River ecosystems are flowing waters that drain the landscape, include the biotic interactions amongst plants and micro-organisms, as well as abiotic physical and chemical interactions of its many parts. River ecosystems are part of larger watershed networks or catchments, where smaller headwater streams drain into mid-size streams, which progressively drain into larger river networks. River ecosystems are prime examples of lotic ecosystems. Lotic refers from the Latin lotus, meaning washed. Lotic waters range from springs only a few centimeters wide to major rivers kilometers in width. Much of this article applies to lotic ecosystems in general, including related lotic systems such as streams and springs. Lotic ecosystems can be contrasted with lentic ecosystems, which involve still terrestrial waters such as lakes and wetlands. Together, these two ecosystems form the more general study area of freshwater or aquatic ecology; the following unifying characteristics make the ecology of running waters unique among aquatic habitats.
Flow is unidirectional. There is a state of continuous physical change. There is a high degree of temporal heterogeneity at all scales. Variability between lotic systems is quite high; the biota is specialized to live with flow conditions. The non living components of an ecosystem are called abiotic components. E.g stone,air,soil,etc. Unidirectional water flow is the key factor in lotic systems influencing their ecology. Stream flow can be intermittent, though. Stream flow is the result of the summative inputs from groundwater and overland flow. Water flow can vary between systems, ranging from torrential rapids to slow backwaters that seem like lentic systems; the speed or velocity of the water flow of the water column can vary within a system and is subject to chaotic turbulence, though water velocity tends to be highest in the middle part of the stream channel. This turbulence results in divergences of flow from the mean downslope flow vector as typified by eddy currents; the mean flow rate vector is based on variability of friction with the bottom or sides of the channel, sinuosity and the incline gradient.
In addition, the amount of water input into the system from direct precipitation, and/or groundwater can affect flow rate. The amount of water in a stream is measured as discharge; as water flows downstream and rivers most gain water volume, so at base flow, smaller headwater streams have low discharge, while larger rivers have much higher discharge. The "flow regime" of a river or stream includes the general patterns of discharge over annual or decadal time scales, may capture seasonal changes in flow. While water flow is determined by slope, flowing waters can alter the general shape or direction of the stream bed, a characteristic known as geomorphology; the profile of the river water column is made up of three primary actions: erosion and deposition. Rivers have been described as "the gutters down which run the ruins of continents". Rivers are continuously eroding and depositing substrate and organic material; the continuous movement of water and entrained material creates a variety of habitats, including riffles and pools.
Light is important to lotic systems, because it provides the energy necessary to drive primary production via photosynthesis, can provide refuge for prey species in shadows it casts. The amount of light that a system receives can be related to a combination of internal and external stream variables; the area surrounding a small stream, for example, might be shaded by surrounding forests or by valley walls. Larger river systems tend to be wide so the influence of external variables is minimized, the sun reaches the surface; these rivers tend to be more turbulent and particles in the water attenuate light as depth increases. Seasonal and diurnal factors might play a role in light availability because the angle of incidence, the angle at which light strikes water can lead to light lost from reflection. Known as Beer's Law, the shallower the angle, the more light is reflected and the amount of solar radiation received declines logarithmically with depth. Additional influences on light availability include cloud cover and geographic position.
Most lotic species are poikilotherms whose internal temperature varies with their environment, thus temperature is a key abiotic factor for them. Water can be heated or cooled through radiation at the surface and conduction to or from the air and surrounding substrate. Shallow streams are well mixed and maintain a uniform temperature within an area. In deeper, slower moving water systems, however, a strong difference between the bottom and surface temperatures may develop. Spring fed systems have little variation as springs are from groundwater sources, which are very close to ambient temperature. Many systems show strong diurnal fluctuations and seasonal variations are most extreme in arctic and temperate systems; the amount of shading and elevation can influence the temperature of lotic systems. Water chemistry in river ecosystems varies depending on which dissolved solutes and gases are present in the water column of the stream. River water can include, apart from the water itself, dissolved inorganic matter and major ions dissolved inorganic nutrients suspended and dissolved organic matter gases (nitrogen, nitrous oxide, carbon dioxide, oxyge
Dicranomyia is a genus of crane fly in the family Limoniidae. Catalogue of the Craneflies of the World
Endopterygota known as Holometabola, is a superorder of insects within the infraclass Neoptera that go through distinctive larval and adult stages. They undergo a radical metamorphosis, with the larval and adult stages differing in their structure and behaviour; this is called complete metamorphism. The Endopterygota are among the most diverse insect superorders, with over 1 Million living species divided between 11 orders, containing insects such as butterflies, fleas, bees and beetles, they are distinguished from the Exopterygota by the way. Endopterygota develop wings inside the body and undergo an elaborate metamorphosis involving a pupal stage. Exopterygota develop; the latter trait is plesiomorphic and not found in the exopterygotes, but in groups such as Odonata, which are not Neoptera, but more basal among insects. The earliest endopterygote fossils date from the Carboniferous. ITIS considers any subdivision of the Neoptera beyond the orders invalid, but this is universally rejected; the Endopterygota are sometimes divided into three assemblages: Neuropteroida and Panorpida.
