Tropical rainforest
Tropical rainforests are rainforests that occur in areas of tropical rainforest climate in which there is no dry season – all months have an average precipitation of at least 60 mm – and may be referred to as lowland equatorial evergreen rainforest. True rainforests are found between 10 degrees north and south of the equator. Within the World Wildlife Fund's biome classification, tropical rainforests are a type of tropical moist broadleaf forest that includes the more extensive seasonal tropical forests. Tropical rainforests can be characterized in two words: wet. Mean monthly temperatures exceed 18 °C during all months of the year. Average annual rainfall is no less than 1,680 mm and can exceed 10 m although it lies between 1,750 mm and 3,000 mm; this high level of precipitation results in poor soils due to leaching of soluble nutrients in the ground. Tropical rainforests exhibit high levels of biodiversity. Around 40% to 75% of all biotic species are indigenous to the rainforests. Rainforests are home to half of all the living plant species on the planet.
Two-thirds of all flowering plants can be found in rainforests. A single hectare of rainforest may contain 42,000 different species of insect, up to 807 trees of 313 species and 1,500 species of higher plants. Tropical rainforests have been called the "world's largest pharmacy", because over one quarter of natural medicines have been discovered within them, it is that there may be many millions of species of plants and microorganisms still undiscovered in tropical rainforests. Tropical rainforests are among the most threatened ecosystems globally due to large-scale fragmentation as a result of human activity. Habitat fragmentation caused by geological processes such as volcanism and climate change occurred in the past, have been identified as important drivers of speciation. However, fast human driven habitat destruction is suspected to be one of the major causes of species extinction. Tropical rain forests have been subjected to heavy logging and agricultural clearance throughout the 20th century, the area covered by rainforests around the world is shrinking.
Tropical rainforests have existed on earth for hundreds of millions of years. Most tropical rainforests today are on fragments of the Mesozoic era supercontinent of Gondwana; the separation of the landmass resulted in a great loss of amphibian diversity while at the same time the drier climate spurred the diversification of reptiles. The division left tropical rainforests located in five major regions of the world: tropical America, Southeast Asia and New Guinea, with smaller outliers in Australia. However, the specifics of the origin of rainforests remain uncertain due to an incomplete fossil record. Several biomes may appear similar-to, or merge via ecotones with, tropical rainforest: Moist seasonal tropical forest Moist seasonal tropical forests receive high overall rainfall with a warm summer wet season and a cooler winter dry season; some trees in these forests drop some or all of their leaves during the winter dry season, thus they are sometimes called "tropical mixed forest". They are found in parts of South America, in Central America and around the Caribbean, in coastal West Africa, parts of the Indian subcontinent, across much of Indochina.
Montane rainforests These are found in cooler-climate mountainous areas, becoming known as cloud forests at higher elevations. Depending on latitude, the lower limit of montane rainforests on large mountains is between 1500 and 2500 m while the upper limit is from 2400 to 3300 m. Flooded rainforests Tropical freshwater swamp forests, or "flooded forests", are found in Amazon basin and elsewhere. Rainforests are divided into different strata, or layers, with vegetation organized into a vertical pattern from the top of the soil to the canopy; each layer is a unique biotic community containing different plants and animals adapted for life in that particular strata. Only the emergent layer is unique to tropical rainforests, while the others are found in temperate rainforests; the forest floor, the bottom-most layer, receives only 2% of the sunlight. Only plants adapted to low light can grow in this region. Away from riverbanks and clearings, where dense undergrowth is found, the forest floor is clear of vegetation because of the low sunlight penetration.
