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95-503: Dicroglossinae Occidozyginae The frog family Dicroglossidae occurs in tropical and subtropical regions of Asia and Africa, with most genera and species being found in Asia. The common name of the family is fork-tongued frogs . The Dicroglossidae were previously considered to be a subfamily in the family Ranidae , but their position as a family is now well established. The two subfamilies contain 231 species in 13–15 genera, depending on

190-410: A collection of polyphagous heterotrophic consumers that network and cycle the flow of energy and nutrients from a productive base of self-feeding autotrophs . The base or basal species in a food web are those species without prey and can include autotrophs or saprophytic detritivores (i.e., the community of decomposers in soil , biofilms , and periphyton ). Feeding connections in

285-469: A few feed on plant matter. Frog skin has a rich microbiome which is important to their health. Frogs are extremely 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

380-543: A food chain was described by a medieval Afro-Arab scholar named Al-Jahiz : "All animals, in short, cannot exist without food, neither can the hunting animal escape being hunted in his turn." The earliest graphical depiction of a food web was by Lorenzo Camerano in 1880, followed independently by those of Pierce and colleagues in 1912 and Victor Shelford in 1913. Two food webs about herring were produced by Victor Summerhayes and Charles Elton and Alister Hardy in 1923 and 1924. Charles Elton subsequently pioneered

475-532: A food web has a historical foothold in the writings of Charles Darwin and his terminology, including an "entangled bank", "web of life", "web of complex relations", and in reference to the decomposition actions of earthworms he talked about "the continued movement of the particles of earth". Even earlier, in 1768 John Bruckner described nature as "one continued web of life". Interest in food webs increased after Robert Paine's experimental and descriptive study of intertidal shores suggesting that food web complexity

570-436: A food web illustrate the feeding pathways, such as where heterotrophs obtain organic matter by feeding on autotrophs and other heterotrophs. The food web is a simplified illustration of the various methods of feeding that link an ecosystem into a unified system of exchange. There are different kinds of consumer–resource interactions that can be roughly divided into herbivory , carnivory , scavenging , and parasitism . Some of

665-418: A food web. In a simple predator-prey example, a deer is one step removed from the plants it eats (chain length = 1) and a wolf that eats the deer is two steps removed from the plants (chain length = 2). The relative amount or strength of influence that these parameters have on the food web address questions about: In a pyramid of numbers, the number of consumers at each level decreases significantly, so that

760-469: A food web. Ecologists use these simplifications in quantitative (or mathematical representation) models of trophic or consumer-resource systems dynamics. Using these models they can measure and test for generalized patterns in the structure of real food web networks. Ecologists have identified non-random properties in the topological structure of food webs. Published examples that are used in meta analysis are of variable quality with omissions. However,

855-460: A food web. Sometimes in food web terminology, complexity is defined as product of the number of species and connectance., though there have been criticisms of this definition and other proposed methods for measuring network complexity. Connectance is "the fraction of all possible links that are realized in a network". These concepts were derived and stimulated through the suggestion that complexity leads to stability in food webs, such as increasing

950-487: A food-web illustrate direct trophic relations among species, but there are also indirect effects that can alter the abundance, distribution, or biomass in the trophic levels. For example, predators eating herbivores indirectly influence the control and regulation of primary production in plants. Although the predators do not eat the plants directly, they regulate the population of herbivores that are directly linked to plant trophism. The net effect of direct and indirect relations

1045-539: A living system (e.g., ecosystem) sways from equilibrium, the greater its complexity. Complexity has multiple meanings in the life sciences and in the public sphere that confuse its application as a precise term for analytical purposes in science. Complexity in the life sciences (or biocomplexity ) is defined by the "properties emerging from the interplay of behavioral, biological, physical, and social interactions that affect, sustain, or are modified by living organisms, including humans". Several concepts have emerged from

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1140-409: A long history in ecology. Like maps of unfamiliar ground, food webs appear bewilderingly complex. They were often published to make just that point. Yet recent studies have shown that food webs from a wide range of terrestrial, freshwater, and marine communities share a remarkable list of patterns. Links in food webs map the feeding connections (who eats whom) in an ecological community . Food cycle

1235-409: A measure mass or energy per m per unit time. Different consumers are going to have different metabolic assimilation efficiencies in their diets. Each trophic level transforms energy into biomass. Energy flow diagrams illustrate the rates and efficiency of transfer from one trophic level into another and up through the hierarchy. It is the case that the biomass of each trophic level decreases from

