Emballonuridae is a family of microbats, many of which are referred to as sac-winged or sheath-tailed bats. They are distributed in tropical and subtropical regions across the world; the emballonurids include some of the smallest of all bats, range from 3.5 to 10 cm in body length. They are brown or grey, although the species of genus Diclidurus are white; the faces are said to be handsome, the heads being comparable to those of domestic dogs, their wings are long and narrow. As with other microchiropteran families, they use ultrasonic echolocation to sense the surrounding environment and their prey; the wing surface extends between the legs, a membrane known as a uropatagium, the structure of these is a characteristic in many of the genera. They have tails which are enclosed, a short part of which projects through the uropatagium to form a sheath; the usual arrangement of the uropatagium is as to be fixed to the tail, but the sheathtail feature is joined by an elastic component which allows greater flexibility.
As a common name indicates, many species possess sac-shaped glands in their wings, which are open to the air and may release pheromones to attract mates. Other species have throat glands, they have the dental formula These bats prefer to roost in better-illuminated areas than other species of bats. Their dwellings can be found in hollow trees and entryways to caves or other structures; some species, such as the genus Taphozous, live in large colonies. Species living away from the tropics may enter periods of torpor or extended hibernation during colder months. Emballonurids feed on insects and on fruit. Most of these bats catch their meals while flying; the common name for some groups,'sheath-tailed bats', is sometimes noted as sheathtails. Family Emballonuridae Genus Balantiopteryx Ecuadorian sac-winged bat, Balantiopteryx infusca Thomas's sac-winged bat, Balantiopteryx io Gray sac-winged bat, Balantiopteryx plicata Genus Centronycteris Thomas's shaggy bat, Centronycteris centralis Shaggy bat, Centronycteris maximiliani Genus Coleura African sheath-tailed bat, Coleura afra Madagascar sheath-tailed bat, Coleura kibomalandy Seychelles sheath-tailed bat, Coleura seychellensis Genus Cormura Chestnut sac-winged bat, Cormura brevirostris Genus Cyttarops Short-eared bat, Cyttarops alecto Genus Diclidurus - ghost bats Northern ghost bat, Diclidurus albus Greater ghost bat, Diclidurus ingens Isabelle's ghost bat, Diclidurus isabella Lesser ghost bat, Diclidurus scutatus Genus Emballonura Small Asian sheath-tailed bat, Emballonura alecto Beccari's sheath-tailed bat, Emballonura beccarii Large-eared sheath-tailed bat, Emballonura dianae Greater sheath-tailed bat, Emballonura furax Lesser sheath-tailed bat, Emballonura monticola Raffray's sheath-tailed bat, Emballonura raffrayana Pacific sheath-tailed bat, Emballonura semicaudata Seri's Sheathtail-bat, Emballonura serii Genus Mosia Dark sheath-tailed bat, Mosia nigrescens Genus Paremballonura Western sheath-tailed bat, Paremballonura tiavato Peters's sheath-tailed bat, Paremballonura atrata Genus Peropteryx Greater dog-like bat, Peropteryx kappleri White-winged dog-like bat, Peropteryx leucoptera Lesser dog-like bat, Peropteryx macrotis Pale-winged dog-like bat, Peropteryx pallidoptera Trinidad dog-like bat, Peropteryx trinitatis Genus Rhynchonycteris Proboscis bat, Rhynchonycteris naso Genus Saccolaimus Yellow-bellied pouched bat, Saccolaimus flaviventris Troughton's pouched bat, Saccolaimus mixtus Pel's pouched bat, Saccolaimus peli Naked-rumped pouched bat, Saccolaimus saccolaimus Genus Saccopteryx Antioquian sac-winged bat, Saccopteryx antioquensis Greater sac-winged bat, Saccopteryx bilineata Frosted sac-winged bat, Saccopteryx canescens Amazonian sac-winged bat, Saccopteryx gymnura Lesser sac-winged bat, Saccopteryx leptura Genus Taphozous Indonesian tomb bat Coastal sheath-tailed bat Common sheath-tailed bat Hamilton's tomb bat Hildegarde's tomb bat Hill's sheath-tailed bat Arnhem sheath-tailed bat Long-winged tomb bat Mauritian tomb bat Black-bearded tomb bat Naked-rumped tomb bat Egyptian tomb bat Theobald's tomb bat Troughton's sheath-tailed bat
Fish are gill-bearing aquatic craniate animals that lack limbs with digits. They form a sister group to the tunicates. Included in this definition are the living hagfish and cartilaginous and bony fish as well as various extinct related groups. Tetrapods emerged within lobe-finned fishes, so cladistically they are fish as well. However, traditionally fish are rendered paraphyletic by excluding the tetrapods; because in this manner the term "fish" is defined negatively as a paraphyletic group, it is not considered a formal taxonomic grouping in systematic biology, unless it is used in the cladistic sense, including tetrapods. The traditional term pisces is considered a typological, but not a phylogenetic classification; the earliest organisms that can be classified as fish were soft-bodied chordates that first appeared during the Cambrian period. Although they lacked a true spine, they possessed notochords which allowed them to be more agile than their invertebrate counterparts. Fish would continue to evolve through the Paleozoic era.
