1.
Precambrian
–
The Precambrian is the earliest period of Earths history, set before the current Phanerozoic Eon. The Precambrian is a supereon that is subdivided into three eons of the time scale. It spans from the formation of Earth about 4.6 billion years ago to the beginning of the Cambrian Period, about 541 million years ago, the Precambrian accounts for 89% of geologic time. Relatively little is known about the Precambrian, despite it making up roughly seven-eighths of the Earths history, the Precambrian fossil record is poorer than that of the succeeding Phanerozoic, and fossils from that time are of limited biostratigraphic use. This is because many Precambrian rocks have been metamorphosed, obscuring their origins, while others have been destroyed by erosion. A stable crust was apparently in place by 4,412 Ma, the term Precambrian is recognized by the International Commission on Stratigraphy as a general term including the Archean and Proterozoic eons. It is still used by geologists and paleontologists for general discussions not requiring the more specific eon names and it was briefly called the Cryptozoic eon. A specific date for the origin of life has not been determined, carbon found in 3.8 billion year old rocks from islands off western Greenland may be of organic origin. Well-preserved microscopic fossils of bacteria older than 3.46 billion years have found in Western Australia. Probable fossils 100 million years older have been found in the same area, there is a fairly solid record of bacterial life throughout the remainder of the Precambrian. The oldest fossil evidence from that era of such complex life comes from the Lantian formation of the Ediacarian period, a very diverse collection of soft-bodied forms is found in a variety of locations worldwide and date to between 635 and 542 Ma. These are referred to as Ediacaran or Vendian biota, hard-shelled creatures appeared toward the end of that time span, marking the beginning of the Phanerozoic era. By the middle of the following Cambrian period, a diverse fauna is recorded in the Burgess Shale. The explosion in diversity of lifeforms during the early Cambrian is called the Cambrian explosion of life, while land seems to have been devoid of plants and animals, cyanobacteria and other microbes formed prokaryotic mats that covered terrestrial areas. Evidence of the details of plate motions and other activity in the Precambrian has been poorly preserved. It is generally believed that small proto-continents existed prior to 4280 Ma, the supercontinent, known as Rodinia, broke up around 750 Ma. A number of glacial periods have been identified going as far back as the Huronian epoch, one of the best studied is the Sturtian-Varangian glaciation, around 850–635 Ma, which may have brought glacial conditions all the way to the equator, resulting in a Snowball Earth. The atmosphere of the early Earth is not well understood, most geologists believe it was composed primarily of nitrogen, carbon dioxide, and other relatively inert gases, and was lacking in free oxygen
Precambrian
Precambrian
2.
Cambrian
–
The Cambrian Period was the first geological period of the Paleozoic Era, of the Phanerozoic Eon. The Cambrian lasted 55.6 million years from the end of the preceding Ediacaran Period 541 million years ago to the beginning of the Ordovician Period 485.4 mya and its subdivisions, and its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinised form of Cymru, the Welsh name for Wales, as a result, our understanding of the Cambrian biology surpasses that of some later periods. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia, the seas were relatively warm, and polar ice was absent for much of the period. The United States Federal Geographic Data Committee uses a barred capital C ⟨Є⟩ character similar to the capital letter Ukrainian Ye ⟨Є⟩ to represent the Cambrian Period, the proper Unicode character is U+A792 Ꞓ LATIN CAPITAL LETTER C WITH BAR. Despite the long recognition of its distinction from younger Ordovician Period rocks and older Supereon Precambrian rocks, the base of the Cambrian lies atop a complex assemblage of trace fossils known as the Treptichnus pedum assemblage. Pedum in Namibia, Spain and Newfoundland, and possibly, in the western USA, the stratigraphic range of T. pedum overlaps the range of the Ediacaran fossils in Namibia, and probably in Spain. The Cambrian Period followed the Ediacaran Period and was followed by the Ordovician Period, the Cambrian is divided into four epochs and ten ages. Currently only two series and five stages are named and have a GSSP, because the international stratigraphic subdivision is not yet complete, many local subdivisions are still widely used. In some of these subdivisions the Cambrian is divided into three epochs with locally differing names – the Early Cambrian, Middle Cambrian and Furongian, rocks of these epochs are referred to as belonging to the Lower, Middle, or Upper Cambrian. Trilobite zones allow biostratigraphic correlation in the Cambrian, each of the local epochs is divided into several stages. The International Commission on Stratigraphy list the Cambrian period as beginning at 541 million years ago, the lower boundary of the Cambrian was originally held to represent the first appearance of complex life, represented by trilobites. The recognition of small shelly fossils before the first trilobites, and Ediacara biota substantially earlier and this formal designation allowed radiometric dates to be obtained from samples across the globe that corresponded to the base of the Cambrian. Early dates of 570 million years ago quickly gained favour, though the used to obtain this number are now considered to be unsuitable. A more precise date using modern radiometric dating yield a date of 541 ±0.3 million years ago, most continental land was clustered in the Southern Hemisphere at this time, but was drifting north. Large, high-velocity rotational movement of Gondwana appears to have occurred in the Early Cambrian, the sea levels fluctuated somewhat, suggesting there were ice ages, associated with pulses of expansion and contraction of a south polar ice cap. In Baltoscandia a Lower Cambrian transgression transformed large swathes of the Sub-Cambrian peneplain into a epicontinental sea, the Earth was generally cold during the early Cambrian, probably due to the ancient continent of Gondwana covering the South Pole and cutting off polar ocean currents
Cambrian
–
Archeocyathids from the
Poleta formation in the
Death Valley area
Cambrian
–
Stromatolites of the Pika Formation (Middle Cambrian) near Helen Lake, Banff National Park, Canada
Cambrian
–
Trilobites were very common during this time
Cambrian
–
Anomalocaris was an early marine predator, among the various
arthropods of the time.
3.
Ordovician
–
The Ordovician is a geologic period and system, the second of six periods of the Paleozoic Era. The Ordovician spans 41.2 million years from the end of the Cambrian Period 485.4 million years ago to the start of the Silurian Period 443.8 Mya. Lapworth recognized that the fauna in the disputed strata were different from those of either the Cambrian or the Silurian periods. It received international sanction in 1960, when it was adopted as a period of the Paleozoic Era by the International Geological Congress. Life continued to flourish during the Ordovician as it did in the earlier Cambrian period, invertebrates, namely molluscs and arthropods, dominated the oceans. The Great Ordovician Biodiversification Event considerably increased the diversity of life, fish, the worlds first true vertebrates, continued to evolve, and those with jaws may have first appeared late in the period. Life had yet to diversify on land, about 100 times as many meteorites struck the Earth during the Ordovician compared with today. The Ordovician Period began with a major extinction called the Cambrian–Ordovician extinction event and it lasted for about 42 million years and ended with the Ordovician–Silurian extinction event, about 443.8 Mya which wiped out 60% of marine genera. The dates given are recent radiometric dates and vary slightly from those found in other sources and this second period of the Paleozoic era created abundant fossils that became major petroleum and gas reservoirs. The boundary chosen for the beginning of both the Ordovician Period and the Tremadocian stage is highly significant and it correlates well with the occurrence of widespread graptolite, conodont, and trilobite species. The base of the Tremadocian allows scientists to relate these species not only to each other and this makes it easier to place many more species in time relative to the beginning of the Ordovician Period. A number of terms have been used to subdivide the Ordovician Period. In 2008, the ICS erected an international system of subdivisions. There exist Baltoscandic, British, Siberian, North American, Australian, the Ordovician Period in Britain was traditionally broken into Early, Middle and Late epochs. The corresponding rocks of the Ordovician System are referred to as coming from the Lower, Middle, the Floian corresponds to the lower Arenig, the Arenig continues until the early Darriwilian, subsuming the Dapingian. The Llanvirn occupies the rest of the Darriwilian, and terminates with it at the base of the Late Ordovician. The Sandbian represents the first half of the Caradoc, the Caradoc ends in the mid-Katian, during the Ordovician, the southern continents were collected into Gondwana. Gondwana started the period in equatorial latitudes and, as the period progressed, drifted toward the South Pole, the small continent Avalonia separated from Gondwana and began to move north towards Baltica and Laurentia, opening the Rheic Ocean between Gondwana and Avalonia
Ordovician
–
External mold of Ordovician
bivalve showing that the original
aragonite shell dissolved on the sea floor, leaving a cemented mold for biological encrustation (
Waynesville Formation of Franklin County, Indiana).
Ordovician
–
A
diorama depicting Ordovician flora and fauna.
Ordovician
–
Nautiloids like
Orthoceras were among the largest predators in the Ordovician.
Ordovician
–
Fossiliferous limestone slab from the Liberty Formation (Upper Ordovician) of Caesar Creek State Park near Waynesville, Ohio.
4.
Silurian
–
The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period,419.2 Mya. As with other periods, the rock beds that define the periods start and end are well identified. The base of the Silurian is set at a major Ordovician-Silurian extinction event when 60% of marine species were wiped out, a significant evolutionary milestone during the Silurian was the diversification of jawed and bony fish. However, terrestrial life would not greatly diversify and affect the landscape until the Devonian, the Silurian system was first identified by British geologist Sir Roderick Impey Murchison, who was examining fossil-bearing sedimentary rock strata in south Wales in the early 1830s. He named the sequences for a Celtic tribe of Wales, the Silures, inspired by his friend Adam Sedgwick and this naming does not indicate any correlation between the occurrence of the Silurian rocks and the land inhabited by the Silures. As it was first identified, the Silurian series when traced farther afield quickly came to overlap Sedgwicks Cambrian sequence, however, charles Lapworth resolved the conflict by defining a new Ordovician system including the contested beds. An early alternative name for the Silurian was Gotlandian after the strata of the Baltic island of Gotland, the French geologist Joachim Barrande, building on Murchisons work, used the term Silurian in a more comprehensive sense than was justified by subsequent knowledge. He divided the Silurian rocks of Bohemia into eight stages and his interpretation was questioned in 1854 by Edward Forbes, and the later stages of Barrande, F, G and H, have since been shown to be Devonian. Despite these modifications in the groupings of the strata, it is recognized that Barrande established Bohemia as a classic ground for the study of the earliest fossils. The epoch is named for the town of Llandovery in Carmarthenshire, the Wenlock, which lasted from 433.4 ±1.5 to 427.4 ±2.8 mya, is subdivided into the Sheinwoodian and Homerian ages. It is named after Wenlock Edge in Shropshire, England, during the Wenlock, the oldest known tracheophytes of the genus Cooksonia, appear. The first terrestrial animals also appear in the Wenlock, represented by air-breathing millipedes from Scotland. The Ludlow, lasting from 427.4 ±1.5 to 423 ±2.8 mya, comprises the Gorstian stage, lasting until 425.6 million years ago, and it is named for the town of Ludlow in Shropshire, England. The Pridoli, lasting from 423 ±1.5 to 419.2 ±2.8 mya, is the final and it is named after one locality at the Homolka a Přídolí nature reserve near the Prague suburb Slivenec in the Czech Republic. Přídolí is the old name of a field area. The high sea levels of the Silurian and the flat land resulted in a number of island chains. The southern continents remained united during this period, the melting of icecaps and glaciers contributed to a rise in sea level, recognizable from the fact that Silurian sediments overlie eroded Ordovician sediments, forming an unconformity. The continents of Avalonia, Baltica, and Laurentia drifted together near the equator and this event is the Caledonian orogeny, a spate of mountain building that stretched from New York State through conjoined Europe and Greenland to Norway
Silurian
–
Ordovician -Silurian boundary on
Hovedøya,
Norway, showing gray Ordovician
sandstone and brown Silurian
mudstone. The layers have been overturned by the
Caledonian orogeny.
Silurian
–
Marine extinction intensity during the
Phanerozoic
Silurian
–
Silurian sea bed fossils collected from Wren's Nest Nature Reserve, Dudley UK
Silurian
–
Crinoid fragments in a Silurian (Pridoli) limestone (
Saaremaa, Estonia)
5.
Devonian
–
The Devonian is a geologic period and system of the Paleozoic, spanning 60 million years from the end of the Silurian,419.2 million years ago, to the beginning of the Carboniferous,358.9 Mya. It is named after Devon, England, where rocks from this period were first studied, the first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents, by the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. Various terrestrial arthropods also became well-established, Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fish. The first ray-finned and lobe-finned bony fish appeared, while the placodermi began dominating almost every aquatic environment. The ancestors of all four-limbed vertebrates began adapting to walking on land, as their strong pectoral, in the oceans, primitive sharks became more numerous than in the Silurian and Late Ordovician. The first ammonites, species of molluscs, appeared, trilobites, the mollusk-like brachiopods and the great coral reefs, were still common. The Late Devonian extinction which started about 375 million years ago severely affected marine life, killing off all placodermi, and all trilobites, save for a few species of the order Proetida. The palaeogeography was dominated by the supercontinent of Gondwana to the south, the continent of Siberia to the north, while the rock beds that define the start and end of the Devonian period are well identified, the exact dates are uncertain. According to the International Commission on Stratigraphy, the Devonian extends from the end of the Silurian 419.2 Mya, another common term is Age of the Fishes, referring to the evolution of several major groups of fish that took place during the period. Older literature on the Anglo-Welsh basin divides it into the Downtonian, Dittonian, Breconian and Farlovian stages, in the Late Devonian, by contrast, arid conditions were less prevalent across the world and temperate climates were more common. The Devonian Period is formally broken into Early, Middle and Late subdivisions, the rocks corresponding to those epochs are referred to as belonging to the Lower, Middle and Upper parts of the Devonian System. Early Devonian The Early Devonian lasted from 419.2 ±2.8 to 393.3 ±2.5 and began with the Lochkovian stage, which lasted until the Pragian. It spanned from 410.8 ±2.8 to 407.6 ±2.5, and was followed by the Emsian, which lasted until the Middle Devonian began,393. 3±2.7 million years ago. Middle Devonian The Middle Devonian comprised two subdivisions, first the Eifelian, which gave way to the Givetian 387. 7±2.7 million years ago. Late Devonian Finally, the Late Devonian started with the Frasnian,382.7 ±2.8 to 372.2 ±2.5, during which the first forests took shape on land. The first tetrapods appeared in the record in the ensuing Famennian subdivision. This lasted until the end of the Devonian,358. 9±2.5 million years ago, the Devonian was a relatively warm period, and probably lacked any glaciers
Devonian
–
The rocks of Lummaton Quarry in
Torquay in Devon played an early role in defining the Devonian period.
