1.
Lancelot
–
Sir Lancelot du Lac was one of the Knights of the Round Table in the Arthurian legend. Traditional scholars thought that they are the same due to the fact that their names are similar. One suggestion has been that the name may have been an invention by Chretien de Troyes, given the evidence of LAncelot. Another suggestion is that the name may have derived from Geoffrey of Monmouths Anguselaus. However, one scholar has suggested that Lancelot may be a variant of the name Lancelin, Lancelot or Lancelin may have instead been the hero of an independent folk-tale which had contact with and was ultimately absorbed into the Arthurian tradition. F. Campbell in his Tales of the West Highlands, the character Lancelot is first introduced by writer Chrétien de Troyes in the 12th century. In Chrétiens earliest known work Erec and Enide, the name Lancelot appears as third on a list of knights at King Arthurs court. The fact that Lancelots name follows Gawain and Erec indicates the importance of the knight at court. Here, Lancelot takes an important role as one of the knights that Cligès must overcome in his quest. It is not until Chrétiens Le Chevalier de la Charrette, however, in this text, he is presented as the most formidable knight at King Arthurs court. His adulterous relationship with the Queen is also introduced in this text, according to Pamela Raabe, Lancelot is portrayed in Chrétien de Troyes’ work as the bravest of knights and one whom everyone is forced to describe as uniquely perfect. His deeds are recounted for their uniqueness, not only among living knights, the problem is that critics have been unable to agree on how to reconcile his perfect “saintliness” with his obvious adultery with King Arthur’s Guinevere. How can the lovers’ consummation be considered a “saintly affair” when it is also adultery, and that adultery is against King Arthur, to whom all knights owe selfless respect, according to Arthurian politics and William Bowman Piper. It is also Chrétien who first gives Lancelot the name Lancelot du Lac which was picked up by the Anglo-French Lancelot-Grail. Lancelot is constantly tied to the Christianity associated with Arthurian Legend, Raabe compares Lancelot’s quest for Guinevere in “Lancelot, the Knight of the Cart” to Everyman’s quest for salvation and Christ’s quest for the human soul. This becomes intensified when he becomes the saviour of the captives of Logres. Danielle MacBain’s study of Thomas Malory’s Le Morte dArthur claims that Lancelot’s affair with Guinevere is often seen as parallel to that of Tristram and Iseult. MacBain suggests that it is Lancelot who is identified with the tragedy of chance
2.
Branchiostoma lanceolatum
–
Branchiostoma lanceolatum is a lancelet in the subphylum Cephalochordata. It is a marine invertebrate found in soft substrates in shallow seas and it is used as a model organism to study the development of vertebrates. The mitochondrial genome has been sequenced, Branchiostoma lanceolatum has an elongated body, flattened laterally and pointed at both ends. A stiffening rod of tightly packed cells, the notochord, extends the length of the body. Above it is a cord with a single frontal eye. The mouth is on the underside of the body and is surrounded by a tuft of 20 or 30 cirri or slender sensory appendages, the gut runs just below the notochord from the mouth to the anus, in front of the tail. There is a flap-like, vertical fin surrounding the pointed tail, gas exchange takes place as water passes through gill slits in the mid region, and segmented gonads lie just behind these. The animal is white and semi-transparent which enables the internal organs to be seen from outside. Its appearance is similar to a primitive fish and it can grow up to 6 cm long. Branchiostoma lanceolatum is found in seas in the north-east Atlantic Ocean, from Norway, Scotland as well as further south to the Mediterranean Sea. Its range has expanded through the Suez Canal to the parts of the Indian Ocean. It burrows in soft substrates such as sand, gravel and shell fragments and is quite particular as to the size of the particles and it occurs from the low tide mark down to about 40 metres. In the North Sea, breeding takes place in June and July, the mature adult Branchiostoma lanceolatum, aged 2 to 3 years, congregate in masses on the sea floor. Individuals are either male or female and spawn once a year, the eggs are laid and fertilisation takes place externally. The early larval stages take place in the substrate but a little later and they are elongated and flattened laterally and have a swollen region around the gill slits. These slits number 6 to 19, the number increasing as the passes through its various stages. The larvae have a daily migration. Each evening they rise to near the surface of the sea and in the morning they sink through the column, feeding on phytoplankton, copepods
3.
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
4.
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
5.
Chordata
–
Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
6.
Cephalochordata
–
A cephalochordate is an animal in the chordate subphylum, Cephalochordata. They are characterized as chordates, as they possess all 5 of the chordate characteristics during larval stages and this includes, notocord, dorsal nerve cord, endostyle, pharynx and post-anal tail. Cephalochordates are represented in the oceans by the Amphioxiformes. Along with its sister phylum, Urochordata, Cephalochordata can be classified as belonging to the taxon Protochordata, the members of this subphylum are very small and have no hard parts, making their fossils difficult to find. Fossilized species have found in very old rocks predating vertebrates. There is a famous fossil shale from the Middle Cambrian, the Burgess Shale of British Columbia, recently, a different cephalochordate fossil has been found in south China. It dates to the early Cambrian period, and is the earliest known fossil of the cephalochordate lineage, members of this lineage have numerous gill slits, and have separate sexes. Phylogeny is based on a combination of studies of extinct and extant species, cephalochordates employ a filter feeding system to consume microorganisms. The oral hood serves as the entrance for food particles, and possesses buccal cirri, epithelial cilia lining the mouth and pharynx form a specialized wheel organ situated at the dorsal and posterior end of the cavity. The motion of the cilia resembles the motion of a wheel, hence the organs name. Behind this organ is the velum, which acts as a filter before food enters the pharynx. The food particles adhere to secreted mucus on the bars before being brought to the epibranchial groove on the dorsal side of the pharynx. Following this, the food is transferred to the gut, and this excess water passes through the atriopore and is then excreted from the body
7.
Asymmetronidae
–
They are the modern representatives of the subphylum Cephalochordata, formerly thought to be the sister group of the craniates. In Asia, they are harvested commercially as food for humans and they are an important object of study in zoology as they provide indications about the evolutionary origins of the vertebrates. Lancelets serve as an intriguing comparison point for tracing how vertebrates have evolved and adapted, although lancelets split from vertebrates more than 520 million years ago, their genomes hold clues about evolution, particularly how vertebrates have employed old genes for new functions. They are regarded as similar to the archetypal vertebrate form, the first representative organism of the group to be described was Branchiostoma lanceolatum. It was described by Peter Simon Pallas in 1774 as molluscan slugs in the genus Limax and it was not until 1834 that Gabriel Costa brought the phylogenetic position of the group closer to the agnathan vertebrates, including it in the new genus Branchiostoma. In 1836, Yarrel renamed the genus as Amphioxus, now considered a synonym of the genus Branchiostoma. Today, the term amphioxus is still used as a name for the Amphioxiformes, along with lancelet. A non-technical review of all aspects of biology is, Stokes, M. D. and Holland. The genome of the Florida lancelet has been sequenced, lancelets are typically 5 centimetres long, or 7 centimetres at the longest. They have a translucent, somewhat fish-like body, but without any paired fins or other limbs, a relatively poorly developed tail fin is present, so they are not especially good swimmers. While they do possess some cartilage-like material stiffening the gill slits, mouth, in common with vertebrates, lancelets have a hollow nerve cord running along the back, pharyngeal slits and a tail that runs past the anus. Also like vertebrates, the muscles are arranged in blocks called myomeres, unlike vertebrates, the dorsal nerve cord is not protected by bone but by a simpler notochord made up of a cylinder of cells that are closely packed to form a toughened rod. The lancelet notochord, unlike the vertebrate spine, extends into the head and this gives the subphylum its name. The nerve cord is only larger in the head region than in the rest of the body. However, developmental gene expression and Transmission electron microscopy indicate the presence of a diencephalic forebrain, a possible midbrain, lancelets have two known kinds of light-sensing structures, Joseph cells, and Hesse organs, as well as a frontal eye and lamellar body. The frontal eye is thought to be light-sensitive, although this has not been confirmed by electrophysiological measurement. The lamellar body, a homologue of the pineal body, was once thought to be light-sensitive. All of these organs and structures are located in the tube, with the frontal eye at the front, followed by the lamellar body, the Joseph cells
8.
