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Evolution Of Mammalian Auditory Ossicles
The evolution of mammalian auditory ossicles was an evolutionary process that resulted in the formation of the mammalian middle ear, where the three middle ear bones or ossicles, namely the incus, malleus and stapes (a.k.a. "the anvil, hammer, and stirrup"), are a defining characteristic of mammals. The event is well-documented and important academically as a demonstration of transitional fossil, transitional forms and exaptation, the re-purposing of existing structures during evolution. The ossicles evolved from skull bones present in most tetrapods, including amphibians, sauropsids (which include extant taxon, extant reptiles and birds) and early synapsids (which include ancestors of mammals). The reptilian quadrate bone, quadrate, articular bone, articular and columella (auditory system), columella bones are homologs of the mammalian incus, malleus and stapes, respectively. In reptiles (and early synapsids by association), the eardrum is connected to the inner ear via a single ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation. The scientific theory of evolution by natural selection was conceived independently by two British naturalists, Charles Darwin and Alfred Russel Wallace, in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory was first set out in detail in Darwin's book ''On the Origin of Species''. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) phenotypic variatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quadrate Bone
The quadrate bone is a skull bone in most tetrapods, including amphibians, sauropsids ( reptiles, birds), and early synapsids. In most tetrapods, the quadrate bone connects to the quadratojugal and squamosal bones in the skull, and forms upper part of the jaw joint. The lower jaw articulates at the articular bone, located at the rear end of the lower jaw. The quadrate bone forms the lower jaw articulation in all classes except mammals. Evolutionarily, it is derived from the hindmost part of the primitive cartilaginous upper jaw. Function in reptiles In certain extinct reptiles, the variation and stability of the morphology of the quadrate bone has helped paleontologists in the species-level taxonomy and identification of mosasaur squamates and spinosaurine dinosaurs. In some lizards and dinosaurs, the quadrate is articulated at both ends and movable. In snakes, the quadrate bone has become elongated and very mobile, and contributes greatly to their ability to swallow ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Martin Rathke
Martin Heinrich Rathke (25 August 1793, Danzig – 3 September 1860, Königsberg) was a German embryologist and anatomist. Along with Karl Ernst von Baer and Christian Heinrich Pander, he is recognized as one of the founders of modern embryology.Martin Heinrich Rathke @ Who Named It He was the father of chemist Bernhard Rathke (1840–1923). He studied medicine and natural history at the University of Göttingen, later relocating to Berlin, where he received his doctorate in medicine (1818). In 1828 he was named professor of physiology, pathology and semiotics at the University of Dorpat. In 1832/33 he undertook research expeditions to Finland and to the Crimea. Rathke was a professor of zoology and anatomy at Königsberg from 1835 to 1860. In 1839, while based in Königsberg, he travelled to Scandinavia, where he conducted studie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carl Gustav Carus
Carl Gustav Carus (3 January 1789 – 28 July 1869) was a German physiologist and painter, born in Leipzig, who played various roles during the Romanticism, Romantic era. A friend of the writer Johann Wolfgang Goethe, he was a many-sided man: a doctor, a naturalist, a scientist, a psychologist, and a landscape painter who studied under Caspar David Friedrich. Life and work In 1811 he graduated as a doctor of medicine and a doctor of philosophy. In 1814 he was appointed professor of obstetrics and director of the maternity clinic at the teaching institution for medicine and surgery in Dresden. He wrote on art theory. From 1814 to 1817 he taught himself oil painting working under Caspar David Friedrich, a Dresden landscape painter. Subsequently, he studied under Julius Schnorr von Carolsfeld at the Oeser drawing academy. When the King of Saxony, Frederick Augustus II of Saxony, Frederick Augustus II, made an informal tour of Britain in 1844, Carus accompanied him as his personal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Johann Friedrich Meckel
Johann Friedrich Meckel (17 October 1781 – 31 October 1833), often referred to as Johann Friedrich Meckel, the Younger, was a German anatomist born in Halle. He worked as a professor of anatomy, pathology and zoology at the University of Halle, Germany. Life and research In 1802, he received his medical doctorate from the University of Halle, defending his doctoral thesis ''De cordis conditionibus abnormibus'' on 8 April 1802. At Halle he had as instructors, Kurt Sprengel (1766-1833) and Johann Christian Reil (1759-1813). After graduation, Meckel continued his education in Würzburg, Vienna and Paris. In Paris, he assisted zoologist Georges Cuvier (1769–1832) with systematic analysis of anatomical and zootomical specimens. In 1810 he finished translating Cuvier's five-volume ''Leçons d’anatomie Comparée'' from French into German. In 1808, he became a full professor of normal and pathological anatomy, surgery and obstetrics at the University of Halle, replacing Justus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Étienne Geoffroy Saint-Hilaire
Étienne Geoffroy Saint-Hilaire (; 15 April 177219 June 1844) 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 (unlike Lamarck's materialistic views) and were similar to those of German morphologists like Lorenz Oken. He believed in the underlying unity of organismal design, and the possibility of the transmutation of species in time, amassing evidence for his claims through research in comparative anatomy, paleontology, and embryology. He is considered as a predecessor of the evo-devo evolutionary concept. Life and early career Geoffroy was born at Étampes (in present-day Essonne), and studied at the Collège de Navarre, in Paris, where he studied natural philosophy under M. J. Brisson. He then attended the lectures of Louis-Jean-Marie Daubenton at the College de France and Fourcroy ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hearing