1330-664: A point of common ancestry. It is based on Frost et al. (2006), Heinicke et al. (2009) and Pyron and Wiens (2011). Leiopelmatidae Ascaphidae Bombinatoridae Alytidae Discoglossidae Pipidae Rhinophrynidae Scaphiopodidae Pelodytidae Pelobatidae Megophryidae Heleophrynidae Sooglossidae Nasikabatrachidae Calyptocephalellidae Myobatrachidae Limnodynastidae Ceuthomantidae Brachycephalidae Eleutherodactylidae Craugastoridae Hemiphractidae Hylidae Bufonidae Aromobatidae Dendrobatidae Leptodactylidae Allophrynidae Food web The linkages in

1425-469: A prefrontal bone, presence of a hyoid plate , a lower jaw without teeth (with the exception of Gastrotheca guentheri ) consisting of three pairs of bones (angulosplenial, dentary, and mentomeckelian, with the last pair being absent in Pipoidea ), an unsupported tongue, lymph spaces underneath the skin, and a muscle, the protractor lentis, attached to the lens of the eye . The anuran larva or tadpole has

1520-412: A process called biomineralization . Bacteria that live in detrital sediments create and cycle nutrients and biominerals. Food web models and nutrient cycles have traditionally been treated separately, but there is a strong functional connection between the two in terms of stability, flux, sources, sinks, and recycling of mineral nutrients. Food webs are necessarily aggregated and only illustrate

1615-400: A single top consumer , (e.g., a polar bear or a human ), will be supported by a much larger number of separate producers. There is usually a maximum of four or five links in a food chain, although food chains in aquatic ecosystems are more often longer than those on land. Eventually, all the energy in a food chain is dispersed as heat. Ecological pyramids place the primary producers at

1710-466: A single central respiratory spiracle and mouthparts consisting of keratinous beaks and denticles . Frogs and toads are broadly classified into three suborders: Archaeobatrachia , which includes four families of primitive frogs; Mesobatrachia , which includes five families of more evolutionary intermediate frogs; and Neobatrachia , by far the largest group, which contains the remaining families of modern frogs, including most common species throughout

1805-527: A single species can directly and indirectly influence many others. Microcosm studies are used to simplify food web research into semi-isolated units such as small springs, decaying logs, and laboratory experiments using organisms that reproduce quickly, such as daphnia feeding on algae grown under controlled environments in jars of water. While the complexity of real food webs connections are difficult to decipher, ecologists have found mathematical models on networks an invaluable tool for gaining insight into

1900-524: A slightly warty skin and prefers a watery habitat whereas the Panamanian golden frog ( Atelopus zeteki ) 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- ( an- from ἀ- before a vowel) 'without', and οὐρά ( ourá ) 'animal tail'. meaning "tailless". It refers to

1995-514: A tangled web of omnivores." A central question in the trophic dynamic literature is the nature of control and regulation over resources and production. Ecologists use simplified one trophic position food chain models (producer, carnivore, decomposer). Using these models, ecologists have tested various types of ecological control mechanisms. For example, herbivores generally have an abundance of vegetative resources, which meant that their populations were largely controlled or regulated by predators. This

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2090-493: A tiny portion of the complexity of real ecosystems. For example, the number of species on the planet are likely in the general order of 10 , over 95% of these species consist of microbes and invertebrates , and relatively few have been named or classified by taxonomists . It is explicitly understood that natural systems are 'sloppy' and that food web trophic positions simplify the complexity of real systems that sometimes overemphasize many rare interactions. Most studies focus on

2185-413: A top carnivore, without specifying which end." Nonetheless, real differences in structure and function have been identified when comparing different kinds of ecological food webs, such as terrestrial vs. aquatic food webs. Food webs serve as a framework to help ecologists organize the complex network of interactions among species observed in nature and around the world. One of the earliest descriptions of

2280-434: A very general sense, energy flow (E) can be defined as the sum of metabolic production (P) and respiration (R), such that E=P+R. Biomass represents stored energy. However, concentration and quality of nutrients and energy is variable. Many plant fibers, for example, are indigestible to many herbivores leaving grazer community food webs more nutrient limited than detrital food webs where bacteria are able to access and release

