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Webbed Foot
The webbed foot is a specialized limb with interdigital membranes (webbings) that aids in aquatic locomotion, present in a variety of tetrapod vertebrates. This adaptation is primarily found in semiaquatic species, and has convergently evolved many times across vertebrate taxa. It likely arose from mutations in developmental genes that normally cause tissue between the digits to apoptose. These mutations were beneficial to many semiaquatic animals because the increased surface area from the webbing allowed for more swimming propulsion and swimming efficiency, especially in surface swimmers. The webbed foot also has enabled other novel behaviors like escape responses and mating behaviors. A webbed foot may also be called a paddle to contrast it from a more hydrofoil-like flipper. Morphology A webbed foot has connecting tissue between the toes of the foot. Several distinct conditions can give rise to webbed feet, including interdigital webbing and syndactyly. The webbing ca ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Webbed Toes
Webbed toes is the informal and common name for syndactyly affecting the feet—the fusion of two or more digits of the feet. This is normal in many birds, such as ducks; amphibians, such as frogs; and some mammals, such as kangaroos. In humans it is rare, occurring once in about 2,000 to 2,500 live births: most commonly the second and third toes are webbed (joined by skin and flexible tissue), which can reach partly or almost fully up the toe. Cause The exact cause of the condition is unknown. In some cases, close family members may share this condition. In other cases, no other related persons have this condition. The scientific name for the condition is syndactyly, although this term covers both webbed fingers and webbed toes. Syndactyly occurs when apoptosis or programmed cell death during gestation is absent or incomplete. Webbed toes occur most commonly in the following circumstances: * Syndactyly or familial syndactyly * Down syndrome It is also associated with a numb ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetrapod
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 aquat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Common Frog
The common frog or grass frog (''Rana temporaria''), also known as the European common frog, European common brown frog, European grass frog, European Holarctic true frog, European pond frog or European brown frog, is a semi-aquatic amphibian of the family Ranidae, found throughout much of Europe as far north as Scandinavia and as far east as the Urals, except for most of Iberia, Southern Italy, and the southern Balkans. The farthest west it can be found is Ireland. It is also found in Asia, and eastward to Japan. The nominative, and most common, subspecies ''Rana temporaria temporaria'' is a largely terrestrial frog native to Europe. It is distributed throughout northern Europe and can be found in Ireland, the Isle of Lewis and as far east as Japan. Common frogs metamorphose through three distinct developmental life stages — aquatic larva, terrestrial juvenile, and adult. They have corpulent bodies with a rounded snout, webbed feet and long hind legs adapted for swim ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Salamander
Salamanders are a group of amphibians typically characterized by their lizard-like appearance, with slender bodies, blunt snouts, short limbs projecting at right angles to the body, and the presence of a tail in both larvae and adults. All ten extant salamander families are grouped together under the order Urodela. Salamander diversity is highest in eastern North America, especially in the Appalachian Mountains; most species are found in the Holarctic realm, with some species present in the Neotropical realm. Salamanders rarely have more than four toes on their front legs and five on their rear legs, but some species have fewer digits and others lack hind limbs. Their permeable skin usually makes them reliant on habitats in or near water or other cool, damp places. Some salamander species are fully aquatic throughout their lives, some take to the water intermittently, and others are entirely terrestrial as adults. This group of amphibians is capable of regenerating los ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Frog
A frog is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-frog" ''Triadobatrachus'' is known from the Early Triassic of Madagascar, but molecular clock dating suggests their split from other amphibians may extend further back to the Permian, 265 million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest. Frogs account for around 88% of extant amphibian species. They are also one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history. An adult frog has a stout body, protruding eyes, anteriorly-attached tongue, limbs folded underneath, and no tail (the tail of tailed frogs is an ext ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amphibian
Amphibians are four-limbed and ectothermic vertebrates of the class Amphibia. All living amphibians belong to the group Lissamphibia. They inhabit a wide variety of habitats, with most species living within terrestrial, fossorial, arboreal or freshwater aquatic ecosystems. Thus amphibians typically start out as larvae living in water, but some species have developed behavioural adaptations to bypass this. The young generally undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely entirely on their skin. They are superficially similar to reptiles like lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are often ecological indicators; in recent decades there has been a dramatic ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Vertebrate Phylogeny With Webbed-Footed Taxa Highlighted
