A frog is any member of a diverse and carnivorous group of short-bodied, tailless amphibians composing the order Anura. The oldest fossil "proto-frog" appeared in the early Triassic of Madagascar, but molecular clock dating suggests their origins may extend further back to the Permian, 265 million years ago. Frogs are distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforests. There are accounting for over 85 % of extant amphibian species, they are one of the five most diverse vertebrate orders. Warty frog species tend to be called toads, but the distinction between frogs and toads is informal, not from taxonomy or evolutionary history. An adult frog has a stout body, protruding eyes, anteriorly-attached tongue, limbs folded underneath, no tail. Frogs have glandular skin, with secretions ranging from distasteful to toxic, their skin varies in colour from well-camouflaged dappled brown and green to vivid patterns of bright red or yellow and black to show toxicity and ward off predators.
Adult frogs live on dry land. Frogs lay their eggs in water; the eggs hatch into aquatic larvae called tadpoles that have internal gills. They have specialized rasping mouth parts suitable for herbivorous, omnivorous or planktivorous diets; the life cycle is completed. A few species bypass the tadpole stage. Adult frogs have a carnivorous diet consisting of small invertebrates, but omnivorous species exist and a few feed on fruit. Frog skin has a rich microbiome, important to their health. Frogs are efficient at converting what they eat into body mass, they are an important food source for predators and part of the food web dynamics of many of the world's ecosystems. The skin is semi-permeable, making them susceptible to dehydration, so they either live in moist places or have special adaptations to deal with dry habitats. Frogs produce a wide range of vocalizations in their breeding season, exhibit many different kinds of complex behaviours to attract mates, to fend off predators and to survive.
Frogs are valued as food by humans and have many cultural roles in literature and religion. Frog populations have declined since the 1950s. More than one third of species are considered to be threatened with extinction and over 120 are believed to have become extinct since the 1980s; the number of malformations among frogs is on the rise and an emerging fungal disease, has spread around the world. Conservation biologists are working to resolve them; the use of the common names "frog" and "toad" has no taxonomic justification. From a classification perspective, all members of the order Anura are frogs, but only members of the family Bufonidae are considered "true toads"; the use of the term "frog" in common names refers to species that are aquatic or semi-aquatic and have smooth, moist skins. There are numerous exceptions to this rule; the European fire-bellied toad has a warty skin and prefers a watery habitat whereas the Panamanian golden frog is in the toad family Bufonidae and has a smooth skin.
The origin of the order name Anura — and its original spelling Anoures — is the Ancient Greek "alpha privative" prefix ἀν- "without", οὐρά, meaning "animal tail". It refers to the tailless character of these amphibians; the origins of the word frog are debated. The word is first attested in Old English as frogga, but the usual Old English word for the frog was frosc, it is agreed that the word frog is somehow related to this. Old English frosc remained in dialectal use in English as frosh and frosk into the nineteenth century, is paralleled in other Germanic languages, with examples in the modern languages including German Frosch, Icelandic froskur, Dutch vors; these words allow us to reconstruct a Common Germanic ancestor *froskaz. The third edition of the Oxford English Dictionary finds that the etymology of *froskaz is uncertain, but agrees with arguments that it could plausibly derive from a Proto-Indo-European base along the lines of *preu = "jump". How Old English frosc gave rise to frogga is, uncertain, as the development does not involve a regular sound-change.
