Binomial nomenclature called binominal nomenclature or binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin grammatical forms, although they can be based on words from other languages. Such a name is called a binomen, binominal name or a scientific name; the first part of the name – the generic name – identifies the genus to which the species belongs, while the second part – the specific name or specific epithet – identifies the species within the genus. For example, humans belong within this genus to the species Homo sapiens. Tyrannosaurus rex is the most known binomial; the formal introduction of this system of naming species is credited to Carl Linnaeus beginning with his work Species Plantarum in 1753. But Gaspard Bauhin, in as early as 1623, had introduced in his book Pinax theatri botanici many names of genera that were adopted by Linnaeus; the application of binomial nomenclature is now governed by various internationally agreed codes of rules, of which the two most important are the International Code of Zoological Nomenclature for animals and the International Code of Nomenclature for algae and plants.
Although the general principles underlying binomial nomenclature are common to these two codes, there are some differences, both in the terminology they use and in their precise rules. In modern usage, the first letter of the first part of the name, the genus, is always capitalized in writing, while that of the second part is not when derived from a proper noun such as the name of a person or place. Both parts are italicized when a binomial name occurs in normal text, thus the binomial name of the annual phlox is now written as Phlox drummondii. In scientific works, the authority for a binomial name is given, at least when it is first mentioned, the date of publication may be specified. In zoology "Patella vulgata Linnaeus, 1758"; the name "Linnaeus" tells the reader who it was that first published a description and name for this species of limpet. "Passer domesticus". The original name given by Linnaeus was Fringilla domestica; the ICZN does not require that the name of the person who changed the genus be given, nor the date on which the change was made, although nomenclatorial catalogs include such information.
In botany "Amaranthus retroflexus L." – "L." is the standard abbreviation used in botany for "Linnaeus". "Hyacinthoides italica Rothm. – Linnaeus first named this bluebell species Scilla italica. The name is composed of two word-forming elements: "bi", a Latin prefix for two, "-nomial", relating to a term or terms; the word "binomium" was used in Medieval Latin to mean a two-term expression in mathematics. Prior to the adoption of the modern binomial system of naming species, a scientific name consisted of a generic name combined with a specific name, from one to several words long. Together they formed a system of polynomial nomenclature; these names had two separate functions. First, to designate or label the species, second, to be a diagnosis or description. In a simple genus, containing only two species, it was easy to tell them apart with a one-word genus and a one-word specific name; such "polynomial names" may sometimes look like binomials, but are different. For example, Gerard's herbal describes various kinds of spiderwort: "The first is called Phalangium ramosum, Branched Spiderwort.
The other... is aptly termed Phalangium Ephemerum Virginianum, Soon-Fading Spiderwort of Virginia". The Latin phrases are short descriptions, rather than identifying labels; the Bauhins, in particular Caspar Bauhin, took some important steps towards the binomial system, by pruning the Latin descriptions, in many cases to two words. The adoption by biologists of a system of binomial nomenclature is due to Swedish botanist and physician Carl von Linné, more known by his Latinized name Carl Linnaeus, it was in his 1753 Species Plantarum that he first began using a one-word "trivial name" together with a generic name in a system of binomial nomenclature. This trivial name is what is now known as specific name; the Bauhins' genus names were retained in many of these, but the descriptive part was reduced to a single word. Linnaeus's trivial names introduced an important new idea, namely that the function of a name could be to give a species a unique label; this meant. Thus Gerard's Phalangium ephemerum virginianum became Tradescantia virgi
The Permian is a geologic period and system which spans 47 million years from the end of the Carboniferous Period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It is the last period of the Paleozoic 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 ancestral groups of the mammals, turtles and archosaurs; the world at the time was dominated by two continents 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 Earth's history, in which nearly 96% of marine species and 70% of terrestrial species died out.
It would take well into the Triassic for life to recover from this catastrophe. Recovery from the Permian–Triassic extinction event was protracted; 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 Édouard de Verneuil; the region now lies in the Perm Krai of Russia. Official ICS 2017 subdivisions of the Permian System from most recent to most ancient rock layers are: Lopingian epoch Changhsingian Wuchiapingian Others: Waiitian Makabewan Ochoan Guadalupian epoch Capitanian stage Wordian stage Roadian stage Others: Kazanian or Maokovian Braxtonian stage Cisuralian epoch Kungurian stage Artinskian stage Sakmarian stage Asselian stage Others: Telfordian Mangapirian Sea levels in the Permian remained low, near-shore environments were reduced as all major landmasses collected into a single continent—Pangaea; this could have in part caused the widespread extinctions of marine species at the end of the period by reducing shallow coastal areas preferred by many marine organisms.
