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Human cloning The Human Fertilisation and Embryology Act 2008, a major review of fertility legislation, repealed the 2001 Cloning Act by making amendments of similar effect to the 1990 Act. The 2008 Act also allows experiments on hybrid human-animal embryos. On December 13, 2001, the United Nations General Assembly beg... | https://en.wikipedia.org/wiki?curid=14094 |
Human cloning [Throughout the following years in February 1997 Dolly was cloned; Clinton launches review of US policy and In May 1997 Federal funding for human cloning [was] banned" divisions in the Senate, or an eventual veto from the sitting President (President George W. Bush in 2005 and 2007), over therapeutic clon... | https://en.wikipedia.org/wiki?curid=14094 |
Human cloning Science fiction has used cloning, most commonly and specifically human cloning, due to the fact that it brings up controversial questions of identity. Humorous fiction, such as "Multiplicity" (1996) and the Maxwell Smart feature "The Nude Bomb" (1980), have featured human cloning. A recurring sub-theme of... | https://en.wikipedia.org/wiki?curid=14094 |
Infusoria is a collective term for minute aquatic creatures such as ciliates, euglenoids, protozoa, unicellular algae and small invertebrates that exist in freshwater ponds. Some authors (e.g., Bütschli) used the term as a synonym for Ciliophora. In modern formal classifications, the term is considered obsolete; the mi... | https://en.wikipedia.org/wiki?curid=15018 |
Katal The katal (symbol: kat) is the unit of catalytic activity in the International System of Units (SI). It is a derived SI unit for quantifying the catalytic activity of enzymes (that is, measuring the enzymatic activity level in enzyme catalysis) and other catalysts. The General Conference on Weights and Measures a... | https://en.wikipedia.org/wiki?curid=17140 |
Microfluidics refers to the behaviour, precise control, and manipulation of fluids that are geometrically constrained to a small scale (typically sub-millimeter) at which capillary penetration governs mass transport. It is a multidisciplinary field that involves engineering, physics, chemistry, biochemistry, nanotechno... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Often, processes normally carried out in a lab are miniaturised on a single chip, which enhances efficiency and mobility, and reduces sample and reagent volumes. The behaviour of fluids at the microscale can differ from "macrofluidic" behaviour in that factors such as surface tension, energy dissipation, ... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Additionally, microfluidic manufacturing advances mean that makers can produce the devices in low-cost plastics and automatically verify part quality. Advances in microfluidics technology are revolutionizing molecular biology procedures for enzymatic analysis (e.g., glucose and lactate assays), DNA analys... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Advantages of open microfluidics include accessibility to the flowing liquid for intervention, larger liquid-gas surface area, and minimized bubble formation. Another advantage of open microfluidics is the ability to integrate open systems with surface-tension driven fluid flow, which eliminates the need ... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Continuous-flow microfluidic operation is the mainstream approach because it is easy to implement and less sensitive to protein fouling problems. Continuous-flow devices are adequate for many well-defined and simple biochemical applications, and for certain tasks such as chemical separation, but they are ... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Microdroplets allow for handling miniature volumes (μl to fl) of fluids conveniently, provide better mixing, encapsulation, sorting, and sensing, and suit high throughput experiments. Exploiting the benefits of droplet-based microfluidics efficiently requires a deep understanding of droplet generation to ... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Moreover, because each droplet can be controlled independently, these systems also have dynamic reconfigurability, whereby groups of unit cells in a microfluidic array can be reconfigured to change their functionality during the concurrent execution of a set of bioassays. Although droplets are manipulated... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics Current applications include portable glucose detection and environmental testing, with hopes of reaching areas that lack advanced medical diagnostic tools. Early biochips were based on the idea of a DNA microarray, e.g., the GeneChip DNAarray from Affymetrix, which is a piece of glass, plastic or silicon... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics The resulting landscapes can be used as physical implementations of an adaptive landscape, by generating a spatial mosaic of patches of opportunity distributed in space and time. The patchy nature of these fluidic landscapes allows for the study of adapting bacterial cells in a metapopulation system. The ... | https://en.wikipedia.org/wiki?curid=18906 |
Microfluidics or superresolution. Acoustic droplet ejection uses a pulse of ultrasound to move low volumes of fluids (typically nanoliters or picoliters) without any physical contact. This technology focuses acoustic energy into a fluid sample to eject droplets as small as a millionth of a millionth of a litre (picolit... | https://en.wikipedia.org/wiki?curid=18906 |