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
9.
Chordates
–
Chordates are deuterostomes, as during the embryo development stage the anus forms before the mouth. They are also bilaterally symmetric coelomates, in the case of vertebrate chordates, the notochord is usually replaced by a vertebral column during development, and they may have body plans organized via segmentation. There are also additional extinct taxa, the Vertebrata are sometimes considered as a subgroup of the clade Craniata, consisting of chordates with a skull, the Craniata and Tunicata compose the clade Olfactores. Of the more than 65,000 living species of chordates, the worlds largest and fastest animals, the blue whale and peregrine falcon respectively, are chordates, as are humans. Fossil chordates are known from at least as early as the Cambrian explosion, Hemichordata, which includes the acorn worms, has been presented as a fourth chordate subphylum, but it now is usually treated as a separate phylum. The Hemichordata, along with the Echinodermata, form the Ambulacraria, the Chordata and Ambulacraria form the superphylum Deuterostomia, composed of the deuterostomes. Attempts to work out the relationships of the chordates have produced several hypotheses. All of the earliest chordate fossils have found in the Early Cambrian Chengjiang fauna. Because the fossil record of early chordates is poor, only molecular phylogenetics offers a prospect of dating their emergence. However, the use of molecular phylogenetics for dating evolutionary transitions is controversial and it has also proved difficult to produce a detailed classification within the living chordates. Attempts to produce family trees shows that many of the traditional classes are paraphyletic. While this has been known since the 19th century, an insistence on only monophyletic taxa has resulted in vertebrate classification being in a state of flux. Although the name Chordata is attributed to William Bateson, it was already in prevalent use by 1880, ernst Haeckel described a taxon comprising tunicates, cephalochordates, and vertebrates in 1866. Though he used the German vernacular form, it is allowed under the ICZN code because of its subsequent latinization, among the vertebrate sub-group of chordates the notochord develops into the spine, and in wholly aquatic species this helps the animal to swim by flexing its tail. In fish and other vertebrates, this develops into the spinal cord, the pharynx is the part of the throat immediately behind the mouth. In fish, the slits are modified to form gills, a muscular tail that extends backwards behind the anus. This is a groove in the wall of the pharynx. In filter-feeding species it produces mucus to gather food particles, which helps in transporting food to the esophagus and it also stores iodine, and may be a precursor of the vertebrate thyroid gland
10.
Temperateness
–
In geography, temperate or tepid latitudes of Earth lie between the tropics and the polar regions. The temperatures in these regions are relatively moderate, rather than extremely hot or cold. The north temperate zone extends from the Tropic of Cancer to the Arctic Circle, the south temperate zone extends from the Tropic of Capricorn to the Antarctic Circle. In some climate classifications, the zone is often divided into several smaller climate zones. These include Humid subtropical climate, Mediterranean climate, oceanic, subtropical climates are located between 23. 5° and 35. 0° north or south latitude on the eastern or leeward sides of landmasses. This climate has long, generally hot, summers and short, mild winters and these climates may occur in southern Asia, the southeastern United States, parts of eastern Australia, and in eastern coastal South America. Mediterranean climates, occur between 30° and 42° north and south latitude, on the sides of landmasses. This climate has hot summers and short mild winters, however, seasonal rainfall is the opposite of that of the subtropical humid type. These climates occur near the rimlands of the Mediterranean Sea, in western Australia, in California, the oceanic climates occur in the higher middle latitudes, between 45° and 60° north and south latitude. They are created by the flow from the cool high latitude oceans to their west. This causes the climate to have cool summers and cool winters, annual rainfall is spread throughout the entire year. Regions with this climate include Western Europe, northwestern North America, the Continental climates occur in middle latitudes, between 35° or 40° to 55°. These climates are normally inland or on sides of landmasses. They feature warm to hot summers and cold winters, with a large temperature variation. Regions with this climate include northern temperate Asia, the northern United States, southern Canada, the vast majority of the worlds human population resides in temperate zones, especially in the northern hemisphere, due to its greater mass of land. The richest temperate flora in the world is found in southern Africa, geographical zone Habitat Köppen climate classification Middle latitudes Polar circle Subtropics
11.
Scotland
–
Scotland is a country that is part of the United Kingdom and covers the northern third of the island of Great Britain. It shares a border with England to the south, and is surrounded by the Atlantic Ocean, with the North Sea to the east. In addition to the mainland, the country is made up of more than 790 islands, including the Northern Isles, the Kingdom of Scotland emerged as an independent sovereign state in the Early Middle Ages and continued to exist until 1707. By inheritance in 1603, James VI, King of Scots, became King of England and King of Ireland, Scotland subsequently entered into a political union with the Kingdom of England on 1 May 1707 to create the new Kingdom of Great Britain. The union also created a new Parliament of Great Britain, which succeeded both the Parliament of Scotland and the Parliament of England. Within Scotland, the monarchy of the United Kingdom has continued to use a variety of styles, titles, the legal system within Scotland has also remained separate from those of England and Wales and Northern Ireland, Scotland constitutes a distinct jurisdiction in both public and private law. Glasgow, Scotlands largest city, was one of the worlds leading industrial cities. Other major urban areas are Aberdeen and Dundee, Scottish waters consist of a large sector of the North Atlantic and the North Sea, containing the largest oil reserves in the European Union. This has given Aberdeen, the third-largest city in Scotland, the title of Europes oil capital, following a referendum in 1997, a Scottish Parliament was re-established, in the form of a devolved unicameral legislature comprising 129 members, having authority over many areas of domestic policy. Scotland is represented in the UK Parliament by 59 MPs and in the European Parliament by 6 MEPs, Scotland is also a member nation of the British–Irish Council, and the British–Irish Parliamentary Assembly. Scotland comes from Scoti, the Latin name for the Gaels, the Late Latin word Scotia was initially used to refer to Ireland. By the 11th century at the latest, Scotia was being used to refer to Scotland north of the River Forth, alongside Albania or Albany, the use of the words Scots and Scotland to encompass all of what is now Scotland became common in the Late Middle Ages. Repeated glaciations, which covered the land mass of modern Scotland. It is believed the first post-glacial groups of hunter-gatherers arrived in Scotland around 12,800 years ago, the groups of settlers began building the first known permanent houses on Scottish soil around 9,500 years ago, and the first villages around 6,000 years ago. The well-preserved village of Skara Brae on the mainland of Orkney dates from this period and it contains the remains of an early Bronze Age ruler laid out on white quartz pebbles and birch bark. It was also discovered for the first time that early Bronze Age people placed flowers in their graves, in the winter of 1850, a severe storm hit Scotland, causing widespread damage and over 200 deaths. In the Bay of Skaill, the storm stripped the earth from a large irregular knoll, when the storm cleared, local villagers found the outline of a village, consisting of a number of small houses without roofs. William Watt of Skaill, the laird, began an amateur excavation of the site, but after uncovering four houses
12.
Tropics
–
The tropics are a region of the Earth surrounding the equator. The tropics are also referred to as the zone and the torrid zone. The tropics include all the areas on the Earth where the Sun is at a point directly overhead at least once during the solar year. The tropics are distinguished from the climatic and biomatic regions of Earth, which are the middle latitudes. Tropical is sometimes used in a sense for a tropical climate to mean warm to hot and moist year-round. Many tropical areas have a dry and wet season, the wet season, rainy season or green season, is the time of year, ranging from one or more months, when most of the average annual rainfall in a region falls. Areas with wet seasons are disseminated across portions of the tropics and subtropics, under the Köppen climate classification, for tropical climates, a wet season month is defined as a month where average precipitation is 60 millimetres or more. Tropical rainforests technically do not have dry or wet seasons, since their rainfall is distributed through the year. When the wet season occurs during the season, or summer, precipitation falls mainly during the late afternoon. The wet season is a time when air quality improves, freshwater quality improves and vegetation grows significantly, floods cause rivers to overflow their banks, and some animals to retreat to higher ground. Soil nutrients diminish and erosion increases, the incidence of malaria increases in areas where the rainy season coincides with high temperatures. Animals have adaptation and survival strategies for the wetter regime, unfortunately, the previous dry season leads to food shortages into the wet season, as the crops have yet to mature. Regions within the tropics may well not have a tropical climate, there are alpine tundra and snow-capped peaks, including Mauna Kea, Mount Kilimanjaro, and the Andes as far south as the northernmost parts of Chile and Argentina. Under the Köppen climate classification, much of the area within the tropics is classed not as tropical but as dry including the Sahara Desert. Tropical plants and animals are those native to the tropics. Tropical ecosystems may consist of rainforests, dry forests, spiny forests, desert. There are often significant areas of biodiversity, and species present, particularly in rainforests. In biogeography, the tropics are divided into Paleotropics and Neotropics, together, they are sometimes referred to as the Pantropic
13.
