Paleontology or palaeontology is the scientific study of life that existed prior to, sometimes including, the start of the Holocene Epoch. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments. 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, developed in the 19th century. The term itself originates from Greek παλαιός, palaios, "old, ancient", ὄν, on, "being, creature" and λόγος, logos, "speech, 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 and engineering. Use of all these techniques has enabled paleontologists to discover much of the evolutionary history of life all the way back to when Earth became capable of supporting life, about 3.8 billion years ago.
As knowledge has increased, paleontology has developed specialised sub-divisions, some of which focus on different types of fossil organisms while others study ecology and environmental history, such as ancient climates. Body fossils and trace fossils are the principal types of evidence about ancient life, geochemical evidence has helped to decipher the evolution of life before there were organisms large enough to leave body fossils. Estimating the dates of these remains is essential but difficult: sometimes adjacent rock layers allow radiometric dating, which provides absolute dates that are accurate to within 0.5%, but more paleontologists have to rely on relative dating by solving the "jigsaw puzzles" of biostratigraphy. Classifying ancient organisms is difficult, as many do not fit well into the Linnaean taxonomy classifying living organisms, paleontologists more use cladistics to draw up evolutionary "family trees"; the final quarter of the 20th century saw the development of molecular phylogenetics, which investigates how organisms are related by measuring the similarity of the DNA in their genomes.
Molecular phylogenetics has been used to estimate the dates when species diverged, but there is controversy about the reliability of the molecular clock on which such estimates depend. The simplest definition of paleontology is "the study of ancient life"; the field seeks information about several aspects of past organisms: "their identity and origin, their environment and evolution, what they can tell us about the Earth's organic and inorganic past". Paleontology is one of the historical sciences, along with archaeology, astronomy, cosmology and history itself: it aims to describe phenomena of the past and reconstruct their causes. Hence it has three main elements: description of past phenomena; when trying to explain the past and other historical scientists construct a set of hypotheses about the causes and look for a smoking gun, a piece of evidence that accords with one hypothesis over the others. Sometimes the smoking gun is discovered by a fortunate accident during other research. For example, the discovery by Luis and Walter Alvarez of iridium, a extra-terrestrial metal, in the Cretaceous–Tertiary boundary layer made asteroid impact the most favored explanation for the Cretaceous–Paleogene extinction event, although the contribution of volcanism continues to be debated.
The other main type of science is experimental science, said to work by conducting experiments to disprove hypotheses about the workings and causes of natural phenomena. This approach cannot prove a hypothesis, since some experiment may disprove it, but the accumulation of failures to disprove is compelling evidence in favor. However, when confronted with unexpected phenomena, such as the first evidence for invisible radiation, experimental scientists use the same approach as historical scientists: construct a set of hypotheses about the causes and look for a "smoking gun". Paleontology lies between biology and geology since it focuses on the record of past life, but its main source of evidence is fossils in rocks. For historical reasons, paleontology is part of the geology department at many universities: in the 19th and early 20th centuries, geology departments found fossil evidence important for dating rocks, while biology departments showed little interest. Paleontology has some overlap with archaeology, which works with objects made by humans and with human remains, while paleontologists are interested in the characteristics and evolution of humans as a species.
When dealing with evidence about humans and paleontologists may work together – for example paleontologists might identify animal or plant fossils around an archaeological site, to discover what the people who lived there ate. In addition, paleontology borrows techniques from other sciences, including biology, ecology, chemistry and mathematics. For example, geochemical signatures from rocks may help to discover when life first arose on Earth, analyses of carbon isotope ratios may help to identify climate changes and to explain major transitions such as the Permian–Triassic extinction event. A recent discipline, molecular phylogenetics, compares the DNA and RNA of modern organisms to re-construct the "family trees" of their
Système universitaire de documentation
The système universitaire de documentation or SUDOC is a system used by the libraries of French universities and higher education establishments to identify and manage the documents in their possession. The catalog, which contains more than 10 million references, allows students and researcher to search for bibliographical and location information in over 3,400 documentation centers, it is maintained by the Bibliographic Agency for Higher Education. Official website
Crustaceans form a large, diverse arthropod taxon which includes such familiar animals as crabs, crayfish, krill and barnacles. The crustacean group is treated as a subphylum, because of recent molecular studies it is now well accepted that the crustacean group is paraphyletic, comprises all animals in the Pancrustacea clade other than hexapods; some crustaceans are more related to insects and other hexapods than they are to certain other crustaceans. The 67,000 described species range in size from Stygotantulus stocki at 0.1 mm, to the Japanese spider crab with a leg span of up to 3.8 m and a mass of 20 kg. Like other arthropods, crustaceans have an exoskeleton, they are distinguished from other groups of arthropods, such as insects and chelicerates, by the possession of biramous limbs, by their larval forms, such as the nauplius stage of branchiopods and copepods. Most crustaceans are free-living aquatic animals, but some are terrestrial, some are parasitic and some are sessile; the group has an extensive fossil record, reaching back to the Cambrian, includes living fossils such as Triops cancriformis, which has existed unchanged since the Triassic period.