2375-502: A wide range of vocalisations , particularly in their breeding season , and exhibit many different kinds of complex behaviors to attract mates, to fend off predators and to generally survive. Frogs are valued as food by humans and also have many cultural roles in literature, symbolism and religion. They are also seen as environmental bellwethers , with declines in frog populations often viewed as early warning signs of environmental damage. Frog populations have declined significantly since

2470-509: Is an obsolete term that is synonymous with food web. Ecologists can broadly group all life forms into one of two trophic layers, the autotrophs and the heterotrophs . Autotrophs produce more biomass energy, either chemically without the sun's energy or by capturing the sun's energy in photosynthesis , than they use during metabolic respiration . Heterotrophs consume rather than produce biomass energy as they metabolize, grow, and add to levels of secondary production . A food web depicts

2565-490: Is any member of a diverse and largely carnivorous group of short-bodied, tailless amphibians composing the order Anura (coming from the Ancient Greek ἀνούρα , literally 'without tail'). The oldest fossil "proto-frog" Triadobatrachus is known from the Early Triassic of Madagascar (250   million years ago ), but molecular clock dating suggests their split from other amphibians may extend further back to

2660-437: Is attributed to different sizes of producers. Aquatic communities are often dominated by producers that are smaller than the consumers that have high growth rates. Aquatic producers, such as planktonic algae or aquatic plants, lack the large accumulation of secondary growth as exists in the woody trees of terrestrial ecosystems. However, they are able to reproduce quickly enough to support a larger biomass of grazers. This inverts

2755-422: Is called trophic cascades. Trophic cascades are separated into species-level cascades, where only a subset of the food-web dynamic is impacted by a change in population numbers, and community-level cascades, where a change in population numbers has a dramatic effect on the entire food-web, such as the distribution of plant biomass. The field of chemical ecology has elucidated multitrophic interactions that entail

2850-649: Is informal, not from taxonomy or evolutionary history. An adult frog has a stout body, protruding eyes , anteriorly-attached tongue , limbs folded underneath, and no tail (the tail of tailed frogs is an extension of the male cloaca). Frogs have glandular skin, with secretions ranging from distasteful to toxic. Their skin varies in colour from well- camouflaged dappled brown, grey and green to vivid patterns of bright red or yellow and black to show toxicity and ward off predators . Adult frogs live in fresh water and on dry land; some species are adapted for living underground or in trees. Frogs typically lay their eggs in

2945-414: Is known as the top-down hypothesis or 'green-world' hypothesis . Alternatively to the top-down hypothesis, not all plant material is edible and the nutritional quality or antiherbivore defenses of plants (structural and chemical) suggests a bottom-up form of regulation or control. Recent studies have concluded that both "top-down" and "bottom-up" forces can influence community structure and the strength of

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3040-442: Is plants, then herbivores (level 2), and then carnivores (level 3). The trophic level equals one more than the chain length, which is the number of links connecting to the base. The base of the food chain (primary producers or detritivores ) is set at zero. Ecologists identify feeding relations and organize species into trophic species through extensive gut content analysis of different species. The technique has been improved through

3135-424: Is the fraction of all possible links that are realized (L/S ) and represents a standard measure of food web complexity..." The distance (d) between every species pair in a web is averaged to compute the mean distance between all nodes in a web (D) and multiplied by the total number of links (L) to obtain link-density (LD), which is influenced by scale-dependent variables such as species richness . These formulas are

3230-524: Is the name of the total group that includes modern frogs in the order Anura as well as their close fossil relatives, the "proto-frogs" or "stem-frogs". The common features possessed by these proto-frogs include 14 presacral vertebrae (modern frogs have eight or 9), a long and forward-sloping ilium in the pelvis , the presence of a frontoparietal bone , and a lower jaw without teeth. The earliest known amphibians that were more closely related to frogs than to salamanders are Triadobatrachus massinoti , from

3325-647: Is uncertain, but agrees with arguments that it could plausibly derive from a Proto-Indo-European base along the lines of * preu , meaning 'jump'. How Old English frosc gave rise to frogga is, however, 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 , hog , pig, stag , and (ear)wig . Frog appears to have been adapted from frosc as part of this trend. Meanwhile,

3420-530: The Antarctic Peninsula , indicating that this region was once home to frogs related to those now living in South American Nothofagus forest . A cladogram showing the relationships of the different families of frogs in the clade Anura can be seen in the table below. This diagram, in the form of a tree , shows how each frog family is related to other families, with each node representing