During the Permian, all the Earth's major landmasses were collected into a single supercontinent known as Pangaea. Pangaea straddled the equator and extended toward the poles, with a corresponding effect on ocean currents in the single great ocean, the Paleo-Tethys Ocean, a large ocean that existed between Asia and Gondwana; the Cimmeria continent rifted away from Gondwana and drifted north to Laurasia, causing the Paleo-Tethys Ocean to shrink. 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 and monsoon conditions with seasonal rainfall patterns. Deserts seem to have been widespread on Pangaea; such dry conditions favored gymnosperms, plants with seeds enclosed in a protective cover, over plants such as ferns that disperse spores in a wetter environment. The first modern trees appeared in the Permian. Three general areas are noted for their extensive Permian deposits—the Ural Mountains and the southwest of North America, including the Texas red beds.
The Permian Basin in the U. S. states of Texas and New Mexico is so named because it has one of the thickest deposits of Permian rocks in the world. 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 warmed, drying the continent's 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 and brachiopods. Fossilized shells of two kinds of invertebrates are used to identify Permian strata and correlate them between sites: fusulinids, a kind of shelled amoeba-like protist, one of the foraminiferans, ammonoids, shelled cephalopods that are distant relatives of the modern nautilus. By the close of the Permian, trilobites and a host of other marine groups became extinct. Terrestrial life in the Permian included diverse plants, fungi and various types of tetrapods; the period saw a massive desert covering the interior of Pangaea.
The warm zone spread in the northern hemisphere. The rocks formed at that time were stained red by iron oxides, the result of intense heating by the sun of a surface devoid of vegetation cover. A number of older types of plants and animals became marginal elements; the Permian began with the Carboniferous flora still flourishing. About the middle of the Permian a major transition in vegetation began; the swamp-loving
The Polychaeta known as the bristle worms or polychaetes, are a paraphyletic class of annelid worms marine. Each body segment has a pair of fleshy protrusions called parapodia that bear many bristles, called chaetae, which are made of chitin; as such, polychaetes are sometimes referred to as bristle worms. More than 10,000 species are described in this class. Common representatives include the sandworm or clam worm Alitta. Polychaetes as a class are robust and widespread, with species that live in the coldest ocean temperatures of the abyssal plain, to forms which tolerate the high temperatures near hydrothermal vents. Polychaetes occur throughout the Earth's oceans at all depths, from forms that live as plankton near the surface, to a 2- to 3-cm specimen observed by the robot ocean probe Nereus at the bottom of the Challenger Deep, the deepest known spot in the Earth's oceans. Only 168 species are known from fresh waters. Polychaetes are segmented worms less than 10 cm in length, although ranging at the extremes from 1 mm to 3 m, in Eunice aphroditois.
They can sometimes be brightly coloured, may be iridescent or luminescent. Each segment bears a pair of paddle-like and vascularized parapodia, which are used for movement and, in many species, act as the worm's primary respiratory surfaces. Bundles of bristles, called setae, project from the parapodia. However, polychaetes vary from this generalised pattern, can display a range of different body forms; the most generalised polychaetes are those that crawl along the bottom, but others have adapted to many different ecological niches, including burrowing, pelagic life, tube-dwelling or boring and parasitism, requiring various modifications to their body structures. The head, or prostomium, is well developed, compared with other annelids, it projects forward over the mouth. The head includes two to four pair of eyes, although some species are blind; these are fairly simple structures, capable of distinguishing only light and dark, although some species have large eyes with lenses that may be capable of more sophisticated vision.
The head includes a pair of antennae, tentacle-like palps, a pair of pits lined with cilia, known as "nuchal organs". These latter appear to be chemoreceptors, help the worm to seek out food; the outer surface of the body wall consists of a simple columnar epithelium covered by a thin cuticle. Underneath this, in order, are a thin layer of connective tissue, a layer of circular muscle, a layer of longitudinal muscle, a peritoneum surrounding the body cavity. Additional oblique muscles move the parapodia. In most species the body cavity is divided into separate compartments by sheets of peritoneum between each segment, but in some species it's more continuous; the mouth of polychaetes is located on the peristomium, the segment behind the prostomium, varies in form depending on their diets, since the group includes predators, filter feeders and parasites. In general, they possess a pair of jaws and a pharynx that can be everted, allowing the worms to grab food and pull it into their mouths. In some species, the pharynx is modified into a lengthy proboscis.