Devonian
–
Dunkleosteus, one of the largest armoured fish to ever roam the planet, lived during the late Devonian
Devonian
–
Enrolled phacopid
trilobite from the Devonian of Ohio
Devonian
–
The common tabulate coral
Aulopora from the Middle Devonian of Ohio – view of colony origin encrusting a
brachiopod valve
6.
Carboniferous
–
The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period,298.9 Mya. The name Carboniferous means coal-bearing and derives from the Latin words carbō and ferō, and was coined by geologists William Conybeare and William Phillips in 1822. Based on a study of the British rock succession, it was the first of the system names to be employed. The Carboniferous is often treated in North America as two periods, the earlier Mississippian and the later Pennsylvanian. Terrestrial life was established by the Carboniferous period. Amphibians were the dominant land vertebrates, of one branch would eventually evolve into amniotes. Arthropods were also common, and many were much larger than those of today. Vast swaths of forest covered the land, which would eventually be laid down, the atmospheric content of oxygen also reached their highest levels in geological history during the period, 35% compared with 21% today, allowing terrestrial invertebrates to evolve to great size. A major marine and terrestrial extinction event, the Carboniferous rainforest collapse, occurred in the middle of the period, the later half of the period experienced glaciations, low sea level, and mountain building as the continents collided to form Pangaea. In the United States the Carboniferous is usually broken into Mississippian and Pennsylvanian subperiods, the Silesian is roughly contemporaneous with the late Mississippian Serpukhovian plus the Pennsylvanian. In Britain the Dinantian is traditionally known as the Carboniferous Limestone, the Namurian as the Millstone Grit, and the Westphalian as the Coal Measures and Pennant Sandstone. There was also a drop in south polar temperatures, southern Gondwanaland was glaciated throughout the period and these conditions apparently had little effect in the deep tropics, where lush swamps, later to become coal, flourished to within 30 degrees of the northernmost glaciers. Mid-Carboniferous, a drop in sea level precipitated a major extinction, one that hit crinoids. This sea level drop and the unconformity in North America separate the Mississippian subperiod from the Pennsylvanian subperiod. This happened about 323 million years ago, at the onset of the Permo-Carboniferous Glaciation, the Carboniferous was a time of active mountain-building, as the supercontinent Pangaea came together. The southern continents remained tied together in the supercontinent Gondwana, which collided with North America–Europe along the present line of eastern North America, in the same time frame, much of present eastern Eurasian plate welded itself to Europe along the line of the Ural mountains. Most of the Mesozoic supercontinent of Pangea was now assembled, although North China, the Late Carboniferous Pangaea was shaped like an O. There were two major oceans in the Carboniferous—Panthalassa and Paleo-Tethys, which was inside the O in the Carboniferous Pangaea, other minor oceans were shrinking and eventually closed - Rheic Ocean, the small, shallow Ural Ocean and Proto-Tethys Ocean
Carboniferous
–
Generalized geographic map of the
United States in Middle
Pennsylvanian time.
Carboniferous
–
Lower Carboniferous marble in Big Cottonwood Canyon,
Wasatch Mountains,
Utah.
Carboniferous
–
Etching depicting some of the most significant plants of the Carboniferous.
Carboniferous
–
Ancient in situ
lycopsid, probably
Sigillaria, with attached
stigmarian roots.
7.
Permian
–
The Permian is a geologic period and system which spans 46.7 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic Period 252.2 Mya. It is the last period of the Paleozoic Era, the following Triassic Period belongs to the Mesozoic Era, the concept of the Permian was introduced in 1841 by geologist Sir Roderick Murchison, who named it after the city of Perm. The Permian witnessed the diversification of the early amniotes into the groups of the mammals, turtles, lepidosaurs. The world at the time was dominated by two known as Pangaea and Siberia, surrounded by a global ocean called Panthalassa. The Carboniferous rainforest collapse left behind vast regions of desert within the continental interior, amniotes, who could better cope with these drier conditions, rose to dominance in place of their amphibian ancestors. The Permian ended with the Permian–Triassic extinction event, the largest mass extinction in Earths history, in which nearly 90% of marine species and it would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian-Triassic extinction event was protracted, on land, the term Permian was introduced into geology in 1841 by Sir R. I. Murchison, president of the Geological Society of London, who identified typical strata in extensive Russian explorations undertaken with Edouard de Verneuil, the region now lies in the Perm Krai of Russia. This could have in part caused the extinctions of marine species at the end of the period by severely reducing shallow coastal areas preferred by many marine organisms. During the Permian, all the Earths major landmasses were collected into a supercontinent known as Pangaea. The Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, a new ocean was growing on its southern end, the Tethys Ocean, an ocean that would dominate much of the Mesozoic Era. Large continental landmass interiors experience climates with extreme variations of heat and cold, deserts seem to have been widespread on Pangaea. Such dry conditions favored gymnosperms, plants with seeds enclosed in a cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian, the climate in the Permian was quite varied. At the start of the Permian, the Earth was still in an Ice Age, glaciers receded around the mid-Permian period as the climate gradually warmed, drying the continents interiors. In the late Permian period, the drying continued although the temperature cycled between warm and cool cycles, Permian marine deposits are rich in fossil mollusks, echinoderms, and brachiopods. By the close of the Permian, trilobites and a host of other groups became extinct. Terrestrial life in the Permian included diverse plants, fungi, arthropods, the period saw a massive desert covering the interior of Pangaea
Permian
–
Selwyn Rock, South Australia - an exhumed
glacial pavement of Permian age
Permian
–
Geography of the Permian world
Permian
–
Hercosestria cribrosa, a
reef -forming productid brachiopod (Middle Permian, Glass Mountains, Texas).
Permian
–
Edaphosaurus pogonias and
Platyhystrix - Early Permian, North America and Europe
8.
Triassic
–
The Triassic is a geologic period and system which spans 50.9 million years from the end of the Permian Period 252.17 million years ago, to the beginning of the Jurassic Period 201.3 Mya. The Triassic is the first period of the Mesozoic Era, both the start and end of the period are marked by major extinction events. Therapsids and archosaurs were the terrestrial vertebrates during this time. A specialized subgroup of archosaurs, called dinosaurs, first appeared in the Late Triassic, the vast supercontinent of Pangaea existed until the mid-Triassic, after which it began to gradually rift into two separate landmasses, Laurasia to the north and Gondwana to the south. The global climate during the Triassic was mostly hot and dry, however, the climate shifted and became more humid as Pangaea began to drift apart. The end of the period was marked by yet another mass extinction, the Triassic-Jurassic extinction event. The Triassic is usually separated into Early, Middle, and Late Triassic Epochs, from the east, along the equator, the Tethys sea penetrated Pangaea, causing the Paleo-Tethys Ocean to be closed. Later in the mid-Triassic a similar sea penetrated along the equator from the west, the remaining shores were surrounded by the world-ocean known as Panthalassa. All the deep-ocean sediments laid down during the Triassic have disappeared through subduction of oceanic plates, thus, the supercontinent Pangaea was rifting during the Triassic—especially late in that period—but had not yet separated. In North America, for example, marine deposits are limited to a few exposures in the west, thus Triassic stratigraphy is mostly based on organisms that lived in lagoons and hypersaline environments, such as Estheria crustaceans. At the beginning of the Mesozoic Era, Africa was joined with Earths other continents in Pangaea, Africa shared the supercontinents relatively uniform fauna which was dominated by theropods, prosauropods and primitive ornithischians by the close of the Triassic period. Late Triassic fossils are found throughout Africa, but are common in the south than north. The time boundary separating the Permian and Triassic marks the advent of an event with global impact. At Paleorrota geopark, located in Rio Grande do Sul, Brazil, in these formations, one of the earliest dinosaurs, Staurikosaurus, as well as the mammal ancestors Brasilitherium and Brasilodon have been discovered. The Triassic continental interior climate was hot and dry, so that typical deposits are red bed sandstones and evaporites. Pangaeas large size limited the effect of the global ocean, its continental climate was highly seasonal, with very hot summers. The strong contrast between the Pangea supercontinent and the global ocean triggered intense cross-equatorial monsoons, the best studied of such episodes of humid climate, and probably the most intense and widespread, was the Carnian Pluvial Event. On land, the vascular plants included the lycophytes, the dominant cycadophytes, ginkgophyta, ferns, horsetails
Triassic
–
Triassic flora as depicted in
Meyers Konversations-Lexikon (1885–90)
Triassic
–
230 Ma plate tectonic reconstruction
Triassic
–
Middle Triassic marginal marine sequence, southwestern
Utah
Triassic
–
Staurikosaurus feeding on a dicynodont, in geopark Paleorrota.
9.
Jurassic
–
The Jurassic is a geologic period and system that spans 56.3 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, also known as the Age of Reptiles, the start of the period is marked by the major Triassic–Jurassic extinction event. The Jurassic is named after the Jura Mountains within the European Alps, by the beginning of the Jurassic, the supercontinent Pangaea had begun rifting into two landmasses, Laurasia to the north and Gondwana to the south. This created more coastlines and shifted the continental climate from dry to humid, 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 also appeared during the Jurassic, having evolved from a branch of theropod dinosaurs, other major events include the appearance of the earliest lizards, and the evolution of therian mammals, including primitive placentals. Crocodilians made the transition from a terrestrial to a mode of life. The oceans were inhabited by marine reptiles such as ichthyosaurs and plesiosaurs, the chronostratigraphic term Jurassic is directly linked to the Jura Mountains. The name Jura is derived from the Celtic root jor, which was Latinised into juria, the Jurassic period is divided into the Early Jurassic, Middle, and Late Jurassic epochs. The Jurassic System, in stratigraphy, is divided into the Lower Jurassic, Middle, the separation of the term Jurassic into three sections goes back to Leopold von Buch. The Jurassic North Atlantic Ocean was relatively narrow, while the South Atlantic did not open until the following Cretaceous period, the Tethys Sea closed, and the Neotethys basin appeared. Climates were warm, with no evidence of glaciation, as in the Triassic, there was apparently no land over either pole, and no extensive ice caps existed. In contrast, the North American Jurassic record is the poorest of the Mesozoic, 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 very common, along with calcitic ooids, calcitic cements, 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, India, South America, Japan, Australasia. As the Jurassic proceeded, larger and more groups of dinosaurs like sauropods and ornithopods proliferated in Africa. Middle Jurassic strata are well represented nor well studied in Africa. Late Jurassic strata are also poorly represented apart from the spectacular Tendaguru fauna in Tanzania, the Late Jurassic life of Tendaguru is very similar to that found in western North Americas Morrison Formation. During the Jurassic period, the primary living in the sea were fish
Jurassic
–
Various
dinosaurs roamed forests of similarly large
conifers during the Jurassic period.
Jurassic
–
Jurassic limestones and marls (the
Matmor Formation) in southern
Israel.
Jurassic
–
The late Jurassic
Morrison Formation in
Colorado is one of the most fertile sources of dinosaur fossils in North America.
Jurassic
–
Gigandipus, a
dinosaur footprint in the Lower Jurassic
Moenave Formation at the St. George Dinosaur Discovery Site at Johnson Farm, southwestern
Utah.
10.