3515-719: The Cretaceous–Paleogene extinction event associated with the Chicxulub impactor . All origins of arboreality (e.g. in Hyloidea and Natatanura) follow from that time and the resurgence of forest that occurred afterwards. Frog fossils have been found on all of the Earth's continents. In 2020, it was announced that 40 million year old helmeted frog fossils had been discovered by a team of vertebrate palaeontologists in Seymour Island on

3610-469: The Permian , 265   million years ago. Frogs are widely distributed, ranging from the tropics to subarctic regions, but the greatest concentration of species diversity is in tropical rainforest . Frogs account for around 88% of extant amphibian species. They are also one of the five most diverse vertebrate orders. Warty frog species tend to be called toads , but the distinction between frogs and toads

3705-548: The Permian , rather less than 300 million years ago, a date in better agreement with the palaeontological data. A further study in 2011 using both extinct and living taxa sampled for morphological, as well as molecular data, came to the conclusion that Lissamphibia is monophyletic and that it should be nested within Lepospondyli rather than within Temnospondyli . The study postulated that Lissamphibia originated no earlier than

3800-519: The divergence of the three groups took place in the Paleozoic or early Mesozoic before the break-up of the supercontinent Pangaea and soon after their divergence from the lobe-finned fishes . This would help account for the relative scarcity of amphibian fossils from the period before the groups split. Another molecular phylogenetic analysis conducted about the same time concluded that lissamphibians first appeared about 330 million years ago and that

3895-623: The edible frog ( Pelophylax esculentus ) is a hybrid between the pool frog ( P. lessonae ) and the marsh frog ( P. ridibundus ). The fire-bellied toads Bombina bombina and B. variegata are similar in forming hybrids. These are less fertile than their parents, giving rise to a hybrid zone where the hybrids are prevalent. The origins and evolutionary relationships between the three main groups of amphibians are hotly debated. A molecular phylogeny based on rDNA analysis dating from 2005 suggests that salamanders and caecilians are more closely related to each other than they are to frogs and

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3990-425: The middle Jurassic is slightly younger, about 155–170 million years old. The main evolutionary changes in this species involved the shortening of the body and the loss of the tail. Tadpoles of N. degiustoi constitute the oldest tadpoles found as of 2024, dating back to 168-161 million years ago. These tadpoles also showed adaptations for filter-feeding , implying residence in temporary pools by filter-feeding larvae

4085-429: The richest in species . The Anura include all modern frogs and 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, radius and ulna fused, tibia and fibula fused, elongated ankle bones , absence of

4180-540: The temnospondyl-origin hypothesis is more credible than other theories. The neobatrachians seemed to have originated in Africa/India, the salamanders in East Asia and the caecilians in tropical Pangaea. Other researchers, while agreeing with the main thrust of this study, questioned the choice of calibration points used to synchronise the data. They proposed that the date of lissamphibian diversification should be placed in

4275-412: 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, chytridiomycosis , has spread around the world. Conservation biologists are working to understand the causes of these problems and to resolve them. The use of

4370-519: The anuran lineage proper all lived in the early Jurassic period. One such early frog species, Prosalirus bitis , was discovered in 1995 in the Kayenta Formation of Arizona and dates back to the Early Jurassic epoch (199.6 to 175 million years ago), making Prosalirus somewhat more recent than Triadobatrachus . Like the latter, Prosalirus did not have greatly enlarged legs, but had

4465-548: The base of the chain to the top. This is because energy is lost to the environment with each transfer as entropy increases. About eighty to ninety percent of the energy is expended for the organism's life processes or is lost as heat or waste. Only about ten to twenty percent of the organism's energy is generally passed to the next organism. The amount can be less than one percent in animals consuming less digestible plants, and it can be as high as forty percent in zooplankton consuming phytoplankton . Graphic representations of

4560-430: The base. They can depict different numerical properties of ecosystems, including numbers of individuals per unit of area, biomass (g/m ), and energy (k cal m yr ). The emergent pyramidal arrangement of trophic levels with amounts of energy transfer decreasing as species become further removed from the source of production is one of several patterns that is repeated amongst the planets ecosystems. The size of each level in

4655-422: The basis for comparing and investigating the nature of non-random patterns in the structure of food web networks among many different types of ecosystems. Scaling laws, complexity, chaos, and pattern correlates are common features attributed to food web structure. Food webs are extremely complex. Complexity is a term that conveys the mental intractability of understanding all possible higher-order effects in

