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| Origin of avian flight ： ウィキペディア英語版 |
:''"Evolution of flight" redirects here. See also flying and gliding animals and insect flight''.Around 350 BCE, Aristotle and other philosophers of the time were attempting to explain the aerodynamics of avian flight. Even after the discovery of the ancestral bird ''Archaeopteryx'', over 150 years ago, debates still persist regarding the evolution of flight. There are three leading hypotheses pertaining to avian flight: Pouncing Proavis model, Cursorial model, and Arboreal model. ''Archaeopteryx'', the oldest known ancestor of modern birds, could provide clues to the origin of avian flight.==Flight characteristics==For flight to occur in Aves, four physical forces (thrust and drag, lift and weight) must be favourably combined. In order for birds to balance these forces, certain physical characteristics are required. Asymmetrical wings, found on all flying birds with the exception of hummingbirds, help in the production of thrust and lift. Anything that moves through the air produces drag due to friction forces. The aerodynamic body of a bird can reduce drag, but when stopping or slowing down a bird will use its tail and feet to increase drag. Weight is the largest obstacle birds must overcome in order to fly. An animal can more easily attain flight by reducing its absolute weight. Birds evolved from other theropod dinosaurs that had already gone through a phase of size reduction during the Middle Jurassic, combined with rapid evolutionary changes.Michael S.Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke, 2014, "Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds", ''Science'' 345(6196): 562-566 Flying birds during their evolution further reduced relative weight through several characteristics such as the loss of teeth, gonadal hypertrophy, and fusion of bones. Teeth have been replaced by a lightweight bill made of keratin, and chewing occurs in the bird's gizzard. Other advanced physical characteristics evolved for flight are a keel for the attachment of flight muscles and an enlarged cerebellum for fine motor coordination. These were gradual changes though and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone, that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs and birds in fact on average do not have a lighter skeleton than mammals of the same size. The same is true for the furcula, a bone which enhances skeletal bracing for the stresses of flight.The mechanics of an avian's wings involve a complex interworking of forces, particularly at the shoulder where most of the wings' motions take place. These functions depend on a precise balance of forces from the muscles, ligaments, and articular cartilages as well as inertial, gravitational, and aerodynamic loads on the wing.
:''"Evolution of flight" redirects here. See also flying and gliding animals and insect flight''.
Around 350 BCE, Aristotle and other philosophers of the time were attempting to explain the aerodynamics of avian flight. Even after the discovery of the ancestral bird ''Archaeopteryx'', over 150 years ago, debates still persist regarding the evolution of flight. There are three leading hypotheses pertaining to avian flight: Pouncing Proavis model, Cursorial model, and Arboreal model. ''Archaeopteryx'', the oldest known ancestor of modern birds, could provide clues to the origin of avian flight.
==Flight characteristics==
For flight to occur in Aves, four physical forces (thrust and drag, lift and weight) must be favourably combined. In order for birds to balance these forces, certain physical characteristics are required. Asymmetrical wings, found on all flying birds with the exception of hummingbirds, help in the production of thrust and lift. Anything that moves through the air produces drag due to friction forces. The aerodynamic body of a bird can reduce drag, but when stopping or slowing down a bird will use its tail and feet to increase drag. Weight is the largest obstacle birds must overcome in order to fly. An animal can more easily attain flight by reducing its absolute weight. Birds evolved from other theropod dinosaurs that had already gone through a phase of size reduction during the Middle Jurassic, combined with rapid evolutionary changes.〔Michael S.Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke, 2014, "Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds", ''Science'' 345(6196): 562-566〕 Flying birds during their evolution further reduced relative weight through several characteristics such as the loss of teeth, gonadal hypertrophy, and fusion of bones. Teeth have been replaced by a lightweight bill made of keratin, and chewing occurs in the bird's gizzard. Other advanced physical characteristics evolved for flight are a keel for the attachment of flight muscles and an enlarged cerebellum for fine motor coordination. These were gradual changes though and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone, that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs and birds in fact on average do not have a lighter skeleton than mammals of the same size. The same is true for the furcula, a bone which enhances skeletal bracing for the stresses of flight.
The mechanics of an avian's wings involve a complex interworking of forces, particularly at the shoulder where most of the wings' motions take place. These functions depend on a precise balance of forces from the muscles, ligaments, and articular cartilages as well as inertial, gravitational, and aerodynamic loads on the wing.