This more open quality permits the easy movement of larger animals such as: ungulates like the okapi, Sumatran rhinoceros, apes like the western lowland gorilla, as well as many species of reptiles and insects. The forest floor contains decaying plant and animal matter, which disappears because the warm, humid conditions promote rapid decay. Many forms of fungi growing here help decay the plant waste; the understory layer lies between the forest floor. The understory is home to a number of birds, small mammals, insects and predators. Examples include leopard, poison dart frogs, ring-tailed coati, boa constrictor, many species of Coleoptera; the vegetation at this layer consists of shade-tolerant shrubs, small trees, large woody vines which climb into the trees to capture sunlight. Only about 5% of sunlight breaches the canopy to arrive at the understory causing true understory plants to grow to 3 m; as an
Ditch
A ditch is a small to moderate depression created to channel water. A ditch can be used for drainage, to drain water from low-lying areas, alongside roadways or fields, or to channel water from a more distant source for plant irrigation. Ditches are seen around farmland in areas that have required drainage, such as The Fens in eastern England and much of the Netherlands. Roadside ditches may provide a hazard to motorists and cyclists, whose vehicles may crash into them and get damaged, flipped over or stuck in poor weather conditions, in rural areas. Ditch is known as for sneaking off like waking up and escaping from bed during bedtime at night, escaping from school or jail and playing Ding Dong Ditch. In Anglo-Saxon, the word dïc existed and was pronounced "deek" in northern England and "deetch" in the south; the origins of the word lie in digging a trench and forming the upcast soil into a bank alongside it. This practice has meant that the name dïc was given to either the excavation or the bank, evolved to both the words "dike"/"dyke" and "ditch".
Thus Offa's Dyke is a combined structure and Car Dyke is a trench, though it once had raised banks as well. In the midlands and north of England, a dike is what a ditch is in the south, a property boundary marker or small drainage channel. Where it carries a stream, it may be called a running dike as in Rippingale Running Dike, which leads water from the catchwater drain, Car Dyke, to the South Forty Foot Drain in Lincolnshire; the Weir Dike is a soak dike near Twenty and alongside the River Glen. Drainage ditches play major roles in agriculture throughout the world. Improper drainage systems accelerate water contamination, excessively desiccate soils during seasonal drought, become a financial burden to maintain. Industrial earth-moving equipment facilitates maintenance of straight drainage trenches, but entrenchment results in increasing environmental and profound economic costs over time. Sustainable channel design can result in ditches that are self-maintaining due to natural geomorphological equilibrium.
Slowed net siltation and erosion result in net reduction in sediment transport. Encouraging development of a natural stream sinuosity and a multi-terraced channel cross section appear to be key to maintain both peak ditch drainage capacity, minimum net pollution and nutrient transport. Flooding can be a major cause of recurring crop loss—particularly in heavy soils—and can disrupt urban economies as well. Subsurface drainage to ditches offers a way to remove excess water from agricultural fields, or vital urban spaces, without the erosion rates and pollution transport that results from direct surface runoff. However, excess drainage results in recurring drought induced crop yield losses and more severe urban heat or desiccation issues. Controlled subsurface drainage from sensitive areas to vegetated drainage ditches makes possible a better balance between water drainage and water retention needs; the initial investment allows a community to draw down local water tables when and where necessary without exacerbating drought problems at other times.
In Colorado, the term ditch is applied to open aqueducts that traverse hillsides as part of transbasin diversion projects. Examples include the Grand Ditch over La Poudre Pass, the Berthoud Pass Ditch, the Boreas Pass Ditch. Barbagallo, Tricia. "Black Beach: The Mucklands of Canastota, New York". Archived from the original on June 25, 2008. Retrieved 2008-06-04
Bengal tiger
The Bengal tiger is a Panthera tigris tigris population in the Indian subcontinent. It is listed as Endangered on the IUCN Red List since 2008, was estimated at comprising fewer than 2,500 individuals by 2011, it is threatened by poaching and fragmentation of habitat. None of the Tiger Conservation Landscapes within its range is considered large enough to support an effective population of more than 250 adult individuals. India's tiger population was estimated at 1,706–1,909 individuals in 2010. By 2014, the population had reputedly increased to an estimated 2,226 individuals. Around 440 tigers are estimated in 103 tigers in Bhutan; the tiger is estimated to be present in the Indian subcontinent since the Late Pleistocene, for about 12,000 to 16,500 years. The Bengal tiger ranks among the biggest wild cats alive today, it is considered to belong to the world's charismatic megafauna. It is the national animal of both Bangladesh, it is known as the Royal Bengal tiger. Felis tigris was the scientific name used by Carl Linnaeus in 1758 for the tiger.
