the other has the oral disc (top); the new polyps must separately generate the missing pieces. Asexual reproduction offers the benefits of high reproductive rate, delaying senescence, and replacement of dead modules, as well as geographical distribution. Whole colonies can reproduce asexually, forming two colonies with
14168-464: The expeditions. He sought to find a method to measure the height of the sun, and created a makeshift quadrant for that purpose. Al-Biruni was able to make much progress in his study over the frequent travels that he went on throughout the lands of India. Belonging to the Sunni Ash'ari school, al-Biruni nevertheless also associated with Maturidi theologians. He was however, very critical of
14322-406: The fact that he followed the textual evidence of the religion without being influenced by Greek philosophers such as Aristotle. Al-Biruni contributed to the introduction of the scientific method to medieval mechanics . He developed experimental methods to determine density, using a particular type of hydrostatic balance . Al-Biruni's method of using the hydrostatic balance was precise, and he
14476-478: The field of physics, but also in those of most of the other sciences. The Iranian Khwarezmian language , which was Biruni's mother tongue, survived for several centuries after Islam until the Turkification of the region – at least some of the culture of ancient Khwarezm endured – for it is hard to imagine that the commanding figure of Biruni, a repository of so much knowledge, should have appeared in
14630-565: The form of species lost . Various coral species have heat shock proteins (HSP) that are also in the category of DE across species. These HSPs help corals combat the increased temperatures they are facing which lead to protein denaturing, growth loss, and eventually coral death. Approximately 33% of coral species are on the International Union for Conservation of Nature's endangered species list and at risk of species loss. Ocean acidification (falling pH levels in
14784-497: The framework of the reef. However, not all reef-building corals in shallow water contain zooxanthellae, and some deep water species, living at depths to which light cannot penetrate, form reefs but do not harbour the symbionts. There are various types of shallow-water coral reef, including fringing reefs, barrier reefs and atolls; most occur in tropical and subtropical seas. They are very slow-growing, adding perhaps one centimetre (0.4 in) in height each year. The Great Barrier Reef
14938-415: The genus Symbiodinium that live within their tissues. These are commonly known as zooxanthellae and give the coral color. Such corals require sunlight and grow in clear, shallow water, typically at depths less than 60 metres (200 feet; 33 fathoms), but corals in the genus Leptoseris have been found as deep as 172 metres (564 feet; 94 fathoms). Corals are major contributors to the physical structure of
15092-500: The geological environment. They were the most used species in regenerative research in the 19th and 20th centuries. Further, it is held by some scientists that the radiation of echinoderms was responsible for the Mesozoic Marine Revolution . Aside from the hard-to-classify Arkarua (a Precambrian animal with echinoderm-like pentamerous radial symmetry), the first definitive members of the phylum appeared near
15246-637: The geological past, corals were very abundant. Like modern corals, their ancestors built reefs, some of which ended as great structures in sedimentary rocks . Fossils of fellow reef-dwellers algae, sponges, and the remains of many echinoids , brachiopods , bivalves , gastropods , and trilobites appear along with coral fossils. This makes some corals useful index fossils . Coral fossils are not restricted to reef remnants, and many solitary fossils are found elsewhere, such as Cyclocyathus , which occurs in England's Gault clay formation. Corals first appeared in
15400-929: The interests of the nation. His details are brief and mostly just list rulers without referring to their real names, and he did not go on about deeds that each one carried out during their reign, which keeps in line with Biruni's mission to try to stay away from political histories. Biruni also described the geography of India in his work. He documented different bodies of water and other natural phenomena. These descriptions are useful to today's modern historians because they are able to use Biruni's scholarship to locate certain destinations in modern-day India. Historians are able to make some matches while also concluding that certain areas seem to have disappeared and been replaced with different cities. Different forts and landmarks were able to be located, legitimizing Biruni's contributions with their usefulness to even modern history and archeology. The dispassionate account of Hinduism given by Biruni
