Birds known as Aves, are a group of endothermic vertebrates, characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, a strong yet lightweight skeleton. Birds range in size from the 5 cm bee hummingbird to the 2.75 m ostrich. They rank as the world's most numerically-successful class of tetrapods, with ten thousand living species, more than half of these being passerines, sometimes known as perching birds. Birds have wings which are less developed depending on the species. 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 and diverse endemic island species of birds; the digestive and respiratory systems of birds are uniquely adapted for flight. Some bird species of aquatic environments seabirds and some waterbirds, have further evolved for swimming; the fossil record demonstrates that birds are modern feathered dinosaurs, having evolved from earlier feathered dinosaurs within the theropod group, which are traditionally placed within the saurischian dinosaurs.
The closest living relatives of birds are the crocodilians. 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 170 million years ago. Many of these early "stem-birds", such as Archaeopteryx, were not yet capable of powered flight, many retained primitive characteristics like toothy jaws in place of beaks, long bony tails. DNA-based evidence finds that birds diversified around the time of the Cretaceous–Palaeogene extinction event 66 million years ago, which killed off the pterosaurs and all the non-avian dinosaur lineages, but birds those in the southern continents, survived this event and migrated to other parts of the world while diversifying during periods of global cooling. This makes them the sole surviving dinosaurs according to cladistics; some birds corvids and parrots, are among the most intelligent animals. Many species annually migrate great distances. Birds are social, communicating with visual signals and bird songs, participating in such social behaviours as cooperative breeding and hunting and mobbing of predators.
The vast majority of bird species are monogamous for one breeding season at a time, sometimes for years, but for life. Other species have breeding systems that are polygynous or polyandrous. Birds produce offspring by laying eggs, they are 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 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 being important sources of eggs and feathers. Songbirds and other species are popular as pets. Guano is harvested for use as a fertiliser. Birds prominently figure throughout human culture. About 120–130 species have become extinct due to human activity since the 17th century, hundreds more before then. Human activity threatens about 1,200 bird species with extinction, though efforts are underway to protect them.
Recreational birdwatching is an important part of the ecotourism industry. The first classification of birds was developed by Francis Willughby and John Ray in their 1676 volume Ornithologiae. Carl Linnaeus modified that work in 1758 to devise the taxonomic classification system in use. Birds are categorised as the biological class Aves in Linnaean taxonomy. Phylogenetic taxonomy places Aves in the dinosaur clade Theropoda. 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 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 21st century, is used by many scientists including adherents of the 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, assigning them, instead, to the Avialae, in part to avoid the uncertainties about the placement of Archaeopteryx in relation to animals traditionally thought of as theropod dinosaurs.
Gauthier identified four different definitions for the same biological name "Aves", 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 all archosaurs closer to birds than to crocodiles Aves can mean those advanced archosaurs with feathers Aves can mean those feathered dinosaurs that fly Aves can mean the last common ancestor of all the living birds and all of its descendants (a "c
In biology, extinction is the termination of an organism or of a group of organisms a species. The moment of extinction is considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point; because a species' potential range may be large, determining this moment is difficult, is done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" after a period of apparent absence. More than 99 percent of all species, amounting to over five billion species, that lived on Earth are estimated to have died out. Estimates on the number of Earth's current species range from 10 million to 14 million, of which about 1.2 million have been documented and over 86 percent have not yet been described. In 2016, scientists reported that 1 trillion species are estimated to be on Earth with only one-thousandth of one percent described. Through evolution, species arise through the process of speciation—where new varieties of organisms arise and thrive when they are able to find and exploit an ecological niche—and species become extinct when they are no longer able to survive in changing conditions or against superior competition.
The relationship between animals and their ecological niches has been established. A typical species becomes extinct within 10 million years of its first appearance, although some species, called living fossils, survive with no morphological change for hundreds of millions of years. Mass extinctions are rare events. Only have extinctions been recorded and scientists have become alarmed at the current high rate of extinctions. Most species that become extinct are never scientifically documented; some scientists estimate that up to half of presently existing plant and animal species may become extinct by 2100. A 2018 report indicated that the phylogenetic diversity of 300 mammalian species erased during the human era since the Late Pleistocene would require 5 to 7 million years to recover. A dagger symbol placed next to the name of a species or other taxon indicates its status as extinct. A species is extinct. Extinction therefore becomes a certainty when there are no surviving individuals that can reproduce and create a new generation.
