The Korean Peninsula is located in East Asia. It extends southwards for about 1,100 km from continental Asia into the Pacific Ocean and is surrounded by the Sea of Japan to the east and the Yellow Sea to the west, the Korea Strait connecting the two bodies of water; the peninsula's names, in Korean and Japanese, all share the same origin, that being Joseon, the old name of Korea under the Joseon Dynasty and Gojoseon longer before that. In North Korea's standard language, the peninsula is called Chosŏn Pando, while in China, as well as in Singapore and Malaysia it is called Cháoxiǎn Bàndǎo. In Japan, it is either Chōsenhantō or Kanhantō. In Vietnam, it is called Bán đảo Triều Tiên. Meanwhile, in South Korea, it is called Hanbando, referring to the Samhan the Three Kingdoms of Korea, not the ancient confederacies in the southern Korean Peninsula, they both use "Korea" as part of their official English names, a name that comes from the Goryeo dynasty. Until the end of World War II, Korea was a single political entity whose territory coincided with the Korean Peninsula.
In August 1945, the Soviet Union declared war on Imperial Japan, as a result of an agreement with the United States, liberated Korea north of the 38th parallel. U. S. forces subsequently moved into the south. By 1948, as a product of the Cold War between the Soviet Union and the United States, Korea was divided into two regions, with separate governments. Both claimed to be the legitimate government of all of Korea, neither accepted the border as permanent; the conflict escalated into open warfare when North Korean forces—supported by the Soviet Union and China—moved into the south on 25 June 1950. Since the Armistice Agreement ended the Korean War in 1953, the northern section of the peninsula has been governed by the Democratic People's Republic of Korea, while the southern portion has been governed by the Republic of Korea; the northern boundaries for the Korean Peninsula are taken to coincide with today's political borders between North Korea and its northern neighbors and Russia. These borders are formed by the rivers Amnok and Duman.
Taking this definition, the Korean Peninsula has an area of 220,847 km2. The Korean Peninsula has a temperate climate with comparatively fewer typhoons than other countries in East Asia. Due to the peninsula's position, it has a unique climate influenced from Siberia in the north, the Pacific Ocean in the east and the rest of Eurasia in the west; the peninsula has four distinct seasons: spring, summer and winter. As influence from Siberia weakens, temperatures begin to increase while the high pressure begins to move away. If the weather is abnormally dry, Siberia will have more influence on the peninsula leading to wintry weather such as snow. During June at the start of the summer, there tends to be a lot of rain due to the cold and wet air from the Sea of Okhotsk and the hot and humid air from the Pacific Ocean combining; when these fronts combine, it leads to a so-called rainy season with cloudy days with rain, sometimes heavy. The hot and humid winds from the south west blow causing an increasing amount of humidity and this leads to the fronts moving towards Manchuria in China and thus there is less rain and this is known as midsummer.
High pressure is dominant during autumn leading to clear conditions. Furthermore, temperatures remain high but the humidity becomes low; the weather becomes dominated by Siberia during winter and the jet stream moves further south causing a drop in temperature. This season is dry with some snow falling at times. Temperatures can drop to -20 °C in the mountainous areas; the Korean Peninsula is located in East Asia. To the northwest, the Amnok River separates the peninsula from China and to the northeast, the Duman River separates it from China and Russia; the peninsula is surrounded by the Yellow Sea to the west, the East China Sea and Korea Strait to the south, the Sea of Japan to the east. Notable islands include Ulleung Island, Dokdo; the southern and western parts of the peninsula have well-developed plains, while the eastern and northern parts are mountainous. The highest mountain in Korea is Mount Paektu; the southern extension of Mount Paektu is a highland called Gaema Heights. This highland was raised during the Cenozoic orogeny and covered by volcanic matter.