15554-502: The internal organs of arthropods are generally built of repeated segments. Their nervous system is "ladder-like", with paired ventral nerve cords running through all segments and forming paired ganglia in each segment. Their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus . The respiratory and excretory systems of arthropods vary, depending as much on their environment as on
15708-423: The length of various historical eras. Biruni is widely considered to be one of the most important Muslim authorities on the history of religion. He is known as a pioneer in the field of comparative religion in his study of, among other creeds, Zoroastrianism , Judaism, Hinduism , Christianity, Buddhism and Islam . He assumed the superiority of Islam: "We have here given an account of these things in order that
15862-701: The marine nemertean worm ( bootlace worm ). Some marine worms occupy a small variety of parasitic niches, living inside the bodies of other animals, while others live more freely in the marine environment or by burrowing underground. Different groups of marine worms are related only distantly, so they are found in several different phyla such as the Annelida (segmented worms), Chaetognatha (arrow worms), Hemichordata , and Phoronida (horseshoe worms). Many of these worms have specialized tentacles used for exchanging oxygen and carbon dioxide and also may be used for reproduction. Some marine worms are tube worms , such as
16016-442: The midst of a world of clashing swords, burning towns, and plundered temples." Biruni's writing was very poetic, which may diminish some of the historical value of the work for modern times. The lack of description of battle and politics makes those parts of the picture completely lost. However, many have used Biruni's work to check facts of history in other works that may have been ambiguous or had their validity questioned. Most of
16170-553: The modern phyla had evolved very rapidly in the Cambrian explosion and that the Burgess Shale's "weird wonders" showed that the Early Cambrian was a uniquely experimental period of animal evolution. Later discoveries of similar animals and the development of new theoretical approaches led to the conclusion that many of the "weird wonders" were evolutionary "aunts" or "cousins" of modern groups —for example that Opabinia
16324-472: The most advanced of the invertebrates. About 800 living species of marine cephalopods have been identified, and an estimated 11,000 extinct taxa have been described. There are no fully freshwater cephalopods. Molluscs have such diverse shapes that many textbooks base their descriptions of molluscan anatomy on a generalized or hypothetical ancestral mollusc . This generalized mollusc is unsegmented and bilaterally symmetrical with an underside consisting of
16478-458: The most diverse genus of hard coral, having over 120 species. Most species within this genus have polyps which are dimorphic: axial polyps grow rapidly and have lighter coloration, while radial polyps are small and are darker in coloration. In the Acropora genus, gamete synthesis and photosynthesis occur at the basal polyps, growth occurs mainly at the radial polyps. Growth at the site of
16632-418: The most diverse of the three coral microbiomes, showed the strongest evidence of phylosymbiosis. Coral microbiome composition and richness were found to reflect coral phylogeny . For example, interactions between bacterial and eukaryotic coral phylogeny influence the abundance of Endozoicomonas , a highly abundant bacterium in the coral holobiont. However, host-microbial cophylogeny appears to influence only
16786-445: The most numerous molluscs in terms of classified species, accounting for 80% of the total. Bivalves include clams , oysters , cockles , mussels , scallops , and numerous other families . There are about 8,000 marine bivalves species (including brackish water and estuarine species), and about 1,200 freshwater species. Cephalopod include octopus , squid and cuttlefish . They are found in all oceans, and neurologically are
16940-637: The new and adult polyps grows, and with it, the coenosarc (the common body of the colony). Budding can be intratentacular, from its oral discs, producing same-sized polyps within the ring of tentacles, or extratentacular, from its base, producing a smaller polyp. Division forms two polyps that each become as large as the original. Longitudinal division begins when a polyp broadens and then divides its coelenteron (body), effectively splitting along its length. The mouth divides and new tentacles form. The two polyps thus created then generate their missing body parts and exoskeleton. Transversal division occurs when polyps and
17094-426: The oceans) is threatening the continued species growth and differentiation of corals. Mutation rates of Vibrio shilonii , the reef pathogen responsible for coral bleaching , heavily outweigh the typical reproduction rates of coral colonies when pH levels fall. Thus, corals are unable to mutate their HSPs and other climate change preventative genes to combat the increase in temperature and decrease in pH at
