In mathematics, two quantities are in the golden ratio if their ratio is the same as the ratio of their sum to the larger of the two quantities. The figure on the right illustrates the geometric relationship. Expressed algebraically, for quantities a and b with a > b > 0, a + b a = a b = def φ, where the Greek letter phi represents the golden ratio. It is an irrational number, a solution to the quadratic equation x 2 − x − 1 = 0, with a value of: φ = 1 + 5 2 = 1.6180339887 …. The golden ratio is called the golden mean or golden section. Other names include extreme and mean ratio, medial section, divine proportion, divine section, golden proportion, golden cut, golden number. Mathematicians since Euclid have studied the properties of the golden ratio, including its appearance in the dimensions of a regular pentagon and in a golden rectangle, which may be cut into a square and a smaller rectangle with the same aspect ratio; the golden ratio has been used to analyze the proportions of natural objects as well as man-made systems such as financial markets, in some cases based on dubious fits to data.
The golden ratio appears in some patterns in nature, including the spiral arrangement of leaves and other plant parts. Some twentieth-century artists and architects, including Le Corbusier and Salvador Dalí, have proportioned their works to approximate the golden ratio—especially in the form of the golden rectangle, in which the ratio of the longer side to the shorter is the golden ratio—believing this proportion to be aesthetically pleasing. Two quantities a and b are said to be in the golden ratio φ if a + b a = a b = φ. One method for finding the value of φ is to start with the left fraction. Through simplifying the fraction and substituting in b/a = 1/φ, a + b a = a a + b a = 1 + b a = 1 + 1 φ. Therefore, 1 + 1 φ = φ. Multiplying by φ gives φ + 1 = φ 2 which can be rearranged to φ 2 − φ − 1 = 0. Using the quadratic formula, two solutions are obtained: 1 + 5 2 = 1.618 033 988 7 … and 1 − 5 2 = − 0.618 033 988 7 … Because φ is the ratio between positive quantities, φ is positive: φ = 1 + 5 2 = 1.61803 39887 … The golden ratio has been claimed to have held a special fascination for at least 2,400 years, although without reliable evidence.
According to Mario Livio: Some of the greatest mathematical minds of all ages, from Pythagoras and Euclid in ancient Greece, through the medieval Italian mathematician Leonardo of Pisa and the Renaissance astronomer Johannes Kepler, to present-day scientific figures such as Oxford physicist Roger Penrose, have spent endless hours over this simple ratio and its properties. But the fascination with the Golden Ratio is not confined just to mathematicians. Biologists, musicians, architects and mystics have pondered and debated the basis of its ubiquity and appeal. In fact, it is fair to say that the Golden Ratio has inspired thinkers of all disciplines like no other number in the history of mathematics. Ancient Greek mathematicians first studied what we now call the golden ratio because of its frequent appearance in geometry. According to one story, 5th-century BC mathematician Hippasus discovered that the golden ratio was neither a whole number nor a fraction, surprising Pythagoreans. Euclid's Elements provides several propositions and their proofs employing the golden ratio and contains the first known definition: A straight line is said to have been cut in extreme and mean ratio when, as the whole line is to the greater segment, so is the greater to the lesser.
The golden ratio was studied peripherally over the next millennium. Abu Kamil employed it in his geometric calculati
Eyes are organs of the visual system. They provide organisms with vision, the ability to receive and process visual detail, as well as enabling several photo response functions that are independent of vision. Eyes convert it into electro-chemical impulses in neurons. In higher organisms, the eye is a complex optical system which collects light from the surrounding environment, regulates its intensity through a diaphragm, focuses it through an adjustable assembly of lenses to form an image, converts this image into a set of electrical signals, transmits these signals to the brain through complex neural pathways that connect the eye via the optic nerve to the visual cortex and other areas of the brain. Eyes with resolving power have come in ten fundamentally different forms, 96% of animal species possess a complex optical system. Image-resolving eyes are present in molluscs and arthropods; the simplest "eyes", such as those in microorganisms, do nothing but detect whether the surroundings are light or dark, sufficient for the entrainment of circadian rhythms.