The digestive tract is a simple tube with a stomach part way along. The smallest species, those adapted to burrowing, lack gills, breathing only through their body surfaces. Most other species have external gills associated with the parapodia. A simple but well-developed circulatory system is present; the two main blood vessels furnish smaller vessels to supply the gut. Blood flows forward in the dorsal vessel, above the gut, returns down the body in the ventral vessel, beneath the gut; the blood vessels themselves are contractile, helping to push the blood along, so most species have no need of a heart. In a few cases, muscular pumps analogous to a heart are found in various parts of the system. Conversely, some species have little or no circulatory system at all, transporting oxygen in the coelomic fluid that fills their body cavities; the blood may have any of three different respiratory pigments. The most common of these is haemoglobin, but some groups have haemerythrin or the green-coloured chlorocruorin, instead.
The nervous system consists of a single or double ventral nerve cord running the length of the body, with ganglia and a series of small nerves in each segment. The brain is large, compared with that of other annelids, lies in the upper part of the head. An endocrine gland is attached to the ventral posterior surface of the brain, appears to be involved in reproductive activity. In addition to the sensory organs on the head, photosensitive eye spots and numerous additional sensory nerve endings, most in involved with the sense of touch occur on the body. Polychaetes have a varying number of protonephridia or metanephridia for excreting waste, which in some cases can be complex in structure; the body contains greenish "chloragogen" tissue, similar to that found in oligochaetes, which appears to function in metabolism, in a similar fashion to that of the vertebrate liver. The cuticle may be 200 nm to 13 mm thick, their jaws are formed from sclerotised collagen, their setae from sclerotised chitin.
Polychaetes are variable in both form and lifestyle, include a few taxa that swim among the plankton or above the abyssal plain. Most burrow or build tubes in the sediment, some live as commensals. A few are pa
Myomere are the blocks of skeletal muscle tissue found in chordates. They are zig-zag, "W" or "V"-shaped muscle fibers; the myomeres are separated from adjacent myomere by connective tissues and most seen in larval fishes or in the olm. Myomere counts are sometimes used for identifying specimens, since their number corresponds to the number of vertebrae in the adults
The Phyllopod bed, designated by USNM locality number 35k, is the most famous fossil-bearing member of the Burgess shale fossil Lagerstätte. It was quarried by Charles Walcott from 1911–1917, was the source of 95% of the fossils he collected during this time; the phyllopod bed is a 2.31 m thick layer of the 7 m thick Greater Phyllopod Bed, found in the Walcott Quarry on Fossil ridge, between Mount Wapta and Mount Field, at an elevation of around 2,300 metres, around 5 kilometres north of the railway town of Field, in the Canadian Rocky Mountains in British Columbia, Canada. Walcott divided the bed into twelve units based on the rock fossil content. Certain fossil beds provide reference levels and can be recognized by the superabundance of a particular type of fossil: for instance, the Great Marrella layer and Great Eldonia layer. After locating soft-bodied fossils in loose fragments of rock in 1907, the Phyllopod bed was located in a source for the fragments' origins by the Walcotts in 1910.
Extensive quarrying was performed in field seasons until 1913, Walcott considered the ton of shale he collected in his next visit, in 1917, to have exhausted the productive potential of the bed. Most of the organisms within the Phyllopod bed had been transported minimal distances before they were buried, decayed in place until they were buried. Mineralization of tissues occurred shortly afterwards; the community of organisms preserved is a good representation of the community. A great deal of compaction occurred after the deposition of the fossils; the unit consists of mudstones that intergrade into coarser shelly sandstones that sometimes form small nodules. There are turbidite layers, but on the whole the unit was deposited in large events that dumped tens of centimetres of sediment at a time as a slurry of mud was washed over the site by a density current, sweeping up and entombing any organisms in its path; the preservation of the fossils – and their pre-burial livelihoods – was facilitated by mats of the cyanobacterium Morania, which served to bind the sediment and allow anoxic conditions to form.