4750-442: The biomass or productivity at each tropic level are called ecological pyramids or trophic pyramids. The transfer of energy from primary producers to top consumers can also be characterized by energy flow diagrams. A common metric used to quantify food web trophic structure is food chain length. Food chain length is another way of describing food webs as a measure of the number of species encountered as energy or nutrients move from

4845-413: The butterfly larvae. Another example of this sort of multitrophic interaction in plants is the transfer of defensive alkaloids produced by endophytes living within a grass host to a hemiparasitic plant that is also using the grass as a host. The Law of Conservation of Mass dates from Antoine Lavoisier's 1789 discovery that mass is neither created nor destroyed in chemical reactions. In other words,

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4940-540: 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 usually refers to species that are aquatic or semi-aquatic and have smooth, moist skins; the term toad generally refers to species that are terrestrial with dry, warty skins. There are numerous exceptions to this rule. The European fire-bellied toad ( Bombina bombina ) has

5035-573: The concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle' was replaced by 'food web' in a subsequent ecological text. After Charles Elton's use of food webs in his 1927 synthesis, they became a central concept in the field of ecology . Elton organized species into functional groups , which formed the basis for the trophic system of classification in Raymond Lindeman 's classic and landmark paper in 1942 on trophic dynamics. The notion of

5130-400: The decomposition actions of earthworms he talked about "the continued movement of the particles of earth". Even earlier, in 1768 John Bruckner described nature as "one continued web of life". Food webs are limited representations of real ecosystems as they necessarily aggregate many species into trophic species , which are functional groups of species that have the same predators and prey in

5225-1514: The detrital web and the grazing web. Mushrooms produced by decomposers in the detrital web become a food source for deer, squirrels, and mice in the grazing web. Earthworms eaten by robins are detritivores consuming decaying leaves. "Detritus can be broadly defined as any form of non-living organic matter, including different types of plant tissue (e.g. leaf litter , dead wood, aquatic macrophytes, algae), animal tissue (carrion), dead microbes, faeces (manure, dung, faecal pellets, guano, frass), as well as products secreted, excreted or exuded from organisms (e.g. extra-cellular polymers, nectar, root exudates and leachates , dissolved organic matter, extra-cellular matrix, mucilage). The relative importance of these forms of detritus, in terms of origin, size and chemical composition, varies across ecosystems." Ecologists collect data on trophic levels and food webs to statistically model and mathematically calculate parameters, such as those used in other kinds of network analysis (e.g., graph theory), to study emergent patterns and properties shared among ecosystems. There are different ecological dimensions that can be mapped to create more complicated food webs, including: species composition (type of species), richness (number of species), biomass (the dry weight of plants and animals), productivity (rates of conversion of energy and nutrients into growth), and stability (food webs over time). A food web diagram illustrating species composition shows how change in

5320-592: The diet of the most specialized species is a subset of the diet of the next more generalized species, and its diet a subset of the next more generalized, and so on." Until recently, it was thought that food webs had little nested structure, but empirical evidence shows that many published webs have nested subwebs in their assembly. Food webs are complex networks . As networks, they exhibit similar structural properties and mathematical laws that have been used to describe other complex systems, such as small world and scale free properties . The small world attribute refers to

5415-439: The diets of smaller predators tend to be nested subsets of those of larger predators (Woodward & Warren 2007; YvonDurocher et al. 2008), and phylogenetic constraints, whereby related taxa are nested based on their common evolutionary history, are also evident (Cattin et al. 2004)." "Compartments in food webs are subgroups of taxa in which many strong interactions occur within the subgroups and few weak interactions occur between

5510-474: The early Triassic period of Madagascar (about 250 million years ago), and Czatkobatrachus polonicus , from the Early Triassic of Poland (about the same age as Triadobatrachus ). The skull of Triadobatrachus is frog-like, being broad with large eye sockets, but the fossil has features diverging from modern frogs. These include a longer body with more vertebrae . The tail has separate vertebrae unlike

5605-458: The ecosystem concept, which assumes that the phenomena under investigation (interactions and feedback loops) are sufficient to explain patterns within boundaries, such as the edge of a forest, an island, a shoreline, or some other pronounced physical characteristic. In a detrital web, plant and animal matter is broken down by decomposers, e.g., bacteria and fungi, and moves to detritivores and then carnivores. There are often relationships between