A species may become functionally extinct when only a handful of individuals survive, which cannot reproduce due to poor health, sparse distribution over a large range, a lack of individuals of both sexes, or other reasons. Pinpointing the extinction of a species requires a clear definition of that species. If it is to be declared extinct, the species in question must be uniquely distinguishable from any ancestor or daughter species, from any other related species. Extinction of a species plays a key role in the punctuated equilibrium hypothesis of Stephen Jay Gould and Niles Eldredge. In ecology, extinction is used informally to refer to local extinction, in which a species ceases to exist in the chosen area of study, but may still exist elsewhere; this phenomenon is known as extirpation. Local extinctions may be followed by a replacement of the species taken from other locations. Species which are not extinct are termed extant; those that are extant but threatened by extinction are referred to as threatened or endangered species.
An important aspect of extinction is human attempts to preserve critically endangered species. These are reflected by the creation of the conservation status "extinct in the wild". Species listed under this status by the International Union for Conservation of Nature are not known to have any living specimens in the wild, are maintained only in zoos or other artificial environments; some of these species are functionally extinct, as they are no longer part of their natural habitat and it is unlikely the species will be restored to the wild. When possible, modern zoological institutions try to maintain a viable population for species preservation and possible future reintroduction to the wild, through use of planned breeding programs; the extinction of one species' wild population can have knock-on effects, causing further extinctions. These are called "chains of extinction"; this is common with extinction of keystone species. A 2018 study indicated that the 6th mass extinction started in the Late Pleistocene could take up to 5 to 7 million years to restore 2.5 billion years of unique mammal diversity to what it was before the human era.
Extinction of a parent species where daughter species or subspecies are still extant is called pseudoextinction or phyletic extinction. The old taxon vanishes, transformed into a successor, or split into more than one. Pseudoextinction is difficult to demonstrate unless one has a strong chain of evidence linking a living species to members of a pre-existing species. For example, it is sometimes claimed that the extinct Hyracotherium, an early horse that shares a common ancestor with the modern horse, is pseudoextinct, rather than extinct, because there are several extant species of Equus, including zebra and donkey. However, as fossil species leave no genetic material behind, one cannot say whether Hyracotherium evolved into more modern horse species or evolved from a common ancestor with modern horses. Pseudoextinction is much easier to demonstrate for larger taxonomic groups; the coelacanth, a fish related to lungfish and tetrapods, was consi
The giant coot is a species of coot from South America. It is found at lakes in the altiplano from central Peru, through western Bolivia, to north-eastern Chile and extreme north-western Argentina. With a total length of 48–64 cm, it is the second largest extant member of the family Rallidae, after the takahe, adults are considered functionally flightless, it is the only coot with reddish legs. It has a small white frontal shield, its beak is tipped black. An adult male weighed 2.7 kg. As in the related horned coot, the giant coot is monogamous and the pair builds a huge nest in a highland lake. However, unlike the horned coot, the nest of the giant coot is made of aquatic vegetation and – as it is fiercely territorial – it never forms colonies
Moorhens — sometimes called marsh hens — are medium-sized water birds that are members of the rail family. Most species are placed in the genus Gallinula, Latin for "little hen", they are close relatives of coots. They are referred to as gallinules. One of the species of Gallinula was found to have enough differences to form a new genus Paragallinula with the only species being the Lesser moorhen. Two species from the Australian region, sometimes separated in Tribonyx, are called "native hens"; the native hens differ visually by shorter and stubbier toes and bills, longer tails that lack the white signal pattern of typical moorhens."Marsh Hens" are mentioned in the Edgar Allan Poe story "The Gold-Bug", as part of a description of the ecology of Sullivan's Island. The main characters prepare Marsh Hens for supper at one point early in the story; these rails are brown and black with some white markings in plumage colour. Unlike many of the rails they are easy to see, feeding in open water margins rather than hidden in reedbeds.
They have short rounded wings and are weak fliers, although capable of covering long distances. The common moorhen in particular migrates up to 2,000 km from some of its breeding areas in the colder parts of Siberia; those that migrate do so at night. The Gough moorhen on the other hand is considered flightless; as common in rails, there has been a marked tendency to evolve flightlessness in island populations. Moorhens can walk well on their strong legs, have long toes that are well adapted to soft uneven surfaces; these birds are omnivorous, consuming plant material, small rodents and eggs. They are aggressively territorial during the breeding season, but are otherwise found in sizeable flocks on the shallow vegetated lakes they prefer; the genus Gallinula was introduced by the French zoologist Mathurin Jacques Brisson in 1760 with the common moorhen as the type species. The genus Gallinula contains seven extant and extinct species: †Samoan moorhen, Gallinula pacifica – sometimes placed in Pareudiastes, extinct †Makira moorhen, Gallinula silvestris – sometimes placed in Pareudiastes or Edithornis, extinct †Tristan moorhen, Gallinula nesiotis – sometimes placed in Porphyriornis.
