Zoology is the branch of biology that studies the animal kingdom, including the structure, evolution, classification and distribution of all animals, both living and extinct, how they interact with their ecosystems. The term is derived from Ancient Greek ζῷον, zōion, i.e. "animal" and λόγος, logos, i.e. "knowledge, study". The history of zoology traces the study of the animal kingdom from ancient to modern times. Although the concept of zoology as a single coherent field arose much the zoological sciences emerged from natural history reaching back to the biological works of Aristotle and Galen in the ancient Greco-Roman world; this ancient work was further developed in the Middle Ages by Muslim physicians and scholars such as Albertus Magnus. During the Renaissance and early modern period, zoological thought was revolutionized in Europe by a renewed interest in empiricism and the discovery of many novel organisms. Prominent in this movement were Vesalius and William Harvey, who used experimentation and careful observation in physiology, naturalists such as Carl Linnaeus, Jean-Baptiste Lamarck, Buffon who began to classify the diversity of life and the fossil record, as well as the development and behavior of organisms.
Microscopy revealed the unknown world of microorganisms, laying the groundwork for cell theory. The growing importance of natural theology a response to the rise of mechanical philosophy, encouraged the growth of natural history. Over the 18th, 19th, 20th centuries, zoology became an professional scientific discipline. Explorer-naturalists such as Alexander von Humboldt investigated the interaction between organisms and their environment, the ways this relationship depends on geography, laying the foundations for biogeography and ethology. Naturalists began to reject essentialism and consider the importance of extinction and the mutability of species. Cell theory provided a new perspective on the fundamental basis of life; these developments, as well as the results from embryology and paleontology, were synthesized in Charles Darwin's theory of evolution by natural selection. In 1859, Darwin placed the theory of organic evolution on a new footing, by his discovery of a process by which organic evolution can occur, provided observational evidence that it had done so.
Darwin gave a new direction to morphology and physiology, by uniting them in a common biological theory: the theory of organic evolution. The result was a reconstruction of the classification of animals upon a genealogical basis, fresh investigation of the development of animals, early attempts to determine their genetic relationships; the end of the 19th century saw the fall of spontaneous generation and the rise of the germ theory of disease, though the mechanism of inheritance remained a mystery. In the early 20th century, the rediscovery of Mendel's work led to the rapid development of genetics, by the 1930s the combination of population genetics and natural selection in the modern synthesis created evolutionary biology. Cell biology studies the structural and physiological properties of cells, including their behavior and environment; this is done on both the microscopic and molecular levels, for single-celled organisms such as bacteria as well as the specialized cells in multicellular organisms such as humans.
Understanding the structure and function of cells is fundamental to all of the biological sciences. The similarities and differences between cell types are relevant to molecular biology. Anatomy considers the forms of macroscopic structures such as organs and organ systems, it focuses on how organs and organ systems work together in the bodies of humans and animals, in addition to how they work independently. Anatomy and cell biology are two studies that are related, can be categorized under "structural" studies. Physiology studies the mechanical and biochemical processes of living organisms by attempting to understand how all of the structures function as a whole; the theme of "structure to function" is central to biology. Physiological studies have traditionally been divided into plant physiology and animal physiology, but some principles of physiology are universal, no matter what particular organism is being studied. For example, what is learned about the physiology of yeast cells can apply to human cells.
The field of animal physiology extends the tools and methods of human physiology to non-human species. Physiology studies how for example nervous, endocrine and circulatory systems and interact. Evolutionary research is concerned with the origin and descent of species, as well as their change over time, includes scientists from many taxonomically oriented disciplines. For example, it involves scientists who have special training in particular organisms such as mammalogy, herpetology, or entomology, but use those organisms as systems to answer general questions about evolution. Evolutionary biology is based on paleontology, which uses the fossil record to answer questions about the mode and tempo of evolution, on the developments in areas such as population genetics and evolutionary theory. Following the development of DNA fingerprinting techniques in the late 20th century, the application of these techniques in zoology has increased the understanding of animal populations. In the 1980s, developmental biology re-entered evolutionary biology from its initial exclusion from the modern synthesis through the study of evolutionary developmental biology.
