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Christian Heinrich Pander
Heinz Christian Pander, also Christian Heinrich Pander ( – ), was a Russian Empire ethnic Baltic German biologist and embryologist. Biography In 1817 he received his doctorate from the University of Würzburg, and spent several years (1827–1842), performing scientific research from his estate in Carnikava (german: Zarnikau) on the banks of the Gauja River near Riga. In 1820 he took part in a scientific expedition to Bokhara as a naturalist. In 1826 he became a member of the Saint Petersburg Academy of Sciences. Research Pander studied the chick embryo and discovered the germ layers (i.e., three distinct regions of the embryo that give rise to the specific organ system). Because of these findings, he is considered by many to be the "founder of embryology". His work in embryology was continued by Karl Ernst von Baer (1792-1876), who expanded Pander's concept of germ layers to include all vertebrates. Pander performed important studies in the field of paleontology, bein ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Riga
Riga (; lv, Rīga , liv, Rīgõ) is the capital and largest city of Latvia and is home to 605,802 inhabitants which is a third of Latvia's population. The city lies on the Gulf of Riga at the mouth of the Daugava river where it meets the Baltic Sea. Riga's territory covers and lies above sea level, on a flat and sandy plain. Riga was founded in 1201 and is a former Hanseatic League member. Riga's historical centre is a UNESCO World Heritage Site, noted for its Art Nouveau/Jugendstil architecture and 19th century wooden architecture. Riga was the European Capital of Culture in 2014, along with Umeå in Sweden. Riga hosted the 2006 NATO Summit, the Eurovision Song Contest 2003, the 2006 IIHF Men's World Ice Hockey Championships, 2013 World Women's Curling Championship and the 2021 IIHF World Championship. It is home to the European Union's office of European Regulators for Electronic Communications (BEREC). In 2017, it was named the European Region of Gastronomy. I ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germ Layer
A germ layer is a primary layer of cells that forms during embryonic development. The three germ layers in vertebrates are particularly pronounced; however, all eumetazoans (animals that are sister taxa to the sponges) produce two or three primary germ layers. Some animals, like cnidarians, produce two germ layers (the ectoderm and endoderm) making them diploblastic. Other animals such as bilaterians produce a third layer (the mesoderm) between these two layers, making them triploblastic. Germ layers eventually give rise to all of an animal’s tissues and organs through the process of organogenesis. History Caspar Friedrich Wolff observed organization of the early embryo in leaf-like layers. In 1817, Heinz Christian Pander discovered three primordial germ layers while studying chick embryos. Between 1850 and 1855, Robert Remak had further refined the germ cell layer (''Keimblatt'') concept, stating that the external, internal and middle layers form respectively the e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blood Island Of Umbilical Vesicle
Blood islands are structures around the developing embryo which lead to many different parts of the circulatory system. Blood islands arise external to the developing embryo on the umbilical vesicle, allantois, connecting stalk and chorion. They are also known as Pander's islands or Wolff's islands, after Heinz Christian Pander or Caspar Friedrich Wolff. Development In humans, the formation of extraembryonic blood vessels starts at the beginning of the third week after fertilization. Vasculogenesis begins as mesodermal cells differentiate into hemangioblasts, which in turn differentiate into angioblasts. Clusters of angioblasts make up the blood islands. Within the blood islands, lumens begin to appear by the growth of intercellular clefts. The flattened cells at the periphery form the endothelium. Mesenchymal cells exterior to this form the muscular and connective tissue components of blood vessels. Roughly 3 weeks after fertilization, red blood cells, still with a nucleus ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pander's Islands
Blood islands are structures around the developing embryo which lead to many different parts of the circulatory system. Blood islands arise external to the developing embryo on the umbilical vesicle, allantois, connecting stalk and chorion. They are also known as Pander's islands or Wolff's islands, after Heinz Christian Pander or Caspar Friedrich Wolff. Development In humans, the formation of extraembryonic blood vessels starts at the beginning of the third week after fertilization. Vasculogenesis begins as mesodermal cells differentiate into hemangioblasts, which in turn differentiate into angioblasts. Clusters of angioblasts make up the blood islands. Within the blood islands, Lumen (anatomy), lumens begin to appear by the growth of intercellular clefts. The flattened cells at the periphery form the endothelium. Mesenchymal cells exterior to this form the muscular and connective tissue components of blood vessels. Roughly 3 weeks after fertilization, red blood cells, still ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stratigrapher
Stratigraphy is a branch of geology concerned with the study of rock layers ( strata) and layering (stratification). It is primarily used in the study of sedimentary and layered volcanic rocks. Stratigraphy has three related subfields: lithostratigraphy (lithologic stratigraphy), biostratigraphy (biologic stratigraphy), and chronostratigraphy (stratigraphy by age). Historical development Catholic priest Nicholas Steno established the theoretical basis for stratigraphy when he introduced the law of superposition, the principle of original horizontality and the principle of lateral continuity in a 1669 work on the fossilization of organic remains in layers of sediment. The first practical large-scale application of stratigraphy was by William Smith in the 1790s and early 19th century. Known as the "Father of English geology", Smith recognized the significance of strata or rock layering and the importance of fossil markers for correlating strata; he created the first geologic ma ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Palaeontologist