Instead, it seems that there was a trend in Old English to coin nicknames for animals ending in -g, with examples—themselves all of uncertain etymology—including dog, pig and wig. Frog appears to have been adapted from frosc as part of this trend. Meanwhile, the word toad, first attested as Old English tādige, is unique to English and is of uncertain etymology, it is the basis for the word tadpole, first attested as Middle English taddepol meaning'toad-head'. About 88% of amphibian species are classified in the order Anura; these include over 7,000 species in 56 families, of which the Craugastoridae, Hylidae and Bufonidae are the richest in species. The Anura include any fossil species that fit within the anuran definition; the characteristics of anuran adults include: 9 or fewer presacral vertebrae, the presence of a urostyle formed of fused vertebrae, no tail, a long and forward-sloping ilium, shorter fore limbs than hind limbs and ulna fused and fibula fused, elongated an
Amphibians are ectothermic, tetrapod vertebrates of the class Amphibia. Modern amphibians are all Lissamphibia, they inhabit a wide variety of habitats, with most species living within terrestrial, arboreal or freshwater aquatic ecosystems. Thus amphibians start out as larvae living in water, but some species have developed behavioural adaptations to bypass this; the young undergo metamorphosis from larva with gills to an adult air-breathing form with lungs. Amphibians use their skin as a secondary respiratory surface and some small terrestrial salamanders and frogs lack lungs and rely on their skin, they are superficially similar to lizards but, along with mammals and birds, reptiles are amniotes and do not require water bodies in which to breed. With their complex reproductive needs and permeable skins, amphibians are ecological indicators; the earliest amphibians evolved in the Devonian period from sarcopterygian fish with lungs and bony-limbed fins, features that were helpful in adapting to dry land.
They diversified and became dominant during the Carboniferous and Permian periods, but were displaced by reptiles and other vertebrates. Over time, amphibians shrank in size and decreased in diversity, leaving only the modern subclass Lissamphibia; the three modern orders of amphibians are Anura and Apoda. The number of known amphibian species is 8,000, of which nearly 90% are frogs; the smallest amphibian in the world is a frog from New Guinea with a length of just 7.7 mm. The largest living amphibian is the 1.8 m Chinese giant salamander, but this is dwarfed by the extinct 9 m Prionosuchus from the middle Permian of Brazil. The study of amphibians is called batrachology, while the study of both reptiles and amphibians is called herpetology; the word "amphibian" is derived from the Ancient Greek term ἀμφίβιος, which means "both kinds of life", ἀμφί meaning "of both kinds" and βιος meaning "life". The term was used as a general adjective for animals that could live on land or in water, including seals and otters.
Traditionally, the class Amphibia includes all tetrapod vertebrates. Amphibia in its widest sense was divided into three subclasses, two of which are extinct: Subclass Lepospondyli† Subclass Temnospondyli† Subclass Lissamphibia Salientia: Jurassic to present—6,200 current species in 53 families Caudata: Jurassic to present—652 current species in 9 families Gymnophiona: Jurassic to present—192 current species in 10 families The actual number of species in each group depends on the taxonomic classification followed; the two most common systems are the classification adopted by the website AmphibiaWeb, University of California and the classification by herpetologist Darrel Frost and the American Museum of Natural History, available as the online reference database "Amphibian Species of the World". The numbers of species cited above follows Frost and the total number of known amphibian species as of March 31, 2019 is 8,000, of which nearly 90% are frogs. With the phylogenetic classification, the taxon Labyrinthodontia has been discarded as it is a polyparaphyletic group without unique defining features apart from shared primitive characteristics.
Classification varies according to the preferred phylogeny of the author and whether they use a stem-based or a node-based classification. Traditionally, amphibians as a class are defined as all tetrapods with a larval stage, while the group that includes the common ancestors of all living amphibians and all their descendants is called Lissamphibia; the phylogeny of Paleozoic amphibians is uncertain, Lissamphibia may fall within extinct groups, like the Temnospondyli or the Lepospondyli, in some analyses in the amniotes. This means that advocates of phylogenetic nomenclature have removed a large number of basal Devonian and Carboniferous amphibian-type tetrapod groups that were placed in Amphibia in Linnaean taxonomy, included them elsewhere under cladistic taxonomy. If the common ancestor of amphibians and amniotes is included in Amphibia, it becomes a paraphyletic group. All modern amphibians are included in the subclass Lissamphibia, considered a clade, a group of species that have evolved from a common ancestor.