Craniata
–
A craniate is a member of the Craniata, a proposed clade of chordate animals with a skull of hard bone or cartilage. Included in the clade are the vertebrates, and non-vertebrate chordates with skulls, living representatives are the Myxini, Hyperoartia, and the much more numerous Gnathostomata. The craniate head consists of a brain, sense organs, including eyes, in addition to distinct crania, craniates possess many derived characteristics, which have allowed for more complexity to follow. In general, craniates are much more active than tunicates and lancelets and, as a result, have greater metabolic demands, aquatic craniates have gill slits, which are connected to muscles and nerves that pump water through the slits, engaging in both feeding and gas exchange. Muscles line the canal, moving food through the canal. Craniates have cardiovascular systems that include a heart with two or more chambers, red cells, and oxygen transporting hemoglobin, as well as kidneys. Linnaeus used the terms Craniata and Vertebrata interchangeably to include lampreys, jawed fishes, hagfishes were classified as Vermes, possibly representing a transitional form between worms and fishes. Dumeril grouped hagfishes and lampreys in the taxon Cyclostomi, characterized by horny teeth borne on an apparatus, a large notochord as adults. Cyclostomes were regarded as either degenerate cartilaginous fishes or primitive vertebrates, cope coined the name Agnatha for a group that included the cyclostomes and a number of fossil groups in which jaws could not be observed. Vertebrates were subsequently divided into two major sister-groups, the Agnatha and the Gnathostomata, stensiö suggested that the two groups of living agnathans arose independently from different groups of fossil agnathans. e. On this basis Janvier proposed to use the names Vertebrata and Craniata as two distinct and nested taxa, the argument is that, if Cyclostomata is indeed monophyletic, Vertebrata would return to its old content and the name Craniata, being superfluous, would become a junior synonym. Lines show probable evolutionary relationships, including extinct taxa, which are denoted with a dagger, the positions of the Lancelet, Tunicate, and Craniata clades are as reported in the scientific journal Nature. Note that this cladogram, in showing the extant cyclostomes as paraphyletic, is contradicted by all recent molecular data. Extinct genera Haikouella and Haikouichthys Campbell, Neil A. Reece, cleveland P. Hickman, J. Roberts, L. S. Keen, S. L. Larson, A. & Eisenhour, D. J. Animal Diversity, Fourth Edition. CS1 maint, Uses authors parameter Cracraft, Joel, Donoghue, new York, Oxford University Press US. Delarbre, Christiane, Gallut, C, Barriel, V, Janvier, P, Gachelin, G, complete Mitochondrial DNA of the Hagfish, Eptatretus burgeri, The Comparative Analysis of Mitochondrial DNA Sequences Strongly Supports the Cyclostome Monophyly. Parker, T. J. Haswell, W. A
14.
Asia
–
Asia covers an area of 44,579,000 square kilometres, about 30% of Earths total land area and 8. 7% of the Earths total surface area. The continent, which has long been home to the majority of the population, was the site of many of the first civilizations. Asia is notable for not only its large size and population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, the western boundary with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. The most commonly accepted boundaries place Asia to the east of the Suez Canal, the Ural River, and the Ural Mountains, and south of the Caucasus Mountains, China and India alternated in being the largest economies in the world from 1 to 1800 A. D. The accidental discovery of America by Columbus in search for India demonstrates this deep fascination, the Silk Road became the main East-West trading route in the Asian hitherland while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may actually have more to do with human geography than physical geography. Asia varies greatly across and within its regions with regard to ethnic groups, cultures, environments, economics, historical ties, the boundary between Asia and Africa is the Red Sea, the Gulf of Suez, and the Suez Canal. This makes Egypt a transcontinental country, with the Sinai peninsula in Asia, the border between Asia and Europe was historically defined by European academics. In Sweden, five years after Peters death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Urals as the border of Asia, the Russians were enthusiastic about the concept, which allowed them to keep their European identity in geography. Tatishchev announced that he had proposed the idea to von Strahlenberg, the latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century, the border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is usually placed along the crest of the Caucasus Mountains, the border between Asia and the loosely defined region of Oceania is usually placed somewhere in the Malay Archipelago. The terms Southeast Asia and Oceania, devised in the 19th century, have had several different geographic meanings since their inception. The chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the possessions of the various empires there. Lewis and Wigen assert, The narrowing of Southeast Asia to its present boundaries was thus a gradual process, Asia is larger and more culturally diverse than Europe. It does not exactly correspond to the borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system on the grounds there is no or is no substantial physical separation between them
15.
Food
–
Food is any substance consumed to provide nutritional support for an organism. It is usually of plant or animal origin, and contains essential nutrients, such as carbohydrates, fats, proteins, vitamins, the substance is ingested by an organism and assimilated by the organisms cells to provide energy, maintain life, or stimulate growth. Historically, humans secured food through two methods, hunting and gathering and agriculture, today, the majority of the food energy required by the ever increasing population of the world is supplied by the food industry. They address issues such as sustainability, biological diversity, climate change, nutritional economics, population growth, water supply, most food has its origin in plants. Some food is obtained directly from plants, but even animals that are used as sources are raised by feeding them food derived from plants. Cereal grain is a food that provides more food energy worldwide than any other type of crop. Corn, wheat, and rice – in all of their varieties – account for 87% of all grain production worldwide, most of the grain that is produced worldwide is fed to livestock. Some foods not from animal or plant sources include various edible fungi, fungi and ambient bacteria are used in the preparation of fermented and pickled foods like leavened bread, alcoholic drinks, cheese, pickles, kombucha, and yogurt. Another example is blue-green algae such as Spirulina, inorganic substances such as salt, baking soda and cream of tartar are used to preserve or chemically alter an ingredient. Many plants and plant parts are eaten as food and around 2,000 plant species are cultivated for food, many of these plant species have several distinct cultivars. Seeds of plants are a source of food for animals, including humans, because they contain the nutrients necessary for the plants initial growth, including many healthful fats. In fact, the majority of food consumed by human beings are seed-based foods, edible seeds include cereals, legumes, and nuts. Oilseeds are often pressed to produce rich oils - sunflower, flaxseed, rapeseed, sesame, seeds are typically high in unsaturated fats and, in moderation, are considered a health food, although not all seeds are edible. Large seeds, such as those from a lemon, pose a choking hazard, fruits are the ripened ovaries of plants, including the seeds within. Many plants and animals have coevolved such that the fruits of the former are a food source to the latter. Fruits, therefore, make up a significant part of the diets of most cultures, some botanical fruits, such as tomatoes, pumpkins, and eggplants, are eaten as vegetables. Vegetables are a type of plant matter that is commonly eaten as food. These include root vegetables, bulbs, leaf vegetables, stem vegetables, animals are used as food either directly or indirectly by the products they produce
16.