Molecule A molecule is an electrically neutral group of two or more atoms held together by chemical bonds. Molecules are distinguished from ions by their lack of electrical charge. However, in quantum physics, organic chemistry, and biochemistry, the term "molecule" is often used less strictly, also being applied to po... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule Also, no typical molecule can be defined for ionic crystals (salts) and covalent crystals (network solids), although these are often composed of repeating unit cells that extend either in a plane (such as in graphene) or three-dimensionally (such as in diamond, quartz, or sodium chloride). The theme of repeate... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule , short-lived assemblies (resonances) of electrons and nuclei, such as radicals, molecular ions, Rydberg molecules, transition states, van der Waals complexes, or systems of colliding atoms as in Bose–Einstein condensate. According to Merriam-Webster and the Online Etymology Dictionary, the word "molecule" der... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. The ions are atoms that have lost one or more electrons (termed cations) and atoms that have gained one or more electrons (termed ani... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule The chemical formula for a molecule uses one line of chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, and "plus" (+) and "minus" (−) signs. These are limited to one typographic line of symbols, which may include subscripts and superscripts. A compound'... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule The molecular mass can be calculated from the chemical formula and is expressed in conventional atomic mass units equal to 1/12 of the mass of a neutral carbon-12 (C isotope) atom. For network solids, the term formula unit is used in stoichiometric calculations. For molecules with a complicated 3-dimensional s... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule Molecular spectroscopy deals with the response (spectrum) of molecules interacting with probing signals of known energy (or frequency, according to Planck's formula). Molecules have quantized energy levels that can be analyzed by detecting the molecule's energy exchange through absorbance or emission. Spectros... | https://en.wikipedia.org/wiki?curid=19555 |
Molecule H is composed of two positively charged protons and one negatively charged electron, which means that the Schrödinger equation for the system can be solved more easily due to the lack of electron–electron repulsion. With the development of fast digital computers, approximate solutions for more complicated mole... | https://en.wikipedia.org/wiki?curid=19555 |
Messenger RNA (mRNA) is a single-stranded RNA molecule that corresponds to the genetic sequence of a gene and is read by the ribosome in the process of producing a protein. mRNA is created during the process of transcription, where the enzyme RNA polymerase converts genes into primary transcript mRNA (also known as pre... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA The existence of mRNA was first suggested by Jacques Monod and François Jacob and was subsequently discovered by Jacob, Sydney Brenner and Matthew Meselson at the California Institute of Technology in 1961. The brief existence of an mRNA molecule begins with transcription, and ultimately ends in degradati... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA The extensive processing of eukaryotic pre-mRNA that leads to the mature mRNA is the RNA splicing, a mechanism by which introns or outrons (non-coding regions) are removed and exons (coding regions) are joined together. A "5' cap" (also termed an RNA cap, an RNA 7-methylguanosine cap, or an RNA mG cap) is... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA In eukaryotic organisms most messenger RNA (mRNA) molecules are polyadenylated at the 3' end, but recent studies have shown that short stretches of uridine (oligouridylation) are also common. The poly(A) tail and the protein bound to it aid in protecting mRNA from degradation by exonucleases. Polyadenylat... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA Because eukaryotic transcription and translation is compartmentally separated, eukaryotic mRNAs must be exported from the nucleus to the cytoplasm—a process that may be regulated by different signaling pathways. Mature mRNAs are recognized by their processed modifications and then exported through the nuc... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA Because prokaryotic mRNA does not need to be processed or transported, translation by the ribosome can begin immediately after the end of transcription. Therefore, it can be said that prokaryotic translation is "coupled" to transcription and occurs "co-transcriptionally". Eukaryotic mRNA that has been pro... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA Untranslated regions (UTRs) are sections of the mRNA before the start codon and after the stop codon that are not translated, termed the five prime untranslated region (5' UTR) and three prime untranslated region (3' UTR), respectively. These regions are transcribed with the coding region and thus are exo... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA Proteins that are needed in a particular region of the cell can also be translated there; in such a case, the 3' UTR may contain sequences that allow the transcript to be localized to this region for translation. Some of the elements contained in untranslated regions form a characteristic secondary struct... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA Most of the mRNA found in bacteria and archaea is polycistronic, as is the human mitochondrial genome. Dicistronic or bicistronic mRNA encodes only two proteins. In eukaryotes mRNA molecules form circular structures due to an interaction between the eIF4E and poly(A)-binding protein, which both bind to eI... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA However, the lifetime averages between 1 and 3 minutes, making bacterial mRNA much less stable than eukaryotic mRNA. In mammalian cells, mRNA lifetimes range from several minutes to days. The greater the stability of an mRNA the more protein may be produced from that mRNA. The limited lifetime of mRNA ena... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA eIF-4E and eIF-4G block the decapping enzyme (DCP2), and poly(A)-binding protein blocks the exosome complex, protecting the ends of the message. The balance between translation and decay is reflected in the size and abundance of cytoplasmic structures known as P-bodies The poly(A) tail of the mRNA is shor... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA AU-rich elements also regulate the biosynthesis of proto-oncogenic transcription factors like c-Jun and c-Fos. Eukaryotic messages are subject to surveillance by nonsense mediated decay (NMD), which checks for the presence of premature stop codons (nonsense codons) in the message. These can arise via inco... | https://en.wikipedia.org/wiki?curid=20232 |