It was subordinated to the genus Panthera by Reginald Innes Pocock in 1929. Bengal is the traditional type locality of the species and the nominate subspecies Panthera tigris tigris; the validity of several tiger subspecies in continental Asia was questioned in 1999. Morphologically, tigers from different regions vary little, gene flow between populations in those regions is considered to have been possible during the Pleistocene. Therefore, it was proposed to recognize only two subspecies as valid, namely P. t. tigris in mainland Asia, P. t. sondaica in the Greater Sunda Islands and in Sundaland. The extinct and living tiger populations in continental Asia have been subsumed to P. t. tigris since the revision of felid taxonomy in 2017. The Bengal tiger is defined by three distinct mitochondrial nucleotide sites and 12 unique microsatellite alleles; the pattern of genetic variation in the Bengal tiger corresponds to the premise that it arrived in India 12,000 years ago. This is consistent with the lack of tiger fossils from the Indian subcontinent prior to the late Pleistocene, the absence of tigers from Sri Lanka, separated from the subcontinent by rising sea levels in the early Holocene.
The Bengal tiger's coat is yellow to light orange, with stripes ranging from dark brown to black. The white tiger is a recessive mutant of the tiger, reported in the wild from time to time in Assam, Bengal and from the former State of Rewa. However, it is not to be mistaken as an occurrence of albinism. In fact, there is only one authenticated case of a true albino tiger, none of black tigers, with the possible exception of one dead specimen examined in Chittagong in 1846. Males have an average total length of 270 to 310 cm including the tail, while females measure 240 to 265 cm on average; the tail is 85 to 110 cm long, on average, tigers are 90 to 110 cm in height at the shoulders. The weight of males ranges from 180 to 258 kg; the smallest recorded weights for Bengal tigers are from the Bangladesh Sundarbans, where adult females are 75 to 80 kg. The tiger has exceptionally stout teeth, its canines are 7.5 to 10 cm long and thus the longest among all cats. The greatest length of its skull is 332 to 376 mm. Bengal tigers weigh up to 325 kg, reach a head and body length of 320 cm.
Several scientists indicated that adult male Bengal tigers from the Terai in Nepal and Bhutan, Assam and West Bengal in north India attain more than 227 kg of body weight. Seven adult males captured in Chitwan National Park in the early 1970s had an average weight of 235 kg ranging from 200 to 261 kg, that of the females was 140 kg ranging from 116 to 164 kg. Thus, the Bengal tiger rivals the Amur tiger in average weight. In addition, the record for the greatest length of a tiger skull was an "over the bone" length of 16.25 in. Verifiable Sundarbans tiger weights are not found in any scientific literature. Forest Department records list weight measurements. There are reports of head and body lengths, some of which are listed as over 366 cm. More researchers from the University of Minnesota and the Bangladesh Forest Department carried out a study for the US Fish and Wildlife Service and weighed three Sundarbans tigresses from Bangladesh. Two of them were captured and sedated for radio-collaring, the other one had been killed by local villagers.
The two collared tigresses were weighed using 150 kg scales, the tigress killed by villagers was weighed using a balance scale and weights. The three tigresses had a mean weight of 76.7 kg. One of the two older female's weight 75 kg weighed less than the mean because of her old age and poor condition at the time of capture; the teeth wear of the two radio-collared females indicated that they were between 12 and 14 years old. The tigress killed by the villagers was a young adult between 3 and 4 years old, she was a pre-territorial transient. Skulls and body weights of Sundarbans tigers were found to be distinct from tigers in other habitats, indicating that they may have adapted to the unique conditions of the mangrove habitat, their small sizes are due to a combination of
Meerkat
The meerkat or suricate is a small carnivoran belonging to the mongoose family. It is the only member of the genus Suricata. Meerkats live in all parts of the Kalahari Desert in Botswana, in much of the Namib Desert in Namibia and southwestern Angola, in South Africa. A group of meerkats is called a "mob", "gang" or "clan". A meerkat clan contains about 20 meerkats, but some super-families have 50 or more members. In captivity, meerkats have an average life span of 12–14 years, about half this in the wild. "Meerkat" is a loanword from Afrikaans. The name by misidentification. In Dutch, meerkat means a monkey of the genus Cercopithecus; the word meerkat is Dutch for "lake cat", but although the suricata is a feliform, it is not of the cat family. In early literature, suricates were referred as mierkat. In colloquial Afrikaans, mier means termite, kat means cat, it has been speculated that the name comes from their frequent association with termite mounds or the termites they eat. Three subspecies are recognized: The meerkat is a small diurnal herpestid weighing on average about 0.5 to 2.5 kilograms.