Human
–
Modern humans are the only extant members of Hominina tribe, a branch of the tribe Hominini belonging to the family of great apes. Several of these hominins used fire, occupied much of Eurasia and they began to exhibit evidence of behavioral modernity around 50,000 years ago. In several waves of migration, anatomically modern humans ventured out of Africa, the spread of humans and their large and increasing population has had a profound impact on large areas of the environment and millions of native species worldwide. Humans are uniquely adept at utilizing systems of communication for self-expression and the exchange of ideas. Humans create complex structures composed of many cooperating and competing groups, from families. Social interactions between humans have established a wide variety of values, social norms, and rituals. These human societies subsequently expanded in size, establishing various forms of government, religion, today the global human population is estimated by the United Nations to be near 7.5 billion. In common usage, the word generally refers to the only extant species of the genus Homo—anatomically and behaviorally modern Homo sapiens. In scientific terms, the meanings of hominid and hominin have changed during the recent decades with advances in the discovery, there is also a distinction between anatomically modern humans and Archaic Homo sapiens, the earliest fossil members of the species. The English adjective human is a Middle English loanword from Old French humain, ultimately from Latin hūmānus, the words use as a noun dates to the 16th century. The native English term man can refer to the species generally, the species binomial Homo sapiens was coined by Carl Linnaeus in his 18th century work Systema Naturae. The generic name Homo is a learned 18th century derivation from Latin homō man, the species-name sapiens means wise or sapient. Note that the Latin word homo refers to humans of either gender, the genus Homo evolved and diverged from other hominins in Africa, after the human clade split from the chimpanzee lineage of the hominids branch of the primates. The closest living relatives of humans are chimpanzees and gorillas, with the sequencing of both the human and chimpanzee genome, current estimates of similarity between human and chimpanzee DNA sequences range between 95% and 99%. The gibbons and orangutans were the first groups to split from the leading to the humans. The splitting date between human and chimpanzee lineages is placed around 4–8 million years ago during the late Miocene epoch, during this split, chromosome 2 was formed from two other chromosomes, leaving humans with only 23 pairs of chromosomes, compared to 24 for the other apes. There is little evidence for the divergence of the gorilla, chimpanzee. Each of these species has been argued to be an ancestor of later hominins
17.
List of domesticated animals
–
This includes species which are semi-domesticated, undomesticated but captive-bred on a commercial scale, or commonly wild-caught, at least occasionally captive-bred, and tameable. A number of factors determine how quickly any changes may occur in a species, however, domestication is a gradual process, i. e. there is no precise moment in the history of a given species when it can be considered to have become fully domesticated. Archaeozoology has identified three classes of animal domesticates, commensals, adapted to a niche, prey animals sought for food. To sort the tables chronologically by date of domestication, refresh your browser window, as clicking the Date column heading will mix AD, due to the somewhat unclear outlines of what, precisely, constitutes domestication, there are some species that may or may not be fully domesticated. There are also species that are used or kept as pets by humans. Most animals on this table are at least somewhat altered from wild animals by their extensive interactions with humans. Many could not be released into the wild, or are in some way dependent on humans
18.
Zoology
–
The term is derived from Ancient Greek ζῷον, zōion, i. e. animal and λόγος, logos, i. e. knowledge, study. The history of zoology traces the study of the kingdom from ancient to modern times. This ancient work was developed in the Middle Ages by Muslim physicians. During the Renaissance and early period, zoological thought was revolutionized in Europe by a renewed interest in empiricism. Microscopy revealed the unknown world of microorganisms, laying the groundwork for cell theory. The growing importance of natural theology, partly a response to the rise of mechanical philosophy, over the 18th and 19th centuries, zoology became an increasingly professional scientific discipline. Naturalists began to reject essentialism and consider the importance of extinction, cell theory provided a new perspective on the fundamental basis of life. These developments, as well as the results from embryology and paleontology, were synthesized in Charles Darwins theory of evolution by natural selection. In 1859, Darwin placed the theory of evolution on a new footing, by his discovery of a process by which organic evolution can occur. Darwin gave new direction to morphology and physiology, by uniting them in a biological theory. The end of the 19th century saw the fall of spontaneous generation, cell biology studies the structural and physiological properties of cells, including their behavior, interactions, and environment. This is done on both the microscopic and molecular levels, for single-celled organisms such as bacteria as well as the cells in multicellular organisms such as humans. Understanding the structure and function of cells is fundamental to all of the biological sciences, the similarities and differences between cell types are particularly relevant to molecular biology. Anatomy considers the forms of macroscopic structures such as organs and organ systems and it focuses on how organs and organ systems work together in the bodies of humans and animals, in addition to how they work independently. Anatomy and cell biology are two studies that are related, and can be categorized under structural studies. Physiology studies the mechanical, physical, and biochemical processes of living organisms by attempting to understand how all of the function as a whole. The theme of structure to function is central to biology, for example, what is learned about the physiology of yeast cells can also apply to human cells. The field of animal physiology extends the tools and methods of physiology to non-human species
19.
Vertebrate
–
Vertebrates /ˈvɜːrtᵻbrᵻts/ comprise all species of animals within the subphylum Vertebrata /-ɑː/. Vertebrates represent the majority of the phylum Chordata, with currently about 66,000 species described. Vertebrates include the fish and the jawed vertebrates, which include the cartilaginous fish. A bony fish known as the lobe-finned fishes is included with tetrapods, which are further divided into amphibians, reptiles, mammals. Extant vertebrates range in size from the frog species Paedophryne amauensis, at as little as 7.7 mm, to the blue whale, vertebrates make up less than five percent of all described animal species, the rest are invertebrates, which lack vertebral columns. The vertebrates traditionally include the hagfish, which do not have proper vertebrae due to their loss in evolution, though their closest living relatives, hagfish do, however, possess a cranium. For this reason, the vertebrate subphylum is sometimes referred to as Craniata when discussing morphology, molecular analysis since 1992 has suggested that hagfish are most closely related to lampreys, and so also are vertebrates in a monophyletic sense. Others consider them a group of vertebrates in the common taxon of craniata. The word origin of vertebrate derives from the Latin word vertebratus, the Proto-Indo-European language origins are still unclear. Vertebrate is derived from the vertebra, which refers to any of the bones or segments of the spinal column. All vertebrates are built along the basic body plan, a stiff rod running through the length of the animal, with a hollow tube of nervous tissue above it. In all vertebrates, the mouth is found at, or right below, the remaining part of the body continuing after the anus forms a tail with vertebrae and spinal cord, but no gut. However, a few vertebrates have secondarily lost this anatomy, retaining the notochord into adulthood, such as the sturgeon, jawed vertebrates are typified by paired appendages, but this trait is not required in order for an animal to be a vertebrate. All basal vertebrates breathe with gills, the gills are carried right behind the head, bordering the posterior margins of a series of openings from the pharynx to the exterior. Each gill is supported by a cartilagenous or bony gill arch, the bony fish have three pairs of arches, cartilaginous fish have five to seven pairs, while the primitive jawless fish have seven. The vertebrate ancestor no doubt had more arches than this, as some of their relatives have more than 50 pairs of gills. In amphibians and some primitive fishes, the larvae bear external gills. These are reduced in adulthood, their function taken over by the gills proper in fishes, some amphibians retain the external larval gills in adulthood, the complex internal gill system as seen in fish apparently being irrevocably lost very early in the evolution of tetrapods
20.
Peter Simon Pallas
–
Peter Simon Pallas was a German zoologist and botanist who worked in Russia. Pallas was born in Berlin, the son of Professor of Surgery Simon Pallas and he studied with private tutors and took an interest in natural history, later attending the University of Halle and the University of Göttingen. In 1760, he moved to the University of Leiden and passed his doctors degree at the age of 19, Pallas traveled throughout the Netherlands and to London, improving his medical and surgical knowledge. He then settled at The Hague, and his new system of classification was praised by Georges Cuvier. Pallas wrote Miscellanea Zoologica, which included descriptions of several new to science which he had discovered in the Dutch museum collections. A planned voyage to southern Africa and the East Indies fell through when his father recalled him to Berlin, there, he began work on his Spicilegia Zoologica. He explored the Caspian Sea, the Ural and Altai Mountains, the regular reports which Pallas sent to St Petersburg were collected and published as Reise durch verschiedene Provinzen des Russischen Reichs. They covered a range of topics, including geology and mineralogy, reports on the native peoples and their religions. In 1776, Pallas was elected a member of the Royal Swedish Academy of Sciences. Pallas settled in St Petersburg, becoming a favourite of Catherine II and teaching history to the Grand Dukes Alexander. He was provided with the plants collected by other naturalists to compile the Flora Rossica, a Russian flora, and started work on his Zoographica Rosso-Asiatica and he also published an account of Johann Anton Güldenstädts travels in the Caucasus. The Empress bought Pallass large natural history collection for 2,000 rubles,500 more than his asking price, during this period, Pallas helped plan the Mulovsky expedition, which was cancelled in October 1787. Between 1793 and 1794, Pallas led an expedition to southern Russia, visiting the Crimea. He was accompanied by his daughter and his new wife, an artist, servants, in February 1793, they travelled to Saratov and then downriver to Tsaritsyn. They spent the spring exploring the country to the east, and in August travelled along the banks of the Caspian Sea, in September, they travelled to the Crimea, wintering in Simferopol. Pallas spent the spring of 1794 exploring to the southeast, and in July travelled up the valley of the Dnieper, Pallas gave his account of the journey in his P. S. Pallas Bemerkungen auf einer Reise in die Südlichen Statthalterschaften des Russischen Reichs. Catherine II gave him an estate at Simferopol, where Pallas lived until the death of his second wife in 1810. He was then granted permission to leave Russia by Emperor Alexander, and returned to Berlin and his grave is preserved in the Protestant Friedhof I der Jerusalems- und Neuen Kirchengemeinde in Berlin-Kreuzberg, south of Hallesches Tor
21.
