Bird Wikipedia. Birds Aves are a group of endothermicvertebrates, characterised by feathers, toothlessbeaked jaws, the laying of hard shelled eggs, a high metabolic rate, a four chambered heart, and a strong yet lightweight skeleton. Samuel Gebru is a candidate for a City Council seat in Cambridge, Massachusetts. Courtesy photo Tadias Magazine By Tadias Staff. October 28th, 2017. Birds live worldwide and range in size from the 5 cm 2 in bee hummingbird to the 2. They rank as the class of tetrapods with the most living species, at approximately ten thousand, with more than half of these being passerines, sometimes known as perching birds. Birds are the closest living relatives of crocodilians. Birds are descendants of extinct dinosaurs with feathers, making them the only surviving dinosaurs according to cladistics. The fossil record indicates that birds evolved from feathered ancestors within the theropod group, which are traditionally placed within the saurischiandinosaurs, though a 2. Ornithoscelida, along with the Ornithischia. True birds first appeared during the Cretaceous period, around 1. DNA based evidence finds that birds diversified dramatically around the time of the CretaceousPalaeogene extinction event 6. Parsons Diseases Of The Eye Pdf Torrent' title='Parsons Diseases Of The Eye Pdf Torrent' />Birds, especially those in the southern continents, survived this event and then migrated to other parts of the world while diversifying during periods of global cooling. Primitive bird like dinosaurs that lie outside class Aves proper, in the broader group Avialae, have been found dating back to the mid Jurassic period, around 1. Many of these early stem birds, such as Archaeopteryx, were not yet capable of fully powered flight, and many retained primitive characteristics like toothy jaws in place of beaks, and long bony tails. Birds have wings which are more or less developed depending on the species the only known groups without wings are the extinctmoa and elephant birds. Wings, which evolved from forelimbs, gave birds the ability to fly, although further evolution has led to the loss of flight in flightless birds, including ratites, penguins, and diverse endemic island species of birds. The digestive and respiratory systems of birds are also uniquely adapted for flight. Some bird species of aquatic environments, particularly seabirds and some waterbirds, have further evolved for swimming. Parsons Diseases Of The Eye Pdf Torrent' title='Parsons Diseases Of The Eye Pdf Torrent' />Some birds, especially corvids and parrots, are among the most intelligent animals several bird species make and use tools, and many social species pass on knowledge across generations, which is considered a form of culture. Many species annually migrate great distances. Google is stepping up its effort to block phishing attempts that use app permissions to gain access to users Gmail accounts. These phishing attacks invite users to. Parsons Diseases Of The Eye Pdf Torrent' title='Parsons Diseases Of The Eye Pdf Torrent' />Byron Shire Echo October 23, 2007 3. Local News. Rescue squad celebrates 30th year Story photo Eve Jeffery Sunday in Brunswick Heads was. Birds are social, communicating with visual signals, calls, and bird songs, and participating in such social behaviours as cooperative breeding and hunting, flocking, and mobbing of predators. The vast majority of bird species are socially monogamous referring to social living arrangement, distinct from genetic monogamy, usually for one breeding season at a time, sometimes for years, but rarely for life. Other species have breeding systems that are polygynous arrangement of one male with many females or, rarely, polyandrous arrangement of one female with many males. Birds produce offspring by laying eggs which are fertilised through sexual reproduction. They are usually laid in a nest and incubated by the parents. Most birds have an extended period of parental care after hatching. Some birds, such as hens, lay eggs even when not fertilised, though unfertilised eggs do not produce offspring. Many species of birds are economically important as food for human consumption and raw material in manufacturing, with domesticated and undomesticated birds poultry and game being important sources of eggs, meat, and feathers. Songbirds, parrots, and other species are popular as pets. Guano bird excrement is harvested for use as a fertiliser. Birds prominently figure throughout human culture. About 1. 201. 30 species have become extinct due to human activity since the 1. Parsons Diseases Of The Eye Pdf Torrent' title='Parsons Diseases Of The Eye Pdf Torrent' />Human activity threatens about 1,2. Recreational birdwatching is an important part of the ecotourism industry. Evolution and classification. The first classification of birds was developed by Francis Willughby and John Ray in their 1. Ornithologiae. 7Carl Linnaeus modified that work in 1. Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade. Smo Arena Fighter'>Smo Arena Fighter. Theropoda. 9Definition. Aves and a sister group, the clade Crocodilia, contain the only living representatives of the reptile clade Archosauria. During the late 1. Aves was most commonly defined phylogenetically as all descendants of the most recent common ancestor of modern birds and Archaeopteryx lithographica. However, an earlier definition proposed by Jacques Gauthier gained wide currency in the 2. Phylocode system. Gauthier defined Aves to include only the crown group of the set of modern birds. This was done by excluding most groups known only from fossils, and assigning them, instead, to the Avialae,1. Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs. Gauthier1. 2 identified four different definitions for the same biological name Aves, which is a problem. Gauthier proposed to reserve the term Aves only for the crown group consisting of the last common ancestor of all living birds and all of its descendants, which corresponds to meaning number 4 below. He assigned other names to the other groups. Aves can mean those advanced archosaurs with feathers alternately AvifiloplumaAves can mean those that fly alternately AvialaeAves can mean all reptiles closer to birds than to crocodiles alternately AvemetatarsaliaAves can mean the last common ancestor of all the currently living birds and all of its descendants a crown group, in this sense synonymous with NeornithesUnder the fourth definition Archaeopteryx is an avialan, and not a member of Aves. Gauthiers proposals have been adopted by many researchers in the field of palaeontology and bird evolution, though the exact definitions applied have been inconsistent. Avialae, initially proposed to replace the traditional fossil content of Aves, is often used synonymously with the vernacular term bird by these researchers. Most researchers define Avialae as branch based clade, though definitions vary. Many authors have used a definition similar to all theropods closer to birds than to Deinonychus. Avialae is also occasionally defined as an apomorphy based clade that is, one based on physical characteristics. Jacques Gauthier, who named Avialae in 1. Dinosaurs and the origin of birds. Based on fossil and biological evidence, most scientists accept that birds are a specialised subgroup of theropoddinosaurs,1. Maniraptora, a group of theropods which includes dromaeosaurs and oviraptorids, among others. As scientists have discovered more theropods closely related to birds, the previously clear distinction between non birds and birds has become blurred. Football Manager 2009 Pc Rip here. Recent discoveries in the Liaoning Province of northeast China, which demonstrate many small theropod feathered dinosaurs, contribute to this ambiguity. The consensus view in contemporary palaeontology is that the flying theropods, or avialans, are the closest relatives of the deinonychosaurs, which include dromaeosaurids and troodontids. Together, these form a group called Paraves. Some basal members of this group, such as Microraptor, have features which may have enabled them to glide or fly. The most basal deinonychosaurs were very small.