Its long slender body and limbs give it a body length of 35 to 50 centimetres and an added tail length of around 25 centimetres. The meerkat uses its tail to balance, as well as for signaling, its face tapers, coming to a point at the nose, brown. The eyes always have black patches around them, they have small black crescent-shaped ears. Like cats, meerkats have binocular vision. At the end of each of a meerkat's "fingers" is a claw used for digging burrows and digging for prey. Claws are used with muscular hindlegs to help climb trees. Meerkats have four toes on long slender limbs; the coat is peppered gray, tan, or brown with silver. They have short parallel stripes across their backs, extending from the base of the tail to the shoulders; the patterns of stripes are unique to each meerkat. The underside of the meerkat has no markings, but the belly has a patch, only sparsely covered with hair and shows the black skin underneath; the meerkat uses this area to absorb heat while standing on its rear legs early in the morning after cold desert nights.
Meerkats are insectivores, but eat other animals and fungi. Meerkats are immune to certain types of venom, including the strong venom of the scorpions of the Kalahari Desert. Baby meerkats do not start foraging for food until they are about 1 month old, do so by following an older member of the group who acts as the pup's tutor. Meerkats forage in a group with one "sentry" on guard watching for predators while the others search for food. Sentry duty is approximately an hour long; the meerkat standing guard makes. A meerkat has the ability to dig through a quantity of sand equal to its own weight in just seconds. Digging is done to create burrows, to get food and to create dust clouds to distract predators. Martial eagles, tawny eagles and jackals are the main predators of meerkats. Meerkats sometimes die of snakebite in confrontations with snakes. Meerkats become sexually mature at about two years of age and can have one to four pups in a litter, with three pups being the most common litter size.
Meerkats can reproduce any time of the year. The pups are allowed to leave the burrow at two to three weeks old. There is no precopulatory display. Gestation lasts 11 weeks and the young are born within the underground burrow and are altricial; the young's ears open at about 10 days of age, their eyes at 10–14 days. They are weaned around 49 to 63 days; the alpha pair reserves the right to mate and kills any young not its own, to ensure that its offspring have the best chance of survival. The dominant couple may evict, or kick out the mothers of the offending offspring. New meerkat groups are formed by evicted females joining a group of males. Females appear to be able to discriminate the odour of their kin from the odour of their non-kin. Kin recognition is a useful ability that facilitates cooperation among relatives and the avoidance of inbreeding; when mating does occur between meerkat relatives, it results in negative fitness consequences or inbreeding depression. Inbreeding depression was evident for a variety of traits: pup mass at emergence from the natal burrow, hind-foot length, growth until independence and juvenile survival.
These negative effects are due to the increased homozygosity that arises from inbreeding and the consequent expression of deleterious recessive mutations. The avoidance of inbreeding and the promotion of outcrossing allow the masking of deleterious recessive mutations. Meerkats are small burrowing animals, living in large underground networks with multiple entrances which they leave only during the day, except to avoid the heat of the afternoon, they are social creatures and they live in colonies together. Animals in the same group groom each other regularly; the alpha pair scent-mark subordinates of the group to express their authority. There may be up to 30 meerkats in a group. To look
Tapir
A tapir is a large, herbivorous mammal, similar in shape to a pig, with a short, prehensile nose trunk. Tapirs inhabit jungle and forest regions of South America, Central America, Southeast Asia; the five extant species of tapirs, all of the family Tapiridae and the genus Tapirus, are the Brazilian tapir, the Malayan tapir, the Baird's tapir, the kabomani tapir and the mountain tapir. The four species that have been evaluated are all classified on the IUCN Red List as Endangered or Vulnerable; the tapirs have a number of extinct relatives in the superfamily Tapiroidea. The closest extant relatives of the tapirs are the other odd-toed ungulates, which include horses, donkeys and rhinoceroses. Five extant species within one extant genus are recognised. Four are in Central and South America, while the fifth is in Asia.: Baird's tapir, Tapirus bairdii South American tapir, Tapirus terrestris Little black tapir, Tapirus kabomani Mountain tapir, Tapirus pinchaque Malayan tapir, Tapirus indicus Tapirus augustus † Tapirus californicus † Tapirus copei † Tapirus cristatellus † Tapirus greslebini † Tapirus johnsoni † Tapirus lundeliusi † Tapirus merriami † Tapirus mesopotamicus † Tapirus oliverasi † Tapirus polkensis † Tapirus rioplatensis † Tapirus rondoniensis † Tapirus tarijensis † Tapirus veroensis † Tapirus webbi † Size varies between types, but most tapirs are about 2 m long, stand about 1 m high at the shoulder, weigh between 150 and 300 kg.