Paleontology (), also spelled palaeontology or palæontology, is the scientific study of life that existed prior to, and sometimes including, the start of the Holocene epoch (roughly 11,700 years before present). It includes the study of fossils to classify organisms and study their interactions with each other and their environments (their paleoecology). Paleontological observations have been documented as far back as the 5th century BC. The science became established in the 18th century as a result of Georges Cuvier's work on comparative anatomy, and developed rapidly in the 19th century. The term itself originates from Greek (, "old, ancient"), (, (gen. ), "being, creature"), and (, "speech, thought, study"). Paleontology lies on the border between biology and geology, but differs from archaeology in that it excludes the study of anatomically modern humans. It now uses techniques drawn from a wide range of sciences, including biochemistry, mathematics, and engineering. Us ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pander Society
The Pander Society is an informal organisation founded in 1967 for the promotion of the study of conodont palaeontology. It publishes an annual newsletter. Although there are regular meetings of the Pander Society, at the Annual Meeting of the Geological Society of America, at European Conodont Symposia (ECOS for short), and elsewhere, any meeting of three or more "Panderers" is considered an official meeting of the "Pander Society". The society is headed by the Chief Panderer, currently Maria Cristina Perri of the Università di Bologna. The society confers two awards, the Pander Medal for a lifetime of achievement in conodont palaeontology, and the Hinde Medal for an outstanding contribution to conodont palaeontology by a young Panderer. Heinz Christian Pander (1794–1865) is credited as the first scientist to describe primitive creatures known as conodonts. [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Conodont
Conodonts (Greek ''kōnos'', "cone", + ''odont'', "tooth") are an extinct group of agnathan (jawless) vertebrates resembling eels, classified in the class Conodonta. For many years, they were known only from their tooth-like oral elements, which are usually found in isolation and are now called conodont elements. Knowledge about soft tissues remains limited. They existed in the world's oceans for over 300 million years, from the Cambrian to the beginning of the Jurassic. Conodont elements are widely used as index fossils, fossils used to define and identify geological periods. The animals are also called Conodontophora (conodont bearers) to avoid ambiguity. Discovery and understanding of conodonts The teeth-like fossils of the conodont were first discovered by Heinz Christian Pander and the results published in Saint Petersburg, Russia, in 1856. The name ''pander'' is commonly used in scientific names of conodonts. It was only in the early 1980s that the first fossil evidence of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elkanah Billings
Elkanah Billings (May 5, 1820 – June 14, 1876) is often referred to as Canada's first paleontologist. Billings was born on a farm by the Rideau River outside Bytown (Ottawa), now known as Billings Estate Museum, Billings Estate. His parents were named Lamira Dow and Braddish Billings. His family included an older sister named Sabra and an older brother Maj Braddish Billings Jr, who practised as an architect and served in the North-West Rebellion. His younger siblings were Samuel, Sarah (known as Sally) and Charles. He was originally educated in law and in 1845, he was called to the Canadian bar. In 1856, he founded the journal the ''Canadian Naturalist (and Geologist)''. He continued to practise law until 1857, when he was hired to be the first paleontologist for Geological Survey of Canada (GSC). In his lifetime, he identified 1065 new species and 61 new genus, genera, including ''Aspidella'', the first documented fossil of the Ediacaran biota. He married Helen Walker Wilso ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trilobite
Trilobites (; meaning "three lobes") are extinct marine arthropods that form the class Trilobita. Trilobites form one of the earliest-known groups of arthropods. The first appearance of trilobites in the fossil record defines the base of the Atdabanian stage of the Early Cambrian period () and they flourished throughout the lower Paleozoic before slipping into a long decline, when, during the Devonian, all trilobite orders except the Proetida died out. The last extant trilobites finally disappeared in the mass extinction at the end of the Permian about 252 million years ago. Trilobites were among the most successful of all early animals, existing in oceans for almost 270 million years, with over 22,000 species having been described. By the time trilobites first appeared in the fossil record, they were already highly diversified and geographically dispersed. Because trilobites had wide diversity and an easily fossilized exoskeleton, they left an extensive fossil record. The stu ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Silurian
The Silurian ( ) is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at million years ago ( Mya), to the beginning of the Devonian Period, Mya. The Silurian is the shortest period of the Paleozoic Era. As with other geologic periods, the rock beds that define the period's start and end are well identified, but the exact dates are uncertain by a few million years. The base of the Silurian is set at a series of major Ordovician–Silurian extinction events when up to 60% of marine genera were wiped out. One important event in this period was the initial establishment of terrestrial life in what is known as the Silurian-Devonian Terrestrial Revolution: vascular plants emerged from more primitive land plants, dikaryan fungi started expanding and diversifying along with glomeromycotan fungi, and three groups of arthropods (myriapods, arachnids and hexapods) became fully terrestrialized. A significant evolutionary milestone during ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Devonian
The Devonian ( ) is a geologic period and system of the Paleozoic era, spanning 60.3 million years from the end of the Silurian, million years ago (Mya), to the beginning of the Carboniferous, Mya. It is named after Devon, England, where rocks from this period were first studied. The first significant adaptive radiation of life on dry land occurred during the Devonian. Free-sporing vascular plants began to spread across dry land, forming extensive forests which covered the continents. By the middle of the Devonian, several groups of plants had evolved leaves and true roots, and by the end of the period the first seed-bearing plants appeared. The arthropod groups of myriapods, arachnids and hexapods also became well-established early in this period, after starting their expansion to land at least from the Ordovician period. Fish reached substantial diversity during this time, leading the Devonian to often be dubbed the Age of Fishes. The placoderms began dominating ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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