Portal:Ediacaran

Topics Culture Geography Health History Mathematics Nature People Philosophy Religion Society Technology The Ediacaran Portal The Cambrian is the first geological period of the Paleozoic Era, lasting from 541.0 ± 1.0 to 485.4 ± 1.9 million years ago (mya) and is succeeded by the Ordovician. Its subdivisions, and indeed its base, are somewhat in flux. The period was established by Adam Sedgwick, who named it after Cambria, the Latinname for Wales, where Britain's Cambrian rocks are best exposed. The Cambrian is unique in its unusually high proportion of lagerstätten. These are sites of exceptional preservation, where 'soft' parts of organisms are preserved as well as their more resistant shells. This means that our understanding of the Cambrian biology surpasses that of some later periods. The Cambrian Period marked a profound change in life on Earth; prior to the Cambrian, living organisms on the whole were small, unicellular and simple. Complex, multicellular organisms gradually became more common in the millions of years immediately preceding the Cambrian, but it was not until this period that mineralized – hence readily fossilized – organisms became common. The rapid diversification of lifeforms in the Cambrian, known as the Cambrian explosion, produced the first representatives of many modern phyla, representing the evolutionary stems of modern groups of species, such as the arthropods. While diverse life forms prospered in the oceans, the land was comparatively barren – with nothing more complex than a microbial soil crust and a few forms that apparently emerged to browse on the microbial materials. Most of the continents were probably dry and rocky due to a lack of vegetation. Shallow seas flanked the margins of several continents created during the breakup of the supercontinent Pannotia. The seas were relatively warm, and polar ice was absent for much of the period. (See more…) Template:/box-footer The Ediacara biota consisted of enigmatic tubular and frond-shaped, mostly sessile organisms that lived during the Ediacaran Period (ca. 635–542 Ma). Trace fossils of these organisms have been found worldwide, and represent the earliest known complex multicellular organisms. The Ediacara biota radiated in an event called the Avalon explosion, 575 million years ago, after the Earth had thawed from the Cryogenian period's extensive glaciation. The biota largely disappeared contemporaneously with the rapid increase in biodiversity known as the Cambrian explosion. Most of the currently existing body plans of animals first appeared in the fossil record of the Cambrian rather than the Ediacaran. For macroorganisms, the Cambrian biota appears to have completely replaced the organisms that populated the Ediacaran fossil record, although relationships are still a matter of debate. Multiple hypotheses exist to explain the disappearance of this biota, including preservation bias, a changing environment, the advent of predators and competition from other life-forms. Breandán MacGabhann argues that the concept of "Ediacara Biota" is artificial and arbitrary as it can not be defined geographically, stratigraphically, taphonomically nor biologically. He points out that 8 particular fossils or groups of fossils considered "Ediacaran" have 5 taphonomic modes (preservation styles), occur in 3 geological periods, and have no phylogenetic meaning as a whole. (see more...) Evolutionary thought, the conception that species change over time, has roots in antiquity. With the beginnings of biological taxonomy in the late 17th century, a new anti-Aristotelian approach to modern science challenged traditional essentialism. Naturalists began to focus on the variability of species; the emergence of paleontology with the concept of extinction further undermined the static view of nature. In the early 19th century, Jean-Baptiste Lamarck proposed the first fully formed theory of evolution. In 1858, Charles Darwin and Alfred Russel Wallace published a new evolutionary theory that was explained in detail in Darwin's On the Origin of Species (1859). Unlike Lamarck, Darwin proposedcommon descent and a branching tree of life. The theory was based on the idea of natural selection, and it synthesized a broad range of evidence from animal husbandry, biogeography, geology, morphology, and embryology. The debate over Darwin's work led to the rapid acceptance of the general concept of evolution, but the specific mechanism he proposed, natural selection, was not widely accepted until it was revived by developments in biology that occurred during the 1920s through the 1940s. Before that time most biologists argued that other factors were responsible for evolution. The synthesis of natural selection with Mendelian genetics during the 1920s and 1930s founded the new discipline of population genetics. Throughout the 1930s and 1940s, population genetics became integrated with other biological fields, resulting in a widely applicable theory of evolution that encompassed much of biology—the modern evolutionary synthesis. (see more...) Agnostus pisiformis (Linnaeus, 1757) as depicted in the 47th plate of Ernst Haeckel's Kunstformen der Natur. Agnostus pisiformis (Linnaeus, 1757) as depicted in the 47th plate of Ernst Haeckel's Kunstformen der Natur.. Photo credit: User:Micha L. Rieser ...that the enigmatic Ediacaran biota (fossil pictured) have been classified into every major group of lifeforms, including their own kingdom? ... that fossils of Yelovichnus were initially believed to be the feeding trails of other organisms? ... that the last common ancestor of bilaterian animals has been reconstructed as a tiny worm with a combined mouth and anus? ... that Andiva (fossil pictured), an enigmatic animal that lived 555 millions of years ago, perhaps had a convex carapace? Template:/box-header Series - Terreneuvian - Cambrian Series 2 - Cambrian Series 3 - Furongian Epochs - Early Cambrian - Middle Cambrian - Late Cambrian Stages - Fortunian - Cambrian Stage 2 - Cambrian Stage 3 - Cambrian Stage 4 - Cambrian Stage 5 - Drumian - Guzhangian -Paibian - Jiangshanian - Cambrian Stage 10 Events - Cambrian Explosion - Cambrian substrate revolution - End-Botomian mass extinction - Cambrian–Ordovician extinction event Geography - Pannotia - Baltica - Gondwanaland - Laurentia - Siberia Animals - Archaeocyathans - Trilobites Trace fossils - Climactichnites - Protichnites Plants - Dalyia - Margaretia Fossil sites - Walcott Quarry Stratigraphic units - Burgess Shale - Maotianshan Shales Researchers - Stephen Jay Gould - Simon Conway Morris - Charles Doolittle Walcott Culture - Wonderful Life (book) Template:/box-footer Template:/box-header Featured Cambrian articles - None Good Cambrian articles - Fossils of the Burgess Shale - Opabinia - Small shelly fauna - Stephen Jay Gould - Waptia Template:/box-footer ▼ Cambrian ► Cambrian life Here are some tasks awaiting attention: Stubs : Cambrian stubs Current Cambrian FACs - none currently Template:/box-footer Time Earth sciences Paleontology Extinct and Endangered Species Paleozoic Cambrian Ordovician Silurian Error creating thumbnail: File missing Devonian Carboniferous Permian What are portals? 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