17248-554: The oceans, from the seashores to the abyssal zone , but some form a significant part of the freshwater fauna and the terrestrial ecosystems . The mollusc phylum is divided into 9 or 10 taxonomic classes , two of which are extinct . These classes include gastropods , bivalves and cephalopods , as well as other lesser-known but distinctive classes. Gastropods with protective shells are referred to as snails ( sea snails ), whereas gastropods without protective shells are referred to as slugs ( sea slugs ). Gastropods are by far
17402-470: The order Algae . For a long time thereafter sponges were assigned to a separate subkingdom, Parazoa (meaning beside the animals ). They are now classified as a paraphyletic phylum from which the higher animals have evolved. Cnidarians (Greek for nettle ) are distinguished by the presence of stinging cells , specialized cells that they use mainly for capturing prey. Cnidarians include corals , sea anemones , jellyfish and hydrozoans . They form
17556-497: The organism. This is deposited by the polyps and by the coenosarc , the living tissue that connects them. The polyps sit in cup-shaped depressions in the skeleton known as corallites . Colonies of stony coral are markedly variable in appearance; a single species may adopt an encrusting, plate-like, bushy, columnar or massive solid structure, the various forms often being linked to different types of habitat, with variations in light level and water movement being significant. The body of
17710-412: The other. There are, however, other reasons which make it impossible. This question is most difficult to solve. The most prominent of both modern and ancient astronomers have deeply studied the question of the moving of the earth, and tried to refute it. We, too, have composed a book on the subject called Miftah-ilm-alhai'a (Key to Astronomy) , in which we think we have surpassed our predecessors, if not in
17864-423: The philosopher Ibn Sina in a multiple letter correspondence. Al-Biruni stated: "Other people, besides, hold this foolish persuasion, that time has no terminus quo at all." He further stated that Aristotle , whose arguments Avicenna uses, contradicted himself when he stated that the universe and matter has a start whilst holding on to the idea that matter is pre-eternal. In his letters to Avicenna, he stated
18018-428: The polyp may be roughly compared in a structure to a sac , the wall of which is composed of two layers of cells . The outer layer is known technically as the ectoderm , the inner layer as the endoderm . Between ectoderm and endoderm is a supporting layer of gelatinous substance termed mesoglea , secreted by the cell layers of the body wall. The mesoglea can contain skeletal elements derived from cells migrated from
18172-612: The polyp varies greatly. The column may be long and slender, or may be so short in the axial direction that the body becomes disk-like. The tentacles may number many hundreds or may be very few, in rare cases only one or two. They may be simple and unbranched, or feathery in pattern. The mouth may be level with the surface of the peristome, or may be projecting and trumpet-shaped. Soft corals have no solid exoskeleton as such. However, their tissues are often reinforced by small supportive elements known as sclerites made of calcium carbonate. The polyps of soft corals have eight-fold symmetry, which
18326-453: The proportion of this metal in seawater being minute. Although these elements are present in vast quantities in the ocean, their extraction by man is not economic. Al-Biruni Abu Rayhan Muhammad ibn Ahmad al-Biruni / æ l b ɪ ˈ r uː n i / ( Persian : ابوریحان بیرونی ; Arabic : أبو الريحان البيروني ; 973 – after 1050), known as al-Biruni , was a Khwarazmian Iranian scholar and polymath during
18480-409: The radial polyps encompasses two processes: asexual reproduction via mitotic cell proliferation , and skeleton deposition of the calcium carbonate via extra cellular matrix (EMC) proteins acting as differentially expressed (DE) signaling genes between both branch tips and bases. These processes lead to colony differentiation , which is the most accurate distinguisher between coral species. In
18634-426: The radius of the Earth using measurements of the height of a hill and measurement of the dip in the horizon from the top of that hill. His calculated radius for the Earth of 3928.77 miles was 2% higher than the actual mean radius of 3847.80 miles. His estimate was given as 12,803,337 cubits , so the accuracy of his estimate compared to the modern value depends on what conversion is used for cubits. The exact length of
18788-524: The reader may learn by the comparative treatment of the subject how much superior the institutions of Islam are, and how more plainly this contrast brings out all customs and usages, differing from those of Islam, in their essential foulness." However he was happy on occasion to express admiration for other cultures, and quoted directly from the sacred texts of other religions when reaching his conclusions. He strove to understand them on their own terms rather than trying to prove them wrong. His underlying concept