Related fields considered part of evolutionary biology are phylogenetics and taxonomy. Scientific classification in zoology, is a method by which
Harz National Park
Harz National Park is a nature reserve in the German federal states of Lower Saxony and Saxony-Anhalt. It comprises portions of the western Harz mountain range, extending from Herzberg and Bad Lauterberg at the southern edge to Bad Harzburg and Ilsenburg on the northern slopes. 95 % of the area is covered with forests with spruce and beech woods, including several bogs, granite rocks and creeks. The park is part of the Natura 2000 network of the European Union. In its current form, the park was created on January 1, 2006 by the merger of the Harz National Park in Lower Saxony, established in 1994, the Upper Harz National Park in Saxony-Anhalt, established in 1990; as the former inner German border ran through the Harz, large parts of the range were prohibited areas, that apart from the fortifications had remained unaffected for decades. Today the park covers parts of the districts of Göttingen and Harz. Rare animals of the Harz National Park include the dipper, the black stork, peregrine falcon, the European wildcat and the Eurasian lynx.
The last lynx in the Harz Mountains had been shot in 1818, but in 1999 a project for reintroducing was established. Since 2002 several wild lynxes gave birth. An attempt to return the capercaillie however did not succeed; the 24,700 hectares of the Harz National Park cover about 10 per cent of the total area of the Harz. The park lies in the western part of the Harz and stretches from Wernigerode and Ilsenburg in the north to Herzberg and Bad Lauterberg in the south. Near its perimeter the park terrain is about 230 m above sea level in the north and 270 m above NN in the south and climbs to 1,141.1 m above NN at the summit of the Brocken. Several rivers have their sources in the national park, including the Bode, the Oder and the Ilse, a tributary of the Oker; the waters of the Oder, flowing southwards, are collected in the historic Oderteich reservoir, finished in 1722 to supply the mines in Sankt Andreasberg, feed the Oder Dam on the southeastern edge of the park. Other dams and lakes within or bordering on the national park include the Ecker Dam and the Silberteich.
The highest elevations are the Bruchberg and the Achtermann. The present, pan-state Nationalpark Harz was formed on 1 January 2006 from the merger of the old park of the same name in Lower Saxony and the High Harz National Park in Saxony-Anhalt. Since the merger the head of this major nature conservation area has been Andreas Pusch; the Upper Harz National Park was established as part of GDR's national park programme on 1 October 1990, two days before the reunification of Germany, on the basis of a ministerial decision by the East German government. The park included large parts of the eastern Harz from the Ecker Dam and the national park municipality of Ilsenburg in the north and Schierke in the south as well as the Brocken; the region is characterised by a undisturbed plant and animal environment, due to its location next to the old Inner German Border. In the German Democratic Republic era, the Brocken was accessible until 1961 with an obtained pass. From 13 August 1961 it became an out-of-bounds area, which meant that tourists could no longer visit it.
In the mid-1980s the first problems appeared in the Harz, such as bark beetle and fungal infestation. In the wake of the spirit of optimism during the time around reunification it was this that gave impetus for the establishment of the national park. On 1 January 1991 a national park headquarters in Wernigerode was set up under the leadership of Hubertus Hlawatsch. Hlawatsch's successor was Peter Gaffert, who ran the eastern park from 1995 until its merger with the Harz National Park in the western Harz on 1 January 2006; the Lower Saxon part of the park was opened on 1 January 1994 after four years of preparation. Its founding father was Dr. Wolf-Eberhard Barth. Although a combined national park project was discussed soon after reunification by both states it was another twelve years before the parks were merged; the Harz National Park belongs to the European umbrella organisation EUROPARC Federation, a federation of national parks, biosphere reserves and nature parks. It concerns itself inter alia with the exchange of information, advanced education and public relations.
The German section, EUROPARC Deutschland, of this umbrella organisation has organised the merger of many large conservation areas in Germany. In 2005 the national park was included in the European Charter for Sustainable Tourism in Protected Areas; the national park employs 188 staff, of which 59 work in the national park head office in Wernigerode or its outpost in Sankt Andreasberg OT Oderhaus. The 40 employees of the national park warden service, who are known as rangers, conduct guided tours and look after tasks in connexion with environmental training, include the maintenance of information posts and national park buildings; the natural forests of the High Harz consist of Norway spruce and rowan. Since the Harz was deforested in the 19th century by ore mining, the count's head forester, Hans Dietrich von Zanthier, developed the concept of reforestation with fast-growing spruce trees; this led to the now widespread spruce monocultures. Unlike "Harz pine", the pines introduced from other regions cope less well with snow and ice conditions in the Harz and are thus more prone to bark beetle infestation.