From more complex eyes, retinal photosensitive ganglion cells send signals along the retinohypothalamic tract to the suprachiasmatic nuclei to effect circadian adjustment and to the pretectal area to control the pupillary light reflex. Complex eyes can distinguish colours; the visual fields of many organisms predators, involve large areas of binocular vision to improve depth perception. In other organisms, eyes are located so as to maximise the field of view, such as in rabbits and horses, which have monocular vision; the first proto-eyes evolved among animals 600 million years ago about the time of the Cambrian explosion. The last common ancestor of animals possessed the biochemical toolkit necessary for vision, more advanced eyes have evolved in 96% of animal species in six of the ~35 main phyla. In most vertebrates and some molluscs, the eye works by allowing light to enter and project onto a light-sensitive panel of cells, known as the retina, at the rear of the eye; the cone cells and the rod cells in the retina detect and convert light into neural signals for vision.
The visual signals are transmitted to the brain via the optic nerve. Such eyes are roughly spherical, filled with a transparent gel-like substance called the vitreous humour, with a focusing lens and an iris; the eyes of most cephalopods, fish and snakes have fixed lens shapes, focusing vision is achieved by telescoping the lens—similar to how a camera focuses. Compound eyes are found among the arthropods and are composed of many simple facets which, depending on the details of anatomy, may give either a single pixelated image or multiple images, per eye; each sensor has its own photosensitive cell. Some eyes have up to 28,000 such sensors, which are arranged hexagonally, which can give a full 360° field of vision. Compound eyes are sensitive to motion; some arthropods, including many Strepsiptera, have compound eyes of only a few facets, each with a retina capable of creating an image, creating vision. With each eye viewing a different thing, a fused image from all the eyes is produced in the brain, providing different, high-resolution images.
Possessing detailed hyperspectral colour vision, the Mantis shrimp has been reported to have the world's most complex colour vision system. Trilobites, which are now extinct, had unique compound eyes, they used clear calcite crystals to form the lenses of their eyes. In this, they differ from most other arthropods; the number of lenses in such an eye varied, however: some trilobites had only one, some had thousands of lenses in one eye. In contrast to compound eyes, simple eyes are those. For example, jumping spiders have a large pair of simple eyes with a narrow field of view, supported by an array of other, smaller eyes for peripheral vision; some insect larvae, like caterpillars, have a different type of simple eye which provides only a rough image, but can possess resolving powers of 4 degrees of arc, be polarization sensitive and capable of increasing its absolute sensitivity at night by a factor of 1,000 or more. Some of the simplest eyes, called ocelli, can be found in animals like some of the snails, which cannot "see" in the normal sense.
They do have photosensitive cells, but no lens and no other means of projecting an image onto these cells. They can no more; this enables snails to keep out of direct sunlight. In organisms dwelling near deep-sea vents, compound eyes have been secondarily simplified and adapted to spot the infra-red light produced by the hot vents—in this way the bearers can spot hot springs and avoid being boiled alive. There are ten different eye layouts—indeed every technological method of capturing an optical image used by human beings, with the exceptions of zoom and Fresnel lenses, occur in nature. Eye types can be categorised into "simple eyes", with one concave photoreceptive surface, "compound eyes", which comprise a number of individual lenses laid out on a convex surface. Note that "simple" does not imply a reduced level of complexity or acuity. Indeed, any eye type can be adapted for any behaviour or environment; the only limitations specific to eye types are that of resolution—the physics of compound eyes prevents them from achieving a resolution better than 1°.
Superposition eyes can achieve greater sensitivity than apposition eyes, so are better suited to
The neck is the part of the body, on many vertebrates, that separates the head from the torso. It contains blood nerves that supply structures in the head to the body; these in humans include part of the esophagus, the larynx and thyroid gland, major blood vessels including the carotid arteries and jugular veins, the top part of the spinal cord. In anatomy, the neck is called by its Latin names, cervix or collum, although when used alone, in context, the word cervix more refers to the uterine cervix, the neck of the uterus, thus the adjective cervical may refer either to the uterine cervix. The neck contains vessels. In humans these structures include part of the esophagus, trachea and parathyroid glands, lymph nodes, the first part of the spinal cord. Major blood vessels include the jugular veins. Cervical lymph nodes surround the blood vessels; the thyroid gland and parathyroid glands are endocrine glands involved in the regulation of cellular metabolism and growth, blood calcium levels. The shape of the neck in humans is formed from the upper part of the vertebral column at the back, a series of cartilage that surrounds the upper part of the respiratory tract.