Apart from the 1–3 extinctions in more recent times, another 1–4 species have gone extinct as a consequence of early human settlement: Hodgen's waterhen of New Zealand—which belongs in subgenus Tribonyx—and a species close to the Samoan moorhen from Buka, Solomon Islands, certainly distinct from the Makira moorhen, as the latter cannot fly. The undescribed Viti Levu gallinule of Fiji would either be separated in Pareudiastes if that genus is considered valid, or may be a new genus; the undescribed "swamphen" of Mangaia tentatively assigned to Porphyrio, may belong to Gallinula/Pareudiastes. Still older fossils document the genus since the Late Oligocene onwards; the genus seems to have originated in the general region of Australia. By the Pliocene, it was distributed worldwide: Gallinula sp. Gallinula kansarum Gallinula balcanica. Gallinula gigantea The ancient "Gallinula" disneyi has been separated as genus Australlus. Among non-Passeriformes, this genus has a long documented existence; some unassigned fragmentary rail fossils might be from moorhens or native hens.
For example, specimen QM F30696, a left distal tibiotarsus piece from the Oligo-Miocene boundary at Riversleigh, is similar to but than and differs in details from "G." disneyi. It can not be said. From size alone, it might have been an ancestor of G. mortierii. In addition to paleosubspecies of Gallinula chloropus, the doubtfully distinct Late Pliocene to Pleistocene Gallinula mortierii reperta was described, referring to the population of the Tasmanian native hen that once inhabited mainland Australia and became extinct at the end of the last ice age, it may be that apart from climate change it was driven to extinction by the introduction of the dingo, which as opposed to the marsupial predators hunted during the day, but this would require a survival of mainland Gallinula mortierii to as late as about 1500 BC."G." disneyi was yet another flightless native hen, indicative of that group's rather basal position among moorhens. Its time and place of occurrence suggest it as an ancestor of G. mortierii, from which it differed in its much smaller size.
However, some limb bone proportions are strikingly different, in any case such a scenario would require a flightless bird to change but little during some 20 million years in an environment rich in predators. As the fossils of G. disneyi as well as the rich recent and subfossil material of G. mortierii shows no evidence of suc
Animals are multicellular eukaryotic organisms that form the biological kingdom Animalia. With few exceptions, animals consume organic material, breathe oxygen, are able to move, can reproduce sexually, grow from a hollow sphere of cells, the blastula, during embryonic development. Over 1.5 million living animal species have been described—of which around 1 million are insects—but it has been estimated there are over 7 million animal species in total. Animals range in length from 8.5 millionths of a metre to 33.6 metres and have complex interactions with each other and their environments, forming intricate food webs. The category includes humans, but in colloquial use the term animal refers only to non-human animals; the study of non-human animals is known as zoology. Most living animal species are in the Bilateria, a clade whose members have a bilaterally symmetric body plan; the Bilateria include the protostomes—in which many groups of invertebrates are found, such as nematodes and molluscs—and the deuterostomes, containing the echinoderms and chordates.
Life forms interpreted. Many modern animal phyla became established in the fossil record as marine species during the Cambrian explosion which began around 542 million years ago. 6,331 groups of genes common to all living animals have been identified. Aristotle divided animals into those with those without. Carl Linnaeus created the first hierarchical biological classification for animals in 1758 with his Systema Naturae, which Jean-Baptiste Lamarck expanded into 14 phyla by 1809. In 1874, Ernst Haeckel divided the animal kingdom into the multicellular Metazoa and the Protozoa, single-celled organisms no longer considered animals. In modern times, the biological classification of animals relies on advanced techniques, such as molecular phylogenetics, which are effective at demonstrating the evolutionary relationships between animal taxa. Humans make use of many other animal species for food, including meat and eggs. Dogs have been used in hunting, while many aquatic animals are hunted for sport.
Non-human animals have appeared in art from the earliest times and are featured in mythology and religion. The word "animal" comes from the Latin animalis, having soul or living being; the biological definition includes all members of the kingdom Animalia. In colloquial usage, as a consequence of anthropocentrism, the term animal is sometimes used nonscientifically to refer only to non-human animals. Animals have several characteristics. Animals are eukaryotic and multicellular, unlike bacteria, which are prokaryotic, unlike protists, which are eukaryotic but unicellular. Unlike plants and algae, which produce their own nutrients animals are heterotrophic, feeding on organic material and digesting it internally. With few exceptions, animals breathe oxygen and respire aerobically. All animals are motile during at least part of their life cycle, but some animals, such as sponges, corals and barnacles become sessile; the blastula is a stage in embryonic development, unique to most animals, allowing cells to be differentiated into specialised tissues and organs.
