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Polypterus
''Polypterus'' is a genus of freshwater fish in the bichir family (Polypteridae) of order Polypteriformes. The type species is the Nile bichir (''P. bichir''). Fish in this genus live in various areas in Africa. ''Polypterus'' is the only known vertebrate to have lungs, but no trachea. The etymology of the genus name derives from a combination of the Greek prefix πολυ-, ''poly-'' (many) and the root word πτερον, ''pteron'' (wing or fin) – "many fins". Recoil aspiration In shallow water, ''Polypterus'' inhales primarily through its spiracle (blowhole). Exhalation is powered by muscles in the torso. During exhalation, the bony scales in the upper chest become indented. When the muscles are relaxed, the bony scales spring back into position, generating negative pressure within the torso, resulting in a rapid intake of air through the spiracle. The air is nearly sufficient to fill the lungs. This is followed by one cycle of buccal (mouth) pumping, which "tops off ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypteriformes
Bichirs and the reedfish comprise Polypteridae , a family of archaic ray-finned fishes and the only family in the order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries. Cladistia, polypterids and their fossil relatives, are considered the sister group to all other extant ray-finned fishes (Actinopteri).Dai Suzuki, Matthew C. Brandley, Masayoshi Tokita: ''CORRECTION: The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes.'' BMC Evolutionary Biology. Bd. 10, Art.-Nr. 209, 2010, They likely diverged from Actinopteri at least 330 million years ago. A closely related group, the Scanilepiformes, are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bichir
Bichirs and the reedfish comprise Polypteridae , a family of archaic ray-finned fishes and the only family in the order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries. Cladistia, polypterids and their fossil relatives, are considered the sister group to all other extant ray-finned fishes (Actinopteri).Dai Suzuki, Matthew C. Brandley, Masayoshi Tokita: ''CORRECTION: The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes.'' BMC Evolutionary Biology. Bd. 10, Art.-Nr. 209, 2010, They likely diverged from Actinopteri at least 330 million years ago. A closely related group, the Scanilepiformes, a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypteridae
Bichirs and the reedfish comprise Polypteridae , a family of archaic ray-finned fishes and the only family in the order Polypteriformes .Helfman GS, Collette BB, Facey DE, Bowen BW. 2009. The Diversity of Fishes. West Sussex, UK: Blackwell Publishing. 720 p. All the species occur in freshwater habitats in tropical Africa and the Nile River system, mainly swampy, shallow floodplains and estuaries. Cladistia, polypterids and their fossil relatives, are considered the sister group to all other extant ray-finned fishes (Actinopteri).Dai Suzuki, Matthew C. Brandley, Masayoshi Tokita: ''CORRECTION: The mitochondrial phylogeny of an ancient lineage of ray-finned fishes (Polypteridae) with implications for the evolution of body elongation, pelvic fin loss, and craniofacial morphology in Osteichthyes.'' BMC Evolutionary Biology. Bd. 10, Art.-Nr. 209, 2010, They likely diverged from Actinopteri at least 330 million years ago. A closely related group, the Scanilepiformes, are ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Polypterus Bichir
''Polypterus bichir'', the Nile bichir, is a fish which lives in the Nile and some of its tributaries in Africa Africa is the world's second-largest and second-most populous continent, after Asia in both cases. At about 30.3 million km2 (11.7 million square miles) including adjacent islands, it covers 6% of Earth's total surface area .... It is a dark grayish color on the top, with a dark vertical marking and bands on the flank. This marking is more prominent on juveniles, and fades as the fish grows. References * Polypteridae Fish described in 1803 Taxa named by Bernard Germain de Lacépède {{Chondrostei-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Calamoichthys
The reedfish, ropefish (more commonly used in the United States), or snakefish, ''Erpetoichthys calabaricus'', is a species of fish in the bichir family and order. It is the only member of the genus ''Erpetoichthys''. It is native to fresh and brackish waters in West and Central Africa. The reedfish possesses a pair of lungs in addition to gills, allowing it to survive in very oxygen-poor water. It is threatened by habitat loss through palm oil plantations, other agriculture, deforestation, and urban development. Description The largest confirmed reedfish museum specimen was long, and two studies where more than 1,600 wild reedfish were caught (using basket traps, meaning that only individuals longer than were retained) found none that exceeded . Although sometimes claimed to reach up to long, this is incorrect. The reedfish has an eel-like, elongated body without a trace of a ventral fin. The long dorsal fin consist of a series of well-separated spines, each supporting on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fish
Fish are aquatic, craniate, gill-bearing animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish as well as various extinct related groups. Approximately 95% of living fish species are ray-finned fish, belonging to the class Actinopterygii, with around 99% of those being teleosts. The earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era, diversifying into a wide variety of forms. Many fish of the Paleozoic developed external armor that protected them from predators. The first fish with jaws appeared in the Silurian period, after which many (such as sharks) became formidable marine predators rather than just the prey of arthropods. Mos ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lung