18942-957: The reader the theories of the Hindus exactly as they are, and I shall mention in connection with them similar theories of the Greeks in order to show the relationship existing between them. An example of Biruni's analysis is his summary of why many Hindus hate Muslims. Biruni notes in the beginning of his book how the Muslims had a hard time learning about Hindu knowledge and culture. He explains that Hinduism and Islam are totally different from each other. Moreover, Hindus in 11th century India had suffered waves of destructive attacks on many of its cities, and Islamic armies had taken numerous Hindu slaves to Persia, which – claimed Biruni – contributed to Hindus becoming suspicious of all foreigners, not just Muslims. Hindus considered Muslims violent and impure, and did not want to share anything with them. Over time, Biruni won
19096-537: The relationships between various arthropod groups are still actively debated. There are a number of marine invertebrates that use minerals that are present in the sea in such minute quantities that they were undetectable until the advent of spectroscopy . Vanadium is concentrated by some tunicates for use in their blood cells to a level ten million times that of the surrounding seawater. Other tunicates similarly concentrate niobium and tantalum . Lobsters use copper in their respiratory pigment hemocyanin , despite
19250-406: The same genotype. The possible mechanisms include fission, bailout and fragmentation. Fission occurs in some corals, especially among the family Fungiidae , where the colony splits into two or more colonies during early developmental stages. Bailout occurs when a single polyp abandons the colony and settles on a different substrate to create a new colony. Fragmentation involves individuals broken from
19404-559: The same night even when multiple species are present. Synchronous spawning may form hybrids and is perhaps involved in coral speciation . Environmental cues that influence the release of gametes into the water vary from species to species. The cues involve temperature change, lunar cycle , day length , and possibly chemical signalling. Other factors that affect the rhythmicity of organisms in marine habitats include salinity, mechanical forces, and pressure or magnetic field changes. Mass coral spawning often occurs at night on days following
19558-439: The same species release gametes simultaneously overnight, often around a full moon . Fertilized eggs form planulae, a mobile early form of the coral polyp which, when mature, settles to form a new colony. Although some corals are able to catch plankton and small fish using stinging cells on their tentacles, most corals obtain the majority of their energy and nutrients from photosynthetic unicellular dinoflagellates of
19712-479: The scientific language of his age, but al-Tafhim is one of the most important of the early works of science in Persian , and is a rich source for Persian prose and lexicography . The book covers the Quadrivium in a detailed and skilled fashion. Following Al-Biruni's death, his work was neither built upon or referenced by scholars. Centuries later, his writings about India, which had become of interest to
19866-430: The sediment. Their taxonomic affinities are presently unknown, but their mode of growth is consistent with a bilaterian affinity. Apart from Dickinsonia , the earliest widely accepted animal fossils are the rather modern-looking cnidarians (the group that includes jellyfish , sea anemones and Hydra ), possibly from around 580 Ma The Ediacara biota , which flourished for the last 40 million years before
20020-408: The skeleton, with the latter showing the greatest microbial richness. The zooxanthellae benefit from a safe place to live and consume the polyp's carbon dioxide , phosphate and nitrogenous waste. Stressed corals will eject their zooxanthellae, a process that is becoming increasingly common due to strain placed on coral by rising ocean temperatures. Mass ejections are known as coral bleaching because
20174-432: The skeletons allow to differentiate zooxanthellae and non-zooxanthellae specimens. Polyps feed on a variety of small organisms, from microscopic zooplankton to small fish. The polyp's tentacles immobilize or kill prey using stinging cells called nematocysts . These cells carry venom which they rapidly release in response to contact with another organism. A dormant nematocyst discharges in response to nearby prey touching
20328-519: The specific aspects of Hindu life that Biruni studied was the Hindu calendar . His scholarship on the topic exhibited great determination and focus, not to mention the excellence in his approach of the in-depth research he performed. He developed a method for converting the dates of the Hindu calendar to the dates of the three different calendars that were common in the Islamic countries of his time period,