The three modern orders are Anura and Gymnophiona. It has been suggested that salamanders arose separately from a Temnospondyl-like ancestor, that caecilians are the sister group of the advanced reptiliomorph amphibians, thus of amniotes. Although the fossils of several older proto-frogs with primitive characteristics are known, the oldest "true frog" is Prosalirus bitis, from the Early Jurassic Kayenta Formation of Arizona, it is anatomically similar to modern frogs. The oldest known caecilian is another Early Jurassic species, Eocaecilia micropodia from Arizona; the earliest salamander is Beiyanerpeton jianpingensis from the Late Jurassic of northeastern China. Authorities disagree as to whether Salientia is a superorder that includes the order Anura, or whether
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
The Yucatán Peninsula, in southeastern Mexico, separates the Caribbean Sea from the Gulf of Mexico, with the northern coastline on the Yucatán Channel. The peninsula lies east of the Isthmus of Tehuantepec, a northwestern geographic partition separating the region of Central America from the rest of North America, it is 181,000 km2 in area, is entirely composed of limestone. The proper derivation of the word Yucatán is debated. Hernán Cortés, in the first of his letters to Charles V, the Holy Roman Emperor, claimed that the name Yucatán comes from a misunderstanding. In this telling, the first Spanish explorers asked what the area was called and the response they received, "Yucatan", was a Yucatec Maya word meaning "I don't understand what you're saying." Others claim that the source of the name is the Nahuatl word Yocatlān, "place of richness". The Yucatán Peninsula is the site of the Chicxulub crater impact, created 66 million years ago by an asteroid of about 10 to 15 kilometres in diameter at the end of the Cretaceous Period.
The Yucatán Peninsula comprises a significant proportion of the ancient Maya lowlands, was the center of the Mayan civilization. There are many Maya archaeological sites throughout the peninsula. Indigenous Maya and Mestizos of partial Maya descent make up a sizable portion of the region's population, Mayan languages are spoken there; the peninsula comprises the Mexican states of Yucatán, Quintana Roo, as well as large parts of Belize and Guatemala's Petén Department. In the late historic and early modern eras, the Yucatán Peninsula was a cattle ranching, logging and henequen production area. Since the 1970s, the Yucatán Peninsula has reoriented its economy towards tourism in the Mexican state of Quintana Roo. Once a small fishing village, Cancún in the northeast of the peninsula has grown into a thriving city; the Riviera Maya, which stretches along the east coast of the peninsula between Cancún and Tulum, houses over 50,000 beds. The best-known locations are the former fishing town of Playa del Carmen, the ecological parks Xcaret and Xel-Há and the Maya ruins of Tulum and Coba.
The peninsula is the exposed portion of the larger Yucatán Platform, all of, composed of carbonate and soluble rocks, being limestone although dolomite and evaporites are present at various depths. The whole of the Yucatán Peninsula is an unconfined flat lying karst landscape. Sinkholes, known locally as cenotes, are widespread in the northern lowlands. According to the Alvarez hypothesis, the mass extinction of the dinosaurs at the transition from the Cretaceous to the Paleogene Period, the Cretaceous–Paleogene boundary, 65 million years ago was caused by an asteroid impact somewhere in the greater Caribbean Basin; the buried Chicxulub crater is centered off the north coast of the peninsula near the town of Chicxulub. The now-famous "Ring of Cenotes" outlines one of the shock-waves from this impact event in the rock of ~66 million years of age, which lies more than 1 km below the modern ground surface near the centre, with the rock above the impact strata all being younger in age; the presence of the crater has been determined first on the surface from the Ring of Cenotes, but by geophysical methods, direct drilling with recovery of the drill cores.