The hymenopterans, with their developed social systems, were believed to have constituted the most advanced insects, despite their rather "primitive" anatomy compared to flies and beetles, for example. More this has been rejected and DNA sequence data seem to verify that the hymenopterans are indeed among the most basal endopterygotes, whereas flies and fleas are considered the most radically advanced insects; this calls the previous subdivision into question, several new taxa have been proposed, splitting up the Endopterygota. While some groups seem indeed to be good clades, it is not that the relationships of the endopterygotes, or the neopteran insects in general, will be resolved in detail soon. Incertae sedis Glosselytrodea Miomoptera Insect morphology Holometabolism
Amber is fossilized tree resin, appreciated for its color and natural beauty since Neolithic times. Much valued from antiquity to the present as a gemstone, amber is made into a variety of decorative objects. Amber is used in jewelry, it has been used as a healing agent in folk medicine. There are five classes of amber, defined on the basis of their chemical constituents; because it originates as a soft, sticky tree resin, amber sometimes contains animal and plant material as inclusions. Amber occurring in coal seams is called resinite, the term ambrite is applied to that found within New Zealand coal seams; the English word amber derives from Arabic ʿanbar عنبر via Middle Latin ambar and Middle French ambre. The word was adopted in Middle English in the 14th century as referring to what is now known as ambergris, a solid waxy substance derived from the sperm whale. In the Romance languages, the sense of the word had come to be extended to Baltic amber from as early as the late 13th century. At first called white or yellow amber, this meaning was adopted in English by the early 15th century.
As the use of ambergris waned, this became the main sense of the word. The two substances conceivably became associated or confused because they both were found washed up on beaches. Ambergris is less dense than water and floats, whereas amber is too dense to float, though less dense than stone; the classical names for amber, Latin electrum and Ancient Greek ἤλεκτρον, are connected to a term ἠλέκτωρ meaning "beaming Sun". According to myth, when Phaëton son of Helios was killed, his mourning sisters became poplar trees, their tears became elektron, amber; the word elektron gave rise to the words electric and their relatives because of amber's ability to bear a static electricity charge. Theophrastus discussed amber in the 4th century BC, as did Pytheas, whose work "On the Ocean" is lost, but was referenced by Pliny the Elder, according to whose The Natural History: Pytheas says that the Gutones, a people of Germany, inhabit the shores of an estuary of the Ocean called Mentonomon, their territory extending a distance of six thousand stadia.
Earlier Pliny says that Pytheas refers to a large island - three days' sail from the Scythian coast and called Balcia by Xenophon of Lampsacus - as Basilia - a name equated with Abalus. Given the presence of amber, the island could have been Heligoland, the shores of Bay of Gdansk, the Sambia Peninsula or the Curonian Lagoon, which were the richest sources of amber in northern Europe, it is assumed that there were well-established trade routes for amber connecting the Baltic with the Mediterranean. Pliny states explicitly that the Germans exported amber to Pannonia, from where the Veneti distributed it onwards; the ancient Italic peoples of southern Italy used to work amber. Amber used in antiquity as at Mycenae and in the prehistory of the Mediterranean comes from deposits of Sicily. Pliny cites the opinion of Nicias, according to whom amberis a liquid produced by the rays of the sun. Besides the fanciful explanations according to which amber is "produced by the Sun", Pliny cites opinions that are well aware of its origin in tree resin, citing the native Latin name of succinum.
In Book 37, section XI of Natural History, Pliny wrote: Amber is produced from a marrow discharged by trees belonging to the pine genus, like gum from the cherry, resin from the ordinary pine. It is a liquid at first, which issues forth in considerable quantities, is hardened Our forefathers, were of opinion that it is the juice of a tree, for this reason gave it the name of "succinum" and one great proof that it is the produce of a tree of the pine genus, is the fact that it emits a pine-like smell when rubbed, that it burns, when ignited, with the odour and appearance of torch-pine wood, he states that amber is found in Egypt and in India, he refers to the electrostatic properties of amber, by saying that "in Syria the women make the whorls of their spindles of this substance, give it the name of harpax from the circumstance that it attracts leaves towards it, the light fringe of tissues". Pliny says that the German name of amber was glæsum, "for which reason the Romans, when Germanicus Caesar commanded the fleet in those parts, gave to one of these islands the name of Glæsaria, which by the barbarians was known as Austeravia".