82 percent of the forest consists of spruce stands. Only 12 percent of the trees are beeches; the remaining 6 percent are species such as rowan or birch. There are various vegetation zones in
Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire was a French naturalist who established the principle of "unity of composition". He was a colleague of Jean-Baptiste Lamarck and expanded and defended Lamarck's evolutionary theories. Geoffroy's scientific views had a transcendental flavor and were similar to those of German morphologists like Lorenz Oken, he believed in the underlying unity of organismal design, the possibility of the transmutation of species in time, amassing evidence for his claims through research in comparative anatomy and embryology. Geoffroy was born at Étampes, studied at the Collège de Navarre, in Paris, where he studied natural philosophy under M. J. Brisson, he attended the lectures of Daubenton at the College de France and Fourcroy at the Jardin des Plantes. In March 1793 Louis-Jean-Marie Daubenton, through the interest of Bernardin de Saint-Pierre, procured him the office of sub-keeper and assistant demonstrator of the cabinet of natural history, made vacant by the resignation of Bernard Germain Étienne de la Ville, Comte de Lacépède.
By a law passed in June 1793, Geoffroy was appointed one of the twelve professors of the newly constituted Muséum National d'Histoire Naturelle, being assigned the chair of zoology. In the same year he busied himself with the formation of a menagerie at that institution. In 1794, Geoffroy entered into correspondence with Georges Cuvier. Shortly after the appointment of Cuvier as assistant at the Museum d'Histoire Naturelle, Geoffroy received him into his house; the two friends wrote together five memoirs on natural history, one of which, on the classification of mammals, puts forward the idea of the subordination of characters upon which Cuvier based his zoological system. It was in a paper entitled Histoire des Makis, ou singes de Madagascar, written in 1795, that Geoffroy first gave expression to his views on the unity of organic composition, the influence of, perceptible in all his subsequent writings. In 1798, Geoffroy was chosen a member of Napoleon's great scientific expedition to Egypt as part of the natural history and physics section of the Institut d'Égypte.
On the capitulation of Alexandria in August 1801, he took part in resisting the claim made by the British general to the collections of the expedition, declaring that, were that demand persisted in, history would have to record that he had burnt a library in Alexandria. Early in January 1802 Geoffroy returned to Paris, he was elected a member of the French Academy of Sciences in September 1807. In March of the following year Napoleon, who had recognized his national services by the award of the cross of the legion of honor, selected him to visit the museums of Portugal, for the purpose of procuring collections from them, in the face of considerable opposition from the British he was successful in retaining them as a permanent possession for his country. In 1809, the year after his return to France, Geoffroy was made professor of zoology at the faculty of sciences at Paris, from that period he devoted himself more than before to anatomical study. In 1818 he published the first part of his celebrated Philosophie anatomique, the second volume of which, published in 1822, subsequent memoirs account for the formation of monstrosities on the principle of arrest of development, of the attraction of similar parts.
Geoffroy's friend Robert Edmund Grant shared his views on unity of plan and corresponded with him while working on marine invertebrates in the late 1820s in Edinburgh when Grant identified the pancreas in molluscs. When, in 1830, Geoffroy proceeded to apply to the invertebrata his views as to the unity of animal composition, he found a vigorous opponent in Cuvier, his former friend. Geoffroy, a synthesiser, contended, in accordance with his theory of unity of plan in organic composition, that all animals are formed of the same elements, in the same number. With Johann Wolfgang von Goethe he held that there is in nature a law of compensation or balancing of growth, so that if one organ take on an excess of development, it is at the expense of some other part, it was his conviction that, owing to the conditions of life, the same forms had not been perpetuated since the origin of all things, although it was not his belief that existing species are becoming modified. Cuvier, an analytical observer of facts, admitted only the prevalence of laws of co-existence or harmony in animal organs, maintained the absolute invariability of species, which he declared had been created with a regard to the circumstances in which they were placed, each organ contrived with a view to the function it had to fulfil, thus putting, in Geoffroy's considerations, the effect for the cause.