Cretaceous
–
The Cretaceous is a geologic period and system that spans 79 million years from the end of the Jurassic Period 145 million years ago to the beginning of the Paleogene Period 66 Mya. It is the last period of the Mesozoic Era, the Cretaceous Period is usually abbreviated K, for its German translation Kreide. The Cretaceous was a period with a warm climate, resulting in high eustatic sea levels that created numerous shallow inland seas. These oceans and seas were populated with now-extinct marine reptiles, ammonites and rudists, during this time, new groups of mammals and birds, as well as flowering plants, appeared. The Cretaceous ended with a mass extinction, the Cretaceous–Paleogene extinction event, in which many groups, including non-avian dinosaurs, pterosaurs. The end of the Cretaceous is defined by the abrupt Cretaceous–Paleogene boundary, the name Cretaceous was derived from Latin creta, meaning chalk. The Cretaceous is divided into Early and Late Cretaceous epochs, or Lower and Upper Cretaceous series, in older literature the Cretaceous is sometimes divided into three series, Neocomian, Gallic and Senonian. A subdivision in eleven stages, all originating from European stratigraphy, is now used worldwide, in many parts of the world, alternative local subdivisions are still in use. As with other geologic periods, the rock beds of the Cretaceous are well identified. No great extinction or burst of diversity separates the Cretaceous from the Jurassic and this layer has been dated at 66.043 Ma. A140 Ma age for the Jurassic-Cretaceous boundary instead of the usually accepted 145 Ma was proposed in 2014 based on a study of Vaca Muerta Formation in Neuquén Basin. Víctor Ramos, one of the authors of the study proposing the 140 Ma boundary age sees the study as a first step toward formally changing the age in the International Union of Geological Sciences, due to the high sea level there was extensive space for such sedimentation. Because of the young age and great thickness of the system. Chalk is a type characteristic for the Cretaceous. It consists of coccoliths, microscopically small calcite skeletons of coccolithophores, the group is found in England, northern France, the low countries, northern Germany, Denmark and in the subsurface of the southern part of the North Sea. Chalk is not easily consolidated and the Chalk Group still consists of sediments in many places. The group also has other limestones and arenites, among the fossils it contains are sea urchins, belemnites, ammonites and sea reptiles such as Mosasaurus. In southern Europe, the Cretaceous is usually a marine system consisting of competent limestone beds or incompetent marls
Cretaceous
–
Drawing of fossil jaws of
Mosasaurus hoffmanni, from the
Maastrichtian of
Dutch Limburg, by Dutch geologist
Pieter Harting (1866).
Cretaceous
–
Although the first representatives of leafy trees and true grasses emerged in the Cretaceous, the flora was still dominated by conifers like
Araucaria (Here: Modern Araucaria araucana in Chile).
Cretaceous
–
Tyrannosaurus rex, one of the largest land predators of all time, lived during the late Cretaceous.
Cretaceous
–
Up to 2 m-long
Velociraptor was likely feathered and roamed the late Cretaceous.
11.
Paleogene
–
The Paleogene is a geologic period and system that spans 43 million years from the end of the Cretaceous Period 66 million years ago to the beginning of the Neogene Period 23.03 Mya. It is the beginning of the Cenozoic Era of the present Phanerozoic Eon and this period consists of the Paleocene, Eocene and Oligocene epochs. The terms Paleogene System and lower Tertiary System are applied to the rocks deposited during the Paleogene Period. By dividing the Tertiary Period into two periods instead of directly into five epochs, the periods are more comparable to the duration of periods of the preceding Mesozoic and Paleozoic Eras. The trend was caused by the formation of the Antarctic Circumpolar Current. During the Paleogene, the continued to drift closer to their current positions. India was in the process of colliding with Asia, subsequently forming the Himalayas, the Atlantic Ocean continued to widen by a few centimeters each year. Africa was moving north to meet with Europe and form the Mediterranean, inland seas retreated from North America early in the period. Australia had also separated from Antarctica and was drifting towards Southeast Asia, mammals began a rapid diversification during this period. Some of these mammals would evolve into forms that would dominate the land, while others would become capable of living in marine, specialized terrestrial. Those that took to the oceans became modern cetaceans, while those that took to the trees became primates, the group to which humans belong. Birds, which were well established by the end of the Cretaceous. In comparison to birds and mammals, most other branches of life remained unchanged during this period. As the Earth cooled, tropical plants became less numerous and were now restricted to equatorial regions, deciduous plants, which could survive through the seasonal climates the world was now experiencing, became more common. The Paleogene is notable in the context of offshore oil drilling, and especially in Gulf of Mexico oil exploration and these rock formations represent the current cutting edge of deep-water oil discovery. Lower Tertiary explorations to date include, Kaskida Oil Field Tiber Oil Field Jack 2 Paleogene Microfossils, 180+ images of Foraminifera
Paleogene
–
Scene featuring typical Eocene (Mid-Paleogene) flora and fauna
12.
Neogene
–
The Neogene is a geologic period and system that spans 20.45 million years from the end of the Paleogene Period 23.03 million years ago to the beginning of the present Quaternary Period 2.58 Mya. The Neogene is sub-divided into two epochs, the earlier Miocene and the later Pliocene, some geologists assert that the Neogene cannot be clearly delineated from the modern geological period, the Quaternary. During this period, mammals and birds continued to evolve into modern forms. Early hominids, the ancestors of humans, appeared in Africa near the end of the period, some continental movement took place, the most significant event being the connection of North and South America at the Isthmus of Panama, late in the Pliocene. This cut off the ocean currents from the Pacific to the Atlantic ocean. The global climate cooled considerably over the course of the Neogene, the terms Neogene System and upper Tertiary System describe the rocks deposited during the Neogene Period. The continents in the Neogene were very close to their current positions, the Isthmus of Panama formed, connecting North and South America. The Indian subcontinent continued to collide with Asia, forming the Himalayas, sea levels fell, creating land bridges between Africa and Eurasia and between Eurasia and North America. The global climate became seasonal and continued an overall drying and cooling trend which began at the start of the Paleogene. The ice caps on both poles began to grow and thicken, and by the end of the period the first of a series of glaciations of the current Ice Age began, marine and continental flora and fauna have a modern appearance. The reptile group Choristodera became extinct in the part of the period. Mammals and birds continued to be the dominant terrestrial vertebrates, the first hominids, the ancestors of humans, appeared in Africa and spread into Eurasia. In response to the cooler, seasonal climate, tropical plant species gave way to deciduous ones, grasses therefore greatly diversified, and herbivorous mammals evolved alongside it, creating the many grazing animals of today such as horses, antelope, and bison. The Neogene traditionally ended at the end of the Pliocene Epoch, just before the definition of the beginning of the Quaternary Period. However, there was a movement amongst geologists to also include ongoing geological time in the Neogene, by dividing the Cenozoic Era into three periods instead of seven epochs, the periods are more closely comparable to the duration of periods in the Mesozoic and Paleozoic eras. The International Commission on Stratigraphy once proposed that the Quaternary be considered a sub-era of the Neogene, with a date of 2.58 Ma. In the 2004 proposal of the ICS, the Neogene would have consisted of the Miocene and Pliocene epochs, thus the Neogene Period ends bounding the succeeding Quaternary Period at 2.58 Mya. Digital Atlas of Neogene Life for the Southeastern United States — by San Jose State University via Web Archive
Neogene
–
Scene featuring Miocene (Early Neogene) fauna
13.
Chthamalus stellatus
–
Chthamalus stellatus, common name Polis stellate barnacle, is a species of acorn barnacle common on rocky shores in South West England, Ireland, and Southern Europe. It is named after Giuseppe Saverio Poli, C. stellatus is a sessile barnacle that attaches to rocks and other firm materials in the intertidal zone using its membranous base. It is basically cone-shaped but can assume a more tubular shape in a crowded colony, like other sessile barnacles, as an adult C. The chalky white shell of C. stellatus has a kite-shaped opercular opening when it is a juvenile, the shell is made up of six solid wall plates of approximately equal size. Its relatively narrow rostral plates remain separate from its rostrolateral plates, C. stellatus has bright blue tissue with black and orange markings which can be seen when its opercular aperture is not tightly closed. Depending upon environmental conditions and the amount of available, it can reach up to 14 millimetres in diameter. Like most barnacles, C. stellatus is hermaphroditic and capable of self-fertilisation when isolated and their penises are significantly longer than their bodies and are used by the stationary functional males to search the area for an equally stationary functional female neighbour to fertilise. Barnacles of this species produce about 1,000 to 4,000 eggs per brood when functioning as female, the fertilised eggs remain inside the shell of the adult until they are released as nauplii, free swimming larvae which float on currents along with other plankton. After several moults they metamorphose into a cyprid, a stage at which they cannot feed, the cyprid swims in search of a suitable surface on which to attach itself, head first, in order to metamorphose into the familiar, hard-shelled, immobile form. The duration of its breeding season can be dependent. C. stellatus attaches to exposed rocky shores in the mid to low eulittoral zone in the northeastern Atlantic Ocean and it especially favours islands and headlands as opposed to bays and more protected areas. It is a southern, warm-water species but has discovered as far north as Shetland
Chthamalus stellatus
–
Chthamalus stellatus
14.
Taxonomy (biology)
–
Taxonomy is the science of defining groups of biological organisms on the basis of shared characteristics and giving names to those groups. The exact definition of taxonomy varies from source to source, but the core of the remains, the conception, naming. There is some disagreement as to whether biological nomenclature is considered a part of taxonomy, the broadest meaning of taxonomy is used here. The word taxonomy was introduced in 1813 by Candolle, in his Théorie élémentaire de la botanique, the term alpha taxonomy is primarily used today to refer to the discipline of finding, describing, and naming taxa, particularly species. In earlier literature, the term had a different meaning, referring to morphological taxonomy, ideals can, it may be said, never be completely realized. They have, however, a value of acting as permanent stimulants. Some of us please ourselves by thinking we are now groping in a beta taxonomy, turrill thus explicitly excludes from alpha taxonomy various areas of study that he includes within taxonomy as a whole, such as ecology, physiology, genetics, and cytology. He further excludes phylogenetic reconstruction from alpha taxonomy, thus, Ernst Mayr in 1968 defined beta taxonomy as the classification of ranks higher than species. This activity is what the term denotes, it is also referred to as beta taxonomy. How species should be defined in a group of organisms gives rise to practical and theoretical problems that are referred to as the species problem. The scientific work of deciding how to define species has been called microtaxonomy, by extension, macrotaxonomy is the study of groups at higher taxonomic ranks, from subgenus and above only, than species. While some descriptions of taxonomic history attempt to date taxonomy to ancient civilizations, earlier works were primarily descriptive, and focused on plants that were useful in agriculture or medicine. There are a number of stages in scientific thinking. Early taxonomy was based on criteria, the so-called artificial systems. Later came systems based on a complete consideration of the characteristics of taxa, referred to as natural systems, such as those of de Jussieu, de Candolle and Bentham. The publication of Charles Darwins Origin of Species led to new ways of thinking about classification based on evolutionary relationships and this was the concept of phyletic systems, from 1883 onwards. This approach was typified by those of Eichler and Engler, the advent of molecular genetics and statistical methodology allowed the creation of the modern era of phylogenetic systems based on cladistics, rather than morphology alone. Taxonomy has been called the worlds oldest profession, and naming and classifying our surroundings has likely been taking place as long as mankind has been able to communicate
Taxonomy (biology)
–
Title page of
Systema Naturae, Leiden, 1735
Taxonomy (biology)
–
Evolution of the
vertebrates at class level, width of spindles indicating number of families. Spindle diagrams are typical for
Evolutionary taxonomy
Taxonomy (biology)
–
The same relationship, expressed as a
cladogram typical for
cladistics
Taxonomy (biology)
–
Type specimen for
Nepenthes smilesii, a tropical
pitcher plant.
15.
Animal
–
Animals are multicellular, eukaryotic organisms of the kingdom Animalia. The animal kingdom emerged as a clade within Apoikozoa as the group to the choanoflagellates. Animals are motile, meaning they can move spontaneously and independently at some point in their lives and their body plan eventually becomes fixed as they develop, although some undergo a process of metamorphosis later in their lives. All animals are heterotrophs, they must ingest other organisms or their products for sustenance, most known animal phyla appeared in the fossil record as marine species during the Cambrian explosion, about 542 million years ago. Animals can be divided broadly into vertebrates and invertebrates, vertebrates have a backbone or spine, and amount to less than five percent of all described animal species. They include fish, amphibians, reptiles, birds and mammals, the remaining animals are the invertebrates, which lack a backbone. These include molluscs, arthropods, annelids, nematodes, flatworms, cnidarians, ctenophores, the study of animals is called zoology. The word animal comes from the Latin animalis, meaning having breath, the biological definition of the word refers to all members of the kingdom Animalia, encompassing creatures as diverse as sponges, jellyfish, insects, and humans. Aristotle divided the world between animals and plants, and this was followed by Carl Linnaeus, in the first hierarchical classification. In Linnaeuss original scheme, the animals were one of three kingdoms, divided into the classes of Vermes, Insecta, Pisces, Amphibia, Aves, and Mammalia. Since then the last four have all been subsumed into a single phylum, in 1874, Ernst Haeckel divided the animal kingdom into two subkingdoms, Metazoa and Protozoa. The protozoa were later moved to the kingdom Protista, leaving only the metazoa, thus Metazoa is now considered a synonym of Animalia. Animals have several characteristics that set apart from other living things. Animals are eukaryotic and multicellular, which separates them from bacteria and they are heterotrophic, generally digesting food in an internal chamber, which separates them from plants and algae. They are also distinguished from plants, algae, and fungi by lacking cell walls. All animals are motile, if only at life stages. In most animals, embryos pass through a stage, which is a characteristic exclusive to animals. With a few exceptions, most notably the sponges and Placozoa and these include muscles, which are able to contract and control locomotion, and nerve tissues, which send and process signals
Animal
–
Carl Linnaeus, known as the father of modern
taxonomy
Animal
–
Had'n
Animal
–
The use of
love darts by the land snail
Monachoides vicinus is a form of
sexual selection
Animal
–
A
newt lung cell stained with
fluorescent dyes undergoing the early
anaphase stage of
mitosis
16.