This is confirmed by the recorded Old High German word glas and by the Old English word glær for "amber". In Middle Low German, amber was known as berne-, barn-, börnstēn; the Low German term became dominant in High Germ
Limnophila schranki is a cranefly in the family Limoniidae. It is a Palearctic species with a limited distribution in Europe, it is found in a wide range of habitats and micro habitats: in earth rich in humus, in swamps and marshes, along streams, in leaf litter and in wet spots in woods. Ecology of Commanster
The Tipulomorpha are an infraorder of Nematocera, containing the crane flies, a large group, allied families. One recent classification based on fossils splits this group into a series of extinct superfamilies, includes members of other infraorders, but this has not gained wide acceptance. Superfamily Eopolyneuroidea Family Eopolyneuridae - Family Musidoromimidae - Superfamily Tipulodictyoidea extinct Family Tipulodictyidae - Superfamily Tanyderophryneoidea extinct Family Tanyderophryneidae - Superfamily Tipuloidea Family Architipulidae extinct - Family Eolimnobiidae extinct Superfamily Eoptychopteroidea extinct Family Eoptychopteridae - Tree of Life Tipulomorpha
The Jurassic period was a geologic period and system that spanned 56 million years from the end of the Triassic Period 201.3 million years ago to the beginning of the Cretaceous Period 145 Mya. The Jurassic constitutes the middle period of the Mesozoic Era known as the Age of Reptiles; the start of the period was marked by the major Triassic–Jurassic extinction event. Two other extinction events occurred during the period: the Pliensbachian-Toarcian extinction in the Early Jurassic, the Tithonian event at the end; the Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations; the Jurassic is named after the Jura Mountains within the European Alps, where limestone strata from the period were first identified. By the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses: Laurasia to the north, Gondwana to the south; this created more coastlines and shifted the continental climate from dry to humid, many of the arid deserts of the Triassic were replaced by lush rainforests.
On land, the fauna transitioned from the Triassic fauna, dominated by both dinosauromorph and crocodylomorph archosaurs, to one dominated by dinosaurs alone. The first birds appeared during the Jurassic, having evolved from a branch of theropod dinosaurs. Other major events include the appearance of the earliest lizards, the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to an aquatic mode of life; the oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, while pterosaurs were the dominant flying vertebrates. The chronostratigraphic term "Jurassic" is directly linked to the Jura Mountains, a mountain range following the course of the France–Switzerland border. During a tour of the region in 1795, Alexander von Humboldt recognized the limestone dominated mountain range of the Jura Mountains as a separate formation that had not been included in the established stratigraphic system defined by Abraham Gottlob Werner, he named it "Jura-Kalkstein" in 1799.
The name "Jura" is derived from the Celtic root *jor via Gaulish *iuris "wooded mountain", borrowed into Latin as a place name, evolved into Juria and Jura. The Jurassic period is divided into three epochs: Early and Late. In stratigraphy, the Jurassic is divided into the Lower Jurassic, Middle Jurassic, Upper Jurassic series of rock formations known as Lias and Malm in Europe; the separation of the term Jurassic into three sections originated with Leopold von Buch. The faunal stages from youngest to oldest are: During the early Jurassic period, the supercontinent Pangaea broke up into the northern supercontinent Laurasia and the southern supercontinent Gondwana; the Jurassic North Atlantic Ocean was narrow, while the South Atlantic did not open until the following Cretaceous period, when Gondwana itself rifted apart. The Tethys Sea closed, the Neotethys basin appeared. Climates were warm, with no evidence of a glacier having appeared; as in the Triassic, there was no land over either pole, no extensive ice caps existed.
The Jurassic geological record is good in western Europe, where extensive marine sequences indicate a time when much of that future landmass was submerged under shallow tropical seas. In contrast, the North American Jurassic record is the poorest of the Mesozoic, with few outcrops at the surface. Though the epicontinental Sundance Sea left marine deposits in parts of the northern plains of the United States and Canada during the late Jurassic, most exposed sediments from this period are continental, such as the alluvial deposits of the Morrison Formation; the Jurassic was a time of calcite sea geochemistry in which low-magnesium calcite was the primary inorganic marine precipitate of calcium carbonate. Carbonate hardgrounds were thus common, along with calcitic ooids, calcitic cements, invertebrate faunas with dominantly calcitic skeletons; the first of several massive batholiths were emplaced in the northern American cordillera beginning in the mid-Jurassic, marking the Nevadan orogeny. Important Jurassic exposures are found in Russia, South America, Japan and the United Kingdom.
In Africa, Early Jurassic strata are distributed in a similar fashion to Late Triassic beds, with more common outcrops in the south and less common fossil beds which are predominated by tracks to the north. As the Jurassic proceeded and more iconic groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are neither well studied in Africa. Late Jurassic strata are poorly represented apart from the spectacular Tendaguru fauna in Tanzania; the Late Jurassic life of Tendaguru is similar to that found in western North America's Morrison Formation. During the Jurassic period, the primary vertebrates living in the sea were marine reptiles; the latter include ichthyosaurs, which were at the peak of their diversity, plesiosaurs and marine crocodiles of the families Teleosauridae and Metriorhynchidae. Numerous turtles could be found in rivers. In the invertebrate world, several new groups appeared, including rudists (a reef-formi