In 1836 he coined the term phocomelia. In July 1840, Geoffroy became blind, some months he had a paralytic attack. From that time his strength failed him, he resigned his chair at the museum in 1841, was succeeded by his son, Isidore Geoffroy Saint
University of Jena
Friedrich Schiller University Jena is a public research university located in Jena, Germany. The university is counted among the ten oldest universities in Germany, it is affiliated with six Nobel Prize winners, most in 2000 when Jena graduate Herbert Kroemer won the Nobel Prize for physics. It was renamed after the poet Friedrich Schiller, teaching as professor of philosophy when Jena attracted some of the most influential minds at the turn of the 19th century. With Karl Leonhard Reinhold, Johann Gottlieb Fichte, G. W. F. Hegel, F. W. J. Schelling and Friedrich von Schlegel on its teaching staff, the university has been at the centre of the emergence of German idealism and early Romanticism; as of 2014, the university has around 19,000 students enrolled and 375 professors. Its current president, Walter Rosenthal, was elected in 2014 for a six-year term. Elector John Frederick of Saxony first thought of a plan to establish a university at Jena upon Saale in 1547 while he was being held captive by emperor Charles V.
The plan was put into motion by his three sons and, after having obtained a charter from the Emperor Ferdinand I, the university was established on 2 February 1558. The university, jointly maintained by the Saxon Duchies who derived from partitioning of John Frederick's duchy, was thus named Ducal Pan-Saxon University or Salana. Prior to the 20th century, University enrollment peaked in the 18th century; the university's reputation peaked under the auspices of Duke Charles Augustus, Goethe's patron, when Gottlieb Fichte, G. W. F. Hegel, Friedrich Schelling, Friedrich von Schlegel and Friedrich Schiller were on its teaching staff. Founded as a home for the new religious opinions of the sixteenth century, it has since been one of the most politically radical universities in Germany. Jena was noted among other German universities at the time for allowing students to duel and to have a passion for Freiheit, which were popularly regarded as the necessary characteristics of German student life; the University of Jena has preserved a historical detention room or Karzer with famous caricatures by Swiss painter Martin Disteli.
In the latter 19th century, the department of zoology taught evolutionary theory, with Carl Gegenbaur, Ernst Haeckel and others publishing detailed theories at the time of Darwin's "Origin of Species". The fame of Ernst Haeckel eclipsed Darwin in some European countries, as the term "Haeckelism" was more common than Darwinism. In 1905, Jena had 1,100 students enrolled and its teaching staff numbered 112. Amongst its numerous auxiliaries were the library, with 200,000 volumes. After the end of the Saxon duchies in 1918, their merger with further principalities into the Free State of Thuringia in 1920, the university was renamed as the Thuringian State University in 1921. In 1934 the university was renamed again, receiving its present name of Friedrich Schiller University. During the 20th century, the cooperation between Zeiss corporation and the university brought new prosperity and attention to Jena, resulting in a dramatic increase in funding and enrollment. During the Third Reich, staunch Nazis moved into leading positions at the university.
The racial researcher and SS-Hauptscharführer Karl Astel was appointed professor in 1933, bypassing traditional qualifications and process. In 1933, many professors had to leave the university as a consequence of the Law for the Restoration of the Professional Civil Service. Student fraternities - in particular the Burschenschaften - were dissolved and incorporated into the Nazi student federation; the Nazi student federation enjoyed before the transfer of power and won great support among the student body elections in January 1933, achieving 49.3% of the vote, which represents the second best result. Between the Jena connections and the NS students wide-ranging human and ideological connections were recorded; when the Allied air raids to Jena in February and March struck in 1945, the University Library, the University main building and several clinics in the Bachstraße received total or significant physical damage. Destroyed were the Botanical Garden, the psychological and the physiological institute and three chemical Institutes.
An important event for the National Socialist period was the investigation of the pediatrician Yusuf Ibrahim. A Senate Commission noted the participation of the physician to the "euthanasia" murders of physically or mentally disabled children. In the 20th century the university was promoted through cooperation with Carl Zeiss and became thereby a mass university. In 1905 the university had 1,100 students and 112 university teachers, so this figure has since been twenty-fold; the Thuringian State University is the only comprehensive university of the Free State. Since 1995, there is a university association with the Martin Luther University of Halle-Wittenberg and the University of Leipzig; the aim is firstly to give the students the opportunity to visit with few problems at the partner universities and events in order to broaden the range of subjects and topics. E. g. has joined a cooperation in teaching in the field of bioinformatics. In addition, the cooperation provides the university management the opportunity to share experiences with their regular meetings and initiate common projects.