Their coats are short and range in color from reddish brown, to grey, to nearly black, with the notable exceptions of the Malayan tapir, which has a white, saddle-shaped marking on its back, the mountain tapir, which has longer, woolly fur. All tapirs have oval, white-tipped ears, protruding rumps with stubby tails, splayed, hooved toes, with four toes on the front feet and three on the hind feet, which help them to walk on muddy and soft ground. Baby tapirs of all types have striped-and-spotted coats for camouflage. Females have a single pair of mammary glands, males have long penises relative to their body size; the proboscis of the tapir is a flexible organ, able to move in all directions, allowing the animals to grab foliage that would otherwise be out of reach. Tapirs exhibit the flehmen response, a posture in which they raise their snouts and show their teeth to detect scents; this response is exhibited by bulls sniffing for signs of other males or females in oestrus in the area. The length of the proboscis varies among species.
The evolution of tapir probosces, made up entirely of soft tissues rather than bony internal structures, gives the Tapiridae skull a unique form in comparison to other perissodactyls, with a larger sagittal crest, orbits positioned more rostrally, a posteriorly telescoped cranium, a more elongated and retracted nasoincisive incisure. Tapirs have brachyodont, or that lack cementum, their dental formula is: Totaling 42 to 44 teeth, this dentition is closer to that of equids, which may differ by one less canine, than their other perissodactyl relatives, rhinoceroses. Their incisors are chisel-shaped, with the third large, conical upper incisor separated by a short gap from the smaller canine. A much longer gap is found between the premolars, the first of which may be absent. Tapirs are lophodonts, their cheek teeth have distinct lophs between protocones, paracones and hypocones. Tapirs have brown eyes with a bluish cast to them, identified as corneal cloudiness, a condition most found in Malayan tapirs.
The exact etiology is unknown, but the cloudiness may be caused by excessive exposure to light or by trauma. However, the tapir's sensitive ears and strong sense of smell help to compensate for deficiencies in vision. Tapirs are hindgut fermenters that ferment digested food in a large cecum. Young tapirs reach sexual maturity between three and five years of age, with females maturing earlier than males. Under good conditions, a healthy female tapir can reproduce every two years; the natural lifespan of a tapir is about 25 to 30 years, both in zoos. Apart from mothers and their young offspring, tapirs lead exclusively solitary lives. Although they live in dryland forests, tapirs with access to rivers spend a good deal of time in and underwater, feeding on soft vegetation, taking refuge from predators, cooling off during hot periods. Tapirs near a water source will swim, sink to the bottom, walk along the riverbed to feed, have been known to submerge themselves under water to allow small fish to pick parasites off their bulky bodies.
Along with freshwater lounging, tapirs wallow in mud pits, which help to keep them cool and free of insects. In the wild, the tapir's diet consists of fruit and leaves young, tender growth. Tapirs will spend many of their waking hours foraging along well-worn trails, snout
Komodo dragon
The Komodo dragon known as the Komodo monitor, is a species of lizard found in the Indonesian islands of Komodo, Rinca and Gili Motang. A member of the monitor lizard family Varanidae, it is the largest living species of lizard, growing to a maximum length of 3 metres in rare cases and weighing up to 70 kilograms, their unusually large size has been attributed to island gigantism, since no other carnivorous animals fill the niche on the islands where they live. However, recent research suggests the large size of Komodo dragons may be better understood as representative of a relict population of large varanid lizards that once lived across Indonesia and Australia, most of which, along with other megafauna, died out after the Pleistocene. Fossils similar to V. komodoensis have been found in Australia dating to greater than 3.8 million years ago, its body size remained stable on Flores, one of the handful of Indonesian islands where it is found, over the last 900,000 years, "a time marked by major faunal turnovers, extinction of the island's megafauna, the arrival of early hominids by 880 ka."As a result of their size, these lizards dominate the ecosystems in which they live.