20482-428: The start of the Cambrian , were the first animals more than a very few centimetres long. Like Dickinsonia , many were flat with a "quilted" appearance, and seemed so strange that there was a proposal to classify them as a separate kingdom , Vendozoa . Others, however, have been interpreted as early molluscs ( Kimberella ), echinoderms ( Arkarua ), and arthropods ( Spriggina , Parvancorina ). There
20636-452: The start of the Cambrian . Molluscs (Latin for soft ) form a phylum with about 85,000 extant recognized species . By species count they are the largest marine phylum, comprising about 23% of all the named marine organisms . Molluscs have more varied forms than other invertebrate phyla. They are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The majority of species still live in
20790-412: The sub-classes Hexacorallia and Octocorallia of the class Anthozoa in the phylum Cnidaria . Hexacorallia includes the stony corals and these groups have polyps that generally have a 6-fold symmetry. Octocorallia includes blue coral and soft corals and species of Octocorallia have polyps with an eightfold symmetry, each polyp having eight tentacles and eight mesenteries . The group of corals
20944-463: The tentacles are retracted by day and spread out at night to catch plankton and other small organisms. Shallow-water species of both stony and soft corals can be zooxanthellate , the corals supplementing their plankton diet with the products of photosynthesis produced by these symbionts . The polyps interconnect by a complex and well-developed system of gastrovascular canals, allowing significant sharing of nutrients and symbionts. The external form of
21098-516: The topic of density, including the different types of densities and how they are measured. His work on the subject was very influential and was later used by scientists like Galileo and Newton in their own research. Bīrūnī devised a novel method of determining the Earth's radius by means of the observation of the height of a mountain. He carried it out at Nandana in Pind Dadan Khan (present-day Pakistan). He used trigonometry to calculate
21252-452: The trigger ( Cnidocil ). A flap ( operculum ) opens and its stinging apparatus fires the barb into the prey. The venom is injected through the hollow filament to immobilise the prey; the tentacles then manoeuvre the prey into the stomach. Once the prey is digested the stomach reopens allowing the elimination of waste products and the beginning of the next hunting cycle. Many corals, as well as other cnidarian groups such as sea anemones form
21406-596: The true value. In his Codex Masudicus (1037), Al-Biruni theorized the existence of a landmass along the vast ocean between Asia and Europe, or what is today known as the Americas. He argued for its existence on the basis of his accurate estimations of the Earth's circumference and Afro-Eurasia 's size, which he found spanned only two-fifths of the Earth's circumference, reasoning that the geological processes that gave rise to Eurasia must surely have given rise to lands in
21560-605: The vast ocean between Asia and Europe. He also theorized that at least some of the unknown landmass would lie within the known latitudes which humans could inhabit, and therefore would be inhabited. Biruni wrote a pharmacopoeia , the Kitab al-saydala fi al-tibb (" Book on the Pharmacopoeia of Medicine "). It lists synonyms for drug names in Syriac, Persian, Greek, Baluchi, Afghan, Kurdi, and some Indian languages. He used
21714-425: The water where they meet and fertilize to spread offspring. Corals often synchronize their time of spawning. This reproductive synchrony is essential so that male and female gametes can meet. Spawning frequently takes place in the evening or at night, and can occur as infrequently as once a year, and within a window of 10–30 minutes. Synchronous spawning is very typical on the coral reef, and often, all corals spawn on
21868-540: The water's surface and form a microscopic larva called a planula , typically pink and elliptical in shape. A typical coral colony needs to release several thousand larvae per year to overcome the odds against formation of a new colony. Studies suggest that light pollution desynchronizes spawning in some coral species. In areas such as the Red Sea , as many as 10 out of 50 species may be showing spawning asynchrony, compared to 30 years ago. The establishment of new corals in
22022-554: The water's surface before descending to seek a hard surface on the benthos to which they can attach and begin a new colony. The larvae often need a biological cue to induce settlement such as specific crustose coralline algae species or microbial biofilms. High failure rates afflict many stages of this process, and even though thousands of eggs are released by each colony, few new colonies form. During settlement, larvae are inhibited by physical barriers such as sediment, as well as chemical (allelopathic) barriers. The larvae metamorphose into