So z. B. we
Zürich or Zurich is the largest city in Switzerland and the capital of the canton of Zürich. It is located in north-central Switzerland at the northwestern tip of Lake Zürich; the municipality has 409,000 inhabitants, the urban agglomeration 1.315 million and the Zürich metropolitan area 1.83 million. Zürich is a hub for railways and air traffic. Both Zürich Airport and railway station are the busiest in the country. Permanently settled for over 2,000 years, Zürich was founded by the Romans, who, in 15 BC, called it Turicum. However, early settlements have been found dating back more than 6,400 years ago. During the Middle Ages, Zürich gained the independent and privileged status of imperial immediacy and, in 1519, became a primary centre of the Protestant Reformation in Europe under the leadership of Huldrych Zwingli; the official language of Zürich is German, but the main spoken language is the local variant of the Alemannic Swiss German dialect, Zürich German. Many museums and art galleries can be found in the city, including the Swiss National Museum and the Kunsthaus.
Schauspielhaus Zürich is one of the most important theatres in the German-speaking world. Zürich is a leading global city and among the world's largest financial centres despite having a small population; the city is home to a large number of financial institutions and banking companies. Most of Switzerland's research and development centres are concentrated in Zürich and the low tax rates attract overseas companies to set up their headquarters there. Monocle's 2012 "Quality of Life Survey" ranked Zürich first on a list of the top 25 cities in the world "to make a base within". According to several surveys from 2006 to 2008, Zürich was named the city with the best quality of life in the world as well as the wealthiest city in Europe in terms of GDP per capita; the Economist Intelligence Unit's Global Liveability Ranking sees Zürich rank among the top ten most liveable cities in the world. In German, the city name is written Zürich, pronounced in Swiss Standard German. In Zürich German, the local dialect of Swiss German, the name is pronounced without the final consonant, as Züri, although the adjective remains Zürcher.
The city is called Zurich in French, Zurigo in Italian, Turitg in Romansh. In English, the name used to be written without the umlaut. So, standard English practice for German calques is to either preserve the umlaut or replace it with the base letter followed by e, it is pronounced ZEWR-ik, more sometimes with /ts/, as in German. The earliest known form of the city's name is Turicum, attested on a tombstone of the late 2nd century AD in the form STA TURICEN; the name is interpreted as a derivation from a given name Gaulish personal name Tūros, for a reconstructed native form of the toponym of *Turīcon. The Latin stress on the long vowel of the Gaulish name, was lost in German but is preserved in Italian and in Romansh; the first development towards its Germanic form is attested as early as the 6th century with the form Ziurichi. From the 9th century onward, the name is established in an Old High German form Zurih. In the early modern period, the name became associated with the name of the Tigurini, the name Tigurum rather than the historical Turicum is sometimes encountered in Modern Latin contexts.
Settlements of the Neolithic and Bronze Age were found around Lake Zürich. Traces of pre-Roman Celtic, La Tène settlements were discovered near the Lindenhof, a morainic hill dominating the SE - NW waterway constituted by Lake Zurich and the river Limmat. In Roman times, during the conquest of the alpine region in 15 BC, the Romans built a castellum on the Lindenhof. Here was erected Turicum, a tax-collecting point for goods trafficked on the Limmat, which constituted part of the border between Gallia Belgica and Raetia: this customs point developed into a vicus. After Emperor Constantine's reforms in AD 318, the border between Gaul and Italy was located east of Turicum, crossing the river Linth between Lake Walen and Lake Zürich, where a castle and garrison looked over Turicum's safety; the earliest written record of the town dates from the 2nd century, with a tombstone referring to it as to the Statio Turicensis Quadragesima Galliarum, discovered at the Lindenhof. In the 5th century, the Germanic Alemanni tribe settled in the Swiss Plateau.