Messenger RNA There are other ways by which messages can be degraded, including non-stop decay and silencing by Piwi-interacting RNA (piRNA), among others. Full length mRNA molecules have been proposed as therapeutics since the beginning of the biotech era but there was little traction until the 2010s, when Moderna The... | https://en.wikipedia.org/wiki?curid=20232 |
Mineraloid A mineraloid is a naturally occurring mineral-like substance that does not demonstrate crystallinity. Mineraloids possess chemical compositions that vary beyond the generally accepted ranges for specific minerals. For example, obsidian is an amorphous glass and not a crystal. Jet is derived from decaying woo... | https://en.wikipedia.org/wiki?curid=20725 |
Menilite is a greyish-brown form of the mineraloid opal. It is also known as "liver opal" or "leberopal" (German), due to its color. It is called menilite because it was first described from Ménilmontant (Paris), France, where it occurs as concretions within bituminous Early Oligocene Shales. | https://en.wikipedia.org/wiki?curid=20834 |
Organic chemistry is a branch of chemistry that studies the structure, properties and reactions of organic compounds, which contain carbon in covalent bonding. Study of structure determines their chemical composition and formula. Study of properties includes physical and chemical properties, and evaluation of chemical ... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry They form the basis of, or are constituents of, many commercial products including pharmaceuticals; petrochemicals and agrichemicals, and products made from them including lubricants, solvents; plastics; fuels and explosives. The study of organic chemistry overlaps organometallic chemistry and biochem... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Although Wöhler himself was cautious about claiming he had disproved vitalism, this was the first time a substance thought to be organic was synthesized in the laboratory without biological (organic) starting materials. The event is now generally accepted as indeed disproving the doctrine of vitalism.... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry His laboratory made decisive contributions to developing antiserum for diphtheria and standardizing therapeutic serums. Early examples of organic reactions and applications were often found because of a combination of luck and preparation for unexpected observations. The latter half of the 19th centur... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Converting individual petroleum compounds into "types" of compounds by various chemical processes led to organic reactions enabling a broad range of industrial and commercial products including, among (many) others: plastics, synthetic rubber, organic adhesives, and various property-modifying petroleu... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Traditional methods of separation include distillation, crystallization, and solvent extraction. Organic compounds were traditionally characterized by a variety of chemical tests, called "wet methods", but such tests have been largely displaced by spectroscopic or other computer-intensive methods of a... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry A well-known example of a sublimable organic compound is para-dichlorobenzene, the odiferous constituent of modern mothballs. Organic compounds are usually not very stable at temperatures above 300 °C, although some exceptions exist. Neutral organic compounds tend to be hydrophobic; that is, they are ... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry This parent name is then modified by prefixes, suffixes, and numbers to unambiguously convey the structure. Given that millions of organic compounds are known, rigorous use of systematic names can be cumbersome. Thus, IUPAC recommendations are more closely followed for simple compounds, but not comple... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry By 1880 an explosion in the number of chemical compounds being discovered occurred assisted by new synthetic and analytical techniques. Grignard described the situation as "chaos le plus complet" as due to the lack of convention it was possible to have multiple names for the same compound. This led to... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry The degree of branching affects characteristics, such as the octane number or cetane number in petroleum chemistry. Both saturated (alicyclic) compounds and unsaturated compounds exist as cyclic derivatives. The most stable rings contain five or six carbon atoms, but large rings (macrocycles) and smal... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Pyridine and furan are examples of aromatic heterocycles while piperidine and tetrahydrofuran are the corresponding alicyclic heterocycles. The heteroatom of heterocyclic molecules is generally oxygen, sulfur, or nitrogen, with the latter being particularly common in biochemical systems. Heterocycles ... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Biomolecular chemistry is a major category within organic chemistry which is frequently studied by biochemists. Many complex multi-functional group molecules are important in living organisms. Some are long-chain biopolymers, and these include peptides, DNA, RNA and the polysaccharides such as starche... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Fullerenes and carbon nanotubes, carbon compounds with spheroidal and tubular structures, have stimulated much research into the related field of materials science. The first fullerene was discovered in 1985 by Sir Harold W. Kroto of the United Kingdom and by Richard E. Smalley and Robert F. Curl, Jr.... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry The general theory of these reactions involves careful analysis of such properties as the electron affinity of key atoms, bond strengths and steric hindrance. These factors can determine the relative stability of short-lived reactive intermediates, which usually directly determine the path of the reac... | https://en.wikipedia.org/wiki?curid=22208 |