To the south of Gaema Gowon, successive high mountains are located along the eastern coast of the peninsula. This mountain range is named Baekdudaegan; some significant mountains include Mount Sobaek or Sobaeksan, Mount Kumgang, Mount Seorak, Mount Taebaek, Mount Jiri. There are several lower, secondary mountain series whose direction is perpendicular to that of Baekdudaegan, they are developed along the tectonic line of Mesozoic orogeny and their directions are northwest. Unlike most ancient mountains on the mainland, many important islands in Korea were formed by volcanic activity in the Cenozoic orogeny. Jeju Island, situated off the southern coast, is a large volcanic island whose main mountain Mount Halla or Hallasan is the highest in South Korea. Ulleung Island is a volcanic island in the Sea of
Mark Catesby was an English naturalist. Between 1729 and 1747 Catesby published his Natural History of Carolina and the Bahama Islands, the first published account of the flora and fauna of North America, it included 220 plates of birds, amphibians, insects and plants. Catesby was born on 24 March 1683 and baptised at Castle Hedingham, Essex on 30 March 1683, his father, John Catesby, was a local gentleman farmer. His mother was Elizabeth Jekyll; the family owned Holgate, in Sudbury, Suffolk as well as property in London. An acquaintance with the naturalist John Ray led to Catesby becoming interested in natural history; the death of his father left Catesby enough to live on, so in 1712, he accompanied his sister Elizabeth to Williamsburg, Virginia. She was the wife of Dr. William Cocke, a member of the Council and Secretary of State for the Colony of Virginia. According to their father's will, Elizabeth had married Dr. Cocke against her father's wishes. Catesby visited the West Indies in 1714, returned to Virginia home to England in 1719.
Catesby had collected seeds and botanical specimens in Jamaica. He sent the pressed specimens to Dr Samuel Dale of Braintree in Essex, gave seeds to a Hoxton nurseryman Thomas Fairchild as well as to Dale and to the Bishop of London, Dr Henry Compton. Plants from Virginia, raised from Catesby's seeds, made his name known to gardeners and scientists in England, in 1722 he was recommended by William Sherard to undertake a plant-collecting expedition to Carolina on behalf of certain members of the Royal Society. From May 1722, Catesby was based in Charleston, South Carolina, travelled to other parts of that colony, collecting plants and animals, he sent preserved specimens to Hans Sloane and to William Sherard, seeds to various contacts including Sherard and Peter Collinson. Catesby was responsible for introducing such plants as Catalpa bignonioides and the eponymous Catesbaea spinosa to cultivation in Europe. Catesby returned to England in 1726. Catesby spent the next twenty years publishing his Natural History.
Publication was financed by subscriptions from his "Encouragers" as well as an interest-free loan from one of the fellows of the Royal Society, the Quaker Peter Collinson. Catesby learnt; the first eight plates had no backgrounds, but from on Catesby included plants with his animals. He presented it to Queen Caroline. Mark Catesby was elected a fellow of the Royal Society in February 1733 and was made a member of the Society of Gentlemen of Spalding in December 1743; the second volume containing another five parts was completed in December 1743, in 1747 he produced a supplement from material sent to him by friends in America John Bartram, his younger brother, based with a British regiment in Gibraltar. Not all the plates in Natural history are by Catesby: several, including the splendid and famous image of Magnolia grandiflora were by Georg Ehret. Catesby's original preparatory drawings for Natural History of Carolina and the Bahama Islands are in the Royal Library, Windsor Castle, selections have been exhibited in USA, Japan and various places in England including at the Queen's Gallery, London, in 1997–1998, Gainsborough House in Sudbury in 2015.
On 5 March 1747, Catesby read a paper entitled "Of birds of passage" to the Royal Society in London, he is now recognised as one of the first people to describe bird migration. Mark Catesby married Elizabeth Rowland on 8 October 1747 in St George's Chapel, Hyde Park Corner, but they had been a couple for about 17 years, having at least six children between April 1731 and June 1740, they were parishioners of St Giles Cripplegate in London and when that parish was subdivided, of St Luke Old Street. He died just before Christmas 1749 on Saturday 23 December in his house behind St Luke Old Street and was buried in its churchyard, his grave is now lost. Catesby's Hortus britanno-americanus... was published posthumously in 1763, a second edition, entitled Hortus Europae americanus... was issued in 1767. The Swedish naturalist Carl Linnaeus included information from Catesby's Natural History in the 10th edition of his Systema Naturae. Catesbaea, lilythorn, a genus of thorny shrubs belonging to Rubiaceae from the West Indies and southeastern USA was named after Catesby by J. K. Gronovius.