More than 10 million tons of crustaceans are produced by fishery or farming for human consumption, the majority of it being shrimp and prawns. Krill and copepods are not as fished, but may be the animals with the greatest biomass on the planet, form a vital part of the food chain; the scientific study of crustaceans is known as carcinology, a scientist who works in carcinology is a carcinologist. The body of a crustacean is composed of segments, which are grouped into three regions: the cephalon or head, the pereon or thorax, the pleon or abdomen; the head and thorax may be fused together to form a cephalothorax, which may be covered by a single large carapace. The crustacean body is protected by the hard exoskeleton, which must be moulted for the animal to grow; the shell around each somite can be divided into a dorsal tergum, ventral sternum and a lateral pleuron. Various parts of the exoskeleton may be fused together; each somite, or body segment can bear a pair of appendages: on the segments of the head, these include two pairs of antennae, the mandibles and maxillae.
The abdomen bears pleopods, ends in a telson, which bears the anus, is flanked by uropods to form a tail fan. The number and variety of appendages in different crustaceans may be responsible for the group's success. Crustacean appendages are biramous, meaning they are divided into two parts, it is unclear whether the biramous condition is a derived state which evolved in crustaceans, or whether the second branch of the limb has been lost in all other groups. Trilobites, for instance possessed biramous appendages; the main body cavity is an open circulatory system, where blood is pumped into the haemocoel by a heart located near the dorsum. Malacostraca have haemocyanin as the oxygen-carrying pigment, while copepods, ostracods and branchiopods have haemoglobins; the alimentary canal consists of a straight tube that has a gizzard-like "gastric mill" for grinding food and a pair of digestive glands that absorb food. Structures that function as kidneys are located near the antennae. A brain exists in the form of ganglia close to the antennae, a collection of major ganglia is found below the gut.
In many decapods, the first pair of pleopods are specialised in the male for sperm transfer. Many terrestrial crustaceans return to the sea to release the eggs. Others, such as woodlice, lay their eggs on land, albeit in damp conditions. In most decapods, the females retain the eggs; the majority of crustaceans are aquatic, living in either marine or freshwater environments, but a few groups have adapted to life on land, such as terrestrial crabs, terrestrial hermit crabs, woodlice. Marine crustaceans are as ubiquitous in the oceans; the majority of crustaceans are motile, moving about independently, although a few taxonomic units are parasitic and live attached to their hosts, adult barnacles live a sessile life – they are attached headfirst to the substrate and cannot move independently. Some branchiurans are able to withstand rapid changes of salinity and will switch hosts from marine to non-marine species. Krill are the bottom layer and the most important part of the food chain in Antarctic animal communities.
Some crustaceans are significant invasive species, such as the Chinese mitten crab, Eriocheir sinensis, the Asian shore crab, Hemigrapsus sanguineus. The majority of crustaceans have separate sexes, reproduce sexually. A small number are hermaphrodites, including barnacles and Cephalocarida; some may change sex during the course of their life. Parthenogenesis is widespread among crustaceans, where viable eggs are produced by a female without needing fertilisation by a male; this occurs in many branchiopods, some os
Invertebrates are animals that neither possess nor develop a vertebral column, derived from the notochord. This includes all animals apart from the subphylum Vertebrata. Familiar examples of invertebrates include arthropods, mollusks and cnidarians; the majority of animal species are invertebrates. Many invertebrate taxa have a greater number and variety of species than the entire subphylum of Vertebrata; some of the so-called invertebrates, such as the Tunicata and Cephalochordata are more related to the vertebrates than to other invertebrates. This makes the invertebrates paraphyletic, so the term has little meaning in taxonomy; the word "invertebrate" comes from the Latin word vertebra, which means a joint in general, sometimes a joint from the spinal column of a vertebrate. The jointed aspect of vertebra is derived from the concept of turning, expressed in the root verto or vorto, to turn; the prefix in- means "not" or "without". The term invertebrates is not always precise among non-biologists since it does not describe a taxon in the same way that Arthropoda, Vertebrata or Manidae do.