5700-450: The ecosystem to another. The trophic dynamic concept has served as a useful quantitative heuristic, but it has several major limitations including the precision by which an organism can be allocated to a specific trophic level. Omnivores, for example, are not restricted to any single level. Nonetheless, recent research has found that discrete trophic levels do exist, but "above the herbivore trophic level, food webs are better characterized as

5795-518: The fused urostyle or coccyx in modern frogs. The tibia and fibula bones are also separate, making it probable that Triadobatrachus was not an efficient leaper. A 2019 study has noted the presence of Salientia from the Chinle Formation , and suggested that anurans might have first appeared during the Late Triassic . On the basis of fossil evidence, the earliest known "true frogs" that fall into

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5890-496: The influence is environmentally context dependent. These complex multitrophic interactions involve more than two trophic levels in a food web. For example, such interactions have been discovered in the context of arbuscular mycorrhizal fungi and aphid herbivores that utilize the same plant species . Another example of a multitrophic interaction is a trophic cascade , in which predators help to increase plant growth and prevent overgrazing by suppressing herbivores. Links in

5985-431: The inverted pyramidal pattern. Population structure, migration rates, and environmental refuge for prey are other possible causes for pyramids with biomass inverted. Energy pyramids, however, will always have an upright pyramid shape if all sources of food energy are included and this is dictated by the second law of thermodynamics . Many of the Earth's elements and minerals (or mineral nutrients) are contained within

6080-618: The larger influences where the bulk of energy transfer occurs. "These omissions and problems are causes for concern, but on present evidence do not present insurmountable difficulties." There are different kinds or categories of food webs: Within these categories, food webs can be further organized according to the different kinds of ecosystems being investigated. For example, human food webs, agricultural food webs, detrital food webs, marine food webs , aquatic food webs, soil food webs , Arctic (or polar) food webs, terrestrial food webs, and microbial food webs . These characterizations stem from

6175-477: The late Carboniferous , some 290 to 305 million years ago. The split between Anura and Caudata was estimated as taking place 292 million years ago, rather later than most molecular studies suggest, with the caecilians splitting off 239 million years ago. In 2008, Gerobatrachus hottoni , a temnospondyl with many frog- and salamander-like characteristics, was discovered in Texas . It dated back 290 million years and

6270-594: The many loosely connected nodes, non-random dense clustering of a few nodes (i.e., trophic or keystone species in ecology), and small path length compared to a regular lattice. "Ecological networks, especially mutualistic networks, are generally very heterogeneous, consisting of areas with sparse links among species and distinct areas of tightly linked species. These regions of high link density are often referred to as cliques, hubs, compartments, cohesive sub-groups, or modules...Within food webs, especially in aquatic systems, nestedness appears to be related to body size because

6365-436: The mass of any one element at the beginning of a reaction will equal the mass of that element at the end of the reaction. Food webs depict energy flow via trophic linkages. Energy flow is directional, which contrasts against the cyclic flows of material through the food web systems. Energy flow "typically includes production, consumption, assimilation, non-assimilation losses (feces), and respiration (maintenance costs)." In

6460-478: The nineteenth century, and is paralleled widely in other Germanic languages , with examples in the modern languages including German Frosch , Norwegian frosk , Icelandic froskur , and Dutch (kik)vors . These words allow reconstruction of a Common Germanic ancestor * froskaz . The third edition of the Oxford English Dictionary finds that the etymology of * froskaz

6555-403: The number of empirical studies on community webs is on the rise and the mathematical treatment of food webs using network theory had identified patterns that are common to all. Scaling laws , for example, predict a relationship between the topology of food web predator-prey linkages and levels of species richness . Food webs are the road-maps through Darwin's famous 'entangled bank' and have

6650-414: The number of trophic levels in more species rich ecosystems. This hypothesis was challenged through mathematical models suggesting otherwise, but subsequent studies have shown that the premise holds in real systems. At different levels in the hierarchy of life, such as the stability of a food web, "the same overall structure is maintained in spite of an ongoing flow and change of components." The farther

6745-426: The nutrient and energy stores. "Organisms usually extract energy in the form of carbohydrates, lipids, and proteins. These polymers have a dual role as supplies of energy as well as building blocks; the part that functions as energy supply results in the production of nutrients (and carbon dioxide, water, and heat). Excretion of nutrients is, therefore, basic to metabolism." The units in energy flow webs are typically