Komodo dragons hunt and ambush prey including invertebrates and mammals. It has been claimed; the biological significance of these proteins is disputed, but the glands have been shown to secrete an anticoagulant. Komodo dragons' group behaviour in hunting is exceptional in the reptile world; the diet of big Komodo dragons consists of Timor deer, though they eat considerable amounts of carrion. Komodo dragons occasionally attack humans. Mating begins between May and August, the eggs are laid in September. About 20 eggs are deposited in a self-dug nesting hole; the eggs are incubated for seven to eight months, hatching in April, when insects are most plentiful. Young Komodo dragons are vulnerable and therefore dwell in trees, safe from predators and cannibalistic adults, they take 8 to 9 years to mature, are estimated to live up to 30 years. Komodo dragons were first recorded by Western scientists in 1910, their large size and fearsome reputation make them popular zoo exhibits. In the wild, their range has contracted due to human activities, they are listed as vulnerable by the IUCN.
They are protected under Indonesian law, a national park, Komodo National Park, was founded to aid protection efforts. Komodo dragons were first documented by Europeans in 1910, when rumors of a "land crocodile" reached Lieutenant van Steyn van Hensbroek of the Dutch colonial administration. Widespread notoriety came after 1912, when Peter Ouwens, the director of the Zoological Museum at Bogor, published a paper on the topic after receiving a photo and a skin from the lieutenant, as well as two other specimens from a collector; the first two live Komodo dragons to arrive in Europe were exhibited in the Reptile House at London Zoo when it opened in 1927. Joan Beauchamp Procter made some of the earliest observations of these animals in captivity and she demonstrated the behaviour of one of these animals at a Scientific Meeting of the Zoological Society of London in 1928; the Komodo dragon was the driving factor for an expedition to Komodo Island by W. Douglas Burden in 1926. After returning with 12 preserved specimens and 2 live ones, this expedition provided the inspiration for the 1933 movie King Kong.
It was Burden who coined the common name "Komodo dragon." Three of his specimens were stuffed and are still on display in the American Museum of Natural History. The Dutch, realizing the limited number of individuals in the wild, outlawed sport hunting and limited the number of individuals taken for scientific study. Collecting expeditions ground to a halt with the occurrence of World War II, not resuming until the 1950s and 1960s, when studies examined the Komodo dragon's feeding behavior and body temperature. At around this time, an expedition was planned in which a long-term study of the Komodo dragon would be undertaken; this task was given to the Auffenberg family, who stayed on Komodo Island for 11 months in 1969. During their stay, Walter Auffenberg and his assistant Putra Sastrawan captured and tagged more than 50 Komodo dragons; the research from the Auffenberg expedition would prove to be enormously influential in raising Komodo dragons in captivity. Research after that of the Auffenberg family has shed more light on the nature of the Komodo dragon, with biologists such as Claudio Ciofi continuing to study the creatures.
The Komodo dragon is known as the Komodo monitor or the Komodo Island monitor in scientific literature, although this is not common. To the natives of Komodo Island, it is referred to buaya darat, or biawak raksasa; the evolutionary development of the Komodo dragon started with the genus Varanus, which originated in Asia about 40 million years ago and migrated to Australia, where it evolved into giant forms, helped by the absence of competing placental carnivorans. Around 15 million years ago, a collision between Australia and Southeast Asia allowed these larger varanids to move back into what is now the Indonesian archipelago, extending their range as far east as the island of Timor; the Komodo dragon was believed to have differentiated from its Australian ancestors 4 million years ago. However, recent fossil evidence from Queensland suggests the Komodo dragon evolved in Australia before spreading to Indonesia. Dramatic lowering of sea level during the last
Personal digital assistant
A personal digital assistant known as a handheld PC, is a variety mobile device which functions as a personal information manager. PDAs were discontinued in the early 2010s after the widespread adoption of capable smartphones, in particular those based on iOS and Android. Nearly all PDAs have the ability to connect to the Internet. A PDA has an electronic visual display. Most models have audio capabilities, allowing usage as a portable media player, enabling most of them to be used as telephones. Most PDAs can access intranets or extranets via Wi-Fi or Wireless Wide Area Networks. Sometimes, instead of buttons, PDAs employ touchscreen technology; the technology industry has recycled the term personal digital assistance. The term is more used for software that identifies a user's voice to reply to the queries; the first PDA, the Organizer, was released in 1984 by Psion, followed by Psion's Series 3, in 1991. The latter began to resemble the more familiar PDA style, including a full keyboard; the term PDA was first used on January 7, 1992 by Apple Computer CEO John Sculley at the Consumer Electronics Show in Las Vegas, referring to the Apple Newton.