Each of these terms describes a valid taxon, subphylum or family. "Invertebrata" is a term of convenience, not a taxon. The Vertebrata as a subphylum comprises such a small proportion of the Metazoa that to speak of the kingdom Animalia in terms of "Vertebrata" and "Invertebrata" has limited practicality. In the more formal taxonomy of Animalia other attributes that logically should precede the presence or absence of the vertebral column in constructing a cladogram, for example, the presence of a notochord; that would at least circumscribe the Chordata. However the notochord would be a less fundamental criterion than aspects of embryological development and symmetry or bauplan. Despite this, the concept of invertebrates as a taxon of animals has persisted for over a century among the laity, within the zoological community and in its literature it remains in use as a term of convenience for animals that are not members of the Vertebrata; the following text reflects earlier scientific understanding of the term and of those animals which have constituted it.
According to this understanding, invertebrates do not possess a skeleton of bone, either internal or external. They include hugely varied body plans. Many have like jellyfish or worms. Others have outer shells like those of insects and crustaceans; the most familiar invertebrates include the Protozoa, Coelenterata, Nematoda, Echinodermata and Arthropoda. Arthropoda include insects and arachnids. By far the largest number of described invertebrate species are insects; the following table lists the number of described extant species for major invertebrate groups as estimated in the IUCN Red List of Threatened Species, 2014.3. The IUCN estimates that 66,178 extant vertebrate species have been described, which means that over 95% of the described animal species in the world are invertebrates; the trait, common to all invertebrates is the absence of a vertebral column: this creates a distinction between invertebrates and vertebrates. The distinction is one of convenience only. Being animals, invertebrates are heterotrophs, require sustenance in the form of the consumption of other organisms.
With a few exceptions, such as the Porifera, invertebrates have bodies composed of differentiated tissues. There is typically a digestive chamber with one or two openings to the exterior; the body plans of most multicellular organisms exhibit some form of symmetry, whether radial, bilateral, or spherical. A minority, exhibit no symmetry. One example of asymmetric invertebrates includes all gastropod species; this is seen in snails and sea snails, which have helical shells. Slugs appear externally symmetrical. Other gastropods develop external asymmetry, such as Glaucus atlanticus that develops asymmetrical cerata as they mature; the origin of gastropod asymmetry is a subject of scientific debate. Other examples of asymmetry are found in hermit crabs, they have one claw much larger than the other. If a male fiddler loses its large claw, it will grow another on the opposite side after moulting. Sessile animals such as sponges are asymmetrical alongside coral colonies. Neurons differ in invertebrates from mammalian cells.
Invertebrates cells fire in response to similar stimuli as mammals, such as tissue trauma, high temperature, or changes in pH. The first invertebrate in which a neuron cell was identified was the medicinal leech, Hirudo medicinalis. Learning and memory using nociceptors in the sea hare, Aplysia has been described. Mollusk neurons are able to detect tissue trauma. Neurons have been identified in a wide range of invertebrate species, including annelids, molluscs and arthropods. One type of invertebrate respi
Geological Society of London
The Geological Society of London, known as the Geological Society, is a learned society based in the United Kingdom. It is the oldest national geological society in the world and the largest in Europe with more than 12,000 Fellows. Fellows are entitled to the postnominal FGS; the Society is a Registered Charity, No. 210161. It is a member of the Science Council, is licensed to award Chartered Scientist to qualifying members; the mission of the society: "Making geologists acquainted with each other, stimulating their zeal, inducing them to adopt one nomenclature, facilitating the communication of new facts and ascertaining what is known in their science and what remains to be discovered". The Society was founded on 13 October 1807 at the Freemasons' Tavern, Great Queen Street, in the Covent Garden district of London, it was the outcome of a previous club known as the Askesian Society. There were 13 founder members: William Babington, James Parkinson, Humphry Davy, George Bellas Greenough, Arthur Aikin, William Allen, Jacques Louis, Comte de Bournon, Richard Knight, James Laird, James Franck, William Haseldine Pepys, Richard Phillips, William Phillips.