Many fish of the Paleozoic developed external armor. The first fish with jaws appeared in the Silurian period, after which many became formidable marine predators rather than just the prey of arthropods. Most fish are ectothermic, allowing their body temperatures to vary as ambient temperatures change, though some of the large active swimmers like white shark and tuna can hold a higher core temperature. Fish can communicate in their underwater environments through the use of acoustic communication. Acoustic communication in fish involves the transmission of acoustic signals from one individual of a species to another; the production of sounds as a means of communication among fish is most used in the context of feeding, aggression or courtship behaviour. The sounds emitted by fish can vary depending on the stimulus involved, they can produce either stridulatory sounds by moving components of the skeletal system, or can produce non-stridulatory sounds by manipulating specialized organs such as the swimbladder.
Fish are abundant in most bodies of water. They can be found in nearly all aquatic environments, from high mountain streams to the abyssal and hadal depths of the deepest oceans, although no species has yet been documented in the deepest 25% of the ocean. With 33,600 described species, fish exhibit greater species diversity than any other group of vertebrates. Fish are an important resource for humans worldwide as food. Commercial and subsistence fishers hunt fish in wild fisheries or farm them in ponds or in cages in the ocean, they are caught by recreational fishers, kept as pets, raised by fishkeepers, exhibited in public aquaria. Fish have had a role in culture through the ages, serving as deities, religious symbols, as the subjects of art and movies. Fish do not represent a monophyletic group, therefore the "evolution of fish" is not studied as a single event. Early fish from the fossil record are represented by a group of small, armored fish known as ostracoderms. Jawless fish lineages are extinct.
An extant clade, the lampreys may approximate ancient pre-jawed fish. The first jaws are found in Placodermi fossils; the diversity of jawed vertebrates may indicate the evolutionary advantage of a jawed mouth. It is unclear if the advantage of a hinged jaw is greater biting force, improved respiration, or a combination of factors. Fish may have evolved from a creature similar to a coral-like sea squirt, whose larvae resemble primitive fish in important ways; the first ancestors of fish may have kept the larval form into adulthood, although the reverse is the case. Fish are a paraphyletic group: that is, any clade containing all fish contains the tetrapods, which are not fish. For this reason, groups such as the "Class Pisces" seen in older reference works are no longer used in formal classifications. Traditional classification divides fish into three extant classes, with extinct forms sometimes classified within the tree, sometimes as their own classes: Class Agnatha Subclass Cyclostomata Subclass Ostracodermi † Class Chondrichthyes Subclass Elasmobranchii Subclass Holocephali Class Placodermi † Class Acanthodii † Class Osteichthyes Subclass Actinopterygii Subclass Sarcopterygii The above scheme is the one most encountered in non-specialist and general works.