The Arrowsmith Bank is a submerged bank located off the northeastern end of the peninsula. Due to the extreme karst nature of the whole peninsula, the northern half is devoid of rivers. Where lakes and swamps are present, the water is marshy and unpotable. Due to its coastal situation, the whole of the peninsula is underlain by an extensive contiguous density stratified coastal aquifer, where a fresh water lens formed from meteoric water floats on top of intruding saline water from the coastal margins; the thousands of sinkholes known as cenotes throughout the region provide access to the groundwater system. The cenotes have long been relied on by contemporary Maya people. Short and tall tropical jungles are the predominant natural vegetation types of the Yucatán Peninsula; the boundaries between northern Guatemala and western Belize are still occupied by the largest continuous tracts of tropical rainforest in Central America. However, these forests are suffering extensive deforestation. Like much of the Caribbean, the peninsula lies within the Atlantic Hurricane Belt, with its uniformly flat terrain it is vulnerable to these large storms coming from the east.
The 2005 Atlantic Hurricane Season was a bad season for Mexico's tourism industry, with two forceful category 5 storms hitting, Hurricane Emily and Hurricane Wilma. The 2006 Atlantic Hurricane Season was a typical year which left the Yucatán untouched, but in the 2007 Atlantic Hurricane season Yucatán was hit by Hurricane Dean Dean left little damage on the peninsula despite heavy localized flooding. Strong storms called nortes can descend on the Yucatán Peninsula any time of year. Although these storms pummel the area with heavy rains and high winds, they tend to be short-lived, clearing after about an hour; the average percentage of days with rain per month ranges from a monthly low of 7% in April to a high of 25% in October. Breezes can have a cooling effect, humidity is high, particularl
The Hylinae are the largest of three subfamilies of Hylidae, the "tree frogs". It contains nearly 700 species in 41 genera, they are found in North and South America, temperate Asia, Africa north of the Sahara. The 41 recognized genera are: http://www.tolweb.org/Hylinae
A chordate is an animal constituting the phylum Chordata. During some period of their life cycle, chordates possess a notochord, a dorsal nerve cord, pharyngeal slits, an endostyle, a post-anal tail: these five anatomical features define this phylum. Chordates are bilaterally symmetric; the Chordata and Ambulacraria together form the superphylum Deuterostomia. Chordates are divided into three subphyla: Vertebrata. There are extinct taxa such as the Vetulicolia. Hemichordata has been presented as a fourth chordate subphylum, but now is treated as a separate phylum: hemichordates and Echinodermata form the Ambulacraria, the sister phylum of the Chordates. Of the more than 65,000 living species of chordates, about half are bony fish that are members of the superclass Osteichthyes. Chordate fossils have been found from as early as the Cambrian explosion, 541 million years ago. Cladistically, vertebrates - chordates with the notochord replaced by a vertebral column during development - are considered to be a subgroup of the clade Craniata, which consists of chordates with a skull.
The Craniata and Tunicata compose the clade Olfactores. Chordates form a phylum of animals that are defined by having at some stage in their lives all of the following anatomical features: A notochord, a stiff rod of cartilage that extends along the inside of the body. Among the vertebrate sub-group of chordates the notochord develops into the spine, in wholly aquatic species this helps the animal to swim by flexing its tail. A dorsal neural tube. In fish and other vertebrates, this develops into the spinal cord, the main communications trunk of the nervous system. Pharyngeal slits; the pharynx is the part of the throat behind the mouth. In fish, the slits are modified to form gills, but in some other chordates they are part of a filter-feeding system that extracts particles of food from the water in which the animals live. Post-anal tail. A muscular tail that extends backwards behind the anus. An endostyle; this is a groove in the ventral wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus.