Arthropod
–
An arthropod is an invertebrate animal having an exoskeleton, a segmented body, and jointed appendages. Arthropods form the phylum Arthropoda, which includes the insects, arachnids, myriapods, arthropods are characterized by their jointed limbs and cuticle made of chitin, often mineralised with calcium carbonate. The arthropod body plan consists of segments, each with a pair of appendages, the rigid cuticle inhibits growth, so arthropods replace it periodically by moulting. Their versatility has enabled them to become the most species-rich members of all guilds in most environments. They have over a million described species, making up more than 80% of all described living species, some of which. Arthropods range in size from the microscopic crustacean Stygotantulus up to the Japanese spider crab, arthropods primary internal cavity is a hemocoel, which accommodates their internal organs, and through which their haemolymph – analogue of blood – circulates, they have open circulatory systems. Like their exteriors, the organs of arthropods are generally built of repeated segments. Their nervous system is ladder-like, with paired ventral nerve cords running through all segments and their heads are formed by fusion of varying numbers of segments, and their brains are formed by fusion of the ganglia of these segments and encircle the esophagus. The respiratory and excretory systems of arthropods vary, depending as much on their environment as on the subphylum to which they belong, arthropods also have a wide range of chemical and mechanical sensors, mostly based on modifications of the many setae that project through their cuticles. Aquatic species use internal or external fertilization. Almost all arthropods lay eggs, but scorpions give birth to live young after the eggs have hatched inside the mother, arthropod hatchlings vary from miniature adults to grubs and caterpillars that lack jointed limbs and eventually undergo a total metamorphosis to produce the adult form. The level of care for hatchlings varies from nonexistent to the prolonged care provided by scorpions. The evolutionary ancestry of arthropods dates back to the Cambrian period, the group is generally regarded as monophyletic, and many analyses support the placement of arthropods with cycloneuralians in a superphylum Ecdysozoa. Overall however, the relationships of Metazoa are not yet well resolved. Likewise, the relationships between various groups are still actively debated. Arthropods contribute to the food supply both directly as food, and more importantly indirectly as pollinators of crops. Some species are known to spread disease to humans, livestock. The word arthropod comes from the Greek ἄρθρον árthron, joint, and πούς pous, i. e. foot or leg, arthropods are invertebrates with segmented bodies and jointed limbs
Arthropod
Arthropod
–
Head
Arthropod
–
Cicada climbing out of its exoskeleton while attached to tree
Arthropod
–
Head of a
wasp with three ocelli (centre), and
compound eyes at the left and right
17.
Crustacean
–
Crustaceans form a large, diverse arthropod taxon which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill, woodlice and barnacles. In other words, some crustaceans are more related to insects. The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm, to the Japanese spider crab with a leg span of up to 3.8 m, like other arthropods, crustaceans have an exoskeleton, which they moult to grow. Most crustaceans are free-living aquatic animals, but some are terrestrial, some are parasitic, the group has an extensive fossil record, reaching back to the Cambrian, and includes living fossils such as Triops cancriformis, which has existed apparently unchanged since the Triassic period. More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, krill and copepods are not as widely fished, but may be the animals with the greatest biomass on the planet, and form a vital part of the food chain. The scientific study of crustaceans is known as carcinology, and a scientist who works in carcinology is a carcinologist, the body of a crustacean is composed of segments, which are grouped into three regions, the cephalon or head, the thorax, and the pleon or abdomen. The head and thorax may be fused together to form a cephalothorax, the crustacean body is protected by the hard exoskeleton, which must be moulted for the animal to grow. The shell around each somite can be divided into a dorsal tergum, ventral sternum, various parts of the exoskeleton may be fused together. The abdomen bears pleopods, and ends in a telson, which bears the anus, the number and variety of appendages in different crustaceans may be partly responsible for the groups success. It is unclear whether the condition is a derived state which evolved in crustaceans. Trilobites, for instance, also possessed biramous appendages, the main body cavity is an open circulatory system, where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the pigment, while copepods, ostracods, barnacles. The alimentary canal consists of a tube that often has a gizzard-like gastric mill for grinding food and a pair of digestive glands that absorb food. Structures that function as kidneys are located near the antennae, a brain exists in the form of ganglia close to the antennae, and a collection of major ganglia is found below the gut. In many decapods, the first pair of pleopods are specialised in the male for sperm transfer, many terrestrial crustaceans mate seasonally and return to the sea to release the eggs. Others, such as woodlice, lay their eggs on land, in most decapods, the females retain the eggs until they hatch into free-swimming larvae. Marine crustaceans are as ubiquitous in the oceans as insects are on land, some branchiurans are able to withstand rapid changes of salinity and will also switch hosts from marine to non-marine species. Krill are the layer and the most important part of the food chain in Antarctic animal communities
Crustacean
Crustacean
–
A shed
carapace of a
lady crab, part of the hard
exoskeleton
Crustacean
–
Body structure of a typical crustacean – krill
Crustacean
–
Eggs of
Potamon fluviatile, a freshwater crab
18.
Maxillopoda
–
Maxillopoda is a diverse class of crustaceans including barnacles, copepods and a number of related animals. It does not appear to be a group, and no single character unites all the members. With the exception of some barnacles, maxillopodans are mostly small, including the smallest known arthropod and they often have short bodies, with the abdomen reduced in size, and generally lacking any appendages. This may have arisen through paedomorphosis, apart from barnacles, which use their legs for filter feeding, most maxillopodans feed with their maxillae. They have a bauplan comprising 5 cephalic segments,6 thoracic segments and 4 abdominal segments, the fossil record of the group extends back into the Cambrian, with fossils of both barnacles and tongue worms known from that period. Six subclasses are generally recognised, although many works have included the ostracods among the Maxillopoda. Skaracarida Media related to Maxillopoda at Wikimedia Commons
Maxillopoda
Maxillopoda
–
Calocalanus pavo (
Calanoida:
Calocalanidae)
Maxillopoda
–
Chthamalus stellatus (
Sessilia:
Chthamalidae)
Maxillopoda
–
Argulus on a
stickleback (
Argulidae)
19.
Thecostraca
–
Thecostraca is a subclass of marine invertebrates containing about 1,320 described species. Many species have larvae which become sessile or parasitic as adults. The most important subgroup are the barnacles, constituting about 1,220 known species, the subgroup Facetotecta contains a single genus, Hansenocaris, known only from the tiny planktonic nauplii called y-larvae. These larvae have no known form, though it is suspected that they are parasites. The group Ascothoracida contains about 100 species, all parasites of coelenterates and echinoderms
Thecostraca
–
Thecostraca
20.
Hermann Burmeister
–
Karl Hermann Konrad Burmeister was a German Argentine zoologist, entomologist, herpetologist, and botanist. He was born in Stralsund and died in Buenos Aires, a brief biography, with particular reference to his work on phasmids was published by Bragg in 2007. He studied medicine at Greifswald and Halle, and in 1830 went to Berlin to qualify himself to be a teacher of natural history and he was soon after appointed an instructor in the gymnasium at Cologne. He later became a professor of zoology at the Martin Luther University of Halle-Wittenberg from 1837 to 1861. In 1848, during the excitement, he was sent by the city of Halle as deputy to the national assembly. He traveled to Brazil from 1850 to 1852 and Argentina from 1857 to 1860, in 1861 he went to live in Argentina, founding the Institute at the Museo Nacional in Buenos Aires. He also headed the Academy of Sciences, formed from the faculty of Argentinas National University of Córdoba. In the field of herpetology he described new species of amphibians. 1832 Handbuch der Entomologie Vol.1, xvi+696 + pp. Reimer, bericht über die Fortschritte der Entomologie 1834-35. Bio Anales Museum of Natural History in Buenos Aires,4, bio Anales de la Sociedad Argentina Science,41, 97-107. Buenos Aires, Argentina Anonymous Germán Burmeister,25 † anniversary of his death Physis,3, houssay The personality of German Burmeister Physis,19, 279-283. Buenos Aires, Argentina WITNESS Mendilaharzu Burmeister unpublished Deutsche Lehrerzeitung für Argentinien, memorias del Museo de Entre Rios. Parana Province of Entre Rios, Argentina G. Araoz Alfaro A wise German in the service of Argentina, German Burmeister Argentine-German cultural institutions, Buenos Aires, Argentina R. Ardissone Homage to Burmeister. Burmeister contribution to geography Bulletin EAG, 9-10, Buenos Aires, Argentina A. Burkart Burmeister as botanical Revista de la Universidad Nacional de la Plata,4, 89-95. La Plata, Buenos Aires, Argentina M. Buraben Germán Burmeister, his life, his work Cultural issues Argentinas, Buenos Aires, Argentina K. Müller Hermann Burmeister Die Natur,36, 136-138. Halle M. Asua Official support for the Physics Description de la République Argentine H. Burmeister Quipu,6, méxico NT Auza Germán Burmeister and Paleontological Society 1866-1868 Investigations and Trials,46, 137-155. Iconibus illustravit et descripsit Hermannus Burmeister, grundiss der Naturgeschichte, Für Gymnasien und höhere Bürgerschulen A Manual of entomology, / tr. from the German of Dr. Herman Burmeister by W. E. Jens Andermannn-Relics and Selves Cooper, Thompson. Gaedike, R. Groll, E. K. & Taeger, A.2012, Bibliography of the literature from the beginning until 1863
Hermann Burmeister
–
Hermann Burmeister
21.
Superorder
–
In biological classification, the order is a taxonomic rank used in the classification of organisms and recognized by the nomenclature codes. Other well-known ranks are life, domain, kingdom, phylum, class, family, genus, an immediately higher rank, superorder, may be added directly above order, while suborder would be a lower rank. A taxonomic unit, a taxon, in that rank, in that case the plural is orders. Example, The Juglans and Hickory trees belong to the family Juglandaceae, what does and does not belong to each order is determined by a taxonomist, as is whether a particular order should be recognized at all. Often there is no agreement, with different taxonomists each taking a different position. There are no rules that a taxonomist needs to follow in describing or recognizing an order. Some taxa are accepted almost universally, while others are recognised only rarely, for some groups of organisms, consistent suffixes are used to denote that the rank is an order. The Latin suffix -formes meaning having the form of is used for the name of orders of birds and fishes. The suffix -ales is for the name of orders of plants, fungi, for some clades covered by the International Code of Zoological Nomenclature, a number of additional classifications are sometimes used, although not all of these are officially recognised. In their 1997 classification of mammals, McKenna and Bell used two levels between superorder and order, grandorder and mirorder. Michael Novacek inserted them at the same position, michael Benton inserted them between superorder and magnorder instead. This position was adopted by Systema Naturae 2000 and others, in botany, the ranks of subclass and suborder are secondary ranks pre-defined as respectively above and below the rank of order. Any number of further ranks can be used as long as they are clearly defined, the superorder rank is commonly used, with the ending -anae that was initiated by Armen Takhtajans publications from 1966 onwards. Carl Linnaeus was the first to apply it consistently to the division of all three kingdoms of nature in his Systema Naturae, for plants, Linnaeus orders in the Systema Naturae and the Species Plantarum were strictly artificial, introduced to subdivide the artificial classes into more comprehensible smaller groups. In French botanical publications, from Michel Adansons Familles naturelles des plantes and until the end of the 19th century, some of the plant families still retain the names of Linnaean natural orders or even the names of pre-Linnaean natural groups recognised by Linnaeus as orders in his natural classification. Such names are known as family names. In zoology, the Linnaean orders were used more consistently and that is, the orders in the zoology part of the Systema Naturae refer to natural groups. Some of his names are still in use
Superorder
–
Title page of the 1758 edition of Linnaeus's Systema Naturæ.
Superorder
–
The hierarchy of
biological classification 's eight major
taxonomic ranks. A
class contains one or more orders. Intermediate minor rankings are not shown.
22.
Acrothoracica
–
The Acrothoracica are a superorder of barnacles. Acrothoracicans bore into calcareous material such as shells, coral, crinoids or hardgrounds. Acrothoracicans are typically smaller than other types of barnacle, being only a few millimetres in length and they have from four to six pairs of feathery limbs, or cirri, which they project out of their borings to catch drifting detritus for food. The mouthparts consist of mandibles, maxillules and maxillae, one pair of cirri is close to these while the others are at the other end of the body. Each individual acrothoracican is either male or female, a dwarf male is sometimes found attached to the mantle or wall of a females burrow. The developing larva may omit the nauplius stage but always has a cyprid stage and this has chitinous teeth which are used after the larva has settled to abrade the surface and commence a burrow. Two orders, three families,11 genera and 63 species are recognized, and many more species remain to be identified
Acrothoracica
–
Acrothoracica
23.
Rhizocephala
–
Rhizocephala are derived barnacles that parasitise decapod crustaceans. Their body plan is uniquely reduced in an adaptation to their parasitic lifestyle. The name Rhizocephala derives from the Greek roots ῥίζα and κεφαλή, describing the adult female, as adults they lack appendages, segmentation, and all internal organs except gonads, a few muscles, and the remains of the nervous system. Other than the minute nauplius stages, the only portion of a rhizocephalan body is the externa or reproductive portion of adult females. Nauplii released from adult females swim in water for days without taking any food. In some species, for example, Thompsonia, embryos develop directly into cypris larvae before they are released from adult females, a female cypris settles on a host and metamorphoses and injects its internal cell mass into host animal. The cell mass then grows into root-like threads through the host and this network of threads is called the interna. The female then grows a sac-like externa extruding from the abdomen of the host, the mature females externa produces two types of eggs, small eggs, when fertilised, become female cypres and the large eggs become male cypres. A female externa produces several batches of larvae before it drops off the host, the host soon moults and a new young externa, budded from the interna, emerges from the hosts body. In some species, such as Peltogasterella gracilis, many externae develop from one interna, the externa is where the hosts egg sac would be, and the hosts behaviour is chemically altered, it is castrated and does not moult until aged externa drop off. The host treats the externa as if it were its own egg sac and this behaviour even extends to male hosts, which would never have carried eggs, but care for the externa in the same way as females
Rhizocephala
–
Rhizocephala
24.