抄文引用元・出典: フリー百科事典『 origin of avian flight.==Flight characteristics==For flight to occur in Aves, four physical forces (thrust and drag, lift and weight) must be favourably combined. In order for birds to balance these forces, certain physical characteristics are required. Asymmetrical wings, found on all flying birds with the exception of hummingbirds, help in the production of thrust and lift. Anything that moves through the air produces drag due to friction forces. The aerodynamic body of a bird can reduce drag, but when stopping or slowing down a bird will use its tail and feet to increase drag. Weight is the largest obstacle birds must overcome in order to fly. An animal can more easily attain flight by reducing its absolute weight. Birds evolved from other theropod dinosaurs that had already gone through a phase of size reduction during the Middle Jurassic, combined with rapid evolutionary changes.Michael S.Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke, 2014, "Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds", ''Science'' 345(6196): 562-566 Flying birds during their evolution further reduced relative weight through several characteristics such as the loss of teeth, gonadal hypertrophy, and fusion of bones. Teeth have been replaced by a lightweight bill made of keratin, and chewing occurs in the bird's gizzard. Other advanced physical characteristics evolved for flight are a keel for the attachment of flight muscles and an enlarged cerebellum for fine motor coordination. These were gradual changes though and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone, that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs and birds in fact on average do not have a lighter skeleton than mammals of the same size. The same is true for the furcula, a bone which enhances skeletal bracing for the stresses of flight.The mechanics of an avian's wings involve a complex interworking of forces, particularly at the shoulder where most of the wings' motions take place. These functions depend on a precise balance of forces from the muscles, ligaments, and articular cartilages as well as inertial, gravitational, and aerodynamic loads on the wing.">ウィキペディア（Wikipedia）』
■origin of avian flight.==Flight characteristics==For flight to occur in Aves, four physical forces (thrust and drag, lift and weight) must be favourably combined. In order for birds to balance these forces, certain physical characteristics are required. Asymmetrical wings, found on all flying birds with the exception of hummingbirds, help in the production of thrust and lift. Anything that moves through the air produces drag due to friction forces. The aerodynamic body of a bird can reduce drag, but when stopping or slowing down a bird will use its tail and feet to increase drag. Weight is the largest obstacle birds must overcome in order to fly. An animal can more easily attain flight by reducing its absolute weight. Birds evolved from other theropod dinosaurs that had already gone through a phase of size reduction during the Middle Jurassic, combined with rapid evolutionary changes.Michael S.Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke, 2014, "Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds", ''Science'' 345(6196): 562-566 Flying birds during their evolution further reduced relative weight through several characteristics such as the loss of teeth, gonadal hypertrophy, and fusion of bones. Teeth have been replaced by a lightweight bill made of keratin, and chewing occurs in the bird's gizzard. Other advanced physical characteristics evolved for flight are a keel for the attachment of flight muscles and an enlarged cerebellum for fine motor coordination. These were gradual changes though and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone, that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs and birds in fact on average do not have a lighter skeleton than mammals of the same size. The same is true for the furcula, a bone which enhances skeletal bracing for the stresses of flight.The mechanics of an avian's wings involve a complex interworking of forces, particularly at the shoulder where most of the wings' motions take place. These functions depend on a precise balance of forces from the muscles, ligaments, and articular cartilages as well as inertial, gravitational, and aerodynamic loads on the wing.">ウィキペディアで「:''"Evolution of flight" redirects here. See also flying and gliding animals and insect flight''.Around 350 BCE, Aristotle and other philosophers of the time were attempting to explain the aerodynamics of avian flight. Even after the discovery of the ancestral bird ''Archaeopteryx'', over 150 years ago, debates still persist regarding the evolution of flight. There are three leading hypotheses pertaining to avian flight: Pouncing Proavis model, Cursorial model, and Arboreal model. ''Archaeopteryx'', the oldest known ancestor of modern birds, could provide clues to the origin of avian flight.==Flight characteristics==For flight to occur in Aves, four physical forces (thrust and drag, lift and weight) must be favourably combined. In order for birds to balance these forces, certain physical characteristics are required. Asymmetrical wings, found on all flying birds with the exception of hummingbirds, help in the production of thrust and lift. Anything that moves through the air produces drag due to friction forces. The aerodynamic body of a bird can reduce drag, but when stopping or slowing down a bird will use its tail and feet to increase drag. Weight is the largest obstacle birds must overcome in order to fly. An animal can more easily attain flight by reducing its absolute weight. Birds evolved from other theropod dinosaurs that had already gone through a phase of size reduction during the Middle Jurassic, combined with rapid evolutionary changes.Michael S.Y. Lee, Andrea Cau, Darren Naish, and Gareth J. Dyke, 2014, "Sustained miniaturization and anatomical innovation in the dinosaurian ancestors of birds", ''Science'' 345(6196): 562-566 Flying birds during their evolution further reduced relative weight through several characteristics such as the loss of teeth, gonadal hypertrophy, and fusion of bones. Teeth have been replaced by a lightweight bill made of keratin, and chewing occurs in the bird's gizzard. Other advanced physical characteristics evolved for flight are a keel for the attachment of flight muscles and an enlarged cerebellum for fine motor coordination. These were gradual changes though and not strict conditions for flight: the first birds had teeth, at best a small keel and relatively unfused bones. Pneumatic bone, that is hollow or filled with air sacs, has often been seen as an adaptation reducing weight, but it was already present in non-flying dinosaurs and birds in fact on average do not have a lighter skeleton than mammals of the same size. The same is true for the furcula, a bone which enhances skeletal bracing for the stresses of flight.The mechanics of an avian's wings involve a complex interworking of forces, particularly at the shoulder where most of the wings' motions take place. These functions depend on a precise balance of forces from the muscles, ligaments, and articular cartilages as well as inertial, gravitational, and aerodynamic loads on the wing.」の詳細全文を読む
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