6840-408: The organic matter eaten by heterotrophs, such as sugars , provides energy. Autotrophs and heterotrophs come in all sizes, from microscopic to many tonnes - from cyanobacteria to giant redwoods , and from viruses and bdellovibrio to blue whales . Charles Elton pioneered the concept of food cycles, food chains, and food size in his classical 1927 book "Animal Ecology"; Elton's 'food cycle'

6935-417: The plants to top predators. There are different ways of calculating food chain length depending on what parameters of the food web dynamic are being considered: connectance, energy, or interaction. In its simplest form, the length of a chain is the number of links between a trophic consumer and the base of the web. The mean chain length of an entire web is the arithmetic average of the lengths of all chains in

7030-437: The pyramid generally represents biomass, which can be measured as the dry weight of an organism. Autotrophs may have the highest global proportion of biomass, but they are closely rivaled or surpassed by microbes. Pyramid structure can vary across ecosystems and across time. In some instances biomass pyramids can be inverted. This pattern is often identified in aquatic and coral reef ecosystems. The pattern of biomass inversion

7125-424: The pyramid. Primary consumers have longer lifespans and slower growth rates that accumulates more biomass than the producers they consume. Phytoplankton live just a few days, whereas the zooplankton eating the phytoplankton live for several weeks and the fish eating the zooplankton live for several consecutive years. Aquatic predators also tend to have a lower death rate than the smaller consumers, which contributes to

7220-466: The same predators and prey in a food web. Common examples of an aggregated node in a food web might include parasites , microbes, decomposers , saprotrophs , consumers , or predators , each containing many species in a web that can otherwise be connected to other trophic species. Food webs have trophic levels and positions. Basal species, such as plants, form the first level and are the resource-limited species that feed on no other living creature in

7315-492: The source. Dicroglossinae Anderson, 1871 — 211 species in 12 genera: Occidozyginae Fei, Ye, and Huang, 1990 — 20 species in two genera: The following phylogeny of Dicroglossidae is from Pyron & Wiens (2011). Dicroglossidae is a sister group of Ranixalidae . Ingerana Occidozyga Nanorana Limnonectes Nannophrys Euphlyctis Hoplobatrachus Sphaerotheca Fejervarya Minervarya Frog See text A frog

7410-406: The structure, stability, and laws of food web behaviours relative to observable outcomes. "Food web theory centers around the idea of connectance." Quantitative formulas simplify the complexity of food web structure. The number of trophic links (t L ), for example, is converted into a connectance value: where, S(S-1)/2 is the maximum number of binary connections among S species. "Connectance (C)

7505-405: The study of complexity in food webs. Complexity explains many principals pertaining to self-organization, non-linearity, interaction, cybernetic feedback, discontinuity, emergence, and stability in food webs. Nestedness, for example, is defined as "a pattern of interaction in which specialists interact with species that form perfect subsets of the species with which generalists interact", "—that is,

7600-508: The subgroups. Theoretically, compartments increase the stability in networks, such as food webs." Food webs are also complex in the way that they change in scale, seasonally, and geographically. The components of food webs, including organisms and mineral nutrients, cross the thresholds of ecosystem boundaries. This has led to the concept or area of study known as cross-boundary subsidy . "This leads to anomalies, such as food web calculations determining that an ecosystem can support one half of

7695-423: The sulfur bacterium Thiobacillus , which lives in hot sulfur springs . The top level has top (or apex) predators that no other species kills directly for their food resource needs. The intermediate levels are filled with omnivores that feed on more than one trophic level and cause energy to flow through several food pathways starting from a basal species. In the simplest scheme, the first trophic level (level 1)

7790-533: The tailless character of these amphibians. The origins of the word frog are uncertain and debated. The word is first attested in Old English as frogga , but the usual Old English word for the frog was frosc (with variants such as frox and forsc ), and 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

7885-427: The tissues and diets of organisms. Hence, mineral and nutrient cycles trace food web energy pathways. Ecologists employ stoichiometry to analyze the ratios of the main elements found in all organisms: carbon (C), nitrogen (N), phosphorus (P). There is a large transitional difference between many terrestrial and aquatic systems as C:P and C:N ratios are much higher in terrestrial systems while N:P ratios are equal between

7980-610: The transfer of defensive compounds across multiple trophic levels. For example, certain plant species in the Castilleja and Plantago genera have been found to produce defensive compounds called iridoid glycosides that are sequestered in the tissues of the Taylor's checkerspot butterfly larvae that have developed a tolerance for these compounds and are able to consume the foliage of these plants. These sequestered iridoid glycosides then confer chemical protection against bird predators to