Organic chemistry Complex compounds can have tens of reaction steps that sequentially build the desired molecule. The synthesis proceeds by utilizing the reactivity of the functional groups in the molecule. For example, a carbonyl compound can be used as a nucleophile by converting it into an enolate, or as an electrop... | https://en.wikipedia.org/wiki?curid=22208 |
Physics (from , from "phýsis" 'nature') is the natural science that studies matter, its motion and behavior through space and time, and the related entities of energy and force. is one of the most fundamental scientific disciplines, and its main goal is to understand how the universe behaves. is one of the oldest acade... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Early civilizations dating back before 3000 BCE, such as the Sumerians, ancient Egyptians, and the Indus Valley Civilisation, had a predictive knowledge and a basic understanding of the motions of the Sun, Moon, and stars. The stars and planets, believed to represent gods, were often worshipped. While the expla... | https://en.wikipedia.org/wiki?curid=22939 |
Physics They proposed ideas verified by reason and observation, and many of their hypotheses proved successful in experiment; for example, atomism was found to be correct approximately 2000 years after it was proposed by Leucippus and his pupil Democritus. The Western Roman Empire fell in the fifth century, and this re... | https://en.wikipedia.org/wiki?curid=22939 |
Physics And so, if the difference in the weights is not considerable, that is, of one is, let us say, double the other, there will be no difference, or else an imperceptible difference, in time, though the difference in weight is by no means negligible, with one body weighing twice as much as the otherPhiloponus' criti... | https://en.wikipedia.org/wiki?curid=22939 |
Physics In the book, he presented a study of the phenomenon of the camera obscura (his thousand-year-old version of the pinhole camera) and delved further into the way the eye itself works. Using dissections and the knowledge of previous scholars, he was able to begin to explain how light enters the eye. He asserted th... | https://en.wikipedia.org/wiki?curid=22939 |
Physics became a separate science when early modern Europeans used experimental and quantitative methods to discover what are now considered to be the laws of physics. Major developments in this period include the replacement of the geocentric model of the Solar System with the heliocentric Copernican model, the laws g... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Modern physics began in the early 20th century with the work of Max Planck in quantum theory and Albert Einstein's theory of relativity. Both of these theories came about due to inaccuracies in classical mechanics in certain situations. Classical mechanics predicted a varying speed of light, which could not be ... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Areas of mathematics in general are important to this field, such as the study of probabilities and groups. In many ways, physics stems from ancient Greek philosophy. From Thales' first attempt to characterise matter, to Democritus' deduction that matter ought to reduce to an invariant state, the Ptolemaic astr... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Many physicists have written about the philosophical implications of their work, for instance Laplace, who championed causal determinism, and Erwin Schrödinger, who wrote on quantum mechanics. The mathematical physicist Roger Penrose had been called a Platonist by Stephen Hawking, a view Penrose discusses in hi... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Classical physics includes the traditional branches and topics that were recognised and well-developed before the beginning of the 20th century—classical mechanics, acoustics, optics, thermodynamics, and electromagnetism. Classical mechanics is concerned with bodies acted on by forces and bodies in motion and m... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Heat is a form of energy, the internal energy possessed by the particles of which a substance is composed; thermodynamics deals with the relationships between heat and other forms of energy. Electricity and magnetism have been studied as a single branch of physics since the intimate connection between them was ... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Classical mechanics approximates nature as continuous, while quantum theory is concerned with the discrete nature of many phenomena at the atomic and subatomic level and with the complementary aspects of particles and waves in the description of such phenomena. The theory of relativity is concerned with the des... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Later, quantum field theory unified quantum mechanics and special relativity. General relativity allowed for a dynamical, curved spacetime, with which highly massive systems and the large-scale structure of the universe can be well-described. General relativity has not yet been unified with the other fundamenta... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Mathematics statements have to be only logically true, while predictions of physics statements must match observed and experimental data. The distinction is clear-cut, but not always obvious. For example, mathematical physics is the application of mathematics in physics. Its methods are mathematical, but its su... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Applied physics is a general term for physics research which is intended for a particular use. An applied physics curriculum usually contains a few classes in an applied discipline, like geology or electrical engineering. It usually differs from engineering in that an applied physicist may not be designing some... | https://en.wikipedia.org/wiki?curid=22939 |