Synonym (taxonomy)
–
For example, Linnaeus was the first to give a scientific name to the Norway spruce, which he called Pinus abies. This name is no longer in use, it is now a synonym of the current scientific name which is Picea abies, unlike synonyms in other contexts, in taxonomy a synonym is not interchangeable with the name of which it is a synonym. In taxonomy, synonyms are not equals, but have a different status, for any taxon with a particular circumscription, position, and rank, only one scientific name is considered to be the correct one at any given time. A synonym cannot exist in isolation, it is always an alternative to a different scientific name, given that the correct name of a taxon depends on the taxonomic viewpoint used a name that is one taxonomists synonym may be another taxonomists correct name. Synonyms may arise whenever the same taxon is described and named more than once, independently. They may also arise when existing taxa are changed, as when two taxa are joined to one, a species is moved to a different genus. To the general user of scientific names, in such as agriculture, horticulture, ecology, general science. A synonym is a name that was used as the correct scientific name but which has been displaced by another scientific name. Thus Oxford Dictionaries Online defines the term as a name which has the same application as another. In handbooks and general texts, it is useful to have mentioned as such after the current scientific name. Synonyms used in this way may not always meet the strict definitions of the synonym in the formal rules of nomenclature which govern scientific names. Changes of scientific name have two causes, they may be taxonomic or nomenclatural, a name change may be caused by changes in the circumscription, position or rank of a taxon, representing a change in taxonomic, scientific insight. A name change may be due to purely nomenclatural reasons, that is, based on the rules of nomenclature, the earliest such name is called the senior synonym, while the later name is the junior synonym. One basic principle of zoological nomenclature is that the earliest correctly published name, synonyms are important because if the earliest name cannot be used, then the next available junior synonym must be used for the taxon. Objective synonyms refer to taxa with the type and same rank. For example, John Edward Gray published the name Antilocapra anteflexa in 1855 for a species of pronghorn, however, it is now commonly accepted that his specimen was an unusual individual of the species Antilocapra americana published by George Ord in 1815. Ords name thus takes precedence, with Antilocapra anteflexa being a subjective synonym. Objective synonyms are common at the level of genera, because for various reasons two genera may contain the type species, these are objective synonyms
Synonym (taxonomy)
–
The
Latin Caudata and
Greek Urodela both mean "tailed" and have been used as a scientific name at the rank of order for the
salamanders (as opposed to the tail-less
frogs). Thus they are synonyms.
Synonym (taxonomy)
–
The common dandelion
Taraxacum officinale sensu lato is an extremely widespread group of
apomictic lineages, and some scientists apply the "biological species concept" to divide it into many distinct species; other scientists regard all the names for those independent species as synonyms.
25.
Infraclass
–
In biological classification, class is, a taxonomic rank. Other well-known ranks in descending order of size are life, domain, kingdom, phylum, order, family, genus, as for the other well-known ranks, there is the option of an immediately lower rank, indicated by the prefix sub-, subclass. A taxonomic unit, a taxon, in that rank, in that case the plural is classes The composition of each class is determined by a taxonomist. Often there is no agreement, with different taxonomists taking different positions. There are no rules that a taxonomist needs to follow in describing a class. For example, dogs are assigned to the phylum Chordata, in the class Mammalia. In botany, classes are now rarely discussed, for some clades, a number of alternative classifications are used. In the first edition of his Systema Naturae, carl Linnaeus divided all three of his kingdoms of Nature into classes. The class was considered the highest level of the hierarchy until George Cuviers embranchements. Cladistics List of animal classes Phylogenetics Systematics Taxonomy
Infraclass
–
The hierarchy of
biological classification 's eight major
taxonomic ranks. Intermediate minor rankings are not shown.
26.
Crab
–
Crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting tail, usually entirely hidden under the thorax. They live in all the oceans, in fresh water. Many other animals with similar names – such as crabs, king crabs, porcelain crabs, horseshoe crabs. Crabs are generally covered with an exoskeleton, composed primarily of calcium carbonate. Crabs are found in all of the oceans, while many crabs live in fresh water and on land. Crabs vary in size from the pea crab, a few wide, to the Japanese spider crab. About 850 species of crab are freshwater, terrestrial or semi-terrestrial species and they were previously thought to be a monophyletic group, but are now believed to represent at least two distinct lineages, one in the Old World and one in the New World. The earliest unambiguous crab fossils date from the Jurassic, although Carboniferous Imocaris, known only from its carapace, the radiation of crabs in the Cretaceous and afterward may be linked either to the break-up of Gondwana or to the concurrent radiation of bony fish, crabs main predators. Crabs often show marked sexual dimorphism, males often have larger claws, a tendency which is particularly pronounced in the fiddler crabs of the genus Uca. In fiddler crabs, males have one claw which is greatly enlarged, another conspicuous difference is the form of the pleon, in most male crabs, this is narrow and triangular in form, while females have a broader, rounded abdomen. This is because female crabs brood fertilised eggs on their pleopods, crabs attract a mate through chemical, visual, acoustic, or vibratory means. Pheromones are used by most fully aquatic crabs, while terrestrial and semiterrestrial crabs often use visual signals, the vast number of brachyuran crabs have internal fertilisation and mate belly-to-belly. For many aquatic species, mating takes place just after the female has moulted and is still soft, females can store the sperm for a long time before using it to fertilise their eggs. When fertilisation has taken place, the eggs are released onto the abdomen, below the tail flap. In this location, they are protected during embryonic development, females carrying eggs are called berried since the eggs resemble round berries. When development is complete, the releases the newly hatched larvae into the water. The release is timed with the tides. The free-swimming tiny zoea larvae can float and take advantage of water currents and they have a spine, which probably reduces the rate of predation by larger animals
Crab
Crab
–
Gecarcinus quadratus, a
land crab from
Central and
South America
Crab
–
Crab (Pachygrapsus marmoratus) on Istrian coast,
Adriatic Sea.
Crab
–
Female crab
Xantho poressa at spawning time in the
Black Sea, carrying eggs under her abdomen.
27.
Lobster
–
Lobsters comprise a family of large marine crustaceans. They have long bodies with muscular tails, and live in crevices or burrows on the sea floor, three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others. Highly prized as seafood, lobsters are economically important, and are one of the most profitable commodities in coastal areas they populate. Commercially important species include two species of Homarus from the northern Atlantic Ocean, and scampi – the Northern Hemisphere genus Nephrops, although several other groups of crustaceans have the word lobster in their names, the unqualified term lobster generally refers to the clawed lobsters of the family Nephropidae. Clawed lobsters are not closely related to spiny lobsters or slipper lobsters, the closest living relatives of clawed lobsters are the reef lobsters and the three families of freshwater crayfish. Lobsters are invertebrates with a protective exoskeleton. Like most arthropods, lobsters must moult to grow, which leaves them vulnerable, during the moulting process, several species change colour. Lobsters have 10 walking legs, the front three pairs bear claws, the first of which are larger than the others, although lobsters are largely bilaterally symmetrical like most other arthropods, some genera possess unequal, specialised claws. Lobster anatomy includes the cephalothorax which fuses the head and the thorax, the lobsters head bears antennae, antennules, mandibles, the first and second maxillae, and the first, second, and third maxillipeds. Because lobsters live in murky environments at the bottom of the ocean, the lobster eye has a reflective structure above a convex retina. In contrast, most complex eyes use refractive ray concentrators and a concave retina, the abdomen includes swimmerets and its tail is composed of uropods and the telson. Lobsters, like snails and spiders, have blue blood due to the presence of hemocyanin which contains copper, in contrast, vertebrates and many other animals have red blood from iron-rich hemoglobin. Lobsters possess a green hepatopancreas, called the tomalley by chefs, Lobsters of the family Nephropidae are similar in overall form to a number of other related groups. The distinctions from fossil families such as the Chilenophoberidae are based on the pattern of grooves on the carapace, Lobsters live up to an estimated 45 to 50 years in the wild, although determining age is difficult. Research suggests that lobsters may not slow down, weaken or lose fertility with age, and this longevity may be due to telomerase, an enzyme that repairs long repetitive sections of DNA sequences at the ends of chromosomes, referred to as telomeres. Telomerase is expressed by most vertebrates during embryonic stages, but is absent from adult stages of life. However, unlike most vertebrates, lobsters express telomerase as adults through most tissue, Lobster longevity is limited by their size. Lobsters, like many other crustaceans, grow throughout life and are able to add new muscle cells at each moult
Lobster
Lobster
–
Lobsters awaiting purchase in
Trenton in
Hancock County,
Maine
Lobster
–
Steamed whole lobster, with claws cracked and tail split
Lobster
–
Lobsters in a tank at a fish market
28.
Sessility (zoology)
–
In biology, sessility refers to organisms that do not possess a means of self-locomotion and are normally immobile. This is distinct from the meaning of sessility which refers to an organism or biological structure attached directly by its base without a stalk. Sessile organisms can move through outside sources but are permanently attached to something. Organisms such as corals lay down their own substrate from which they grow, other organisms grow from a solid such as a rock, dead tree trunk, or a manmade object such as a buoy or ships hull. Sessile animals typically have a phase in their development. Sponges have a larval stage, which becomes sessile at maturity. In contrast, many jellyfish develop as sessile polyps early in their life cycle, in the case of the cochineal, it is in the nymph stage that the cochineal disperses. The juveniles move to a spot and produce long wax filaments. Later they move to the edge of the cactus pad where the wind catches the wax filaments, many sessile animals, including sponges, corals and hydra, are capable of asexual reproduction in situ by the process of budding. Sessile organisms such as barnacles and tunicates need some mechanism to move their young into new territory and this is why the most widely accepted theory explaining the evolution of a larval stage is the need for long-distance dispersal ability. This allows for faster reproduction and better protection from predators, the circalittoral zone of coastal environments and biomes are dominated by sessile organisms such as oysters. Carbonate platforms grow due to the buildup of skeletal remains of organisms, usually microorganisms. In anatomy and botany, sessility refers to an organism or biological structure that has no peduncle or stalk, a sessile structure has no stalk
Sessility (zoology)
–
Blue mussels,
Mytilus edulis, are sessile and exhibit clumping.
29.
Filter feeder
–
Some animals that use this method of feeding are clams, krill, sponges, baleen whales, and many fish. Some birds, such as flamingos and certain species of duck, are filter feeders. Filter feeders can play an important role in clarifying water, and are therefore considered ecosystem engineers, most forage fish are filter feeders. For example, the Atlantic menhaden, a type of herring, adult menhaden can filter up to four gallons of water a minute and play an important role in clarifying ocean water. They are also a check to the deadly red tide. In addition to bony fish, four types of cartilaginous fishes are also filter feeders. The whale shark sucks in a mouthful of water, closes its mouth, during the slight delay between closing the mouth and opening the gill flaps, plankton is trapped against the dermal denticles which line its gill plates and pharynx. This fine sieve-like apparatus, which is a modification of the gill rakers, prevents the passage of anything. Any material caught in the filter between the bars is swallowed. Whale sharks have been observed coughing and it is presumed that this is a method of clearing a build up of particles in the gill rakers. The megamouth shark has luminous organs called photophores around its mouth and it is believed they may exist to lure plankton or small fish into its mouth. The basking shark is a filter feeder, filtering zooplankton, small fish. Unlike the megamouth and whale sharks, the shark does not appear to actively seek its quarry. Unlike the other filter feeders, it relies only on the water that is pushed through the gills by swimming. Manta rays can time their arrival at the spawning of large shoals of fish and feed on the free-floating eggs and this stratagem is also employed by whale sharks. Mysidacea are small crustaceans that live close to shore and hover above the sea floor and they are an important food source for herring, cod, flounder, and striped bass. Mysids have a resistance to toxins in polluted areas. Antarctic krill manages to directly utilize the minute phytoplankton cells, which no other animal of krill size can do
Filter feeder
–
Filter basket of a
mysid
Filter feeder
–
Krill feeding under high
phytoplankton concentration (slowed down by a factor of 12)
Filter feeder
–
Baleen of a right whale
Filter feeder
–
Tube sponges attracting small
reef fish
30.
Nekton
–
Nekton or necton refers to the aggregate of actively swimming aquatic organisms in a body of water. As a guideline, nektonic organisms have a high Reynolds number, for this reason, some biologists choose not to use this term. Today it is considered an obsolete term because it often does not allow for the meaningful quantifiable distinction between these two groups. Some biologists no longer use it, as a guideline, nekton were larger and tend to swim largely at biologically high Reynolds numbers, where inertial flows are the rule, and eddies are easily shed. Plankton, on the hand, are small and, if they swim at all, do so at biologically low Reynolds numbers, where the viscous behavior of water dominates. Many animals considered classic examples of nekton start out life as members of the plankton and then, it was argued. Oceanic nekton comprised animals largely from three clades Vertebrates formed the largest contribution, these animals are supported by bones or cartilage. Mollusks are animals such as squids and scallops, crustaceans are animals such as lobsters and crabs. There are organisms whose initial part of their lives were identified as being planktonic but when they grew, a typical example was the medusa of the jellyfish. Neuston pleuston plankton benthos Stefan Nehring and Ute Albrecht, „hell und das redundante Benthon, in, Lauterbornia H.31, 17-30, Dinkelscherben, December 1997 E-Text The dictionary definition of nekton at Wiktionary
Nekton
–
General
Nekton
–
Marine
31.