Around these sit soft tissues, including muscles, between and around these sit the other structures mentioned above. Muscles of the neck attach to the base of the skull, the hyoid bone, the clavicles, the sternum; the large platysma, sternocleidomastoid muscles contribute to the shape at the front, the trapezius and lattissimus dorsi at the back. A number of other muscles attach to and stem from the hyoid bone, facilitating speech and playing a role in swallowing. Sensation to the front areas of the neck comes from the roots of nerves C2-4, at the back of the neck from the roots of C4-5; the cervical region of the human spine is made up of seven cervical vertebrae referred to as C-1 to C-7, with cartilaginous discs between each vertebral body. The spinal cord sits within the cervical part of the vertebral column; the spinal column carries nerves that carry sensory and motor information from the brain down to the rest of the body. From top to bottom the cervical spine is curved in convex-forward fashion.
In addition to nerves coming from and within the human spine, the accessory nerve and vagus nerve both cranial nerves, travel down the neck. In the middle line below the chin can be felt the body of the hyoid bone, just below, the prominence of the thyroid cartilage called "Adam's apple", better marked in men than in women. Neck lines appear at a age as a development of skin wrinkles. Still, lower the cricoid cartilage is felt, while between this and the suprasternal notch, the trachea and the isthmus of the thyroid gland may be made out. At the side, the outline of the sternomastoid muscle is the most striking mark; the upper part of the former contains the submaxillary gland known as the submandibular glands, which lies just below the posterior half of the body of the jaw. The line of the common and the external carotid arteries may be marked by joining the sterno-clavicular articulation to the angle of the jaw; the eleventh or spinal accessory nerve corresponds to a line drawn from a point midway between the angle of the jaw and the mastoid process to the middle of the posterior border of the sterno-mastoid muscle and thence across the posterior triangle to the deep surface of the trapezius.
The external jugular vein can be seen through the skin. The anterior jugular vein is smaller, runs down about half an inch from the middle line of the neck; the clavicle or collar-bone forms the lower limit of the neck, laterally the outward slope of the neck to the shoulder is caused by the trapezius muscle. The neck supports the weight of the head and protects the nerves that carry sensory and motor information from the brain down to the rest of the body. In addition, the neck is flexible and allows the head to turn and flex in all directions. Disorders of the neck are a common source of pain; the neck has a great deal of functionality but is subject to a lot of stress. Common sources of neck pain include: Whiplash, strained a muscle or another soft tissue injury Cervical herniated disc Cervical spinal stenosis Osteoarthritis Vascular sources of pain, like arterial dissections or internal jugular vein thrombosis Cervical adenitis The neck appears in some of the earliest of tetrapod fossils, the functionality provided has led to its being retained in all land vertebrates as well as marine-adapted tetrapods such as turtles and penguins.
Some degree of flexibility is retained where the outside physical manifestation has been secondarily lost, as in whales and porpoises. A morphologically functioning neck appears among insects, its absence in fish and aquatic arthropods is notable, as many have life stations similar to a terrestrial or tetrapod counterpart, or could otherwise make use of the added flexibility. The word "neck" is sometimes used as a convenience to refer to the region behind the head in some snails, gastropod mollusks though there is no clear distinction between this area, the head area, the rest of the body. Throat Adam's apple Hickey Nape American Head and Neck Society The Anatomy Wiz. An Interactive Cross-Sectional Anatomy Atlas
In animal anatomy, the mouth known as the oral cavity, buccal cavity, or in Latin cavum oris, is the opening through which many animals take in food and issue vocal sounds. It is the cavity lying at the upper end of the alimentary canal, bounded on the outside by the lips and inside by the pharynx and containing in higher vertebrates the tongue and teeth; this cavity is known as the buccal cavity, from the Latin bucca. Some animal phyla, including vertebrates, have a complete digestive system, with a mouth at one end and an anus at the other. Which end forms first in ontogeny is a criterion used to classify animals into protostomes and deuterostomes. In the first multicellular animals, there was no mouth or gut and food particles were engulfed by the cells on the exterior surface by a process known as endocytosis; the particles became enclosed in vacuoles into which enzymes were secreted and digestion took place intracellularly. The digestive products were diffused into other cells; this form of digestion is used nowadays by simple organisms such as Amoeba and Paramecium and by sponges which, despite their large size, have no mouth or gut and capture their food by endocytosis.