Vertebrates () comprise all animal taxa within the subphylum Vertebrata () ( chordates with backbones), including all mammals, birds, reptiles, amphibians, and fish. Vertebrates represent the overwhelming majority of the phylum Chordata, with currently about 69,963 species described. Vertebrates comprise such groups as the following: * jawless fish, which include hagfish and lampreys * jawed vertebrates, which include: ** cartilaginous fish (sharks, rays, and ratfish) ** bony vertebrates, which include: *** ray-fins (the majority of living bony fish) *** lobe-fins, which include: **** coelacanths and lungfish **** tetrapods (limbed vertebrates) Extant vertebrates range in size from the frog species ''Paedophryne amauensis'', at as little as , to the blue whale, at up to . Vertebrates make up less than five percent of all described animal species; the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bigfoot Splayfoot Salamander
The bigfoot splayfoot salamander (''Chiropterotriton magnipes''), also known as the big-footed salamander, is a species of salamander in the family Plethodontidae. It is endemic to Mexico and only known from north-eastern Queretaro, at elevations of asl. Its natural habitats are caves and crevices in pine-oak forest. It has also been spotted in a tunnel under a church. It is threatened by habitat loss Habitat destruction (also termed habitat loss and habitat reduction) is the process by which a natural habitat becomes incapable of supporting its native species. The organisms that previously inhabited the site are displaced or dead, thereby ...: removing the forest causes caves to dry up. The species has never been common. References Chiropterotriton Cave salamanders Endemic amphibians of Mexico Amphibians described in 1965 Taxonomy articles created by Polbot Fauna of the Sierra Madre Oriental {{Plethodontidae-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chondrogenesis
Chondrogenesis is the process by which cartilage is developed. Cartilage in fetal development In embryogenesis, the skeletal system is derived from the mesoderm germ layer. Chondrification (also known as chondrogenesis) is the process by which cartilage is formed from condensed mesenchyme tissue, which differentiates into chondrocytes and begins secreting the molecules that form the extracellular matrix. Early in fetal development, the greater part of the skeleton is cartilaginous. This ''temporary'' cartilage is gradually replaced by bone ( Endochondral ossification), a process that ends at puberty. In contrast, the cartilage in the joints remains unossified during the whole of life and is, therefore, ''permanent''. Mineralization Adult hyaline articular cartilage is progressively mineralized at the junction between cartilage and bone. It is then termed ''articular calcified cartilage''. A mineralization front advances through the base of the hyaline articular cartilage at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
TGFβ
Transforming growth factor beta (TGF-β) is a multifunctional cytokine belonging to the transforming growth factor superfamily that includes three different mammalian isoforms (TGF-β 1 to 3, HGNC symbols TGFB1, TGFB2, TGFB3) and many other signaling proteins. TGFB proteins are produced by all white blood cell lineages. Activated TGF-β complexes with other factors to form a serine/threonine kinase complex that binds to TGF-β receptors. TGF-β receptors are composed of both type 1 and type 2 receptor subunits. After the binding of TGF-β, the type 2 receptor kinase phosphorylates and activates the type 1 receptor kinase that activates a signaling cascade. This leads to the activation of different downstream substrates and regulatory proteins, inducing transcription of different target genes that function in differentiation, chemotaxis, proliferation, and activation of many immune cells. TGF-β is secreted by many cell types, including macrophages, in a latent form in which i ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cell Signaling
In biology, cell signaling (cell signalling in British English) or cell communication is the ability of a cell to receive, process, and transmit signals with its environment and with itself. Cell signaling is a fundamental property of all cellular life in prokaryotes and eukaryotes. Signals that originate from outside a cell (or extracellular signals) can be physical agents like mechanical pressure, voltage, temperature, light, or chemical signals (e.g., small molecules, peptides, or gas). Cell signaling can occur over short or long distances, and as a result can be classified as autocrine, juxtacrine, intracrine, paracrine, or endocrine. Signaling molecules can be synthesized from various biosynthetic pathways and released through passive or active transports, or even from cell damage. Receptors play a key role in cell signaling as they are able to detect chemical signals or physical stimuli. Receptors are generally proteins located on the cell surface or within the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bone Morphogenetic Protein
Bone morphogenetic proteins (BMPs) are a group of growth factors also known as cytokines and as metabologens. Originally discovered by their ability to induce the formation of bone and cartilage, BMPs are now considered to constitute a group of pivotal morphogenetic signals, orchestrating tissue architecture throughout the body. The important functioning of BMP signals in physiology is emphasized by the multitude of roles for dysregulated BMP signalling in pathological processes. Cancerous disease often involves misregulation of the BMP signalling system. Absence of BMP signalling is, for instance, an important factor in the progression of colon cancer, and conversely, overactivation of BMP signalling following reflux-induced esophagitis provokes Barrett's esophagus and is thus instrumental in the development of esophageal adenocarcinoma. Recombinant human BMPs (rhBMPs) are used in orthopedic applications such as spinal fusions, nonunions, and oral surgery. rhBMP-2 and rhBMP-7 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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