Species
–
In biology, a species is the basic unit of biological classification and a taxonomic rank. A species is defined as the largest group of organisms in which two individuals can produce fertile offspring, typically by sexual reproduction. While this definition is often adequate, looked at more closely it is problematic, for example, with hybridisation, in a species complex of hundreds of similar microspecies, or in a ring species, the boundaries between closely related species become unclear. Other ways of defining species include similarity of DNA, morphology, all species are given a two-part name, a binomial. The first part of a binomial is the genus to which the species belongs, the second part is called the specific name or the specific epithet. For example, Boa constrictor is one of four species of the Boa genus, Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped that species could evolve given sufficient time, Charles Darwins 1859 book The Origin of Species explained how species could arise by natural selection. Genes can sometimes be exchanged between species by horizontal transfer, and species may become extinct for a variety of reasons. In his biology, Aristotle used the term γένος to mean a kind, such as a bird or fish, a kind was distinguished by its attributes, for instance, a bird has feathers, a beak, wings, a hard-shelled egg, and warm blood. A form was distinguished by being shared by all its members, Aristotle believed all kinds and forms to be distinct and unchanging. His approach remained influential until the Renaissance, when observers in the Early Modern period began to develop systems of organization for living things, they placed each kind of animal or plant into a context. Many of these early delineation schemes would now be considered whimsical, animals likewise that differ specifically preserve their distinct species permanently, one species never springs from the seed of another nor vice versa. In the 18th century, the Swedish scientist Carl Linnaeus classified organisms according to shared physical characteristics and he established the idea of a taxonomic hierarchy of classification based upon observable characteristics and intended to reflect natural relationships. At the time, however, it was widely believed that there was no organic connection between species, no matter how similar they appeared. However, whether or not it was supposed to be fixed, by the 19th century, naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. Jean-Baptiste Lamarck, in his 1809 Zoological Philosophy, described the transmutation of species, proposing that a species could change over time, in 1859, Charles Darwin and Alfred Russel Wallace provided a compelling account of evolution and the formation of new species. Darwin argued that it was populations that evolved, not individuals and this required a new definition of species. Darwin concluded that species are what appear to be, ideas
Species
–
John Ray
Species
–
Carl Linnaeus believed in the fixity of species.
32.
Latin
–
Latin is a classical language belonging to the Italic branch of the Indo-European languages. The Latin alphabet is derived from the Etruscan and Greek alphabets, Latin was originally spoken in Latium, in the Italian Peninsula. Through the power of the Roman Republic, it became the dominant language, Vulgar Latin developed into the Romance languages, such as Italian, Portuguese, Spanish, French, and Romanian. Latin, Italian and French have contributed many words to the English language, Latin and Ancient Greek roots are used in theology, biology, and medicine. By the late Roman Republic, Old Latin had been standardised into Classical Latin, Vulgar Latin was the colloquial form spoken during the same time and attested in inscriptions and the works of comic playwrights like Plautus and Terence. Late Latin is the language from the 3rd century. Later, Early Modern Latin and Modern Latin evolved, Latin was used as the language of international communication, scholarship, and science until well into the 18th century, when it began to be supplanted by vernaculars. Ecclesiastical Latin remains the language of the Holy See and the Roman Rite of the Catholic Church. Today, many students, scholars and members of the Catholic clergy speak Latin fluently and it is taught in primary, secondary and postsecondary educational institutions around the world. The language has been passed down through various forms, some inscriptions have been published in an internationally agreed, monumental, multivolume series, the Corpus Inscriptionum Latinarum. Authors and publishers vary, but the format is about the same, volumes detailing inscriptions with a critical apparatus stating the provenance, the reading and interpretation of these inscriptions is the subject matter of the field of epigraphy. The works of several hundred ancient authors who wrote in Latin have survived in whole or in part and they are in part the subject matter of the field of classics. The Cat in the Hat, and a book of fairy tales, additional resources include phrasebooks and resources for rendering everyday phrases and concepts into Latin, such as Meissners Latin Phrasebook. The Latin influence in English has been significant at all stages of its insular development. From the 16th to the 18th centuries, English writers cobbled together huge numbers of new words from Latin and Greek words, dubbed inkhorn terms, as if they had spilled from a pot of ink. Many of these words were used once by the author and then forgotten, many of the most common polysyllabic English words are of Latin origin through the medium of Old French. Romance words make respectively 59%, 20% and 14% of English, German and those figures can rise dramatically when only non-compound and non-derived words are included. Accordingly, Romance words make roughly 35% of the vocabulary of Dutch, Roman engineering had the same effect on scientific terminology as a whole
Latin
–
Latin inscription, in the
Colosseum
Latin
–
Julius Caesar 's
Commentarii de Bello Gallico is one of the most famous classical Latin texts of the Golden Age of Latin. The unvarnished, journalistic style of this
patrician general has long been taught as a model of the urbane Latin officially spoken and written in the floruit of the
Roman republic.
Latin
–
A multi-volume Latin dictionary in the
University Library of Graz
Latin
–
Latin and Ancient Greek Language - Culture - Linguistics at
Duke University in 2014.
33.
Sessilia
–
Sessilia is an order of barnacles, comprising the barnacles without stalks, or acorn barnacles. They form a group and are probably derived from stalked barnacles. The order is divided into three suborders, brachylepadomorpha contains a single family, Neobrachylepadidae, while Verrucomorpha contains two families, Verrucidae and Neoverrucidae. The remaining twelve families are in the suborder Balanomorpha, data related to Sessilia at Wikispecies
Sessilia
–
Sessilia
34.
Goose barnacle
–
Goose barnacles, also called stalked barnacles or gooseneck barnacles, are filter-feeding crustaceans that live attached to hard surfaces of rocks and flotsam in the ocean intertidal zone. Some species of goose barnacles such as Lepas anatifera are pelagic and are most frequently found on tidewrack on oceanic coasts, the confusion was prompted by the similarities in colour and shape. Because they were found on driftwood, it was assumed that the barnacles were attached to branches before they fell in the water. The Welsh archdeacon of Brecon, Giraldus Cambrensis, made this claim in his Topographia Hiberniae. Since barnacle geese were thought to be flesh, nor born of flesh, they were allowed to be eaten on days when eating meat was forbidden by Christianity. The order Pedunculata is divided into the following suborders and families, In Portugal and Spain, they are a widely consumed, in Spain, Percebes are lightly boiled in brine and served whole and hot under a napkin. To eat percebes, the diamond shaped foot is pinched between thumb and finger and the inner tube pulled out of the scaly case, the claw is removed and the remaining flesh is swallowed. The indigenous peoples of California eat the stem after cooking it in hot ashes, media related to Pedunculata at Wikimedia Commons Data related to Pedunculata at Wikispecies
Goose barnacle
–
Goose barnacle
Goose barnacle
–
Lepas anatifera
Goose barnacle
–
"The goose-tree" from
Gerard's Herbal (1597), displaying the belief that goose barnacles produced barnacle geese.
Goose barnacle
–
Gooseneck barnacles being enjoyed in a Spanish restaurant in
Madrid.
35.
Antenna (biology)
–
Antennae, sometimes referred to as feelers, are paired appendages used for sensing in arthropods. Antennae are connected to the first one or two segments of the arthropod head and they vary widely in form, but are always made of one or more jointed segments. While they are sensory organs, the exact nature of what they sense. Functions may variously include sensing touch, air motion, heat, vibration, antennae are sometimes modified for other purposes, such as mating, brooding, swimming, and even anchoring the arthropod to a substrate. Larval arthropods have antennae that differ from those of the adult, many crustaceans, for example, have free-swimming larval forms that use their antennae for swimming. Except the chelicerates and proturans, which have none, all non-crustacean arthropods have a pair of antennae. Crustaceans bear two pairs of antennae, the pair attached to the first segment of the head are called primary antennae or antennules. This pair is generally uniramous, but is biramous in crabs and lobsters, the pair attached to the second segment are called secondary antennae or simply antennae. The second antennae are biramous, but many species later evolved uniramous pairs. The second antennae may be reduced, apparently absent, or modified to such an extent that they no longer resemble antennae. The subdivisions of crustacean antennae have many names, including flagellomeres, annuli, articles, the terminal ends of crustacean antennae have two major categorizations, segmented and flagellate. An antenna is considered segmented if each of the annuli is separate from those around it and has individual muscle attachments. Flagellate antennae, on the hand, have muscle attachments only around the base. There are several notable uses of antennae in crustaceans. Many crustaceans have a larval stage called a nauplius, which is characterized by its use of antennae for swimming. Barnacles, a highly modified crustacean, use their antennae to attach to rocks, insects evolved from prehistoric crustaceans, and they have secondary antennae like crustaceans, but not primary antennae. Antennae are the primary olfactory sensors of insects and are accordingly well-equipped with a variety of sensilla. Paired, mobile, and segmented, they are located between the eyes on the forehead, embryologically, they represent the appendages of the second head segment
Antenna (biology)
–
Electron micrograph of antenna surface detail of a wasp (
Vespula vulgaris)
Antenna (biology)
–
Terms used to describe shapes of insect antennae
Antenna (biology)
–
A
spiny lobster, showing the enlarged second antennae
Antenna (biology)
–
The large flattened plates in front of the eyes of a
slipper lobster are the modified second antennae.
36.
Carapace
–
A carapace is a dorsal section of the exoskeleton or shell in a number of animal groups, including arthropods, such as crustaceans and arachnids, as well as vertebrates, such as turtles and tortoises. In turtles and tortoises, the underside is called the plastron, in crustaceans, the carapace functions as a protective cover over the cephalothorax. Where it projects forward beyond the eyes, this projection is called a rostrum, the carapace is calcified to varying degrees in different crustaceans. Zooplankton within the phylum Crustacea also have a carapace and these include Cladocera, ostracods, and isopods, but isopods only have a developed cephalic shield carapace covering the head. In arachnids, the carapace is formed by the fusion of prosomal tergites into a plate which carries the eyes, ocularium, ozopores. In a few orders, such as Solifugae and Schizomida, the carapace may be subdivided, alternative terms for the carapace of arachnids and their relatives, which avoids confusion with crustaceans, are prosomal dorsal shield and peltidium. The carapace is the convex part of the shell structure of a turtle, consisting primarily of the animals rib cage, dermal armor
Carapace
–
The molted carapace of a
lady crab from
Long Beach, New York.
Carapace
–
Diagram of a
prawn, with the carapace highlighted in red.
Carapace
–
Diagram of an
arachnid, with the carapace highlighted in purple
Carapace
–
A Greek tortoise shell opened to show the skeleton from below
37.
Rostrum (anatomy)
–
In anatomy, the term rostrum is used for a number of phylogenetically unrelated structures in different groups of animals. In crustaceans, the rostrum is the extension of the carapace in front of the eyes. It is generally a rigid structure, but can be connected by a hinged joint, among insects, the rostrum is the name for the piercing mouthparts of the order Hemiptera. The long snout of weevils may also be called a rostrum, gastropod molluscs have a rostrum or proboscis. Cephalopod molluscs have hard beak-like mouthparts referred to as the rostrum, invertebrate rostrums The beak or snout of a vertebrate may also be referred to as the rostrum. Some cetaceans, including toothed whales such as dolphins and beaked whales, have rostrums which evolved from their jawbones, the narwhal possesses a large rostrum which evolved from a protruding canine tooth. Some fish have permanently protruding rostrums which evolved from their upper jawbones, billfish use rostrums to slash and stun prey. Paddlefish, goblin sharks and hammerhead sharks have rostrums packed with electroreceptors which signal the presence of prey by detecting weak electrical fields, sawsharks and the critically endangered sawfish have rostrums which are both electro-sensitive and used for slashing. The rostrums extend ventrally in front of the fish, in the case of hammerheads the rostrum extends both ventrally and laterally. The upper jawbones of some fish have evolved into rostrums Beak Nostril
Rostrum (anatomy)
–
The rostrum (beak) of a
bottlenose dolphin
Rostrum (anatomy)
–
Crustacean: the rostrum of the shrimp
Macrobrachium rosenbergii is
serrated along both edges.
Rostrum (anatomy)
–
Insect:
assassin bug piercing its prey with its rostrum
Rostrum (anatomy)
–
Cephalopod: the two-part beak of a
giant squid
38.