The vast majority of other multicellular organisms have a mouth and a gut, the lining of, continuous with the epithelial cells on the surface of the body. A few animals which live parasitically had guts but have secondarily lost these structures; the original gut of multicellular organisms consisted of a simple sac with a single opening, the mouth. Many modern invertebrates have such a system, food being ingested through the mouth broken down by enzymes secreted in the gut, the resulting particles engulfed by the other cells in the gut lining. Indigestible waste is ejected through the mouth. In animals at least as complex as an earthworm, the embryo forms a dent on one side, the blastopore, which deepens to become the archenteron, the first phase in the formation of the gut. In deuterostomes, the blastopore becomes the anus while the gut tunnels through to make another opening, which forms the mouth. In the protostomes, it used to be thought that the blastopore formed the mouth while the anus formed as an opening made by the other end of the gut.
More recent research, shows that in protostomes the edges of the slit-like blastopore close up in the middle, leaving openings at both ends that become the mouth and anus. Apart from sponges and placozoans all animals have an internal gut cavity, lined with gastrodermal cells. In less advanced invertebrates such as the sea anemone, the mouth acts as an anus. Circular muscles around the mouth are able to contract in order to open or close it. A fringe of tentacles thrusts food into the cavity and it can gape enough to accommodate large prey items. Food passes first into a pharynx and digestion occurs extracellularly in the gastrovascular cavity. Annelids have simple tube-like gets and the possession of an anus allows them to separate the digestion of their foodstuffs from the absorption of the nutrients. Many molluscs have a radula, used to scrape microscopic particles off surfaces. In invertebrates with hard exoskeletons, various mouthparts may be involved in feeding behaviour. Insects have a range of mouthparts suited to their mode of feeding.
These include mandibles and labium and can be modified into suitable appendages for chewing, piercing and sucking. Decapods have six pairs of mouth appendages, one pair of mandibles, two pairs of maxillae and three of maxillipeds. Sea urchins have a set of five sharp calcareous plates which are used as jaws and are known as Aristotle's lantern. In vertebrates, the first part of the digestive system is the buccal cavity known as the mouth; the buccal cavity of a fish is separated from the opercular cavity by the gills. Water flows in through passes over the gills and exits via the operculum or gill slits. Nearly all fish have jaws and may seize food with them but most feed by opening their jaws, expanding their pharynx and sucking in food items; the food may be held or chewed by teeth located in the jaws, on the roof of the mouth, on the pharynx or on the gill arches. Nearly all amphibians are carnivorous as adults. Many catch their prey by flicking out an elongated tongue with a sticky tip and drawing it back into the mouth where they hold the prey with their jaws.
They swallow their food whole without much chewing. They have many small hinged pedicellate teeth, the bases of which are attached to the jaws while the crowns break off at intervals and are replaced. Most amphibians have one or two rows of teeth in both jaws but some frogs lack teeth in the lower jaw. In many amphibians there are vomerine teeth attached to the bone in the roof of the mouth; the mouths of reptiles are similar to those of mammals. The crocodilians are the only reptiles to have teeth anchored in sockets in their jaws, they are able to replace each of their 80 teeth up to 50 times during their lives. Most reptiles are either carnivorous or insectivorous but turtles are herbivorous. Lacking teeth that are suitable for efficiently chewing of their food, turtles have gastroliths in their stomach to further grind the plant material. Snakes have a flexible lower jaw, the two halves of which are not rigidly attached, numerous other joints in their skull; these modifications allow them to open their mouths wide enough to swallow their prey whole if it is wider than they are.