Many of the above groups are paraphyletic, in that they have given rise to successive groups: Agnathans are ancestral to Chondrichthyes, who again have given rise to Acanthodiians, the ancestors of Osteichthyes. With the arrival of phylogenetic nomenclature, the fishes has been split up into a more detailed scheme, with the following major groups: Class Myxini Class Pteraspidomorphi † Class Thelodonti † Class Anaspida † Class Petromyzontida or Hyperoartia Petromyzontidae Class Conodonta † Class Cephalaspidomorphi † Galeaspida † Pituriaspida † Osteostraci † Infraphylum Gnathostomata Class Placodermi † Class Chondrichthyes Class Acanthodii † Superclass Osteichthy
Humans are the only extant members of the subtribe Hominina. Together with chimpanzees and orangutans, they are part of the family Hominidae. A terrestrial animal, humans are characterized by their erect bipedal locomotion. Early hominins—particularly the australopithecines, whose brains and anatomy are in many ways more similar to ancestral non-human apes—are less referred to as "human" than hominins of the genus Homo. Several of these hominins used fire, occupied much of Eurasia, gave rise to anatomically modern Homo sapiens in Africa about 315,000 years ago. Humans began to exhibit evidence of behavioral modernity around 50,000 years ago, in several waves of migration, they ventured out of Africa and populated most of the world; the spread of the large and increasing population of humans has profoundly affected much of the biosphere and millions of species worldwide. Advantages that explain this evolutionary success include a larger brain with a well-developed neocortex, prefrontal cortex and temporal lobes, which enable advanced abstract reasoning, problem solving and culture through social learning.
Humans use tools better than any other animal. Humans uniquely use such systems of symbolic communication as language and art to express themselves and exchange ideas, organize themselves into purposeful groups. Humans create complex social structures composed of many cooperating and competing groups, from families and kinship networks to political states. Social interactions between humans have established an wide variety of values, social norms, rituals, which together undergird human society. Curiosity and the human desire to understand and influence the environment and to explain and manipulate phenomena have motivated humanity's development of science, mythology, religion and numerous other fields of knowledge. Though most of human existence has been sustained by hunting and gathering in band societies many human societies transitioned to sedentary agriculture some 10,000 years ago, domesticating plants and animals, thus enabling the growth of civilization; these human societies subsequently expanded, establishing various forms of government and culture around the world, unifying people within regions to form states and empires.
The rapid advancement of scientific and medical understanding in the 19th and 20th centuries permitted the development of fuel-driven technologies and increased lifespans, causing the human population to rise exponentially. The global human population was estimated to be near 7.7 billion in 2015. In common usage, the word "human" refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of "hominid" and "hominin" have changed during the recent decades with advances in the discovery and study of the fossil ancestors of modern humans; the clear boundary between humans and apes has blurred, resulting in now acknowledging the hominids as encompassing multiple species, Homo and close relatives since the split from chimpanzees as the only hominins. There is a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species; the English adjective human is a Middle English loanword from Old French humain from Latin hūmānus, the adjective form of homō "man."
The word's use as a noun dates to the 16th century. The native English term man can refer to the species as well as to human males, or individuals of either sex; the species binomial "Homo sapiens" was coined by Carl Linnaeus in his 18th-century work Systema Naturae. The generic name "Homo" is a learned 18th-century derivation from Latin homō "man," "earthly being"; the species-name "sapiens" means "wise" or "sapient". Note that the Latin word homo refers to humans of either gender, that "sapiens" is the singular form; the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. Modern humans, defined as the species Homo sapiens or to the single extant subspecies Homo sapiens sapiens, proceeded to colonize all the continents and larger islands, arriving in Eurasia 125,000–60,000 years ago, Australia around 40,000 years ago, the Americas around 15,000 years ago, remote islands such as Hawaii, Easter Island and New Zealand between the years 300 and 1280.