It received its Royal Charter on 23 April 1825 from George IV. Since 1874, the Society has been based at Burlington House, London; this building houses the Society's library, which contains more than 300,000 volumes of books and journals. It is a member of the UK Science Council. Women were first allowed to become Fellows of the Society in 1919. In 1991, it merged with the Institution of Geologists, formed in 1977 to represent the geological profession; the Society celebrated its bicentenary in 2007. It ran programmes in the geosciences in Britain and abroad, under the auspices of the science writer and palaeontologist Professor Richard Fortey, the president that year; the Society has 24 specialist groups and 15 regional groups which serve as an opportunity for those with specific interests to meet and discuss their subject or region. They are all free for members to join and some are open to non-members; the Regional Groups are: Central Scotland East Anglian East Midlands Home Counties North Hong Kong North West Northern Solent South East South West Southern Wales Thames Valley West Midlands Western YorkshireThe Specialist Groups are: Borehole Research Group British Geophysical Association British Sedimentological Research Group British Society for Geomorphology Coal Geology Group Engineering Group Environment Group Environmental and Industrial Geophysics Group Forensic Geoscience Group Gaia: Earth Systems Science Group Geochemistry Group Geological Curators Group Geological Remote Sensing Group Geoscience Information Group History of Geology Group Hydrogeological Group Joint Association for Quaternary Research Joint Association of Geoscientists for International Development Marine Studies Group Metamorphic Studies Group Mineral Deposits Studies Group Petroleum Group Tectonic Studies Group Volcanic and Magmatic Studies Group The society publishes two of its own journals, the Journal of the Geological Society and the Quarterly Journal of Engineering Geology and Hydrogeology.
It publishes the magazine Geoscientist for Fellows, has a share in Geology Today, published by Blackwell Science. It co-publishes journals and publishes on behalf of other organisations; these include Petroleum Geoscience with the European Association of Geoscientists and Engineers, Geochemistry: Exploration, Analysis with the Association of Applied Geochemists, Journal of Micropalaeontology for the Micropalaeontological Society, Proceedings of the Yorkshire Geological Society for the Yorkshire Geological Society, Scottish Journal of Geology for the Geological Societies of Edinburgh and Glasgow. The society counts many famous geologists amongst its past presidents; these include pioneers of geology William Buckland, Adam Sedgwick, Roderick Impey Murchison, Charles Lyell, Henry Thomas De la Beche, T. H. Huxley, Joseph Prestwich, Archibald Geikie, Jethro Teall, Charles Lapworth. Well-known names include Alfred Harker, Arthur Trueman, H. H. Read, Frederick Shotton, Janet Watson. In 1831 it began issuing an annual scientific award for geology, known as the Wollaston Medal.
This is still the Society's premier medal, which in 2006 was awarded to James Lovelock, the originator of the Gaia Hypothesis. Wollaston Medal Lyell Medal Murchison Medal Prestwich Medal William Smith Medal Aberconway Medal Major John Sacheverell A'Deane Coke Medal Major Edward D'Ewes Fitzgerald Coke Medal Sue Tyler Friedman Medal Bigsby Medal The Wollaston Fund The Murchison Fund The Lyell Fund The R. H. Worth Prize The William Smith Fund The Distinguished Service Award Herries Davies, G. L. Whatever is Under the Earth: The Geological Society of London 1807 to 2007, London: Geological Society, ISBN 1-86239-214-5 Geology of the United Kingdom William Smith The Geological Society The Lyell Collection
Pteropoda are specialized free-swimming pelagic sea snails and sea slugs, marine opisthobranch gastropods. The monophyly of Pteropoda is the subject of a lengthy debate. Current consensus, guided by molecular studies, leans towards interpreting the group as monophyletic. Pteropoda encompasses the two clades Thecosomata, the sea butterflies, Gymnosomata, the sea angels; the Thecosomata have a shell. The two clades may not be sister taxa; the group Pteropoda was established by Georges Cuvier as "ptéropodes" in 1804. François Péron and Charles Alexandre Lesueur thought the group to be larger, so they included the opisthobranch taxa, the heteropoda taxa, the Ctenophora. In 1810 these authors divided the whole group in two separate groups: those with a shell and those without a shell. In 1824 Henri Marie Ducrotay de Blainville named these two groups Gymnosomata and Thecosomata and named the combining order Aporobranchia instead of Pteropoda, he rejected the additional genera, except Phyllirhoë which he upgraded to a third group that he called Psilosomata.