In 1994, IBM introduced the first PDA with full telephone functionality, the IBM Simon, which can be considered the first smartphone. In 1996, Nokia introduced a PDA with telephone functionality, the 9000 Communicator, which became the world's best-selling PDA. Another early entrant in this market was Palm, with a line of PDA products which began in March 1996. A typical PDA has a touchscreen for navigation, a memory card slot for data storage, IrDA, Bluetooth and/or Wi-Fi. However, some PDAs may not have a touchscreen, using softkeys, a directional pad, a numeric keypad or a thumb keyboard for input. To have the functions expected of a PDA, a device's software includes an appointment calendar, a to-do list, an address book for contacts, a calculator, some sort of memo program. PDAs with wireless data connections typically include an email client and a Web browser, may or may not include telephony functionality. Many of the original PDAs, such as the Apple Newton and Palm Pilot, featured a touchscreen for user interaction, having only a few buttons—usually reserved for shortcuts to often-used programs.
Some touchscreen PDAs, including Windows Mobile devices, had a detachable stylus to facilitate making selections. The user interacts with the device by tapping the screen to select buttons or issue commands, or by dragging a finger on the screen to make selections or scroll. Typical methods of entering text on touchscreen PDAs include: A virtual keyboard, where a keyboard is shown on the touchscreen. Text is entered by tapping the on-screen keyboard with stylus. An external keyboard connected via Infrared port, or Bluetooth; some users may choose a chorded keyboard for one-handed use. Handwriting recognition, where letters or words are written on the touchscreen with a stylus, the PDA converts the input to text. Recognition and computation of handwritten horizontal and vertical formulas, such as "1 + 2 =", may be a feature. Stroke recognition allows the user to make a predefined set of strokes on the touchscreen, sometimes in a special input area, representing the various characters to be input.
The strokes are simplified character shapes, making them easier for the device to recognize. One known stroke recognition system is Palm's Graffiti. Despite research and development projects, end-users experience mixed results with handwriting recognition systems; some find it frustrating and inaccurate, while others are satisfied with the quality of the recognition. Touchscreen PDAs intended for business use, such as the BlackBerry and Palm Treo also offer full keyboards and scroll wheels or thumbwheels to facilitate data entry and navigation. Many touchscreen PDAs support some form of external keyboard as well. Specialized folding keyboards, which offer a full-sized keyboard but collapse into a compact size for transport, are available for many models. External keyboards may attach to the PDA directly, using a cable, or may use wireless technology such as infrared or Bluetooth to connect to the PDA. Newer PDAs, such as the HTC HD2, Apple iPhone, Apple iPod Touch, Palm Pre, Palm Pre Plus, Palm Pixi, Palm Pixi Plus, Google Android include more advanced forms of touchscreen that can register multiple touches simultaneously.
These "multi-touch" displays allow for more sophisticated interfaces using various gestures entered with one or more fingers. Although many early PDAs did not have memory card slots, now most have either some form of Secure Digital slot, a CompactFlash slot or a combination of the two. Although designed for memory, Secure Digital Input/Output and CompactFlash cards are available that provide accessories like Wi-Fi or digital cameras, if the device can support them; some PDAs have a USB port for USB flash drives. Some PDAs use microSD cards, which are electronically compatible with SD cards, but have a much smaller physical size. While early PDAs connected to a user's personal computer via serial ports or another proprietary connection, many today connect via a USB cable. Older PDAs were unable to connect to each other via USB, as their implementations of USB didn't support acting as the "host"; some early PDAs were able to connect to the Internet indirectly by means of an external modem connected via the PDA's serial port or "sync" connector, or directly by using an expansion card that provided an Ethernet port.
Most modern PDAs have a popular wireless protocol for mobile devices. Bluetooth can be used to connect keyboards, headsets, GPS receiver