Birds do not have teeth, macerating their food. Their beaks have a range of sizes and shapes according to their diet and are compose
In vertebrates, cervical vertebrae are the vertebrae of the neck below the skull. Thoracic vertebrae in all mammalian species are those vertebrae that carry a pair of ribs, lie caudal to the cervical vertebrae. Further caudally follow the lumbar vertebrae, which belong to the trunk, but do not carry ribs. In reptiles, all trunk vertebrae are called dorsal vertebrae. In many species, though not in mammals, the cervical vertebrae bear ribs. In many other groups, such as lizards and saurischian dinosaurs, the cervical ribs are large; the vertebral transverse processes of mammals are homologous to the cervical ribs of other amniotes. Most mammals have 7 cervical vertebrae. In humans, cervical vertebrae are the smallest of the true vertebrae, can be distinguished from those of the thoracic or lumbar regions by the presence of a foramen in each transverse process, through which the vertebral artery, vertebral veins and inferior cervical ganglion pass; the remainder of this article focuses upon human anatomy.
By convention, the cervical vertebrae are numbered, with the first one closest to the skull and higher numbered vertebrae proceeding away from the skull and down the spine. The general characteristics of the third through sixth cervical vertebrae are described here; the first and seventh vertebrae are extraordinary, are detailed later. The bodies of these four vertebrae are small, broader from side to side than from front to back; the anterior and posterior surfaces are flattened and of equal depth. The upper surface is concave transversely, presents a projecting lip on either side; the lower surface is concave from front to back, convex from side to side, presents laterally shallow concavities that receive the corresponding projecting lips of the underlying vertebra. The pedicles are directed laterally and backward, attach to the body midway between its upper and lower borders, so that the superior vertebral notch is as deep as the inferior, but it is, at the same time, narrower; the laminae are narrow, thinner above than below.
The spinous process is short and bifid, the two divisions being of unequal size. Because the spinous processes are so short, certain superficial muscles attach to the nuchal ligament rather than directly to the vertebrae; the superior and inferior articular processes of cervical vertebrae have fused on either or both sides to form articular pillars, columns of bone that project laterally from the junction of the pedicle and lamina. The articular facets are flat and of an oval form: the superior face backward and medially; the inferior face forward and laterally. The transverse processes are each pierced by the foramen transversarium, which, in the upper six vertebrae, gives passage to the vertebral artery and vein, as well as a plexus of sympathetic nerves; each process consists of a posterior part. These two parts are joined, outside the foramen, by a bar of bone that exhibits a deep sulcus on its upper surface for the passage of the corresponding spinal nerve; the anterior portion is the homologue of the rib in the thoracic region, is therefore named the costal process or costal element.
It arises from the side of the body, is directed laterally in front of the foramen, ends in a tubercle, the anterior tubercle. The posterior part, the true transverse process, springs from the vertebral arch behind the foramen, is directed forward and laterally; the anterior tubercle of the sixth cervical vertebra is known as the carotid tubercle or Chassaignac tubercle. This separates the carotid artery from the vertebral artery and the carotid artery can be massaged against this tubercle to relieve the symptoms of supraventricular tachycardia; the carotid tubercle is used as a landmark for anaesthesia of the brachial plexus and cervical plexus. The cervical spinal nerves emerge from above the cervical vertebrae. For example, the cervical spinal nerve 3 passes above C3; the atlas and axis are the two topmost vertebrae. The atlas, C1, is the topmost vertebra, along with the axis, its chief peculiarity is that it has no body because the body of the atlas has been fused with that of the axis. The axis, C2, forms the pivot.
The most distinctive characteristic of this bone is the strong odontoid process that rises perpendicularly from the upper surface of the body. The body is deeper in front than behind, prolonged downward anteriorly so as to overlap the upper and front part of the third vertebra; the vertebra prominens, or C7, has a distinctive long and prominent spinous process, palpable from the skin surface. Sometimes, the seventh cervical vertebra is associated with an abnormal extra rib, known as a cervical rib, which develops from the anterior root of the transverse process; these ribs are small, but may compress blood vessels or nerves in the brachial plexus, causing pain, numbness and weakness in the upper limb, a condition known as thoracic outlet syndrome. This rib occurs in a pair; the long spinous process of C7 is thick and nearly horizontal in dire
The Dayak or Dyak or Dayuh are the native people of Borneo. It is a loose term for over 200 riverine and hill-dwelling ethnic subgroups, located principally in the central and southern interior of Borneo, each with its own dialect, laws and culture, although common distinguishing traits are identifiable. Dayak languages are categorised as part of the Austronesian languages in Asia; the Dayak were animist in belief. The Dayak people of Borneo possess an indigenous account of their history in oral literature in writing in papan turai, in common cultural customary practices. Among prominent accounts of the origin of the Dayak people is the mythical oral epic of "Tetek Tahtum" by the Ngaju Dayak of Central Kalimantan; the independent state of Nansarunai, established by the Ma'anyan Dayaks prior to the 12th century, flourished in southern Kalimantan. The kingdom suffered two major attacks from the Majapahit forces that caused the decline and fall of the kingdom by the year 1389; these attacks contributed to the migration of the Ma'anyans to the South Borneo region.