Mollusc
–
The molluscs compose the large phylum Mollusca of invertebrate animals. Around 85,000 extant species of molluscs are recognized, molluscs are the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats and they are highly diverse, not just in size and in anatomical structure, but also in behaviour and in habitat. The phylum is divided into 9 or 10 taxonomic classes. The gastropods are by far the most numerous molluscs in terms of classified species, the three most universal features defining modern molluscs are a mantle with a significant cavity used for breathing and excretion, the presence of a radula, and the structure of the nervous system. Other than these things, molluscs express great morphological diversity, so many textbooks base their descriptions on an ancestral mollusc. This has a single, limpet-like shell on top, which is made of proteins and chitin reinforced with calcium carbonate, the underside of the animal consists of a single muscular foot. Although molluscs are coelomates, the coelom tends to be small, the main body cavity is a hemocoel through which blood circulates, their circulatory systems are mainly open. The generalized mollusc has two paired nerve cords, or three in bivalves, the brain, in species that have one, encircles the esophagus. Most molluscs have eyes, and all have sensors to detect chemicals, vibrations, the simplest type of molluscan reproductive system relies on external fertilization, but more complex variations occur. All produce eggs, from which may emerge trochophore larvae, more complex veliger larvae, good evidence exists for the appearance of gastropods, cephalopods and bivalves in the Cambrian period 541 to 485.4 million years ago. Molluscs have, for centuries, also been the source of important luxury goods, notably pearls, mother of pearl, Tyrian purple dye and their shells have also been used as money in some preindustrial societies. Mollusc species can also represent hazards or pests for human activities, the bite of the blue-ringed octopus is often fatal, and that of Octopus apollyon causes inflammation that can last for over a month. Stings from a few species of large tropical cone shells can also kill, schistosomiasis is transmitted to humans via water snail hosts, and affects about 200 million people. Snails and slugs can also be serious pests, and accidental or deliberate introduction of some snail species into new environments has seriously damaged some ecosystems. The words mollusc and mollusk are both derived from the French mollusque, which originated from the Latin molluscus, from mollis, molluscus was itself an adaptation of Aristotles τα μαλακά, the soft things, which he applied to cuttlefish. The scientific study of molluscs is accordingly called malacology, as it is now known these groups have no relation to molluscs, and very little to one another, the name Molluscoida has been abandoned. The most universal features of the structure of molluscs are a mantle with a significant cavity used for breathing and excretion
22.
Limax
–
Limax is a genus of air-breathing land slugs in the terrestrial pulmonate gastropod mollusk family Limacidae. The generic name Limax literally means slug, some species, such as the leopard slug and the tawny garden slug, are considered serious garden pests. The genus Limax sensu stricto is probably monophyletic and this genus is native to Europe, but at least one species has been introduced into North America
23.
Hagfish
–
Hagfish, the class Myxini, are eel-shaped, slime-producing marine fish. They are the known living animals that have a skull. Along with lampreys, hagfish are jawless, they are the group to vertebrates. The classification of hagfish has been controversial, the issue is whether the hagfish is a degenerate type of vertebrate-fish, or represents a stage that precedes the evolution of the vertebral column. The original scheme groups hagfish and lampreys together as cyclostomes, as the oldest surviving class of vertebrates alongside gnathostomes, an alternative scheme proposed that jawed vertebrates are more closely related to lampreys than to hagfish, and introduces the category craniata to group vertebrates near hagfish. Recent DNA evidence has supported the original scheme, Hagfish average about 0.5 m in length. The largest known species is Eptatretus goliath with a recorded at 127 cm, while Myxine kuoi. Hagfish have elongated, eel-like bodies, and paddle-like tails, the skin is naked and covers the body like a loosely fitting sock. They have cartilaginous skulls and tooth-like structures composed of keratin, colors depend on the species, ranging from pink to blue-grey, and black or white spots may be present. Eyes are simple eyespots, not compound eyes that can resolve images, Hagfish have no true fins and have six or eight barbels around the mouth and a single nostril. Instead of vertically articulating jaws like Gnathostomata, they have a pair of horizontally moving structures with tooth-like projections for pulling off food, the mouth of the hagfish has two pairs of horny, comb-shaped teeth on a cartilaginous plate that protracts and retracts. These teeth are used to food and draw it toward the pharynx. Hagfish are long and vermiform, and can exude copious quantities of a milky, the typical species Myxine glutinosa was named for this slime. When captured and held, e. g. by the tail, they secrete the microfibrous slime, which expands into up to 20 litres of sticky, gelatinous material when combined with water. This singular behavior may assist them in extricating themselves from the jaws of predatory fish or from the interior of their own prey, recently, the slime was reported to entrain water in its microfilaments, creating a slow-to-dissipate, viscoelastic substance, rather than a simple gel. It has been proven to impair the function of a predator fishs gills, in this case, the hagfishs mucus would clog up the predators gills, disabling their ability to breathe. The predator would release the hagfish as it focused less on eating and it is because of the mucus that there are very few marine predators that target the hagfish. The other known predators of hagfish are varieties of birds or mammals, free-swimming hagfish also slime when agitated and later clear the mucus off by way of the same travelling-knot behavior
24.
Lampreys
–
Lampreys are any jawless fish of the order Petromyzontiformes, placed in the superclass Cyclostomata. The adult lamprey may be characterized by a toothed, funnel-like sucking mouth, the common name lamprey is probably derived from Latin lampetra, which may mean stone licker, though the etymology is uncertain. Currently there are about 38 known extant species of lampreys, parasitic species are the best known, and feed by boring into the flesh of other fish to suck their blood, but only 18 species of lampreys are parasitic. Adults of the species do not feed, they live off reserves acquired as ammocoetes. The lampreys are an ancient lineage of vertebrates, though their exact relationship to hagfishes. Adults superficially resemble eels in that they have scaleless, elongated bodies, lacking paired fins, adult lampreys have large eyes, one nostril on the top of the head, and seven gill pores on each side of the head. The pharynx is subdivided, the part forming a respiratory tube that is isolated from the mouth by a valve called the velum. Near the gills are the eyes, which are developed and buried under skin in the larvae. The eyes complete their development during metamorphosis, and in adults are covered by a thin, instead of true vertebrae, they have a series of cartilaginous structures called arcualia arranged above the notochord. Hagfish, which resemble lampreys, have traditionally considered the sister taxon of the true vertebrates. Studies have shown that lampreys are amongst the most energy-efficient swimmers and their swimming movements generate low-pressure zones around their body, which pull rather than push their bodies through the water. Parasitic lampreys feed on prey as adults by attaching their mouthparts to the animals body, then using their teeth to cut through surface tissues until they reach blood. A study of stomach content of some lampreys have also shown remains of intestines, fins, although attacks on humans do occur, they will generally not attack humans unless starved. Non-parasitic lampreys, which are freshwater species, do not feed as adults, they live off reserves acquired as ammocoetes. Lamprey leukocytes express surface variable lymphocyte receptors generated from somatic recombination of leucine-rich repeat gene segments in a recombination activating gene-independent manner, northern lampreys have the highest number of chromosomes among vertebrates. Pouched lamprey larvae also have a high tolerance for free iron in their bodies. Adult lampreys spawn in rivers and then die, the young larvae, ammocoetes, spend several years in the rivers, where they live burrowed in fine sediment, filter feeding on detritus and microorganisms. Then, ammocoetes undergo a metamorphosis lasting several months, some species do not feed after metamorphosis, while others migrate to the sea or lakes, where they feed on different species of fish and even on marine mammals
25.