However, under present rules of nomenclature, this name was formally published by Linnaeus in 1753 in his Species plantarum, based on plate 100 in volume two of Catesby's Natural history of Carolina and the Bahama Islands. The American bullfrog, Rana catesbeiana, is named in honor of Catesby. Catesby is commemorated in the scientific names of two species of New World snakes: Dipsas catesbyi and Uromacer catesbyi. List of wildlife artists Jackson, Christine E.. Bird Etchings: The Illustrators and Their Books, 1655-1855. Ithaca: Cornell University Press. ISBN 0-8014-9684-5. Walters, Michael. A Concise History of Ornithology. London: Christopher Helm. ISBN 1-873403-97-6. Wiatt, Alex L.. The Descendants of Stephen Field of King and Queen County, Virginia, 1721. Fredericksburg, Virginia: BookCrafters. McBurney, Henrietta. Mark Catesby's Natural History of America; the watercolours from the Royal Library Windsor Castle. London: Merrell Holberton, in association with The Museum of Fine Arts, Houston. ISBN 185894038-9.
Myers, Amy R. W.. B
Mollusca is the second largest phylum of invertebrate animals. The members are known as mollusks. Around 85,000 extant species of molluscs are recognized; the number of fossil species is estimated between 100,000 additional species. Molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs live in freshwater and terrestrial habitats, they are diverse, not just in size and in anatomical structure, but in behaviour and in habitat. The phylum is divided into 8 or 9 taxonomic classes, of which two are extinct. Cephalopod molluscs, such as squid and octopus, are among the most neurologically advanced of all invertebrates—and either the giant squid or the colossal squid is the largest known invertebrate species; the gastropods are by far the most numerous molluscs and account for 80% of the total classified species. The three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, the structure of the nervous system.
Other than these common elements, molluscs express great morphological diversity, so many textbooks base their descriptions on a "hypothetical ancestral mollusc". This has a single, "limpet-like" shell on top, made of proteins and chitin reinforced with calcium carbonate, is secreted by a mantle covering the whole upper surface; the underside of the animal consists of a single muscular "foot". Although molluscs are coelomates, the coelom tends to be small; the main body cavity is a hemocoel. The "generalized" mollusc's feeding system consists of a rasping "tongue", the radula, a complex digestive system in which exuded mucus and microscopic, muscle-powered "hairs" called cilia play various important roles; the generalized mollusc has three in bivalves. The brain, in species that have one, encircles the esophagus. Most molluscs have eyes, all have sensors to detect chemicals and touch; the simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur.
All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, or miniature adults. The coelomic cavity is reduced, they have kidney-like organs for excretion. Good evidence exists for the appearance of gastropods and bivalves in the Cambrian period, 541 to 485.4 million years ago. However, the evolutionary history both of molluscs' emergence from the ancestral Lophotrochozoa and of their diversification into the well-known living and fossil forms are still subjects of vigorous debate among scientists. Molluscs still are an important food source for anatomically modern humans. There is a risk of food poisoning from toxins which can accumulate in certain molluscs under specific conditions and because of this, many countries have regulations to reduce this risk. Molluscs have, for centuries been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye, sea silk, their shells have been used as money in some preindustrial societies. Mollusc species can represent hazards or pests for human activities.
The bite of the blue-ringed octopus is fatal, that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can kill, but their sophisticated, though produced, venoms have become important tools in neurological research. Schistosomiasis is transmitted to humans via water snail hosts, affects about 200 million people. Snails and slugs can be serious agricultural pests, accidental or deliberate introduction of some snail species into new environments has damaged some ecosystems; the words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, soft. Molluscus was itself an adaptation of Aristotle's τὰ μαλάκια ta malákia, which he applied inter alia to cuttlefish; the scientific study of molluscs is accordingly called malacology. The name Molluscoida was used to denote a division of the animal kingdom containing the brachiopods and tunicates, the members of the three groups having been supposed to somewhat resemble the molluscs.
As it is now known these groups have no relation to molluscs, little to one another, the name Molluscoida has been abandoned. The most universal features of the body structure of molluscs are a mantle with a significant cavity used for breathing and excretion, the organization of the nervous system. Many have a calcareous shell. Molluscs have developed such a varied range of body structures, it is difficult to find synapomorphies to apply to all modern groups; the most general characteristic of molluscs is they are bilaterally symmetrical. The following are present in all modern molluscs: The dorsal part of the body wall is a mantle which secretes calcareous spicules, plates or shells, it overlaps the body with enough spare room to form a mantle cavity. The anus and genitals open into the mantle cavity. There are two pairs of main nerve cords. Other characteristics that appear in textbooks have significant exceptions: Estimates of accepted described living species of molluscs vary from 50,000 to a maximum of 120,000 species.