Only much was Phyllirhoë classified within the order Nudibranchia. Other attempts were made to describe the Pteropoda. John Edward Gray divided the Pteropoda into Pterobranchia. Cuvier did not accept the classification by de Blainville. In 1829 Paul Rang followed the Cuvierian classification, but tried to include the character of having a distinct head or not; the German naturalist Lorenz Oken went one step further and, for the sake of symmetry, wanted each order to contain four families and each family to contain four genera. Pierre André Latreille divided the Pteropoda according to the size of their fins: "Macroptérygiens" and "Microptérygiens". In 1851 William Bullock Clark treated the Pteropoda as a family and emended the spelling to Pteropodidae Finally all these attempts were abandoned and, as more and more species were described as a result of several scientific expeditions, the classification of the Pteropoda into Thecosomata and Gymnosomata was adopted. Many of these new species were first described by French zoologists, for example Jean René Constant Quoy and Joseph Paul Gaimard, Paul Rang, Alcide d'Orbigny and Louis François Auguste Souleyet.
The relationship between these two clades is not unequivocally established, but it seems that they are sister taxa. Pteropods are found in all major oceans 0–10 meters below the surface below the ocean surface and in all levels of latitude. Pteropods can be found lower than 10 meters, but in less amounts in terms of biomass, however pteropod distribution is more spread out deeper based on findings; this can be explained as Pteropods from tropical areas become more common in deeper areas. They are not found in the deep sea, in fact, few live lower than 500 meters below sea level. Continental shelves, areas containing many opportunities for nutrients, productivity are locations in which Pteropods are populous, according to patterns in data. Springtime is a peak season for pteropoda, as they reach higher populations, though data shows that pteropoda south of the equator are less abundant seasonally. In addition, current data suggests that, 93% of the world's pteropods are part of the Thecosomata family, while the 7% are Gymnosomata.
A study was conducted on the West Coast of the United States to see ocean acidification’s effects on pteropods. Limacina helicina was used to test the sensitivity to decreasing pH; this species of pteropod is vulnerable to the corrosive waters associated with ocean acidification due to their calcium carbonate shell. The shell of a pteropod was immersed in ocean water with the projected pH level that the water will reach by the year 2100. After a month and a half in the water, the shell had completely dissolved. Wissenschaftliche Ergebnisse der Deutschen Tiefsee-Expedition auf dem Dampfer "Valdivia" 1898-1899. Part 9 Atlas by German planktologist Carl Chun Plankton Chronicles Short documentary films & photos http://www.marinespecies.org/aphia.php?p=taxdetails&id=325345 Report of the Scientific results of the Voyage of the H. M. S. Challenger, part LVIII: Report on the Pteropoda by Paul Pelseneer Alice K. Burridge, Christine Hörnlein, Arie W. Janssen, Martin Hughes, Stephanie L. Bush, Ferdinand Marlétaz, Rebeca Gasca, Annelies C.
Pierrot-Bults, Ellinor Michel, Jonathan A. Todd, Jeremy R. Young, Karen J. Osborn, Steph B. J. Menken, Katja T. C. A. Peijnenburg: Time-calibrated molecular phylogeny of pteropods.
Swedish Museum of Natural History
The Swedish Royal Museum of Natural History, in Stockholm, is one of two major museums of natural history in Sweden, the other one being located in Gothenburg. The museum was founded in 1819 by the Royal Swedish Academy of Sciences, but goes back to the collections acquired through donations by the academy since its foundation in 1739; these collections had first been made available to the public in 1786. The museum was separated from the Academy in 1965. One of the keepers of the collections of the academy during its earlier history was Anders Sparrman, a student of Carl Linnaeus and participant in the voyages of Captain James Cook. Another important name in the history of the museum is the zoologist and archaeologist Sven Nilsson, who brought the disorganised zoological collections of the museum into order during his time as keeper before returning to Lund as professor; the present buildings for the museum in Frescati, was designed by the architect Axel Anderberg and completed in 1916, topped with a dome.
As of 2014 it is the largest museum building in Sweden. The main campus of Stockholm University was built next to the museum; the museum has an IMAX cinema called Cosmonova. The cinema is the largest planetarium in Sweden. Swedish Museum of Natural History official website