Branchiostoma
–
Branchiostoma is one of the few living genera of lancelets. It is the genus of family Branchiostomidae. These small vaguely eel- or snake-like animals are close relatives of vertebrates, like all lancelets, they are filter feeders that hide in the sediment most of the time. The genus inhabits coastal waters throughout the world, media related to Branchiostoma at Wikimedia Commons Branchiostoma
26.
Cartilage
–
It is not as hard and rigid as bone, but it is stiffer and less flexible than muscle. Because of its rigidity, cartilage often serves the purpose of holding tubes open in the body, cartilage is classified in three types, elastic cartilage, hyaline cartilage and fibrocartilage, which differ in relative amounts of collagen and proteoglycan. Cartilage does not contain blood vessels or nerves, nutrition is supplied to the chondrocytes by diffusion. The compression of the cartilage or flexion of the elastic cartilage generates fluid flow. Compared to other tissues, cartilage has a very slow turnover of its extracellular matrix. In embryogenesis, the system is derived from the mesoderm germ layer. Following the initial chondrification that occurs during embryogenesis, cartilage growth consists mostly of the maturing of immature cartilage to a mature state. The division of cells within cartilage occurs very slowly, and thus growth in cartilage is not based on an increase in size or mass of the cartilage itself. The articular cartilage function is dependent on the composition of the extracellular matrix. The ECM consists mainly of proteoglycan and collagens, the main proteoglycan in cartilage is aggrecan, which, as its name suggests, forms large aggregates with hyaluronan. These aggregates are negatively charged and hold water in the tissue, the collagen, mostly collagen type II, constrains the proteoglycans. The ECM responds to tensile and compressive forces that are experienced by the cartilage, cartilage growth thus refers to the matrix deposition, but can also refer to both the growth and remodeling of the extracellular matrix. Due to the stress on the patellofemoral joint during resisted knee flexion. The mechanical properties of articular cartilage in load bearing joints such as knee and hip have been studied extensively at macro, micro and these mechanical properties include the response of cartilage in frictional, compressive, shear and tensile loading. Cartilage is resilient and displays viscoelastic properties, lubricin, a glycoprotein abundant in cartilage and synovial fluid, plays a major role in bio-lubrication and wear protection of cartilage. Cartilage has limited capabilities, Because chondrocytes are bound in lacunae. Therefore, cartilage damage is difficult to heal, also, because hyaline cartilage does not have a blood supply, the deposition of new matrix is slow. Damaged hyaline cartilage is replaced by fibrocartilage scar tissue
27.
Gill slit
–
Gill slits are individual openings to gills, i. e. multiple gill arches, which lack a single outer cover. Such gills are characteristic of fish such as sharks, and rays. In contrast, bony fishes have a single outer bony gill covering called an operculum, most sharks and rays have five pairs of gill slits, but a few species have 6 or 7 pairs. Shark gill slits lie in a row behind the head, the anterior edge of a gill slit is motile, moving outward to allow water to exit, but closing to prevent reverse flow. A modified slit, called a spiracle, lies just behind the eye, spiracles are reduced or missing in active pelagic sharks. While the shark is moving, water passes through the mouth, while at rest, most sharks pump water over their gills to ensure a constant supply of oxygenated water. A small number of species have lost the ability to pump water through their gills and these species are obligate ram ventilators and would presumably asphyxiate if unable to move. Obligate ram ventilation is also true of some pelagic bony fish species, the true gill slits in embryonic fish develop into fish gills. However, the slits in tetrapods do not, so a general name for the vertebral structures is pharyngeal slits. Gill slits likely originated from pharyngeal slits in tunicates that were used for filter-feeding, the term gill slits has also been used to refer to the folds of skin in the pharyngeal region in embryos. It is now accepted that it is the pharyngeal pouches. External gills Gill raker Operculum Pharyngeal slit
28.
Pharyngeal slit
–
Pharyngeal slits are filter-feeding organs found in Invertebrate chordates and hemichordates living in aquatic environments. These repeated segments are controlled by similar developmental mechanisms, some hemichordate species can have as many as 200 gill slits. Pharyngeal slits resembling gill slits are present during the embryonic stages of tetrapod development. However, it is now accepted that it is the pharyngeal pouches. Gill slits are, at stage of life, found in all chordates. In vertebrates, the arches are derived from all three germ layers. Neural crest cells enter these arches where they contribute to features such as bone. However, the existence of pharyngeal structures before neural crest cells evolved is indicated by the existence of neural crest-independent mechanisms of pharyngeal arch development, the first, most anterior pharyngeal arch gives rise to the oral jaw. The second arch becomes the hyoid and jaw support, in fish, the other posterior arches contribute to the brachial skeleton, which support the gills, in tetrapods the anterior arches develop into components of the ear, tonsils, and thymus. The genetic and developmental basis of pharyngeal arch development is well characterized and it has been shown that Hox genes and other developmental genes such as dlx are important for patterning the anterior/posterior and dorsal/ventral axes of the branchial arches. Some fish species have jaws in their throat, known as pharyngeal jaws, the presence of pharyngeal slits in hemichordates led to debates of whether this structure was homologous to the slits found in chordates or a result of convergent evolution. With the placement of hemichordates and echinoderms as a group to chordates. Intriguingly, extant echinoderms lack pharyngeal structures, but fossil records reveal that ancestral forms of echinoderms had gill-like structures, applying excess retinoic acid leads to the absence of gill slits in developing Amphioxus, suggesting that retinoic acid may act through the same mechanism in vertebrates and amphioxus. These studies indicate that the slits found in hemichordates and chordates are indeed homologous in a molecular sense
29.
Tail
–
The tail is the section at the rear end of an animals body, in general, the term refers to a distinct, flexible appendage to the torso. It is the part of the body that corresponds roughly to the sacrum and coccyx in mammals, reptiles, tailed objects are sometimes referred to as caudate and the part of the body associated with or proximal to the tail are given the adjective caudal. Animal tails are used in a variety of ways and they provide a source of locomotion for fish and some other forms of marine life. Many land animals use their tails to brush away flies and other biting insects, tails are also used for social signaling. Some species tails are armored, and some, such as those of scorpions, some species of lizard can detach their tails from their bodies. This can help them to escape predators, which are either distracted by the wriggling, tails cast in this manner generally grow back over time, though the replacement is typically darker in colour than the original. Most birds tails end in long feathers called rectrices and these feathers are used as a rudder, helping the bird steer and maneuver in flight, they also help the bird to balance while it is perched. In some species—such as birds of paradise, lyrebirds, and most notably peafowl—modified tail feathers play an important role in courtship displays, the extra-stiff tail feathers of other species, including woodpeckers and woodcreepers, allow them to brace themselves firmly against tree trunks. The tails of grazing animals, such as horses, are used both to sweep away insects and positioned or moved in ways that indicate the physical or emotional state. Human embryos have a tail measures about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the tail is absorbed by the growing body, humans have a tail bone attached to the pelvis, formed of fused vertebrae, usually four, at the bottom of the vertebral column. Rump Empennage, the tail of an aircraft
30.
Anus
–
The anus is an opening at the opposite end of an animals digestive tract from the mouth. Amphibians, reptiles, and birds use the same orifice for excreting liquid and solid wastes, for copulation, monotreme mammals also have a cloaca, which is thought to be a feature inherited from the earliest amniotes via the therapsids. Marsupials have a single orifice for excreting both solids and liquids and, in females, a vagina for reproduction. The development of the anus was an important stage in the evolution of multicellular animals and it appears to have happened at least twice, following different paths in protostomes and deuterostomes. In animals at least as complex as an earthworm, the forms a dent on one side, the blastopore, which deepens to become the archenteron. In deuterostomes, the original dent becomes the anus while the gut tunnels through to make another opening. The protostomes were so named because it was thought that in their embryos the dent formed the mouth first and the anus was formed later at the opening made by the other end of the gut. More recent research, however, shows that in protostomes the edges of the dent close up in the middle, leaving openings at the ends become the mouth. Anal canal Imperforate anus, a birth defect, media related to Anus at Wikimedia Commons
31.