Thorax
–
The thorax or chest is a part of the anatomy of humans and various other animals located between the neck and the abdomen. The thorax includes the thoracic cavity and the thoracic wall and it contains organs including the heart, lungs, and thymus gland, as well as muscles and various other internal structures. Many diseases may affect the chest, and one of the most common symptoms is chest pain, in humans and other hominids, the thorax is the chest region of the body between the neck and the abdomen, along with its internal organs and other contents. It is mostly protected and supported by the rib cage, spine, arteries and veins are also contained –, bones. The area exposed by open-necked shirts, the V of the chest is sometimes the location of a skin disease polymorphous light eruption. In the human body, the region of the thorax between the neck and diaphragm in the front of the body is called the chest, the corresponding area in an animal can also be referred to as the chest. The shape of the chest does not correspond to part of the thoracic skeleton that encloses the heart. All the breadth of the shoulders is due to the girdle, and contains the axillae. Level with this line the second ribs join the sternum, at the lower part of the sternum, where the seventh or last true ribs join it, the ensiform cartilage begins, and above this there is often a depression known as the pit of the stomach. The bones of the thorax, called the thoracic skeleton is a component of the axial skeleton and it consists of the ribs and sternum. The ribs of the thorax are numbered in ascending order from 1-12. 11 &12 are known as floating ribs because they have no anterior attachment point in particular the cartilage attached to the sternum, as 1-7 are, whereas ribs 8-10 are termed false ribs as their costal cartilage articulates with the rib aboves costal cartilage. The anatomy of the chest can also be described through the use of anatomical landmarks, the female nipple is surrounded for half an inch by a more or less pigmented disc, the areola. The apex of a heart is in the fifth left intercostal space. Different types of diseases or conditions that affect the chest include pleurisy, flail chest, atelectasis, and these conditions can be hereditary or caused by birth defects or trauma. Any condition that lowers the ability to breathe deeply or to cough is considered a chest disease or condition. Injury to the chest results in up to ¼ of all due to trauma in the United States. The major pathophysiologies encountered in blunt chest trauma involve derangements in the flow of air, blood, sepsis due to leakage of alimentary tract contents, as in esophageal perforations, also must be considered. Blunt trauma commonly results in chest wall injuries, the pain associated with these injuries can make breathing difficult, and this may compromise ventilation
Thorax
–
X-ray image of the chest showing the internal anatomy of the
rib cage,
lungs and
heart as well as the inferior thoracic border–made up of the
diaphragm.
Thorax
–
Thorax. Anterior view.
Thorax
39.
Abdomen
–
The abdomen constitutes the part of the body between the thorax and pelvis, in humans and in other vertebrates. The region occupied by the abdomen is termed the abdominal cavity, in arthropods it is the posterior tagma of the body, it follows the thorax or cephalothorax. The abdomen stretches from the thorax at the diaphragm to the pelvis at the pelvic brim. The pelvic brim stretches from the joint to the pubic symphysis and is the edge of the pelvic inlet. The space above this inlet and under the thoracic diaphragm is termed the abdominal cavity, the boundary of the abdominal cavity is the abdominal wall in the front and the peritoneal surface at the rear. The abdomen contains most of the organs of the digestive tract. Hollow abdominal organs include the stomach, the intestine. Organs such as the liver, its attached gallbladder, and the function in close association with the digestive tract. The spleen, kidneys, and adrenal glands also lie within the abdomen, along with blood vessels including the aorta. Anatomists may consider the urinary bladder, uterus, fallopian tubes, finally, the abdomen contains an extensive membrane called the peritoneum. A fold of peritoneum may completely cover certain organs, whereas it may only one side of organs that usually lie closer to the abdominal wall. Anatomists call the type of organs retroperitoneal. For example, the stomach of ruminants is divided into four chambers – rumen, in vertebrates, the abdomen is a large cavity enclosed by the abdominal muscles, ventrally and laterally, and by the vertebral column dorsally. Lower ribs can also enclose ventral and lateral walls, the abdominal cavity is upper part of the pelvic cavity. It is attached to the cavity by the diaphragm. Structures such as the aorta, inferior vena cava and esophagus pass through the diaphragm, both the abdominal and pelvic cavities are lined by a serous membrane known as the parietal peritoneum. This membrane is continuous with the visceral peritoneum lining the organs, the abdomen in vertebrates contains a number of organs belonging, for instance, to the digestive tract and urinary system. There are three layers of the abdominal wall and they are, from the outside to the inside, external oblique, internal oblique, and transverse abdominal
Abdomen
–
The human abdomen and organs which can be found beneath the surface
Abdomen
–
(left) Henry Gray (1825–1861). Anatomy of the Human Body. (Right) A modern example of a human
male abdomen above
Abdomen
–
The analogous gross morphologies of a human and an ant
40.
Gill
–
A gill is a respiratory organ found in many aquatic organisms that extracts dissolved oxygen from water and excretes carbon dioxide. The gills of species, such as hermit crabs, have adapted to allow respiration on land provided they are kept moist. The microscopic structure of a gill presents a surface area to the external environment. Many microscopic aquatic animals, and some larger but inactive ones, can absorb oxygen through the entire surface of their bodies. However, more complex or more active aquatic organisms usually require a gill or gills, Gills usually consist of thin filaments of tissue, branches, or slender, tufted processes that have a highly folded surface to increase surface area. A high surface area is crucial to the gas exchange of aquatic organisms, a cubic meter of air contains about 250 grams of oxygen at STP. The concentration of oxygen in water is lower than in air, in fresh water, the dissolved oxygen content is approximately 8 cm3/L compared to that of air which is 210 cm3/L. Water is 777 times more dense than air and is 100 times more viscous, oxygen has a diffusion rate in air 10,000 times greater than in water. The use of sac-like lungs to remove oxygen from water would not be efficient enough to sustain life, rather than using lungs, aseous exchange takes place across the surface of highly vascularised gills over which a one-way current of water is kept flowing by a specialised pumping mechanism. The density of the water prevents the gills from collapsing and lying on top of each other, with the exception of some aquatic insects, the filaments and lamellae contain blood or coelomic fluid, from which gases are exchanged through the thin walls. The blood carries oxygen to other parts of the body, carbon dioxide passes from the blood through the thin gill tissue into the water. Gills or gill-like organs, located in different parts of the body, are found in groups of aquatic animals, including mollusks, crustaceans, insects, fish. The gills of vertebrates typically develop in the walls of the pharynx, most species employ a countercurrent exchange system to enhance the diffusion of substances in and out of the gill, with blood and water flowing in opposite directions to each other. The gills are composed of filaments, the gill lamellae. When a fish breathes, it draws in a mouthful of water at regular intervals, then it draws the sides of its throat together, forcing the water through the gill openings, so it passes over the gills to the outside. Fish gill slits may be the ancestors of the tonsils, thymus glands. Adjacent slits are separated by a gill arch from which projects a cartilaginous gill ray. This gill ray is the support for the sheet-like interbranchial septum, the base of the arch may also support gill rakers, projections into the pharyngeal cavity that help to prevent large pieces of debris from damaging the delicate gills
Gill
–
The red gills of this
common carp are visible as a result of a
gill flap birth defect.
Gill
–
Freshwater Fish Gills magnified 400 times
Gill
–
The red gills inside a detached
tuna head (viewed from behind)
Gill
–
An
Alpine newt larva showing the
external gills, which flare just behind the head
41.
Crustacean larvae
–
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult and this is especially true of crustaceans which live as benthic adults, more so than where the larvae are planktonic and therefore more easily caught. Many crustacean larvae were not immediately recognised as larvae when they were discovered, the names of these genera have become generalised to cover specific larval stages across wide groups of crustaceans, such as zoea and nauplius. Other terms described forms which are found in particular groups, such as the glaucothoe of hermit crabs, or the phyllosoma of slipper lobsters. At its most complete, a life cycle begins with an egg, which is usually fertilised. This egg hatches into a pre-larva or pre-zoea, through a series of moults, the young animal then passes through various zoea stages, followed by a megalopa or post-larva. This is followed by metamorphosis into a form, which broadly resembles the adult, and after further moults. Some crustaceans continue to moult as adults, while for others, antonie van Leeuwenhoek was the first person to observe the difference between larval crustaceans and the adults when he watched the eggs of Cyclops hatching in 1699. This controversy persisted until the 1840s, and the first descriptions of a series of larval forms were not published until the 1870s. The genus name Nauplius was published posthumously by Otto Friedrich Müller in 1785 for animals now known to be the larvae of copepods, the nauplius stage is characterised by the use of the appendages of the head for swimming. The nauplius is also the stage at which a simple, unpaired eye first appears. The eye is known for that reason as the naupliar eye, the genus Zoea was initially described by Louis Augustin Guillaume Bosc in 1802 for an animal now known to be the larva of a crab. The zoea stage is characterised by the use of the thoracic appendages for swimming, the post-larva is characterised by the use of abdominal appendages for propulsion. The post-larva is usually similar to the form, and so many names have been erected for the stage in different groups. William Elford Leach erected the genus Megalopa in 1813 for a post-larval crab, every other crustacean group with free larvae shows a metamorphosis, and this difference in the larvae is thought to reflect a fundamental cleavage of the crustaceans. The larvae of remipedes are lecithotrophic, consuming egg yolk rather than using external food sources and this characteristic, which is shared with malacostracan groups such as the Decapoda and Euphausiacea has been used to suggest a link between Remipedia and Malacostraca. Young isopod crustaceans hatch directly into a stage, which is similar in appearance to the adult
Crustacean larvae
–
Nauplius larva
Crustacean larvae
–
Adult
Penaeus monodon
Crustacean larvae
–
Nauplius
Crustacean larvae
–
Adult
42.
Nauplius (larva)
–
Crustaceans may pass through a number of larval and immature stages between hatching from their eggs and reaching their adult form. Each of the stages is separated by a moult, in which the hard exoskeleton is shed to allow the animal to grow. The larvae of crustaceans often bear little resemblance to the adult and this is especially true of crustaceans which live as benthic adults, more so than where the larvae are planktonic and therefore more easily caught. Many crustacean larvae were not immediately recognised as larvae when they were discovered, the names of these genera have become generalised to cover specific larval stages across wide groups of crustaceans, such as zoea and nauplius. Other terms described forms which are found in particular groups, such as the glaucothoe of hermit crabs, or the phyllosoma of slipper lobsters. At its most complete, a life cycle begins with an egg, which is usually fertilised. This egg hatches into a pre-larva or pre-zoea, through a series of moults, the young animal then passes through various zoea stages, followed by a megalopa or post-larva. This is followed by metamorphosis into a form, which broadly resembles the adult, and after further moults. Some crustaceans continue to moult as adults, while for others, antonie van Leeuwenhoek was the first person to observe the difference between larval crustaceans and the adults when he watched the eggs of Cyclops hatching in 1699. This controversy persisted until the 1840s, and the first descriptions of a series of larval forms were not published until the 1870s. The genus name Nauplius was published posthumously by Otto Friedrich Müller in 1785 for animals now known to be the larvae of copepods, the nauplius stage is characterised by the use of the appendages of the head for swimming. The nauplius is also the stage at which a simple, unpaired eye first appears. The eye is known for that reason as the naupliar eye, the genus Zoea was initially described by Louis Augustin Guillaume Bosc in 1802 for an animal now known to be the larva of a crab. The zoea stage is characterised by the use of the thoracic appendages for swimming, the post-larva is characterised by the use of abdominal appendages for propulsion. The post-larva is usually similar to the form, and so many names have been erected for the stage in different groups. William Elford Leach erected the genus Megalopa in 1813 for a post-larval crab, every other crustacean group with free larvae shows a metamorphosis, and this difference in the larvae is thought to reflect a fundamental cleavage of the crustaceans. The larvae of remipedes are lecithotrophic, consuming egg yolk rather than using external food sources and this characteristic, which is shared with malacostracan groups such as the Decapoda and Euphausiacea has been used to suggest a link between Remipedia and Malacostraca. Young isopod crustaceans hatch directly into a stage, which is similar in appearance to the adult
Nauplius (larva)
–
Nauplius larva
Nauplius (larva)
–
Adult
Penaeus monodon
Nauplius (larva)
–
Nauplius
Nauplius (larva)
–
Adult
43.
Elminius modestus
–
Elminius modestus is a species of barnacle in the family Balanidae, native to Australia, Tasmania and New Zealand, but now spread to Britain and the north west coasts of Europe. It reaches a size of about 10 millimetres in diameter. E. modestus is a grey, semi-translucent barnacle. It is composed of four plates and leans a little to one side. E. modestus originated in Australia and was first seen in British waters, in Chichester Harbour and it was believed to have arrived on the hulls of ships, or possibly the larval stages travelled in bilge water. It has become common in southern England and Wales and is spreading northwards. It is found on the middle shore and is tolerant of low salinity levels where fresh water enters the sea. It had reached the Scottish Borders by 1960 and Shetland by 1978 and it is found on the Atlantic coasts of Europe from Gibraltar to Germany. E. modestus is a suspension feeder and it has feathery appendages which beat rhythmically to draw plankton and other organic particles into the shell for consumption. Eggs are laid and develop into larvae which are released into the phytoplankton. These then develop into larvae which later settle and cement themselves onto a rocky substrate. In the British Isles, E. modestus competes with Semibalanus balanoides and it is particularly successful because it grows fast, tolerates reduced salinity, has a lower temperature tolerance than Chthamalus spp and a higher tolerance than Balanus spp. It is also a threat to native species because it reaches maturity in its first season and it has an extended habitat as it grows both high up the shore and in the neritic zone. Elminius modestus, Marine Life Information Network for Britain & Ireland Michael Miller & Gary Batt, reef and Beach Life of New Zealand. Auckland, New Zealand, William Collins Ltd
Elminius modestus
–
Elminius modestus
Elminius modestus
–
Nauplius of E. modestus
44.