In 1969 David Nicol estimated the probable total number of living mollusc species at 107,000 of which were ab
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
Europe is a continent located in the Northern Hemisphere and in the Eastern Hemisphere. It is bordered by the Arctic Ocean to the north, the Atlantic Ocean to the west and the Mediterranean Sea to the south, it comprises the westernmost part of Eurasia. Since around 1850, Europe is most considered to be separated from Asia by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas and the waterways of the Turkish Straits. Although the term "continent" implies physical geography, the land border is somewhat arbitrary and has been redefined several times since its first conception in classical antiquity; the division of Eurasia into two continents reflects East-West cultural and ethnic differences which vary on a spectrum rather than with a sharp dividing line. The geographic border does not follow political boundaries, with Turkey and Kazakhstan being transcontinental countries. A strict application of the Caucasus Mountains boundary places two comparatively small countries and Georgia, in both continents.
Europe covers 2 % of the Earth's surface. Politically, Europe is divided into about fifty sovereign states of which the Russian Federation is the largest and most populous, spanning 39% of the continent and comprising 15% of its population. Europe had a total population of about 741 million as of 2016; the European climate is affected by warm Atlantic currents that temper winters and summers on much of the continent at latitudes along which the climate in Asia and North America is severe. Further from the sea, seasonal differences are more noticeable than close to the coast. Europe, in particular ancient Greece, was the birthplace of Western civilization; the fall of the Western Roman Empire in 476 AD and the subsequent Migration Period marked the end of ancient history and the beginning of the Middle Ages. Renaissance humanism, exploration and science led to the modern era. Since the Age of Discovery started by Portugal and Spain, Europe played a predominant role in global affairs. Between the 16th and 20th centuries, European powers controlled at various times the Americas all of Africa and Oceania and the majority of Asia.
The Age of Enlightenment, the subsequent French Revolution and the Napoleonic Wars shaped the continent culturally and economically from the end of the 17th century until the first half of the 19th century. The Industrial Revolution, which began in Great Britain at the end of the 18th century, gave rise to radical economic and social change in Western Europe and the wider world. Both world wars took place for the most part in Europe, contributing to a decline in Western European dominance in world affairs by the mid-20th century as the Soviet Union and the United States took prominence. During the Cold War, Europe was divided along the Iron Curtain between NATO in the West and the Warsaw Pact in the East, until the revolutions of 1989 and fall of the Berlin Wall. In 1949 the Council of Europe was founded, following a speech by Sir Winston Churchill, with the idea of unifying Europe to achieve common goals, it includes all European states except for Belarus and Vatican City. Further European integration by some states led to the formation of the European Union, a separate political entity that lies between a confederation and a federation.
The EU originated in Western Europe but has been expanding eastward since the fall of the Soviet Union in 1991. The currency of most countries of the European Union, the euro, is the most used among Europeans. In classical Greek mythology, Europa was a Phoenician princess; the word Europe is derived from her name. The name contains the elements εὐρύς, "wide, broad" and ὤψ "eye, countenance", hence their composite Eurṓpē would mean "wide-gazing" or "broad of aspect". Broad has been an epithet of Earth herself in the reconstructed Proto-Indo-European religion and the poetry devoted to it. There have been attempts to connect Eurṓpē to a Semitic term for "west", this being either Akkadian erebu meaning "to go down, set" or Phoenician'ereb "evening, west", at the origin of Arabic Maghreb and Hebrew ma'arav. Michael A. Barry, professor in Princeton University's Near Eastern Studies Department, finds the mention of the word Ereb on an Assyrian stele with the meaning of "night, sunset", in opposition to Asu " sunrise", i.e. Asia.