Cylinder (geometry)
–
In its simplest form, a cylinder is the surface formed by the points at a fixed distance from a given straight line called the axis of the cylinder. It is one of the most basic curvilinear geometric shapes, commonly the word cylinder is understood to refer to a finite section of a right circular cylinder having a finite height with circular ends perpendicular to the axis as shown in the figure. If the ends are open, it is called an open cylinder, if the ends are closed by flat surfaces it is called a solid cylinder. The formulae for the area and the volume of such a cylinder have been known since deep antiquity. The area of the side is known as the lateral area. An open cylinder does not include either top or bottom elements, the surface area of a closed cylinder is made up the sum of all three components, top, bottom and side. Its surface area is A = 2πr2 + 2πrh = 2πr = πd=L+2B, for a given volume, the closed cylinder with the smallest surface area has h = 2r. Equivalently, for a surface area, the closed cylinder with the largest volume has h = 2r. Cylindric sections are the intersections of cylinders with planes, for a right circular cylinder, there are four possibilities. A plane tangent to the cylinder meets the cylinder in a straight line segment. Moved while parallel to itself, the plane either does not intersect the cylinder or intersects it in two line segments. All other planes intersect the cylinder in an ellipse or, when they are perpendicular to the axis of the cylinder, a cylinder whose cross section is an ellipse, parabola, or hyperbola is called an elliptic cylinder, parabolic cylinder, or hyperbolic cylinder respectively. Elliptic cylinders are also known as cylindroids, but that name is ambiguous, as it can also refer to the Plücker conoid. The volume of a cylinder with height h is V = ∫0 h A d x = ∫0 h π a b d x = π a b ∫0 h d x = π a b h. Even more general than the cylinder is the generalized cylinder. The cylinder is a degenerate quadric because at least one of the coordinates does not appear in the equation, an oblique cylinder has the top and bottom surfaces displaced from one another. There are other unusual types of cylinders. Let the height be h, internal radius r, and external radius R, the volume is given by V = π h
32.
Cell (biology)
–
The cell is the basic structural, functional, and biological unit of all known living organisms. A cell is the smallest unit of life that can replicate independently, the study of cells is called cell biology. Cells consist of cytoplasm enclosed within a membrane, which contains many such as proteins. Organisms can be classified as unicellular or multicellular, while the number of cells in plants and animals varies from species to species, humans contain more than 10 trillion cells. Most plant and animal cells are only under a microscope. The cell was discovered by Robert Hooke in 1665, who named the unit for its resemblance to cells inhabited by Christian monks in a monastery. Cells emerged on Earth at least 3.5 billion years ago, Cells are of two types, eukaryotic, which contain a nucleus, and prokaryotic, which do not. Prokaryotes are single-celled organisms, while eukaryotes can be either single-celled or multicellular, prokaryotic cells were the first form of life on Earth, characterised by having vital biological processes including cell signaling and being self-sustaining. They are simpler and smaller than eukaryotic cells, and lack membrane-bound organelles such as the nucleus, prokaryotes include two of the domains of life, bacteria and archaea. The DNA of a prokaryotic cell consists of a chromosome that is in direct contact with the cytoplasm. The nuclear region in the cytoplasm is called the nucleoid, most prokaryotes are the smallest of all organisms ranging from 0.5 to 2.0 µm in diameter. Though most prokaryotes have both a cell membrane and a wall, there are exceptions such as Mycoplasma and Thermoplasma which only possess the cell membrane layer. The envelope gives rigidity to the cell and separates the interior of the cell from its environment, the cell wall consists of peptidoglycan in bacteria, and acts as an additional barrier against exterior forces. It also prevents the cell from expanding and bursting from osmotic pressure due to a hypotonic environment, some eukaryotic cells also have a cell wall. Inside the cell is the region that contains the genome, ribosomes. The genetic material is found in the cytoplasm. Prokaryotes can carry extrachromosomal DNA elements called plasmids, which are usually circular, linear bacterial plasmids have been identified in several species of spirochete bacteria, including members of the genus Borrelia notably Borrelia burgdorferi, which causes Lyme disease. Though not forming a nucleus, the DNA is condensed in a nucleoid, plasmids encode additional genes, such as antibiotic resistance genes
33.
Vertebral column
–
The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column houses the spinal canal, a cavity that encloses, there are about 50,000 species of animals that have a vertebral column. The human vertebral column is one of the most-studied examples, the articulating vertebrae are named according to their region of the spine. There are seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae, the number of vertebrae in a region can vary but overall the number remains the same. The number of those in the region however is only rarely changed. There are ligaments extending the length of the column at the front and the back, the vertebrae in the human vertebral column are divided into different regions, which correspond to the curves of the spinal column. The articulating vertebrae are named according to their region of the spine, vertebrae in these regions are essentially alike, with minor variation. These regions are called the spine, thoracic spine, lumbar spine, sacrum. There are seven cervical vertebrae, twelve thoracic vertebrae and five lumbar vertebrae, the number of vertebrae in a region can vary but overall the number remains the same. The number of those in the region however is only rarely changed. The vertebrae of the cervical, thoracic and lumbar spines are independent bones, the vertebrae of the sacrum and coccyx are usually fused and unable to move independently. Two special vertebrae are the atlas and axis, on which the head rests, a typical vertebra consists of two parts, the vertebral body and the vertebral arch. The vertebral arch is posterior, meaning it faces the back of a person, together, these enclose the vertebral foramen, which contains the spinal cord. Because the spinal cord ends in the spine, and the sacrum and coccyx are fused. Two transverse processes and one process are posterior to the vertebral body. The spinous process comes out the back, one transverse process comes out the left, the spinous processes of the cervical and lumbar regions can be felt through the skin. Above and below each vertebra are joints called facet joints and these restrict the range of movement possible, and are joined by a thin portion of the neural arch called the pars interarticularis. In between each pair of vertebrae are two small holes called intervertebral foramina, the spinal nerves leave the spinal cord through these holes
34.
Brain
–
The brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. The brain is located in the head, usually close to the organs for senses such as vision. The brain is the most complex organ in a vertebrates body, in a human, the cerebral cortex contains approximately 15–33 billion neurons, each connected by synapses to several thousand other neurons. Physiologically, the function of the brain is to exert centralized control over the other organs of the body, the brain acts on the rest of the body both by generating patterns of muscle activity and by driving the secretion of chemicals called hormones. This centralized control allows rapid and coordinated responses to changes in the environment, the operations of individual brain cells are now understood in considerable detail but the way they cooperate in ensembles of millions is yet to be solved. This article compares the properties of brains across the range of animal species. It deals with the human brain insofar as it shares the properties of other brains, the ways in which the human brain differs from other brains are covered in the human brain article. Several topics that might be covered here are instead covered there because more can be said about them in a human context. The most important is brain disease and the effects of brain damage, the shape and size of the brain varies greatly between species, and identifying common features is often difficult. Nevertheless, there are a number of principles of architecture that apply across a wide range of species. Some aspects of structure are common to almost the entire range of animal species, others distinguish advanced brains from more primitive ones. The simplest way to gain information about brain anatomy is by visual inspection, Brain tissue in its natural state is too soft to work with, but it can be hardened by immersion in alcohol or other fixatives, and then sliced apart for examination of the interior. Visually, the interior of the consists of areas of so-called grey matter, with a dark color, separated by areas of white matter. Further information can be gained by staining slices of tissue with a variety of chemicals that bring out areas where specific types of molecules are present in high concentrations. It is also possible to examine the microstructure of brain tissue using a microscope, the brains of all species are composed primarily of two broad classes of cells, neurons and glial cells. Glial cells come in types, and perform a number of critical functions, including structural support, metabolic support, insulation. Neurons, however, are considered the most important cells in the brain. The property that makes neurons unique is their ability to send signals to target cells over long distances
35.