Fertilisation
–
The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms the haploid male gamete combines with two polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. In 1784, Spallanzani established the need of interaction between the females ovum and males sperm to form a zygote, oscar Hertwig, in Germany, described the fusion of nuclei of spermatozoa and of ova from sea urchin. In flowering plants there are two sperm from each pollen grain, in seed plants, after pollination, a pollen grain germinates, and a pollen tube grows and penetrates the ovule through a tiny pore called a micropyle. The sperm are transferred from the pollen through the pollen tube, bryophyte is a traditional name used to refer to all embryophytes that do not have true vascular tissue and are therefore called non-vascular plants. Some bryophytes do have specialised tissues for the transport of water, however, since these do not contain lignin, a fern is a member of a group of roughly 12,000 species of vascular plants that reproduce via spores and have neither seeds nor flowers. They differ from mosses by being vascular and they have stems and leaves, like other vascular plants. Most ferns have what are called fiddleheads that expand into fronds, the gymnosperms are a group of seed-producing plants that includes conifers, Cycads, Ginkgo, and Gnetales. The term gymnosperm comes from the Greek composite word γυμνόσπερμος, meaning naked seeds and their naked condition stands in contrast to the seeds and ovules of flowering plants, which are enclosed within an ovary. Gymnosperm seeds develop either on the surface of scales or leaves, often modified to form cones, the pollen tube does not directly reach the ovary in a straight line. It travels near the skin of the style and curls to the bottom of the ovary, then near the receptacle, it breaks through the ovule through the micropyle, after being fertilised, the ovary starts to swell and develop into the fruit. With multi-seeded fruits, multiple grains of pollen are necessary for syngamy with each ovule, the growth of the pollen tube is controlled by the vegetative cytoplasm. The sperms are interconnected and dimorphic, the one, in a number of plants, is also linked to the tube nucleus and the interconnected sperm. Double fertilisation is the process in angiosperms in which two sperm from each pollen tube fertilise two cells in a gametophyte that is inside an ovule. After the pollen tube enters the gametophyte, the tube nucleus disintegrates. This is the point when fertilisation actually occurs, pollination and fertilisation are two separate processes, the nucleus of the other sperm cell fuses with two haploid polar nuclei in the centre of the gametophyte. This triploid cell divides through mitosis and forms the endosperm, a nutrient-rich tissue, the two central-cell maternal nuclei that contribute to the endosperm arise by mitosis from the single meiotic product that also gave rise to the egg. Therefore, maternal contribution to the constitution of the triploid endosperm is double that of the embryo
Fertilisation
–
Sperm and ovum fusing
Fertilisation
–
In the
Bryophyte land plants, fertilization takes place within the
archegonium. This
moss has been
genetically modified so that the unfertilized egg within the archegonium produces a blue colour.
Fertilisation
–
Red-veined darters (
Sympetrum fonscolombii) flying "in cop" (male ahead), enabling the male to prevent other males from mating. The eggs are fertilised as they are laid, one at a time.
45.
Telson
–
The telson is the posterior-most division of the body of an arthropod. It is not considered a true segment because it does not arise in the embryo from teloblast areas as do real segments and it never carries any appendages, but a forked tail called the caudal furca may be present. The shape and composition of the telson differs between arthropod groups, in lobsters, shrimp and other decapods, the telson, along with the uropods forms the tail fan. This is used as a paddle in the caridoid escape reaction, whereby an alarmed animal rapidly flexes its tail, krill can reach speeds of over 60 cm per second by this means. The trigger time to optical stimulus is, in spite of the low temperatures, in the Isopoda and Tanaidacea, the last abdominal body segment is fused with the telson, forming a pleotelson. The term telson is used for the caudal spine of some chelicerates. The chelicerate telson can be seen in a number of fossil species. Some authorities have urged that the usage of word in this context be discouraged. In millipedes, the telson consists of a legless pre-anal body segment, a pair of valves or plates closing off the anus. In centipedes the telson is the rear-most body segment, posterior to the genital openings, bearing two anal valves
Telson
–
Telson (arrow no. 3) of the horseshoe crab
Carcinoscorpius rotundicauda
Telson
–
Diagram highlighting the telson of the prawn
Litopenaeus setiferus
Telson
–
Telson of a millipede, including an epiproct (e), hypoproct (h) and paraprocts (p)
46.
Instar
–
An instar is a developmental stage of arthropods, such as insects, between each moult, until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or assume a new form, differences between instars can often be seen in altered body proportions, colors, patterns, changes in the number of body segments or head width. After moulting, i. e. shedding their exoskeleton, the juvenile arthropods continue in their life cycle until they pupate or moult again. This period of growth, instar, is fixed, some arthropods can continue to moult after sexual maturity, but the stages between these subsequent moults are generally not called instars. The number of instars an insect undergoes depends on the species, lower temperatures and humidity often slow the rate of development. The dictionary definition of instar at Wiktionary
Instar
–
Imperial moth (
Eacles imperialis) development from egg to pupa, showing all the different instars
Instar
–
Two instars of a caterpillar of
Papilio polytes
47.
Seta
–
In biology, setae /ˈsiːtiː/ are any of a number of different bristle- or hair-like structures on living organisms. Annelid setae are stiff bristles present on the body and they help, for example, earthworms to attach to the surface and prevent backsliding during peristaltic motion. These hairs are what make it difficult to pull a worm straight from the ground, setae in oligochaetes are largely composed of chitin. They are classified according to the limb to which they are attached, for instance, notosetae are attached to notopodia, crustaceans have mechano- and chemosensory setae. Setae are especially present on the mouthparts of crustaceans and can also be found on grooming limbs, in some cases, setae are modified into scale like structures. Setae on the legs of krill and other small crustaceans help them to gather phytoplankton and it captures them and allows them to be eaten. Insect setae are variously called hairs, macrotrichia, or chaetae and they are unicellular and formed by the outgrowth of a single epidermal cell. They are generally hollow and project through a secondary or accessory cell as it develops, the setal membrane is not cuticularized and movement is possible. This serves to protect the body, the pads on a geckos feet are small hair-like processes that play a role in the animals ability to cling to vertical surfaces. The micrometer-scale setae branch into nanometer-scale projections called spatulae, gekkos seta, According to Kellar Autumn, Two front feet of a tokay gecko can withstand 20.1 N of force parallel to the surface with 227 mm2 of pad area. In mycology, setae refer to dark brown, thick-walled, thorn-like cystidia found in corticioid and poroid fungi in the family Hymenochaetaceae, though mainly microscopic, the setae of some species may be sufficiently prominent to be visible with a hand lens. In botany, seta refers to the supporting the capsule of a moss or liverwort. The seta is part of the sporophyte and has a short foot embedded in the gametophyte on which it is parasitic, setae are not present in all mosses, but in some species they may reach 15 to 20 centimeters in height. In the diatom family Chaetocerotaceae, seta refers to the hairlike outgrowths of the valve and these setae have a different structure than the valve. Such setae may prevent rapid sinking and also protect the cells from grazing, Synthetic setae are a class of synthetic adhesives that detach at will, sometimes called resetable adhesives, yet display substantial stickiness. The development of synthetic materials is a matter of current research. Chaeta Synthetic setae Van der Waals force
Seta
–
Setae on the foreleg of a
mayfly
Seta
Seta
–
Close-up of the underside of a gecko's foot as it walks on vertical glass
48.
Biofilm
–
A biofilm is any group of microorganisms in which cells stick to each other and often these cells adhere to a surface. These adherent cells are embedded within a self-produced matrix of extracellular polymeric substance. Biofilm extracellular polymeric substance, which is referred to as slime, is a polymeric conglomeration generally composed of extracellular DNA, proteins. Biofilms may form on living or non-living surfaces and can be prevalent in natural, industrial and hospital settings. The microbial cells growing in a biofilm are physiologically distinct from planktonic cells of the same organism, when a cell switches to the biofilm mode of growth, it undergoes a phenotypic shift in behavior in which large suites of genes are differentially regulated. Formation of a biofilm begins with the attachment of free-floating microorganisms to a surface, if the colonists are not immediately separated from the surface, they can anchor themselves more permanently using cell adhesion structures such as pili. Some species are not able to attach to a surface on their own but are able to anchor themselves to the matrix or directly to earlier colonists. It is during this colonization that the cells are able to communicate via quorum sensing using products such as N-acyl homoserine lactone, some bacteria are unable to form biofilms as successfully due to their limited motility. Non-motile bacteria cannot recognize the surface or aggregate together as easily as motile bacteria, once colonization has begun, the biofilm grows through a combination of cell division and recruitment. Polysaccharide matrices typically enclose bacterial biofilms, the final stage of biofilm formation is known as dispersion, and is the stage in which the biofilm is established and may only change in shape and size. The development of a biofilm may allow for an aggregate cell colony to be resistant to antibiotics. Cell-cell communication or quorum sensing has shown to be involved in the formation of biofilm in several bacterial species. There are five stages of development, Initial attachment. Dispersal of cells from the colony is an essential stage of the biofilm life cycle. Dispersal enables biofilms to spread and colonize new surfaces, enzymes that degrade the biofilm extracellular matrix, such as dispersin B and deoxyribonuclease, may play a role in biofilm dispersal. Biofilm matrix degrading enzymes may be useful as anti-biofilm agents, recent evidence has shown that a fatty acid messenger, cis-2-decenoic acid, is capable of inducing dispersion and inhibiting growth of biofilm colonies. Secreted by Pseudomonas aeruginosa, this compound induces cyclo heteromorphic cells in species of bacteria. Nitric oxide has also shown to trigger the dispersal of biofilms of several bacteria species at sub-toxic concentrations
Biofilm
–
Staphylococcus aureus biofilm on an indwelling
catheter
Biofilm
–
An
iridescent biofilm on the surface of a fishtank.
Biofilm
–
Five stages of biofilm development: (1) Initial attachment, (2) Irreversible attachment, (3) Maturation I, (4) Maturation II, and (5) Dispersion. Each stage of development in the diagram is paired with a photomicrograph of a developing P. aeruginosa biofilm. All photomicrographs are shown to same scale.
Biofilm
–
Biofilm in
Yellowstone National Park. Longest raised mat area is about half a meter long.
49.
Metamorphosis (biology)
–
Metamorphosis is iodothyronine-induced and an ancestral feature of all chordates. Some insects, fishes, amphibians, mollusks, crustaceans, cnidarians, echinoderms, and tunicates undergo metamorphosis, animals that go through metamorphosis are called metamorphoses. Animals can be divided into species that undergo metamorphosis, incomplete metamorphosis. Scientific usage of the term is technically precise, and it is not applied to general aspects of cell growth, the word metamorphosis derives from Greek μεταμόρφωσις, transformation, transforming, from μετα-, change and μορφή, form. Metamorphosis is iodothyronine-induced and a feature of all chordates. In insects growth and metamorphosis are controlled by hormones synthesized by endocrine glands near the front of the body, neurosecretory cells in an insects brain secrete a hormone, the prothoracicotropic hormone that activates prothoracic glands, which secrete a second hormone, usually ecdysone, that induces ecdysis. PTTH also stimulates the corpora allata, an organ, to produce juvenile hormone. Experiments on firebugs have shown how juvenile hormone can affect the number of nymph instar stages in hemimetabolous insects, All three categories can be found in the diversity of insects, including no metamorphosis, incomplete or partial metamorphosis, and complete metamorphosis. In hemimetabolous insects, immature stages are called nymphs, development proceeds in repeated stages of growth and ecdysis, these stages are called instars. The juvenile forms closely resemble adults, but are smaller and lack features such as wings. The size and morphological differences between nymphs in different instars are small, often just differences in proportions and the number of segments, in later instars. In holometabolous insects, immature stages are called larvae, and differ markedly from adults, insects which undergo holometabolism pass through a larval stage, then enter an inactive state called pupa, and finally emerge as adults. The earliest insect forms showed direct development, and the evolution of metamorphosis in insects is thought to have fuelled their dramatic radiation, some early ametabolous true insects are still present today, such as bristletails and silverfish. Hemimetabolous insects include cockroaches, grasshoppers, dragonflies, and true bugs, phylogenetically, all insects in the Pterygota undergo a marked change in form, texture and physical appearance from immature stage to adult. According to research from 2008, adult Manduca sexta is able to retain behavior learned as a caterpillar, many observations have indicated that programmed cell death plays a considerable role during physiological processes of multicellular organisms, particularly during embryogenesis and metamorphosis. Sequence illustrating complete metamorphosis in the white butterfly, Pieris rapae In typical amphibian development, eggs are laid in water. Frogs, toads, and newts all hatch from the eggs as larvae with external gills, afterwards, newt larvae start a predatory lifestyle, while tadpoles mostly scrape food off surfaces with their horny tooth ridges. Metamorphosis in amphibians is regulated by thyroxin concentration in the blood, which stimulates metamorphosis, and prolactin, specific events are dependent on threshold values for different tissues
Metamorphosis (biology)
–
A
dragonfly in its final
moult, undergoing metamorphosis from its
nymph form to an adult
Metamorphosis (biology)
–
larva
Metamorphosis (biology)
–
pupa ready to hatch
Metamorphosis (biology)
–
adult
Calman, William Thomas (1911). "Barnacle". Encyclopædia Britannica. 3 (11th ed.). p. 409.