The lungs are the primary organs of the respiratory system in humans and most other animals, including some snails and a small number of fish. In mammals and most other vertebrates, two lungs are located near the backbone on either side of the heart. Their function in the respiratory system is to extract oxygen from the air and transfer it into the bloodstream, and to release carbon dioxide from the bloodstream into the atmosphere, in a process of gas exchange. Respiration is driven by different muscular systems in different species. Mammals, reptiles and birds use their different muscles to support and foster breathing. In earlier tetrapods, air was driven into the lungs by the pharyngeal muscles via buccal pumping, a mechanism still seen in amphibians. In humans, the main muscle of respiration that drives breathing is the diaphragm. The lungs also provide airflow that makes vocal sounds including human speech possible. Humans have two lungs, one on the left and on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trachea
The trachea, also known as the windpipe, is a Cartilage, cartilaginous tube that connects the larynx to the bronchi of the lungs, allowing the passage of air, and so is present in almost all air-breathing animals with lungs. The trachea extends from the larynx and branches into the two primary bronchi. At the top of the trachea the cricoid cartilage attaches it to the larynx. The trachea is formed by a number of horseshoe-shaped rings, joined together vertically by overlying annular ligaments of trachea, ligaments, and by the trachealis muscle at their ends. The epiglottis closes the opening to the larynx during swallowing. The trachea begins to form in the second month of embryo development, becoming longer and more fixed in its position over time. It is epithelium lined with columnar epithelium, column-shaped cells that have hair-like extensions called cilia, with scattered goblet cells that produce protective mucins. The trachea can be affected by inflammation or infection, us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapods
Tetrapods (; ) are four-limbed vertebrate animals constituting the superclass Tetrapoda (). It includes extant and extinct amphibians, sauropsids (reptiles, including dinosaurs and therefore birds) and synapsids (pelycosaurs, extinct therapsids and all extant mammals). Tetrapods evolved from a clade of primitive semiaquatic animals known as the Tetrapodomorpha which, in turn, evolved from ancient lobe-finned fish (sarcopterygians) around 390 million years ago in the Middle Devonian period; their forms were transitional between lobe-finned fishes and true four-limbed tetrapods. Limbed vertebrates (tetrapods in the broad sense of the word) are first known from Middle Devonian trackways, and body fossils became common near the end of the Late Devonian but these were all aquatic. The first crown-tetrapods (last common ancestors of extant tetrapods capable of terrestrial locomotion) appeared by the very early Carboniferous, 350 million years ago. The specific aquatic ancestors of t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Embryology
Embryology (from Greek ἔμβρυον, ''embryon'', "the unborn, embryo"; and -λογία, '' -logia'') is the branch of animal biology that studies the prenatal development of gametes (sex cells), fertilization, and development of embryos and fetuses. Additionally, embryology encompasses the study of congenital disorders that occur before birth, known as teratology. Early embryology was proposed by Marcello Malpighi, and known as preformationism, the theory that organisms develop from pre-existing miniature versions of themselves. Aristotle proposed the theory that is now accepted, epigenesis. Epigenesis is the idea that organisms develop from seed or egg in a sequence of steps. Modern embryology, developed from the work of Karl Ernst von Baer, though accurate observations had been made in Italy by anatomists such as Aldrovandi and Leonardo da Vinci in the Renaissance. Comparative embryology Preformationism and epigenesis As recently as the 18th century, the prevailin ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Francis Maitland Balfour
Francis (Frank) Maitland Balfour, known as F. M. Balfour, (10 November 1851 – 19 July 1882) was a British biologist. He lost his life while attempting the ascent of Mont Blanc. He was regarded by his colleagues as one of the greatest biologists of his day and Charles Darwin's successor. Life The younger brother of the politician Arthur Balfour, he was born at Edinburgh in Scotland. He attended Harrow School, where he tied with Arthur Evans, the future archaeologist of Knossos, for the Natural History Prize. George Griffith, a teacher at Harrow, encouraged and aided him in the pursuit of natural science, a taste for which, especially geology, he had acquired from his mother. Entering Trinity College, Cambridge, in 1870, he was elected a natural science scholar of his college in the following year, and obtained second place in the Natural Science Tripos of December 1873. Career A course of lectures on embryology, delivered by Sir Michael Foster in 1871, turned Balfour's att ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is change in the heritable characteristics of biological populations over successive generations. These characteristics are the expressions of genes, which are passed on from parent to offspring during reproduction. Variation tends to exist within any given population as a result of genetic mutation and recombination. Evolution occurs when evolutionary processes such as natural selection (including sexual selection) and genetic drift act on this variation, resulting in certain characteristics becoming more common or more rare within a population. The evolutionary pressures that determine whether a characteristic is common or rare within a population constantly change, resulting in a change in heritable characteristics arising over successive generations. It is this process of evolution that has given rise to biodiversity at every level of biological organisation, including the levels of species, individual organisms, and molecules. The theory of evolution by ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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