The phyllopod bed preserves a range of organisms from both a rich benthic community and representatives of the nekton. Many feeding modes are present and a complex food web can be inferred. Whilst some shelly fossils are present, the majority of fossils - 98% of what was alive at the time of burial - do not have biomineralized components. Whilst trace fossils or ichnofauna are locally abundant in other areas of the Burgess Shale, they are completely absent in the Phyllopod bed as a result of the presence of Morania
A tunicate is a marine invertebrate animal, a member of the subphylum Tunicata. It is part of the Chordata, a phylum which includes all animals with dorsal nerve cords and notochords; the subphylum was at one time called Urochordata, the term urochordates is still sometimes used for these animals. They are the only chordates that have lost their myomeric segmentation, with the possible exception of the seriation of the gill slits; some tunicates live as solitary individuals, but others replicate by budding and become colonies, each unit being known as a zooid. They are marine filter feeders with a water-filled, sac-like body structure and two tubular openings, known as siphons, through which they draw in and expel water. During their respiration and feeding, they take in water through the incurrent siphon and expel the filtered water through the excurrent siphon. Most adult tunicates are sessile and permanently attached to rocks or other hard surfaces on the ocean floor. Various species of the subphylum tunicata are known as ascidians, sea squirts, sea pork, sea livers, or sea tulips.
The earliest probable species of tunicate appears in the fossil record in the early Cambrian period. Despite their simple appearance and different adult form, their close relationship to the vertebrates is evidenced by the fact that during their mobile larval stage, they possess a notochord or stiffening rod and resemble a tadpole, their name derives from their unique outer covering or "tunic", formed from proteins and carbohydrates, acts as an exoskeleton. In some species, it is thin and gelatinous, while in others it is thick and stiff. About 2,150 species of tunicate exist in the world's oceans, living in shallow water; the most numerous group is the ascidians. Some are solitary animals leading a sessile existence attached to the seabed, but others are colonial and a few are pelagic; some are supported by a stalk, but most are attached directly to a substrate, which may be a rock, coral, mangrove root, piling, or ship's hull. They are found in a range of solid or translucent colours and may resemble seeds, peaches, barrels, or bottles.
One of the largest is a stalked sea tulip, Pyura pachydermatina, which can grow to be over 1 metre tall. The Tunicata were established by Jean-Baptiste Lamarck in 1816. In 1881, Francis Maitland Balfour introduced a second name for the same group, "Urochorda", to emphasize the affinity of the group to other chordates. No doubt because of his influence, various authors supported the term, either as such, or as "Urochordata", but this usage is invalid because "Tunicata" has precedence, grounds for superseding the name never existed. Accordingly, the current trend is to abandon the name Urochorda or Urochordata in favour of the original Tunicata, the name Tunicata is invariably used in modern scientific works, it is accepted as valid by the World Register of Marine Species but not by the Integrated Taxonomic Information System. Various common names are used for different species. Sea tulips are tunicates with colourful bodies supported on slender stalks. Sea squirts are so named because of their habit of contracting their bodies and squirting out water when disturbed.
Sea liver and sea pork get their names from the resemblance of their dead colonies to pieces of meat. Tunicates are more related to craniates, than to lancelets, hemichordates, Xenoturbella or other invertebrates; the clade consisting of tunicates and vertebrates is called Olfactores. The Tunicata contain 3,051 described species, traditionally divided into these classes: Ascidiacea Thaliacea Appendicularia Members of the Sorberacea were included in Ascidiacea in 2011 as a result of rDNA sequencing studies. Although the traditional classification is provisionally accepted, newer evidence suggests the Ascidiacea are an artificial group of paraphyletic status. Undisputed fossils of tunicates are rare; the best known and earliest unequivocally identified species is Shankouclava shankouense from the Lower Cambrian Maotianshan Shale at Shankou village, near Kunming. There is a common bioimmuration, of a possible tunicate found in Upper Ordovician bryozoan skeletons of the upper midwestern United States.
Three enigmatic species were found from the Ediacaran period – Ausia fenestrata from the Nama Group of Namibia, the sac-like Yarnemia acidiformis, one from a second new Ausia-like genus from the Onega Peninsula of northern Russia, Burykhia hunti. Results of a new study have shown possible affinity of these Ediacaran organisms to the ascidians. Ausia and Burykhia lived in shallow coastal waters more than 555 to 548 million years ago, are believed to be the oldest evidence of the chordate lineage of metazoans; the Russian Precambrian fossil Yarnemia is identified as a tunicate only tentatively, because its fossils are nowhere near as well-preserved as those of Ausia and Burykhia, so this identification has been questioned. Fossils of tunicates are rare because their bodies decay soon after death, but in some tunicate families, microscopic spicules are present, which may be preserved as microfossils; these spicules have been found in Jurassic and rocks, but, as few palaeontologists are familiar with them, they may have been mistaken for sponge spicules.
A multi-taxon molecular study in 2010