All animals are composed of cells, surrounded by a characteristic extracellular matrix composed of collagen and elastic glycoproteins. During development, the animal extracellular matrix forms a flexible framework upon which cells can move about and be reorganised, making the formation of complex structures possible; this may be calcified, forming structures such as shells and spicules. In contrast, the cells of other multicellular organisms are held in place by cell walls, so develop by progressive growth. Animal cells uniquely possess the cell junctions called tight junctions, gap junctions, desmosomes. With few exceptions—in particular, the sponges and placozoans—animal bodies are differentiated into tissues; these include muscles, which enable locomotion, nerve tissues, which transmit signals and coordinate the body. There is an internal digestive chamber with either one opening or two openings. Nearly all animals make use of some form of sexual reproduction, they produce haploid gametes by meiosis.
These fuse to form zygotes, which develop via mitosis into a hollow sphere, called a blastula. In sponges, blastula larvae swim to a new location, attach to the seabed, develop into a new sponge. In most other groups, the blastula undergoes more complicated rearrangement, it first invaginates to form a gastrula with a digestive chamber and two separate germ layers, an external ectoderm and an internal endoderm. In most cases, a third germ layer, the mesoderm develops between them; these germ layers differentiate to form tissues and organs. Repeated instances of mating with a close relative during sexual reproduction leads to inbreeding depression within a population due to the increased prevalence of harmful recessive traits. Animals have evolved numerous mechanisms for avoiding close inbreeding. In some species, such as the splendid fairywren, females benefit by mating with multiple males, thus producing more offspring of higher genetic quality; some animals are capable of asexual reproduction, which results
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
10th edition of Systema Naturae
The 10th edition of Systema Naturae is a book written by Swedish naturalist Carolus Linnaeus and published in two volumes in 1758 and 1759, which marks the starting point of zoological nomenclature. In it, Linnaeus introduced binomial nomenclature for animals, something he had done for plants in his 1753 publication of Species Plantarum. Before 1758, most biological catalogues had used polynomial names for the taxa included, including earlier editions of Systema Naturae; the first work to apply binomial nomenclature across the animal kingdom was the 10th edition of Systema Naturae. The International Commission on Zoological Nomenclature therefore chose 1 January 1758 as the "starting point" for zoological nomenclature, asserted that the 10th edition of Systema Naturae was to be treated as if published on that date. Names published before that date are unavailable if they would otherwise satisfy the rules; the only work which takes priority over the 10th edition is Carl Alexander Clerck's Svenska Spindlar or Aranei Suecici, published in 1757, but is to be treated as if published on January 1, 1758.
During Linnaeus' lifetime, Systema Naturae was under continuous revision. Progress was incorporated into ever-expanding editions; the Animal Kingdom: Animals enjoy sensation by means of a living organization, animated by a medullary substance. They have members for the different purposes of life, they all originate from an egg. Their external and internal structure; the list has been broken down into the original six classes Linnaeus described for animals. These classes were created by studying the internal anatomy, as seen in his key: Heart with 2 auricles, 2 ventricles. Warm, red blood Viviparous: Mammalia Oviparous: Aves Heart with 1 auricle, 1 ventricle. Cold, red blood Lungs voluntary: Amphibia External gills: Pisces Heart with 1 auricle, 0 ventricles. Cold, pus-like blood Have antennae: Insecta Have tentacles: VermesBy current standards Pisces and Vermes are informal groupings, Insecta contained arachnids and crustaceans, one order of Amphibia comprised sharks and sturgeons. Linnaeus described mammals as: Animals.
In external and internal structure they resemble man: most of them are quadrupeds. The largest, though fewest in number, inhabit the ocean. Linnaeus divided the mammals based upon the number and structure of their teeth, into the following orders and genera: Primates: Homo, Lemur & Vespertilio Bruta: Elephas, Bradypus, Myrmecophaga & Manis Ferae: Phoca, Felis, Mustela & Ursus Bestiae: Sus, Erinaceus, Sorex & Didelphis Glires: Rhinoceros, Lepus, Mus & Sciurus Pecora: Camelus, Cervus, Ovis & Bos Belluae: Equus & Hippopotamus Cete: Monodon, Physeter & Delphinus Linnaeus described birds as: A beautiful and cheerful portion of created nature consisting of animals having a body covered with feathers and down, they are areal, vocal and light, destitute of external ears, teeth, womb, epiglottis, corpus callosum and its arch, diaphragm. Linnaeus divided the birds based upon the characters of the bill and feet, into the following 6 orders and 63 genera: Accipitres: Vultur, Strix & Lanius Picae: Psittacus, Buceros, Corvus, Gracula, Cuculus, Picus, Alcedo, Upupa, Certhia & Trochilus Anseres: Anas, Alca, Diomedea, Phaethon, Larus, Sterna & Rhyncops Grallae: Phoenicopterus, Mycteria & Tantulus, Scolopax, Charadrius, Haematopus, Rallus, Otis & Struthio Gallinae: Pavo, Crax, Phasianus & Tetrao Passeres: Columba, Sturnus, Loxia (cardina