It stores iodine, may be a precursor of the vertebrate thyroid gland. There are soft constraints that separate chordates from certain other biological lineages, but are not part of the formal definition: All chordates are deuterostomes; this means. All chordates are based on a bilateral body plan. All chordates are coelomates, have a fluid filled body cavity called a coelom with a complete lining called peritoneum derived from mesoderm; the following schema is from the third edition of Vertebrate Palaeontology. The invertebrate chordate classes are from Fishes of the World. While it is structured so as to reflect evolutionary relationships, it retains the traditional ranks used in Linnaean taxonomy. Phylum Chordata †Vetulicolia? Subphylum Cephalochordata – Class Leptocardii Clade Olfactores Subphylum Tunicata – Class Ascidiacea Class Thaliacea Class Appendicularia Class Sorberacea Subphylum Vertebrata Infraphylum incertae sedis Cyclostomata Superclass'Agnatha' paraphyletic Class Myxini Class Petromyzontida or Hyperoartia Class †Conodonta Class †Myllokunmingiida Class †Pteraspidomorphi Class †Thelodonti Class †Anaspida Class †Cephalaspidomorphi Infraphylum Gnathostomata Class †Placodermi Class Chondrichthyes Class †Acanthodii Superclass Osteichthyes Class Actinopterygii Class Sarcopterygii Superclass Tetrapoda Class Amphibia Class Sauropsida Class Synapsida Craniates, one of the three subdivisions of chordates, all have distinct skulls.
They include the hagfish. Michael J. Benton commented that "craniates are characterized by their heads, just as chordates, or all deuterostomes, are by their tails". Most craniates are vertebrates; these consist of a series of bony or cartilaginous cylindrical vertebrae with neural arches that protect the spinal cord, with projections that link the vertebrae. However hagfish have incomplete braincases and no vertebrae, are therefore not regarded as vertebrates, but as members of the craniates, the group from which vertebrates are thought to have evolved; however the cladistic exclusion of hagfish from the vertebrates is controversial, as they ma
Wikispecies is a wiki-based online project supported by the Wikimedia Foundation. Its aim is to create a comprehensive free content catalogue of all species. Jimmy Wales stated that editors are not required to fax in their degrees, but that submissions will have to pass muster with a technical audience. Wikispecies is available under the GNU Free Documentation License and CC BY-SA 3.0. Started in September 2004, with biologists across the world invited to contribute, the project had grown a framework encompassing the Linnaean taxonomy with links to Wikipedia articles on individual species by April 2005. Benedikt Mandl co-ordinated the efforts of several people who are interested in getting involved with the project and contacted potential supporters in early summer 2004. Databases were evaluated and the administrators contacted, some of them have agreed on providing their data for Wikispecies. Mandl defined two major tasks: Figure out how the contents of the data base would need to be presented—by asking experts, potential non-professional users and comparing that with existing databases Figure out how to do the software, which hardware is required and how to cover the costs—by asking experts, looking for fellow volunteers and potential sponsorsAdvantages and disadvantages were discussed by the wikimedia-I mailing list.
The board of directors of the Wikimedia Foundation voted by 4 to 0 in favor of the establishment of a Wikispecies. The project is hosted at species.wikimedia.org. It was merged to a sister project of Wikimedia Foundation on September 14, 2004. On October 10, 2006, the project exceeded 75,000 articles. On May 20, 2007, the project exceeded 100,000 articles with a total of 5,495 registered users. On September 8, 2008, the project exceeded 150,000 articles with a total of 9,224 registered users. On October 23, 2011, the project reached 300,000 articles. On June 16, 2014, the project reached 400,000 articles. On January 7, 2017, the project reached 500,000 articles. On October 30, 2018, the project reached 600,000 articles, a total of 1.12 million pages. Wikispecies comprises taxon pages, additionally pages about synonyms, taxon authorities, taxonomical publications, institutions or repositories holding type specimen. Wikispecies asks users to use images from Wikimedia Commons. Wikispecies does not allow the use of content.
All Species Foundation Catalogue of Life Encyclopedia of Life Tree of Life Web Project List of online encyclopedias The Plant List Wikispecies, The free species directory that anyone can edit Species Community Portal The Wikispecies Charter, written by Wales