The closest living relatives of humans are gorillas. With the sequencing of the human and chimpanzee genomes, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. By using the technique called a molecular clock which estimates the time required for the number of divergent mutations to accumulate between two lineages, the approximate date for the split between lineages can be calculated; the gibbons and orangutans were the first groups to split from the line leading to the h
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
An insectivore is a carnivorous plant or animal that eats insects. An alternative term is entomophage, which refers to the human practice of eating insects; the first insectivorous vertebrates were amphibians. When they evolved 400 million years ago, the first amphibians were piscivores, with numerous sharp conical teeth, much like a modern crocodile; the same tooth arrangement is however suited for eating animals with exoskeletons, thus the ability to eat insects is an extension of piscivory. At one time, insectivorous mammals were scientifically classified in an order called Insectivora; this order is now abandoned, as not all insectivorous mammals are related. Most of the Insectivora taxa have been reclassified. Although individually small, insects exist in enormous numbers - they number over a million described species and some of those species occur in enormous numbers. Accordingly, insects make up a large part of the animal biomass in all non-marine, non-polar environments, it has been estimated that the global insect biomass is in the region of 1012 kg with an estimated population of 1018 organisms.
Many creatures depend on insects as their primary diet, many that do not use insects as a protein supplement when they are breeding. Examples of insectivores include different kinds of species of carp, frogs, nightingales, echidnas, anteaters, aardvarks, aardwolfs and spiders. Large mammals are recorded as eating insects. Insects can be insectivores. Insectivory features to various degrees amongst primates, such as marmosets, tarsiers and aye-aye. There is some suggestion that the earliest primates were arboreal insectivores. Insectivorous plants are plants that derive some of their nutrients from trapping and consuming animals or protozoan; the benefit they derive from their catch varies considerably. As a rule, such animal food, however valuable it might be as a source of certain critically important minerals, is not the plants' major source of energy, which they derive from photosynthesis. Insectivorous plants might consume insects and other animal material trapped adventitiously, though most species to which such food represents an important part of their intake are often spectacularly, adapted to attract and secure adequate supplies.
Their prey animals but not comprise insects and other arthropods. Plants adapted to reliance on animal food use a variety of mechanisms to secure their prey, such as pitfalls, sticky surfaces, hair-trigger snaps, bladder-traps, entangling furriness, lobster-pot trap mechanisms. Known as carnivorous plants, they appear adapted to grow in places where the soil is thin or poor in nutrients nitrogen, such as acidic bogs and rock outcroppings. Insectivorous plants include the Venus flytrap, several types of pitcher plants, sundews, the waterwheel plant and many members of the Bromeliaceae; the list is far from complete, some plants, such as Roridula species, exploit the prey organisms in a mutualistic relationship with other creatures, such as resident organisms that contribute to the digestion of prey. In particular animal prey organisms supply carnivorous plants with nitrogen, but they are important sources of various other soluble minerals, such as potassium and trace elements that are in short supply in environments where the plants flourish.
This gives them a decisive advantage over other plants, whereas in nutrient-rich soils they tend to be out-competed by plants adapted to aggressive growth where nutrient supplies are not the major constraints. Technically these plants are not insectivorous, as they consume any animal that they can secure and consume. Most of those that do have such a restrictive diet, such as certain parasitoids and hunting wasps, are specialised to exploit particular species, not insects in general. Indeed, much as large mantids and spiders will do, the larger varieties of pitcher plant have been known to consume vertebrates such as small rodents and lizards. Charles Darwin wrote the first well-known treatise on carnivorous plants in 1875; the dictionary definition of insectivore at Wiktionary Entomophagy Insectivora List of feeding behaviours Consumer-resource systems
The spectral bat called the great false vampire bat or Linnaeus's false vampire bat, is a large, carnivorous leaf-nosed bat found in Mexico, Central America, South America. It is the only member of the genus Vampyrum, it is the largest bat species in the New World, as well as the largest carnivorous bat: its wingspan is 0.7–1.0 m. It has teeth, with which it delivers a powerful bite to kill its prey. Birds are frequent prey items, though it may consume rodents and other bats. Unlike the majority of bat species, it is monogamous. Colonies consist of their offspring; the adult male will bring food back to the roost to their offspring. Colonies roost in tree hollows, though individuals may roost in caves. Due to habitat destruction and its low population density, it is listed as a near-threatened species by the International Union for Conservation of Nature; the spectral bat was described in 1758 by Swedish zoologist Carl Linnaeus. The holotype was collected in South America by Daniel Rolander. Linnaeus assigned it to the genus Vespertilio.