Transmission electron microscopy
–
Transmission electron microscopy is a microscopy technique in which a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it. TEMs are capable of imaging at a higher resolution than light microscopes. This enables the user to examine fine detail—even as small as a single column of atoms. TEM forms a major analysis method in a range of scientific fields, TEMs find application in cancer research, virology, materials science as well as pollution, nanotechnology and semiconductor research. At smaller magnifications TEM image contrast is due to absorption of electrons in the material, due to the thickness, at higher magnifications complex wave interactions modulate the intensity of the image, requiring expert analysis of observed images. The first TEM was built by Max Knoll and Ernst Ruska in 1931, with this group developing the first TEM with resolution greater than that of light in 1933, in 1986, Ruska was awarded the Nobel Prize in physics for the development of transmission electron microscopy. Developments into ultraviolet microscopes, led by Köhler and Rohr, allowed for an increase in resolving power of about a factor of two, however this required more expensive quartz optical components, due to the absorption of UV by glass. At this point it was believed that obtaining an image with sub-micrometer information was simply due to this wavelength constraint. It had earlier recognized by Plücker in 1858 that the deflection of cathode rays was possible by the use of magnetic fields. This effect had been utilized to build primitive cathode ray oscilloscopes as early as 1897 by Ferdinand Braun, indeed, in 1891 it was recognized by Riecke that the cathode rays could be focused by these magnetic fields, allowing for simple lens designs. Later this theory was extended by Hans Busch in his published in 1926. The team consisted of several PhD students including Ernst Ruska and Bodo von Borries, in 1931 the group successfully generated magnified images of mesh grids placed over the anode aperture. The device used two lenses to achieve higher magnifications, arguably the first electron microscope. In that same year, Reinhold Rudenberg, the director of the Siemens company, had patented an electrostatic lens electron microscope. At this time the nature of electrons, which were considered charged matter particles, had not been fully realized until the publication of the De Broglie hypothesis in 1927. In April 1932, Ruska suggested the construction of a new microscope for direct imaging of specimens inserted into the microscope. This goal was achieved in September 1933, using images of cotton fibers, research continued on the electron microscope at Siemens in 1936, the aim of the research was the development improvement of TEM imaging properties, particularly with regard to biological specimens. At this time electron microscopes were being fabricated for specific groups, in 1939 the first commercial electron microscope, pictured, was installed in the Physics department of IG Farben-Werke
36.
Forebrain
–
In the anatomy of the brain of vertebrates, the forebrain or prosencephalon is the rostral-most portion of the brain. The forebrain, the midbrain, and hindbrain are the three portions of the brain during early development of the central nervous system. It controls body temperature, reproductive functions, eating, sleeping, at the five-vesicle stage, the forebrain separates into the diencephalon and the telencephalon which develops into the cerebrum. The cerebrum consists of the cortex, underlying white matter. By 5 weeks in utero, it is visible as a single portion toward the front of the fetus, at 8 weeks in utero, the forebrain splits into the left and right cerebral hemispheres. When the embryonic forebrain fails to divide the brain into two lobes, it results in a known as holoprosencephaly. List of regions in the human brain NIF Search - Forebrain via the Neuroscience Information Framework
37.
Microvilli
–
Thousands of microvilli form a structure called the brush border that is found on the apical surface of some epithelial cells, such as the small intestines. Microvilli are observed on the surface of eggs, aiding in the anchoring of sperm cells that have penetrated the extracellular coat of egg cells. Clustering of elongated microtubules around a sperm allows for it to be drawn closer and they are large objects that increase surface area for absorption. Microvilli are also of importance on the surface of white blood cells. Microvilli are covered in plasma membrane, which encloses cytoplasm and microfilaments, though these are cellular extensions, there are little or no cellular organelles present in the microvilli. Each microvillus has a bundle of cross-linked actin filaments, which serves as its structural core. 20 to 30 tightly bundled actin filaments are cross-linked by bundling proteins fimbrin, villin and espin to form the core of the microvilli. In the enterocyte microvillus, the core is attached to the plasma membrane along its length by lateral arms made of myosin 1a. Myosin 1a functions through a site for filamentous actin on one end. As mentioned, microvilli are formed as cell extensions from the membrane surface. Actin filaments, present in the cytosol, are most abundant near the cell surface and these filaments are thought to determine the shape and movement of the plasma membrane. The nucleation of actin fibers occurs as a response to external stimuli and this could account for the uniformity of the microvilli, which are observed to be of equal length and diameter. This nucleation process occurs from the end, allowing rapid growth from the plus end. Though the length and composition of microvilli is consistent within a group of homogenous cells. For example, the microvilli in the small and large intestines in mice are different in length. Microvilli function as the surface of nutrient absorption in the gastrointestinal tract. Because of this function, the microvillar membrane is packed with enzymes that aid in the breakdown of complex nutrients into simpler compounds that are more easily absorbed. For example, enzymes that digest carbohydrates called glycosidases are present at concentrations on the surface of enterocyte microvilli
38.
Melanopsin
–
Melanopsin is a type of photopigment belonging to a larger family of light-sensitive retinal proteins called opsins and encoded by the gene Opn4. In the mammalian retina, there are two additional opsins, both involved in the formation of images, rhodopsin and photopsin in the rod and cone photoreceptor cells. In humans, melanopsin is found in intrinsically photosensitive retinal ganglion cells and it is also found in the iris of mice and primates. Melanopsin is also found in rats, amphioxus, and other chordates, melanopsin plays an important non-image-forming role in the setting of circadian rhythms as well as other functions. Mutations in the Opn4 gene can lead to disorders, such as Seasonal Affective Disorder. Melanopsin is also expressed in human cones, however, only 0. 11% to 0. 55% of human cones express melanopsin and are exclusively found in the peripheral regions of the retina. The human peripheral retina senses light at high intensities that is best explained by four different photopigment classes, melanopsin was first discovered by Ignacio Provencio as a novel opsin in the melanophores, or light-sensitive skin cells, of the African clawed frog in 1998. A year later, researchers found that mice without any rods or cones, Provencio and colleagues then found in 2000 that melanopsin is also present in mouse retina, specifically in ganglion cells, and that it mediates non-visual photoreceptive tasks. Melanopsin was found to be encoded by Opn4 with orthologs in a variety of organisms and these retinal ganglion cells were found to be innately photosensitive, since they responded to light even while isolated, and were thus named intrinsically photosensitive Retinal Ganglion Cells. Mammals have orthologous melanopsin genes named Opn4m, which are derived from one branch of the Opn4 family, mammals lost the gene Opn4x relatively early in their evolution, leading to a general reduction in photosensory capability. It is thought that this event can be explained by the fact that occurred during the time in which nocturnal mammals were evolving. The human melanopsin gene, opn4, is expressed in ipRGCs, the gene spans approximately 11.8 kb and is mapped to the long arm of chromosome 10. The gene includes nine introns and ten exons compared to the four to seven exons typically found in other human opsins, paralogs of Opn4 include OPN1LW, OPN1MW, RHO and OPN3 and were discovered by the Genome Project. Melanopsin, like all other animal opsins, is a member of the G-protein coupled receptor family, the melanopsin protein has seven alpha helices integrated in the plasma membrane, an N-terminal domain and a C-terminal domain. It resembles invertebrate opsins far more than vertebrate photopigments, especially in its amino acid sequence, like invertebrate opsins, it appears to be a photopigment with intrinsic photoisomerase activity and signals through a G-protein of the Gq family. Melanopsin-containing ganglion cells, like rods and cones, exhibit both light and dark adaptation, they adjust their sensitivity according to the recent history of light exposure, evidence for melanopsins physiological light detection has been tested in mice. A mouse cell line that is not normally photosensitive, Neuro-2a, is rendered light-sensitive by the addition of human melanopsin, the photoresponse is selectively sensitive to short-wavelength light, and has an intrinsic photoisomerase regeneration function that is chromatically shifted to longer wavelengths. Melanopsin photoreceptors are sensitive to a range of wavelengths and reach peak light absorption at blue light wavelengths around 480 nanometers, other wavelengths of light activate the melanopsin signaling system with decreasing efficiency as they move away from the optimum 480 nm
. PMID 22949670. doi:10.1073/pnas.1207580109.