22176-478: The welcome of Hindu scholars. Al-Biruni collected books and studied with these Hindu scholars to become fluent in Sanskrit, discover and translate into Arabic the mathematics, science, medicine, astronomy and other fields of arts as practiced in 11th-century India. He was inspired by the arguments offered by Indian scholars who believed earth must be globular in shape, which they felt was the only way to fully explain
22330-529: The well-known living and fossil forms are still subjects of vigorous debate among scientists. Arthropods (Greek for jointed feet ) have an exoskeleton (external skeleton ), a segmented body, and jointed appendages (paired appendages). They form a phylum which includes insects , arachnids , myriapods , and crustaceans . Arthropods are characterized by their jointed limbs and cuticle made of chitin , often mineralised with calcium carbonate . The arthropod body plan consists of segments , each with
22484-582: The words, at all events in the matter. In his major astronomical work, the Mas'ud Canon , Biruni observed that, contrary to Ptolemy , the Sun's apogee (highest point in the heavens) was mobile, not fixed. He wrote a treatise on the astrolabe , describing how to use it to tell the time and as a quadrant for surveying. One particular diagram of an eight-geared device could be considered an ancestor of later Muslim astrolabes and clocks. More recently, Biruni's eclipse data
22638-633: The works of Al-Biruni are in Arabic although he seemingly wrote the Kitab al-Tafhim in both Persian and Arabic, showing his mastery over both languages. Bīrūnī's catalogue of his own literary production up to his 65th lunar/63rd solar year (the end of 427/1036) lists 103 titles divided into 12 categories: astronomy, mathematical geography, mathematics, astrological aspects and transits, astronomical instruments, chronology, comets, an untitled category, astrology, anecdotes, religion, and books he no longer possesses. Biruni wrote most of his works in Arabic ,
22792-407: The zooxanthellae is their ability to photosynthesize which supplies corals with the products of photosynthesis, including glucose, glycerol, also amino acids, which the corals can use for energy. Zooxanthellae also benefit corals by aiding in calcification , for the coral skeleton, and waste removal. In addition to the soft tissue, microbiomes are also found in the coral's mucus and (in stony corals)
22946-438: Was a member of the lobopods , a group which includes the ancestors of the arthropods, and that it may have been closely related to the modern tardigrades . Nevertheless, there is still much debate about whether the Cambrian explosion was really explosive and, if so, how and why it happened and why it appears unique in the history of animals. Invertebrates are grouped into different phyla . Informally phyla can be thought of as
23100-430: Was able to measure the density of many different substances, including precious metals, gems, and even air. He also used this method to determine the radius of the earth, which he did by measuring the angle of elevation of the horizon from the top of a mountain and comparing it to the angle of elevation of the horizon from a nearby plain. In addition to developing the hydrostatic balance, Al-Biruni also wrote extensively on
23254-596: Was himself influenced by the scholars of other nations, such as the Greeks, from whom he took inspiration when he turned to the study of philosophy. A gifted linguist, he was conversant in Khwarezmian , Persian , Arabic, and Sanskrit , and also knew Greek , Hebrew , and Syriac . He spent much of his life in Ghazni , then capital of the Ghaznavids , in modern-day central-eastern Afghanistan. In 1017, he travelled to
23408-496: Was remarkable for its time. He stated that he was fully objective in his writings, remaining unbiased like a proper historian should. Biruni documented everything about India just as it happened. But, he did note how some of the accounts of information that he was given by natives of the land may not have been reliable in terms of complete accuracy, however, he did try to be as honest as possible in his writing. Eduard Sachau compares it to "a magic island of quiet, impartial research in
23562-440: Was that all cultures are at least distant relatives of all other cultures because they are all human constructs. "Rather, what Al-Biruni seems to be arguing is that there is a common human element in every culture that makes all cultures distant relatives, however foreign they might seem to one another." Al-Biruni divides Hindus into an educated and an uneducated class. He describes the educated as monotheistic, believing that God
23716-529: Was used by Dunthorne in 1749 to help determine the acceleration of the Moon , and his data on equinox times and eclipses was used as part of a study of Earth's past rotation. Like later adherents of the Ash'ari school, such as al-Ghazali , al-Biruni is famous for vehemently defending the majority Sunni position that the universe had a beginning, being a strong supporter of creatio ex nihilo , specifically refuting
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