Hearing, or auditory perception, is the ability to perceive sounds through an organ, such as an ear, by detecting vibrations as periodic changes in the pressure of a surrounding medium. The academic field concerned with hearing is auditory science. Sound may be heard through solid, liquid, or gaseous matter. It is one of the traditional five senses. Partial or total inability to hear is called hearing loss. In humans and other vertebrates, hearing is performed primarily by the auditory system: mechanical waves, known as vibrations, are detected by the ear and transduction (physiology), transduced into nerve impulses that are perceived by the brain (primarily in the temporal lobe). Like touch, audition requires sensitivity to the movement of molecules in the world outside the organism. Both hearing and touch are types of mechanosensation. Hearing mechanism There are three main components of the human auditory system: the outer ear, the middle ear, and the inner ear. Outer ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amplifier
An amplifier, electronic amplifier or (informally) amp is an electronic device that can increase the magnitude of a signal (a time-varying voltage or current). It is a two-port electronic circuit that uses electric power from a power supply to increase the amplitude (magnitude of the voltage or current) of a signal applied to its input terminals, producing a proportionally greater amplitude signal at its output. The amount of amplification provided by an amplifier is measured by its gain: the ratio of output voltage, current, or power to input. An amplifier is defined as a circuit that has a power gain greater than one. An amplifier can be either a separate piece of equipment or an electrical circuit contained within another device. Amplification is fundamental to modern electronics, and amplifiers are widely used in almost all electronic equipment. Amplifiers can be categorized in different ways. One is by the frequency of the electronic signal being amplified. For ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Kinematic Chain
In mechanical engineering, a kinematic chain is an assembly of rigid bodies connected by joints to provide constrained motion that is the mathematical model for a mechanical system. Reuleaux, F., 187''The Kinematics of Machinery,''(trans. and annotated by A. B. W. Kennedy), reprinted by Dover, New York (1963) As the word chain suggests, the rigid bodies, or links, are constrained by their connections to other links. An example is the simple open chain formed by links connected in series, like the usual chain, which is the kinematic model for a typical robot manipulator.J. M. McCarthy and G. S. Soh, 2010''Geometric Design of Linkages,''Springer, New York. Mathematical models of the connections, or joints, between two links are termed kinematic pairs. Kinematic pairs model the hinged and sliding joints fundamental to robotics, often called ''lower pairs'' and the surface contact joints critical to cams and gearing, called ''higher pairs.'' These joints are generally modele ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mammalian Evolution
The evolution of mammals has passed through many stages since the first appearance of their synapsid ancestors in the Pennsylvanian (geology), Pennsylvanian sub-period of the late Carboniferous period. By the mid-Triassic, there were many synapsid species that looked like mammals. The lineage leading to today's mammals split up in the Jurassic; synapsids from this period include ''Dryolestes'', more closely related to extant placentals and marsupials than to monotremes, as well as ''Ambondro mahabo, Ambondro'', more closely related to monotremes. Later on, the eutherian and metatherian lineages separated; the metatherians are the animals more closely related to the marsupials, while the eutherians are those more closely related to the placentals. Since ''Juramaia'', the earliest known eutherian, lived 160 million years ago in the Jurassic, this divergence must have occurred in the same period. After the Cretaceous–Paleogene extinction event wiped out the non-avian dinosaurs (bi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Inner Ear
The inner ear (internal ear, auris interna) is the innermost part of the vertebrate ear. In vertebrates, the inner ear is mainly responsible for sound detection and balance. In mammals, it consists of the bony labyrinth, a hollow cavity in the temporal bone of the skull with a system of passages comprising two main functional parts: * The cochlea, dedicated to hearing; converting sound pressure patterns from the outer ear into electrochemical impulses which are passed on to the brain via the auditory nerve. * The vestibular system, dedicated to balance (ability), balance. The inner ear is found in all vertebrates, with substantial variations in form and function. The inner ear is innervated by the eighth cranial nerve in all vertebrates. Structure The labyrinth can be divided by layer or by region. Bony and membranous labyrinths The bony labyrinth, or osseous labyrinth, is the network of passages with bony walls lined with periosteum. The three major parts of the bony labyrin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eardrum
In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit changes in pressure of sound from the air to the ossicles inside the middle ear, and thence to the oval window in the fluid-filled cochlea. The ear thereby converts and amplifies vibration in the air to vibration in cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles. Rupture or perforation of the eardrum can lead to conductive hearing loss. Collapse or retraction of the eardrum can cause conductive hearing loss or cholesteatoma. Structure Orientation and relations The tympanic membrane is oriented obliquely in the anteroposterior, mediolateral, and superoinferior planes. Consequently, its superoposterior end lies lateral to its anteroinferior end. Anatomically, it relates superiorly to the middle crani ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
