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Cute Bird Pictures Biography
Birds (class Aves) are feathered, winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. With around 10,000 living species, they are the most speciose class of tetrapod vertebrates. All present species belong to the subclass Neornithes, and inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich. The fossil record indicates that birds emerged within theropod dinosaurs during the Jurassic period, around 160 million years (Ma) ago. Paleontologists regard birds as the only clade of dinosaurs to have survived the Cretaceous–Paleogene extinction event 65.5 Ma (million years) ago.
Modern birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All living species of birds have wings; the most recent species without wings was the moa, which is generally considered to have become extinct in the 16th century. Wings are evolved forelimbs, and most bird species can fly. Flightless birds include ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly adapted for flight. Some birds, especially corvids and parrots, are among the most intelligent animal species; a number of bird species have been observed manufacturing and using tools, and many social species exhibit cultural transmission of knowledge across generations.
Many species undertake long distance annual migrations, and many more perform shorter irregular movements. Birds are social; they communicate using visual signals and through calls and songs, and participate in social behaviours, including cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially monogamous, usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have polygynous ("many females") or, rarely, polyandrous ("many males") breeding systems. Eggs are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.
Many species are of economic importance, mostly as sources of food acquired through hunting or farming. Some species, particularly songbirds and parrots, are popular as pets. Other uses include the harvesting of guano (droppings) for use as a fertiliser. Birds figure prominently in all aspects of human culture from religion to poetry to popular music. About 120–130 species have become extinct as a result of human activity since the 17th century, and hundreds more before then. Currently about 1,200 species of birds are threatened with extinction by human activities, though efforts are underway to protect them.The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae.[2] Carolus Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use.[3] Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda.[4] Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica.[5] However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the modern bird groups, the crown group. This was done by excluding most groups known only from fossils, and assigning them, instead, to the Avialae,[6] in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
All modern birds lie within the crown group Neornithes, which has two subdivisions: the Palaeognathae, which includes the flightless ratites (such as the ostriches) and the weak-flying tinamous, and the extremely diverse Neognathae, containing all other birds.[4] These two subdivisions are often given the rank of superorder,[7] although Livezey and Zusi assigned them "cohort" rankBased on fossil and biological evidence, most scientists accept that birds are a specialized subgroup of theropod dinosaurs.[10] More specifically, they are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others.[11] As scientists have discovered more nonavian theropods closely related to birds, the previously clear distinction between nonbirds and birds has become blurred. Recent discoveries in the Liaoning Province of northeast China, which demonstrate many small theropod dinosaurs had feathers, contribute to this ambiguity.[12]
The consensus view in contemporary paleontology is that the birds, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids, troodontids and possibly archaeopterygids.[13] Together, these three form a group called Paraves. Some basal members of this group, such as Microraptor and Archaeopteryx, have features which may have enabled them to glide or fly. The most basal deinonychosaurs are very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal, may have been able to glide, or both.[14][15] Unlike Archaeopteryx and the feathered dinosaurs, who primarily ate meat, recent studies suggest that the first birds were herbivores.[16]
The Late Jurassic Archaeopteryx is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to display both clearly reptilian characteristics: teeth, clawed fingers, and a long, lizard-like tail, as well as wings with flight feathers identical to those of modern birds. It is not considered a direct ancestor of modern birds, though it is possibly closely related to the real ancestor.
Cute Bird Pictures Biography
Birds (class Aves) are feathered, winged, bipedal, endothermic (warm-blooded), egg-laying, vertebrate animals. With around 10,000 living species, they are the most speciose class of tetrapod vertebrates. All present species belong to the subclass Neornithes, and inhabit ecosystems across the globe, from the Arctic to the Antarctic. Extant birds range in size from the 5 cm (2 in) Bee Hummingbird to the 2.75 m (9 ft) Ostrich. The fossil record indicates that birds emerged within theropod dinosaurs during the Jurassic period, around 160 million years (Ma) ago. Paleontologists regard birds as the only clade of dinosaurs to have survived the Cretaceous–Paleogene extinction event 65.5 Ma (million years) ago.
Modern birds are characterised by feathers, a beak with no teeth, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a lightweight but strong skeleton. All living species of birds have wings; the most recent species without wings was the moa, which is generally considered to have become extinct in the 16th century. Wings are evolved forelimbs, and most bird species can fly. Flightless birds include ratites, penguins, and a number of diverse endemic island species. Birds also have unique digestive and respiratory systems that are highly adapted for flight. Some birds, especially corvids and parrots, are among the most intelligent animal species; a number of bird species have been observed manufacturing and using tools, and many social species exhibit cultural transmission of knowledge across generations.
Many species undertake long distance annual migrations, and many more perform shorter irregular movements. Birds are social; they communicate using visual signals and through calls and songs, and participate in social behaviours, including cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially monogamous, usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have polygynous ("many females") or, rarely, polyandrous ("many males") breeding systems. Eggs are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching.
Many species are of economic importance, mostly as sources of food acquired through hunting or farming. Some species, particularly songbirds and parrots, are popular as pets. Other uses include the harvesting of guano (droppings) for use as a fertiliser. Birds figure prominently in all aspects of human culture from religion to poetry to popular music. About 120–130 species have become extinct as a result of human activity since the 17th century, and hundreds more before then. Currently about 1,200 species of birds are threatened with extinction by human activities, though efforts are underway to protect them.The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae.[2] Carolus Linnaeus modified that work in 1758 to devise the taxonomic classification system currently in use.[3] Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda.[4] Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1990s, Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica.[5] However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 21st century, and is used by many scientists including adherents of the Phylocode system. Gauthier defined Aves to include only the modern bird groups, the crown group. This was done by excluding most groups known only from fossils, and assigning them, instead, to the Avialae,[6] in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
All modern birds lie within the crown group Neornithes, which has two subdivisions: the Palaeognathae, which includes the flightless ratites (such as the ostriches) and the weak-flying tinamous, and the extremely diverse Neognathae, containing all other birds.[4] These two subdivisions are often given the rank of superorder,[7] although Livezey and Zusi assigned them "cohort" rankBased on fossil and biological evidence, most scientists accept that birds are a specialized subgroup of theropod dinosaurs.[10] More specifically, they are members of Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others.[11] As scientists have discovered more nonavian theropods closely related to birds, the previously clear distinction between nonbirds and birds has become blurred. Recent discoveries in the Liaoning Province of northeast China, which demonstrate many small theropod dinosaurs had feathers, contribute to this ambiguity.[12]
The consensus view in contemporary paleontology is that the birds, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids, troodontids and possibly archaeopterygids.[13] Together, these three form a group called Paraves. Some basal members of this group, such as Microraptor and Archaeopteryx, have features which may have enabled them to glide or fly. The most basal deinonychosaurs are very small. This evidence raises the possibility that the ancestor of all paravians may have been arboreal, may have been able to glide, or both.[14][15] Unlike Archaeopteryx and the feathered dinosaurs, who primarily ate meat, recent studies suggest that the first birds were herbivores.[16]
The Late Jurassic Archaeopteryx is well known as one of the first transitional fossils to be found, and it provided support for the theory of evolution in the late 19th century. Archaeopteryx was the first fossil to display both clearly reptilian characteristics: teeth, clawed fingers, and a long, lizard-like tail, as well as wings with flight feathers identical to those of modern birds. It is not considered a direct ancestor of modern birds, though it is possibly closely related to the real ancestor.
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
Cute Bird Pictures Biography
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