Its species name "spectrum" is from Latin meaning "apparition" or "specter." The genus Vampyrum was not described until 1815 by Constantine Samuel Rafinesque. The genus and species names were not used in their current combination until biologist George Gilbert Goodwin did so in 1942. "Vampyrum" is a New Latin derivative of vampire, thus named because it was once erroneously believed that the species was sanguivorous and consumed blood. Based on mitochondrial DNA and the RAG2 gene, the spectral bat is most related to the monotypic genus Chrotopterus. Vampyrum and Chroptopterus diverged from other leaf-nosed bat species 20.75 million years ago, with the two genera diverging from each other 14.35 million years ago. The spectral and big-eared woolly bats evolved from an insectivorous ancestor; the spectral bat is included within the subfamily Phyllostominae, which includes species of diverse feeding strategies, including carnivory and mixed insectivory/frugivory. The spectral and big-eared woolly bats are the two extant members of the tribe Vampyrini.
Vampyrini additionally includes the extinct genus Notonycteris. Based on dental characteristics and Morgan additionally included the fringe-lipped bat and sometimes the round-eared bats in Vampyrini; the spectral bat is the largest bat species native to the New World and the largest carnivorous bat in the world. The wingspan ranges from 0.7–1.0 m. Its forearm length is 101–110 mm, its body length is 135–147 mm and its mass is 134–189 g. Its wings, though large in an absolute sense, are short relative to its body size; the wings are wide, creating a large surface area. Its wingtips are rounded and squarish; the thumbs are long, at 21.4–22.2 mm. Each of its thumbs has a large, recurved claw, grooved, similar to those of cats, its back fur is reddish-brown and soft, while its belly fur is shorter and paler. The forearm is furred on the half closer to the body, but naked on the half closer to the wrist and fingers, its molars are narrow with W-shaped crests. While six of its molars have three cusps, as in many mammal species, the last upper molars are reduced to two cusps.
The talonids of the molars are small relative to their trigonids. The upper canine teeth are well-developed, its dental formula is 18.104.22.168.1.3.3 for a total of 34 teeth. Its skull is elongated with a pronounced sagittal crest. Overall, its skull resembles a miniature bear skull, its nose-leaf is large, at 17 mm in length. There is no discernible tail, its legs are long, the feet are composed of slender bones. The ears are large and rounded, at 39–42 mm long; the brain is large relative to the body. The cerebral hemispheres of the brain are extensively convoluted; the brain has well-developed olfactory bulbs and its cerebellum is the most ornamented and complex of any member of its subfamily. McDaniel described its corpus callosum and white matter as "exceptionally thick." The spectral bat is carnivorous, consuming birds and other species of bat. Additionally, it consumes some insects such as beetles, it preys on other bats opportunistically, it is known to eat bats out of researchers' mist nets. Prey species include the highland yellow-shouldered bat, Geoffroy's tailless bat, Pallas's long-tongued bat, short-tailed fruit bats, the common vampire bat, fruit-eating bats It was once thought to supplement its diet with fruit, but a captive pair refused to eat any fruit over a 5-year period.
Its diet can be studied passively because it carries prey items back to its roost to consume, discarding unwanted parts such as bird feathers, bat wings, rodent tails. Over the course of a year, 18 bird species were identified from feathers left under a roost in Costa Rica: based on the assemblage, it prefers non-perching bird species that weigh 20–150 g. However, a study in Brazil determined that perching bird species were a majority of prey items. Doves and cuckoos are consumed—they represented over half the prey items documented in the Costa Rican study; some prey species such as cuckoos and motmots are known to have a strong odor, leadi
Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" sound in its physical properties, except that humans cannot hear it; this limit varies from person to person and is 20 kilohertz in healthy young adults. Ultrasound devices operate with frequencies from 20 kHz up to several gigahertz. Ultrasound is used in many different fields. Ultrasonic devices are used to detect objects and measure distances. Ultrasound imaging or sonography is used in medicine. In the nondestructive testing of products and structures, ultrasound is used to detect invisible flaws. Industrially, ultrasound is used for cleaning and accelerating chemical processes. Animals such as bats and porpoises use ultrasound for locating prey and obstacles. Scientists are studying ultrasound using graphene diaphragms as a method of communication. Acoustics, the science of sound, starts as far back as Pythagoras in the 6th century BC, who wrote on the mathematical properties of stringed instruments.