The Roman castle remained standing until the 7th century. A Carolingian castle, built on the site of the Roman castle by the grandson of Charlemagne, Louis the German, is mentioned in 835. Louis founded the Fraumünster abbey in 853 for his daughter Hildegard, he endowed the Benedictine convent with the lands of Zürich and the Albis forest, granted the convent immunity, placing it under his direct authority. In 1045, King Henry III granted the convent the right to hold markets, collect tolls, mint coins, thus made the abbess the ruler of the city. Zürich gained Imperial immediacy in 1218 with the extinction of the main line of the Zähringer family and attained a status comparable to statehood. During the 1230s, a city wall was built, enclosing 38 hectares, when the earliest stone houses on the Rennweg were built as well; the Carolingian castle was used as a quarry, as it had st
University of Zurich
The University of Zurich, located in the city of Zürich, is the largest university in Switzerland, with over 25,000 students. It was founded in 1833 from the existing colleges of theology, medicine and a new faculty of philosophy; the university has seven faculties: Philosophy, Human Medicine, Economic Sciences, Law and Natural Sciences and Veterinary Medicine. The university offers the widest range of subjects and courses of any Swiss higher education institution; as of October 2018, 23 Nobel laureates and 1 Turing Award winner have been affiliated with University of Zurich as alumni, faculty or researchers. The University of Zurich was founded on April 29, 1833, when the existing colleges of theology, the Carolinum founded by Huldrych Zwingli in 1525, law and medicine were merged with a new faculty of Philosophy, it was the first university in Europe to be founded by the state rather than a church. In the University's early years, the 1839 appointment of the German theologian David Friedrich Strauss to its Chair of Theology caused a major controversy, since Strauss argued that the miracles in the Christian New Testament were mythical retellings of normal events as supernatural happenings.
The authorities offered Strauss a pension before he had a chance to start his duties. The university allowed women to attend philosophy lectures from 1847, admitted the first female doctoral student in 1866; the Faculty of Veterinary Medicine was added in the second-oldest such faculty in the world. In 1914, the university moved to new premises designed by the architect Karl Moser on Rämistrasse 71; the university is scattered all over the city of Zurich. Members of the university can use several libraries, including the ETH-library, the Zurich Central Library, with over 5 million volumes. In 1962, the faculty of science proposed to establish the Irchelpark campus on the Strickhofareal; the first stage the construction of the university buildings was begun in 1973, the campus was inaugurated in 1979. The construction of the second stage lasted from 1978 to 1983; the campus houses the anthropological museum Anthropologisches Museum, the cantonal Staatsarchiv Zürich. The Institute and Museum for the History of Medicine is part of the university.
The University of Zurich as a whole ranks in the top ten of Europe and in the top fifty worldwide. Notably in the fields of bioscience and finance, there is a close-knit collaboration between the University of Zurich and the ETH, their faculty of chiropractic medicine is six years. Shanghai Jiao Tong University Ranking 54th 15th in Europe. THES – QS World University Rankings 61st globally and 14th in Europe. QS World University Rankings 201457th globally. Professional Ranking of World Universities 10th in Europe. University Ranking by Academic Performance 201052nd globally and 1st in Switzerland; the university’s Department of Economics is strong and was ranked first in the German-speaking area by the Handelsblatt in 2017. In 2009 the faculty of Business Administration was ranked third in the German-speaking area. Bachelor courses are taught in Swiss Standard German, but use of English is increasing in many faculties; the only bachelors program taught in English is the "English Language and Literature" program.
All Master courses at the Faculty of Science are held in English. Master courses in Economics and Finance are held in English, while the Master of Science in Quantitative Finance is held in English. Rolf Pfeifer – Artificial Intelligence Laboratory, IFI Albert Hofmann - Medicinal Chemistry Albert Einstein - Physics and Philosophy The university's Academic Sports Association offers a wide range of sports facilities to students of the university. Associated with the university are 12 Nobel Prize recipients in Physics and Chemistry. Corpus Córporum, digital library created and maintained by the University's Institute for Greek and Latin Philology. Swiss National Supercomputing Centre List of largest universities by enrollment in Switzerland List of modern universities in Europe Union of students' associations of the University of Zurich The Ranking Forum of Swiss Universities
In biology, homology is the existence of shared ancestry between a pair of structures, or genes, in different taxa. A common example of homologous structures is the forelimbs of vertebrates, where the wings of bats, the arms of primates, the front flippers of whales and the forelegs of dogs and horses are all derived from the same ancestral tetrapod structure. Evolutionary biology explains homologous structures adapted to different purposes as the result of descent with modification from a common ancestor; the term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was explained by Charles Darwin's theory of evolution in 1859, but had been observed before this, from Aristotle onwards, it was explicitly analysed by Pierre Belon in 1555. In developmental biology, organs that developed in the embryo in the same manner and from similar origins, such as from matching primordia in successive segments of the same animal, are serially homologous.