The colonial accounts and reports of Dayak activity in Borneo detail cultivated economic and political relationships with other communities as well as an ample body of research and study concerning the history of Dayak migrations. In particular, the Iban or the Sea Dayak exploits in the South China Seas are documented, owing to their ferocity and aggressive culture of war against sea dwelling groups and emerging Western trade interests in the 18th and 19th centuries. In 1838, British adventurer James Brooke arrived to find the Sultan of Brunei fending off rebellion from warlike inland tribes. Sarawak was in chaos. Brooke put down the rebellion, was made Governor of Sarawak in 1841, with the title of Rajah. Brooke pacified the natives, including the Dayaks, he suppressed piracy. Brooke's most famous Iban enemy was Libau "Rentap". Brooke had many Dayaks in his forces at this battle, famously said "Only Dayaks can kill Dayaks. So he deployed Dayaks to kill Dayaks." Sharif Mashor, a Melanau from Mukah, was another enemy of Brooke.
During World War II, Japanese forces occupied Borneo and treated all of the indigenous peoples poorly - massacres of the Malay and Dayak peoples were common among the Dayaks of the Kapit Division. In response, the Dayaks formed a special force to assist the Allied forces. Eleven US airmen and a few dozen Australian special operatives trained a thousand Dayaks from the Kapit Division in guerrilla warfare; this army of tribesmen killed or captured some 1,500 Japanese soldiers and provided the Allies with vital intelligence about Japanese-held oil fields. Coastal populations in Borneo are Muslim in belief, however these groups are considered to be Malayised and Islamised native of Borneo and amalgated by the Malay people and sultanate system; these groups identified themselves as Melayu or Malay subgroup due to the closer cultural identity to the Malay people, compared from the Dayak umbrella classification, as the latter are traditionally associated for their pagan belief and tribal lifestyle.
The Dayak people classification are limited among the ethnic groups traditionally concentrated in southern and interior Sarawak and Kalimantan. Other native groups in dwelling in northern Sarawak, parts of Brunei and Sabah, chiefly the Bisayah, Orang Ulu, Melanau and dozens of smaller group were categorised under a separate classification apart from the Dayaks due to the difference in culture and history. Other groups in coastal areas of Sabah and northeastern Kalimantan; these groups though may be indigenous to coastal northeastern Borneo, they are nonetheless not Dayak, but instead are grouped under the separate umbrella term of Moro in the Philippines. The term Dayak was coined by Europeans referring to the non-Malay and non-Muslim inhabitants of central and southern Borneo. There are seven main ethnic divisions of Dayaks according to their respective native languages which are: 1. Ngaju 2. Apo Kayan 3. Iban or Hiban 4. Bidayuh or Klemantan 5. Murut 6. Punan 7. Ot DanumUnder the main classifications, there are dozens of ethnics and hundreds of sub-ethnics dwelling in the Borneo island.
There are over 50 ethnic Dayak groups speaking different languages. This cultural and linguistic diversity parallels the high biodiversity and related traditional knowledge of Borneo. Dayaks do not speak just one language if just those on the island of Borneo are considered, their indigenous languages belong in the general classification of Malayo-Polynesian languages and to diverse groups of Bornean and Sabahan languages, the Ibanic languages of the Malayic branch. Most Dayaks today are bilingual, in addition to their native language, they are well-versed in Malay or In
South Asia or Southern Asia, is a term used to represent the southern region of the Asian continent, which comprises the sub-Himalayan SAARC countries and, for some authorities, adjoining countries to the west and east. Topographically, it is dominated by the Indian Plate, which rises above sea level as Nepal and northern parts of India situated south of the Himalayas and the Hindu Kush. South Asia is bounded on the south by the Indian Ocean and on land by West Asia, Central Asia, East Asia, Southeast Asia; the current territories of Afghanistan, Bhutan, Nepal, India and Sri Lanka form South Asia. The South Asian Association for Regional Cooperation is an economic cooperation organisation in the region, established in 1985 and includes all eight nations comprising South Asia. South Asia covers about 5.2 million km2, 11.71% of the Asian continent or 3.5% of the world's land surface area. The population of South Asia is about 1.891 billion or about one fourth of the world's population, making it both the most populous and the most densely populated geographical region in the world.