Physics For example, in the study of the origin of the earth, one can reasonably model earth's mass, temperature, and rate of rotation, as a function of time allowing one to extrapolate forward or backward in time and so predict future or prior events. It also allows for simulations in engineering that drastically spee... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Progress in physics frequently comes about when experimental results defy explanation by existing theories, prompting intense focus on applicable modelling, and when new theories generate experimentally testable predictions, which inspire developing new experiments (and often related equipment, possibly roping ... | https://en.wikipedia.org/wiki?curid=22939 |
Physics covers a wide range of phenomena, from elementary particles (such as quarks, neutrinos, and electrons) to the largest superclusters of galaxies. Included in these phenomena are the most basic objects composing all other things. Therefore, physics is sometimes called the "fundamental science". aims to describe t... | https://en.wikipedia.org/wiki?curid=22939 |
Physics hopes to find an ultimate reason (theory of everything) for why nature is as it is (see section "Current research" below for more information). Contemporary research in physics can be broadly divided into nuclear and particle physics; condensed matter physics; atomic, molecular, and optical physics; astrophysic... | https://en.wikipedia.org/wiki?curid=22939 |
Physics The model accounts for the 12 known particles of matter (quarks and leptons) that interact via the strong, weak, and electromagnetic fundamental forces. Dynamics are described in terms of matter particles exchanging gauge bosons (gluons, W and Z bosons, and photons, respectively). The Standard Model also predic... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Current research focuses on activities in quantum control, cooling and trapping of atoms and ions, low-temperature collision dynamics and the effects of electron correlation on structure and dynamics. Atomic physics is influenced by the nucleus (see hyperfine splitting), but intra-nuclear phenomena such as fiss... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Condensed matter physics is the largest field of contemporary physics. Historically, condensed matter physics grew out of solid-state physics, which is now considered one of its main subfields. The term "condensed matter physics" was apparently coined by Philip Anderson when he renamed his research group—previo... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Physical cosmology is the study of the formation and evolution of the universe on its largest scales. Albert Einstein's theory of relativity plays a central role in all modern cosmological theories. In the early 20th century, Hubble's discovery that the universe is expanding, as shown by the Hubble diagram, pro... | https://en.wikipedia.org/wiki?curid=22939 |
Physics IBEX is already yielding new astrophysical discoveries: "No one knows what is creating the ENA (energetic neutral atoms) ribbon" along the termination shock of the solar wind, "but everyone agrees that it means the textbook picture of the heliosphere—in which the Solar System's enveloping pocket filled with the... | https://en.wikipedia.org/wiki?curid=22939 |
Physics Theoretical attempts to unify quantum mechanics and general relativity into a single theory of quantum gravity, a program ongoing for over half a century, have not yet been decisively resolved. The current leading candidates are M-theory, superstring theory and loop quantum gravity. Many astronomical and cosmol... | https://en.wikipedia.org/wiki?curid=22939 |
Paleontology 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 interactions with each other a... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Body fossils and trace fossils are the principal types of evidence about ancient life, and 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 r... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology William Whewell (1794-1866) classified paleontology as one of the historical sciences, along with archaeology, geology, astronomy, cosmology, philology and history itself: paleontology aims to describe phenomena of the past and to reconstruct their causes. Hence it has three main elements: description of p... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology However, when confronted with totally unexpected phenomena, such as the first evidence for invisible radiation, experimental scientists often use the same approach as historical scientists: construct a set of hypotheses about the causes and then look for a "smoking gun". lies between biology and geology si... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology For example, geochemical signatures from rocks may help to discover when life first arose on Earth, and analyses of carbon isotope ratios may help to identify climate changes and even to explain major transitions such as the Permian–Triassic extinction event. A relatively recent discipline, molecular phylo... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Invertebrate paleontology deals with fossils such as molluscs, arthropods, annelid worms and echinoderms. Paleobotany studies fossil plants, algae, and fungi. Palynology, the study of pollen and spores produced by land plants and protists, straddles paleontology and botany, as it deals with both living and... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Biogeography studies the spatial distribution of organisms, and is also linked to geology, which explains how Earth's geography has changed over time. Fossils of organisms' bodies are usually the most informative type of evidence. The most common types are wood, bones, and shells. Fossilisation is a rare e... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology where soft-bodied organisms can be preserved very quickly by events such as mudslides; and the exceptional events that cause quick burial make it difficult to study the normal environments of the animals. The sparseness of the fossil record means that organisms are expected to exist long before and after t... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Naming groups of organisms in a way that is clear and widely agreed is important, as some disputes in paleontology have been based just on misunderstandings over names. Linnaean taxonomy is commonly used for classifying living organisms, but runs into difficulties when dealing with newly discovered organis... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology The cladistic technique is sometimes fallible, as some features, such as wings or camera eyes, evolved more than once, convergently – this must be taken into account in analyses. Evolutionary developmental biology, commonly abbreviated to "Evo Devo", also helps paleontologists to produce "family trees", an... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Stratigraphy is the science of deciphering the "layer-cake" that is the sedimentary record, and has been compared to a jigsaw puzzle. Rocks normally form relatively horizontal layers, with each layer younger than the one underneath it. If a fossil is found between two layers whose ages are known, the fossi... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology For instance, if fossils of B or C date to X million years ago and the calculated "family tree" says A was an ancestor of B and C, then A must have evolved more than X million years ago. It is also possible to estimate how long ago two living clades diverged – i.e. approximately how long ago their last com... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology For about 2,000 million years microbial mats, multi-layered colonies of different bacteria, were the dominant life on Earth. The evolution of oxygenic photosynthesis enabled them to play the major role in the oxygenation of the atmosphere from about . This change in the atmosphere increased their effective... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology The earliest modern-looking bilaterian animals appear in the Early Cambrian, along with several "weird wonders" that bear little obvious resemblance to any modern animals. There is a long-running debate about whether this Cambrian explosion was truly a very rapid period of evolutionary experimentation; alt... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology During the Permian period, synapsids, including the ancestors of mammals, may have dominated land environments, but this ended with the Permian–Triassic extinction event , which came very close to wiping out all complex life. The extinctions were apparently fairly sudden, at least among vertebrates. During... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Although early members of this lineage had chimp-sized brains, about 25% as big as modern humans', there are signs of a steady increase in brain size after about . There is a long-running debate about whether "modern" humans are descendants of a single small population in Africa, which then migrated all ov... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology Although paleontology became established around 1800, earlier thinkers had noticed aspects of the fossil record. The ancient Greek philosopher Xenophanes (570–480 BC) concluded from fossil sea shells that some areas of land were once under water. During the Middle Ages the Persian naturalist Ibn Sina, know... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology The expanding knowledge of the fossil record also played an increasing role in the development of geology, particularly stratigraphy. The first half of the 19th century saw geological and paleontological activity become increasingly well organised with the growth of geologic societies and museums and an in... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology The trend continued in the 20th century with additional regions of the Earth being opened to systematic fossil collection. Fossils found in China near the end of the 20th century have been particularly important as they have provided new information about the earliest evolution of animals, early fish, dino... | https://en.wikipedia.org/wiki?curid=23084 |
Paleontology In the 1960s molecular phylogenetics, the investigation of evolutionary "family trees" by techniques derived from biochemistry, began to make an impact, particularly when it was proposed that the human lineage had diverged from apes much more recently than was generally thought at the time. Although this e... | https://en.wikipedia.org/wiki?curid=23084 |
Physical geography (also known as geosystems or physiography) is one of the two major fields of geography. is the branch of natural science which deals with the study of processes and patterns in the natural environment such as the atmosphere, hydrosphere, biosphere, and geosphere, as opposed to the cultural or built e... | https://en.wikipedia.org/wiki?curid=23263 |
Physical geography Several works among the best known during this long period could be cited as an example, from Strabo ("Geography"), Eratosthenes ("Geographika") or Dionisio Periegetes ("Periegesis Oiceumene") in the Ancient Age to the Alexander von Humboldt ("Kosmos") in the nineteenth century, in which geography is... | https://en.wikipedia.org/wiki?curid=23263 |
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