8075-422: The two systems. Mineral nutrients are the material resources that organisms need for growth, development, and vitality. Food webs depict the pathways of mineral nutrient cycling as they flow through organisms. Most of the primary production in an ecosystem is not consumed, but is recycled by detritus back into useful nutrients. Many of the Earth's microorganisms are involved in the formation of minerals in

8170-428: The typical three-pronged pelvic structure of modern frogs. Unlike Triadobatrachus , Prosalirus had already lost nearly all of its tail and was well adapted for jumping. Another Early Jurassic frog is Vieraella herbsti , which is known only from dorsal and ventral impressions of a single animal and was estimated to be 33 mm ( 1 + 1 ⁄ 4  in) from snout to vent. Notobatrachus degiustoi from

8265-422: The use of stable isotopes to better trace energy flow through the web. It was once thought that omnivory was rare, but recent evidence suggests otherwise. This realization has made trophic classifications more complex. The trophic level concept was introduced in a historical landmark paper on trophic dynamics in 1942 by Raymond L. Lindeman . The basis of trophic dynamics is the transfer of energy from one part of

8360-467: The water. The eggs hatch into aquatic larvae called tadpoles that have tails and internal gills . They have highly specialised rasping mouth parts suitable for herbivorous , omnivorous or planktivorous diets. The life cycle is completed when they metamorphose into adults. A few species deposit eggs on land or bypass the tadpole stage. Adult frogs generally have a carnivorous diet consisting of small invertebrates , but omnivorous species exist and

8455-520: The web are called trophic links. The number of trophic links per consumer is a measure of food web connectance . Food chains are nested within the trophic links of food webs. Food chains are linear (noncyclic) feeding pathways that trace monophagous consumers from a base species up to the top consumer , which is usually a larger predatory carnivore. Linkages connect to nodes in a food web, which are aggregates of biological taxa called trophic species . Trophic species are functional groups that have

8550-467: The web. Basal species can be autotrophs or detritivores , including "decomposing organic material and its associated microorganisms which we defined as detritus, micro-inorganic material and associated microorganisms (MIP), and vascular plant material." Most autotrophs capture the sun's energy in chlorophyll , but some autotrophs (the chemolithotrophs ) obtain energy by the chemical oxidation of inorganic compounds and can grow in dark environments, such as

8645-543: The word toad , first attested as Old English tādige , is unique to English and is likewise of uncertain etymology. It is the basis for the word tadpole , first attested as Middle English taddepol , apparently meaning 'toad-head'. About 88% of amphibian species are classified in the order Anura. These include over 7,700 species in 59 families , of which the Hylidae (1062 spp.), Strabomantidae (807 spp.), Microhylidae (758 spp.), and Bufonidae (657 spp.) are

8740-438: The world. The suborder Neobatrachia is further divided into the two superfamilies Hyloidea and Ranoidea . This classification is based on such morphological features as the number of vertebrae, the structure of the pectoral girdle , and the morphology of tadpoles. While this classification is largely accepted, relationships among families of frogs are still debated. Some species of anurans hybridise readily. For instance,

8835-540: Was already commonplace. The evolution of modern Anura likely was complete by the Jurassic period. Since then, evolutionary changes in chromosome numbers have taken place about 20 times faster in mammals than in frogs, which means speciation is occurring more rapidly in mammals. According to genetic studies, the families Hyloidea , Microhylidae , and the clade Natatanura (comprising about 88% of living frogs) diversified simultaneously some 66 million years ago, soon after

8930-473: Was hailed as a missing link , a stem batrachian close to the common ancestor of frogs and salamanders, consistent with the widely accepted hypothesis that frogs and salamanders are more closely related to each other (forming a clade called Batrachia) than they are to caecilians. However, others have suggested that Gerobatrachus hottoni was only a dissorophoid temnospondyl unrelated to extant amphibians. Salientia (Latin salire ( salio ), "to jump")

9025-520: Was replaced by 'food web' in a subsequent ecological text. Elton organized species into functional groups , which was the basis for Raymond Lindeman 's classic and landmark paper in 1942 on trophic dynamics. Lindeman emphasized the important role of decomposer organisms in a trophic system of classification . The notion of a food web has a historical foothold in the writings of Charles Darwin and his terminology, including an "entangled bank", "web of life", "web of complex relations", and in reference to

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