Overall, it accounts for about 39.49% of Asia's population, over 24% of the world's population, is home to a vast array of people. In 2010, South Asia had the world's largest population of Hindus and Sikhs, it has the largest population of Muslims in the Asia-Pacific region, as well as over 35 million Christians and 25 million Buddhists. The total area of South Asia and its geographical extent is not clear cut as systemic and foreign policy orientations of its constituents are quite asymmetrical. Aside from the central region of South Asia part of the British Empire, there is a high degree of variation as to which other countries are included in South Asia. Modern definitions of South Asia are consistent in including Afghanistan, Pakistan, Sri Lanka, Nepal and Maldives as the constituent countries. Myanmar is included in Southeast Asia by others; some do not include Afghanistan, others question whether Afghanistan should be considered a part of South Asia or the Middle East. The current territories of Bangladesh and Pakistan, which were the core of the British Empire from 1857 to 1947, form the central region of South Asia, in addition to Afghanistan, a British protectorate until 1919, after the Afghans lost to the British in the Second Anglo-Afghan war.
The mountain countries of Nepal and Bhutan, the island countries of Sri Lanka and Maldives are included as well. Myanmar is added, by various deviating definitions based on substantially different reasons, the British Indian Ocean Territory and the Tibet Autonomous Region are included as well; the common concept of South Asia is inherited from the administrative boundaries of the British Raj, with several exceptions. The Aden Colony, British Somaliland and Singapore, though administered at various times under the Raj, have not been proposed as any part of South Asia. Additionally Burma was administered as part of the Raj until 1937, but is now considered a part of Southeast Asia and is a member state of ASEAN; the 562 princely states that were protected by but not directly ruled by the Raj became administrative parts of South Asia upon joining Union of India or Dominion of Pakistan. Geopolitically, it had formed the whole territory of Greater India,The South Asian Association for Regional Cooperation, a contiguous block of countries, started in 1985 with seven countries – Bangladesh, India, the Maldives, Nepal and Sri Lanka – and added Afghanistan as an eighth member in 2007.
China and Myanmar have applied for the status of full members of SAARC. This bloc of countries include two independent countries that were not part of the British Raj – Nepal, Bhutan. Afghanistan was a British protectorate from 1878 until 1919, after the Afghans lost to the British in the Second Anglo-Afghan war; the World Factbook, based on geo-politics and economy defines South Asia as comprising Afghanistan, Bhutan, British Indian Ocean Territory, Maldives, Nepal and Sri Lanka. The South Asia Free Trade Agreement incorporated Afghanistan in 2011, the World Bank grouping of countries in the region includes all eight members comprising South Asia and SAARC as well, the same goes for the United Nations Children's Fund; the United Nations Statistics Division's scheme of sub-regions include all eight members of the SAARC as part of Southern Asia, along with Iran only for statistical purposes. Population Information Network includes Afghanistan, Burma, Nepal and Sri Lanka as part of South Asia.
Maldives, in view of its characteristics, was admitted as a member Pacific POPIN subregional network only in principle. The Hirschman–Herfindahl index of the United Nations Economic and Social Commission for Asia and the Pacific for the region includes only the original seven signatories of SAARC; the British Indian Ocean Territory is connected to the region by a publication of Jane's for security considerations. The region may include the disputed territory of Aksai Chin, part of the British Indian princely state of Jammu and Kashmir, but is now administered as part of the Chinese autonomous region of Xinjiang; the inclusion of Myanmar in South Asia is without consensus, with many considering it a part of Southeast Asia and others including it within South Asia. Afghanistan was of importance to the British colonial empire after the Second Anglo-Afghan War over 1878–1880. Afghanistan remained a British protectorate until 1919, when a treaty with Vladimir Lenin included the granting of independe