Examples include the legs of a centipede, the maxillary palp and labial palp of an insect, the spinous processes of successive vertebrae in a vertebral column. Male and female reproductive organs are homologous if they develop from the same embryonic tissue, as do the ovaries and testicles of mammals including humans. Sequence homology between protein or DNA sequences is defined in terms of shared ancestry. Two segments of DNA can have shared ancestry because of either a speciation event or a duplication event. Homology among proteins or DNA is inferred from their sequence similarity. Significant similarity is strong evidence that two sequences are related by divergent evolution from a common ancestor. Alignments of multiple sequences are used to discover the homologous regions. Homology remains controversial in animal behaviour, but there is suggestive evidence that, for example, dominance hierarchies are homologous across the primates. Homology was noticed by Aristotle, was explicitly analysed by Pierre Belon in his 1555 Book of Birds, where he systematically compared the skeletons of birds and humans.
The pattern of similarity was interpreted as part of the static great chain of being through the mediaeval and early modern periods: it was not seen as implying evolutionary change. In the German Naturphilosophie tradition, homology was of special interest as demonstrating unity in nature. In 1790, Goethe stated his foliar theory in his essay "Metamorphosis of Plants", showing that flower part are derived from leaves; the serial homology of limbs was described late in the 18th century. The French zoologist Etienne Geoffroy Saint-Hilaire showed in 1818 in his theorie d'analogue that structures were shared between fishes, reptiles and mammals; when Geoffroy went further and sought homologies between Georges Cuvier's embranchements, such as vertebrates and molluscs, his claims triggered the 1830 Cuvier-Geoffroy debate. Geoffroy stated the principle of connections, namely that what is important is the relative position of different structures and their connections to each other; the Estonian embryologist Karl Ernst von Baer stated what are now called von Baer's laws in 1828, noting that related animals begin their development as similar embryos and diverge: thus, animals in the same family are more related and diverge than animals which are only in the same order and have fewer homologies.
Von Baer's theory recognises that each taxon has distinctive shared features, that embryonic development parallels the taxonomic hierarchy: not the same as recapitulation theory. The term "homology" was first used in biology by the anatomist Richard Owen in 1843 when studying the similarities of vertebrate fins and limbs, defining it as the "same organ in different animals under every variety of form and function", contrasting it with the matching term "analogy" which he used to describe different structures with the same function. Owen codified 3 main criteria for determining if features were homologous: position and composition. In 1859, Charles Darwin explained homologous structures as meaning that the organisms concerned shared a body plan from a common ancestor, that taxa were branches of a single tree of life; the word homology, coined in about 1656, is derived from the Greek ὁμόλογος homologos from ὁμός homos "same" and λόγος logos "relation". Biological structures or sequences in different taxa are homologous if they are derived from a common ancestor.
Homology thus implies divergent evolution. For example, many insects possess two pairs of flying wings. In beetles, the first pair of wings has evolved into a pair of hard wing covers, while in Dipteran flies the second pair of wings has evolved into small halteres used for balance; the forelimbs of ancestral vertebrates have evolved into the front flippers of whales, the wings of birds, the running forelegs of dogs and horses, the short forelegs of frogs and lizards, the grasping hands of primates including humans. The same major forearm bones are found in fossils of lobe-finned fish such as Eusthenopteron; the opposite of homologous organs are analogous organs which do similar jobs in two taxa that were not present in their most recent common ancestor but rather evolved separately. For example, the wings of insects and birds evolved independently in separated groups, converged functionally to support powered flight, so they are analogous; the wings of a sycamore maple seed and the wings of a bird are analogous but not homologous, as they develop from quite different structures.
A structure can be only analogous at another. Pterosaur and bat wings are analogous as wings