The same naming motive according to "cartographic convention" appears in Greek Ἀνατολή. Martin Litchfield West stated that "phonologically, the match between Europa's name and any form of the Semitic word is poor." Next to these hypotheses there is a Proto-Indo-European root *h1regʷos, meaning "darkness", which produced Greek Erebus. Most major world languages use words derived from Europa to refer to the continent. Chinese, for example, uses the word Ōuzhōu. In some Turkic languages the Persian name Frangistan is used casually in referring to much of Europe, besides official names such as Avrupa or Evropa; the prevalent definition of Europe as a geographical term has been in use since the mid-19th century. Europe is taken to be bounded by large bodies of water
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
An earthworm is a tube-shaped, segmented worm found in the phylum Annelida. They have a world-wide distribution and are found living in soil, feeding on live and dead organic matter. An earthworm's digestive system runs through the length of its body, it conducts respiration through its skin. It has a double transport system composed of coelomic fluid that moves within the fluid-filled coelom and a simple, closed blood circulatory system, it has a peripheral nervous system. The central nervous system consists of two ganglia above the mouth, one on either side, connected to a nerve cord running back along its length to motor neurons and sensory cells in each segment. Large numbers of chemoreceptors are concentrated near its mouth. Circumferential and longitudinal muscles on the periphery of each segment enable the worm to move. Similar sets of muscles line the gut, their actions move the digesting food toward the worm's anus. Earthworms are hermaphrodites: each individual carries both male and female sex organs.
As invertebrates, they lack either an internal skeleton or exoskeleton, but maintain their structure with fluid-filled coelom chambers that function as a hydrostatic skeleton. "Earthworm" is the common name for the largest members of Oligochaeta. In classical systems, they were placed in the order Opisthopora, on the basis of the male pores opening posterior to the female pores, though the internal male segments are anterior to the female. Theoretical cladistic studies have placed them, instead, in the suborder Lumbricina of the order Haplotaxida, but this may again soon change. Folk names for the earthworm include "dew-worm", "rainworm", "night crawler", "angleworm". Larger terrestrial earthworms are called megadriles, as opposed to the microdriles in the semiaquatic families Tubificidae and Enchytraeidae, among others; the megadriles are characterized by having a distinct clitellum and a vascular system with true capillaries. Depending on the species, an adult earthworm can be from 10 mm long and 1 mm wide to 3 m long and over 25 mm wide, but the typical Lumbricus terrestris grows to about 360 mm long.
The longest worm on confirmed records is Amynthas mekongianus that extends up to 3 m in the mud along the banks of the 4,350 km Mekong River in Southeast Asia. From front to back, the basic shape of the earthworm is a cylindrical tube, divided into a series of segments that compartmentalize the body. Furrows are externally visible on the body demarking the segments. Except for the mouth and anal segments, each segment carries bristle-like hairs called lateral setae used to anchor parts of the body during movement. Special ventral setae are used to anchor mating earthworms by their penetration into the bodies of their mates. Within a species, the number of segments found is consistent across specimens, individuals are born with the number of segments they will have throughout their lives; the first body segment features both the earthworm's mouth and, overhanging the mouth, a fleshy lobe called the prostomium, which seals the entrance when the worm is at rest, but is used to feel and chemically sense the worm's surroundings.
Some species of earthworm can use the prehensile prostomium to grab and drag items such as grasses and leaves into their burrow. An adult earthworm develops a belt-like glandular swelling, called the clitellum, which covers several segments toward the front part of the animal; this produces egg capsules. The posterior is most cylindrical like the rest of the body, but depending on the species, may be quadrangular, trapezoidal, or flattened; the last segment is called the periproct. The exterior of an individual segment is a thin cuticle over skin pigmented red to brown, which has specialized cells that secrete mucus over the cuticle to keep the body moist and ease movement through soil. Under the skin is a layer of nerve tissue, two layers of muscles—a thin outer layer of circular muscle, a much thicker inner layer of longitudinal muscle. Interior to the muscle layer is a fluid-filled chamber called a coelom that by its pressurization provides structure to the worm's boneless body; the segments are separated from each other by septa which are perforated transverse walls, allowing the coelomic fluid to pass between segments.
A pair of structures called. This tubule leads to the main body fluid filtering organ, the nephridium or metanephridium, which removes metabolic waste from the coelomic fluid and expels it through pores called nephridiopores on the worm's sides. At the center of a worm is the digestive tract, which runs straight through from mouth to anus without coiling, is flanked above and below by blood vessels and the ventral nerve cord, is surrounded in each segment by a pair of pallial blood vessels that connect the dorsal to th