Echolocation in bats was discovered by Lazzaro Spallanzani in 1794, when he demonstrated that bats hunted and navigated by inaudible sound, not vision. Francis Galton in 1893 invented the Galton whistle, an adjustable whistle that produced ultrasound, which he used to measure the hearing range of humans and other animals, demonstrating that many animals could hear sounds above the hearing range of humans; the first technological application of ultrasound was an attempt to detect submarines by Paul Langevin in 1917. The piezoelectric effect, discovered by Jacques and Pierre Curie in 1880, was useful in transducers to generate and detect ultrasonic waves in air and water. Ultrasound is defined by the American National Standards Institute as "sound at frequencies greater than 20 kHz". In air at atmospheric pressure, ultrasonic waves have wavelengths of 1.9 cm or less. The upper frequency limit in humans is due to limitations of the middle ear. Auditory sensation can occur if high‐intensity ultrasound is fed directly into the human skull and reaches the cochlea through bone conduction, without passing through the middle ear.
Children can hear some high-pitched sounds that older adults cannot hear, because in humans the upper limit pitch of hearing tends to decrease with age. An American cell phone company has used this to create ring signals that are only audible to younger humans, but many older people can hear the signals, which may be because of the considerable variation of age-related deterioration in the upper hearing threshold; the Mosquito is an electronic device that uses a high pitched frequency to deter loitering by young people. Bats use a variety of ultrasonic ranging techniques to detect their prey, they can detect frequencies beyond 100 kHz up to 200 kHz. Many insects have good ultrasonic hearing, most of these are nocturnal insects listening for echolocating bats; these include many groups of moths, praying mantids and lacewings. Upon hearing a bat, some insects will make evasive manoeuvres to escape being caught. Ultrasonic frequencies trigger a reflex action in the noctuid moth that causes it to drop in its flight to evade attack.
Tiger moths emit clicks which may disturb bats' echolocation, in other cases may advertise the fact that they are poisonous by emitting sound. Dogs and cats' hearing range extends into the ultrasound; the wild ancestors of cats and dogs evolved this higher hearing range to hear high-frequency sounds made by their preferred prey, small rodents. A dog whistle is a whistle that emits ultrasound, used for calling dogs; the frequency of most dog whistles is within the range of 23 to 54 kHz. Toothed whales, including dolphins, can hear ultrasound and use such sounds in their navigational system to orient and to capture prey. Porpoises have the highest known upper hearing limit at around 160 kHz. Several types of fish can detect ultrasound. In the order Clupeiformes, members of the subfamily Alosinae have been shown to be able to detect sounds up to 180 kHz, while the other subfamilies can hear only up to 4 kHz. Ultrasound generator/speaker systems are sold as electronic pest control devices, which are claimed to frighten away rodents and insects, but there is no scientific evidence that the devices work.
An ultrasonic level or sensing system requires no contact with the target. For many processes in the medical, pharmaceutical and general industries this is an advantage over inline sensors that may contaminate the liquids inside a vessel or tube or that may be clogged by the product. Both continuous wave and pulsed systems are used; the principle behind a pulsed-ultrasonic technology is that the transmit signal consists of short bursts of ultrasonic energy. After each burst, the electronics looks for a return signal within a small window of time corresponding to the time it takes for the energy to pass through the vessel. Only a signal received during this window will qualify for additional signal processing. A popular consumer application of ultrasonic ranging was the Polaroid SX-70 camera, which included a lightweight transducer system to focus the camera automatically. Polaroid licensed this ultrasound technology and it became the basis of a variety of ultrasonic products. A common ultrasound application is an automatic door opener, where an ultrasonic sensor detects a person's approach and opens the door.
Ultrasonic sensors are used to detect intruders. The flow in pipes or open channels can be measured by ultrasonic flowmeters, which measure the average veloci