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Extinctions
Extinction is the termination of an organism by the death of its last member. A taxon may become functionally extinct before the death of its last member if it loses the capacity to reproduce and recover. As a species' potential range may be very large, determining this moment is difficult, and is usually done retrospectively. This difficulty leads to phenomena such as Lazarus taxa, where a species presumed extinct abruptly "reappears" (typically in the fossil record) after a period of apparent absence. Over five billion species are estimated to have died out. It is estimated that there are currently around 8.7 million species of eukaryotes globally, possibly many times more if microorganisms are included. Notable extinct animal species include non-avian dinosaurs, saber-toothed cats, and mammoths. Through evolution, species arise through the process of speciation. Species become extinct when they are no longer able to survive in changing conditions or against superior ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Extinction Event
An extinction event (also known as a mass extinction or biotic crisis) is a widespread and rapid decrease in the biodiversity on Earth. Such an event is identified by a sharp fall in the diversity and abundance of multicellular organisms. It occurs when the rate of extinction increases with respect to the background extinction rate and the rate of speciation. Estimates of the number of major mass extinctions in the last 540 million years range from as few as five to more than twenty. These differences stem from disagreement as to what constitutes a "major" extinction event, and the data chosen to measure past diversity. The "Big Five" mass extinctions In a landmark paper published in 1982, Jack Sepkoski and David M. Raup identified five particular geological intervals with excessive diversity loss. They were originally identified as outliers on a general trend of decreasing extinction rates during the Phanerozoic, but as more stringent statistical tests have been applied t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Holocene Extinction
The Holocene extinction, also referred to as the Anthropocene extinction or the sixth mass extinction, is an ongoing extinction event caused exclusively by human activities during the Holocene epoch. This extinction event spans numerous families of plants and animals, including mammals, birds, reptiles, amphibians, fish, and invertebrates, impacting both terrestrial and marine life, marine species. Widespread degradation of biodiversity hotspots such as coral reefs and rainforests has exacerbated the crisis. Many of these extinctions are undocumented, as the species are often undiscovered before their extinctions. Current extinction rates are estimated at 100 to 1,000 times higher than natural background extinction rates and are accelerating. Over the past 100–200 years, biodiversity loss has reached such alarming levels that some conservation biologists now believe humankind, human activities have triggered a mass extinction, or are on the cusp of doing so. As such, after the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dinosaur
Dinosaurs are a diverse group of reptiles of the clade Dinosauria. They first appeared during the Triassic Geological period, period, between 243 and 233.23 million years ago (mya), although the exact origin and timing of the #Evolutionary history, evolution of dinosaurs is a subject of active research. They became the dominant terrestrial vertebrates after the Triassic–Jurassic extinction event 201.3 mya and their dominance continued throughout the Jurassic and Cretaceous periods. The fossil record shows that birds are feathered dinosaurs, Evolution of birds, having evolved from earlier Theropoda, theropods during the Late Jurassic epoch, and are the only dinosaur lineage known to have survived the Cretaceous–Paleogene extinction event approximately 66 mya. Dinosaurs can therefore be divided into avian dinosaurs—birds—and the extinct non-avian dinosaurs, which are all dinosaurs other than birds. Dinosaurs are varied from taxonomy (biology), taxonomic, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Functional Extinction
Functional extinction is the extinction of a species or other taxon such that: #It disappears from the fossil record, or historic reports of its existence cease; #The reduced population no longer plays a significant role in ecosystem function; #The population is no longer viable. There are no individuals able to reproduce, or the small population of breeding individuals will not be able to sustain itself due to inbreeding depression and genetic drift, which leads to a loss of fitness. In plant populations, self-incompatibility mechanisms may cause related plant specimens to be incompatible, which may lead to functional extinction if an entire population becomes self-incompatible. This does not occur in larger populations. In polygynous populations, where only a few males leave offspring, there is a much smaller reproducing population than if all viable males were considered. Furthermore, the successful males act as a genetic bottleneck, leading to more rapid genetic drift ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lazarus Taxon
In paleontology, a Lazarus taxon (plural ''taxa'') is a taxon that disappears for one or more periods from the fossil record, only to appear again either in later fossil records, or as actual living organisms, and often in isolated, obscure, or otherwise very specialized habitats. Likewise in conservation biology and ecology, it can refer to species or populations that were mistakenly thought to be extinct, and are rediscovered to be still living. The term Lazarus taxon was coined by Karl W. Flessa and David Jablonski in 1983 and was then expanded by Jablonski in 1986. Paul Wignall and Michael Benton defined Lazarus taxa as, "At times of biotic crisis many taxa go extinct, but others only temporarily disappeared from the fossil record, often for intervals measured in millions of years, before reappearing unchanged". Earlier work also supports the concept though without using the name Lazarus taxon, like work by Christopher R. C. Paul. The term refers to the story in the Christ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation. The scientific theory of evolution by natural selection was conceived independently by two British naturalists, Charles Darwin and Alfred Russel Wallace, in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory was first set out in detail in Darwin's book ''On the Origin of Species''. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) phenotypic variatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Machairodontinae
Machairodontinae (from Ancient Greek μάχαιρα ''Makhaira, machaira,'' a type of Ancient Greek sword and ὀδόντος ''odontos'' meaning tooth) is an extinct subfamily of carnivoran mammals of the cat family Felidae, representing the earliest diverging major branch of the family. Machairodonts varied in size from comparable to lynxes to exceeding that of lions. The Machairodontinae contain many of the extinct predators commonly known as "saber-toothed cats", including those with greatly elongated upper Maxillary canine, maxillary canines, such as the famed genus ''Smilodon'' and ''Megantereon,'' though the degree of elongation was variable, and in some machairodontines like ''Dinofelis'' the length of the upper canines was much more modest. Sometimes, other carnivorous mammals with elongated teeth are also called saber-toothed cats, although they do not belong to the felids. Besides the machairodonts, other saber-toothed predators also arose in the Nimravidae, nimravid ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thylacinus Cynocephalus (Gould)
The thylacine (; binomial name ''Thylacinus cynocephalus''), also commonly known as the Tasmanian tiger or Tasmanian wolf, was a carnivorous marsupial that was native to the Mainland Australia, Australian mainland and the islands of Tasmania and New Guinea. The thylacine died out in New Guinea and mainland Australia around 3,600–3,200 years ago, prior to the arrival of Europeans, possibly because of the introduction of the dingo, whose earliest record dates to around the same time, but which never reached Tasmania. Prior to European settlement, around 5,000 remained in the wild on the island of Tasmania. Beginning in the nineteenth century, they were perceived as a threat to the livestock of farmers and bounty (reward), bounty hunting was introduced. The last known of its species died in 1936 at Hobart Zoo in Tasmania. The thylacine is widespread in popular culture and is a cultural icon in Australia. The thylacine was known as the Tasmanian tiger because of the dark trans ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
BioScience
''BioScience'' is a monthly peer-reviewed scientific journal that is published by Oxford University Press on behalf of the American Institute of Biological Sciences. It was established in 1964 and was preceded by the ''AIBS Bulletin'' (1951–1963). The journal publishes literature reviews of current research in biology, as well as essays and discussion sections on education, public policy, history of biology, and theoretical issues. Abstracting and indexing The journal is abstracted and indexed in MEDLINE/ PubMed (1973–1979), the Science Citation Index, Current Contents/Agriculture, Biology & Environmental Sciences, The Zoological Record, and BIOSIS Previews. According to the ''Journal Citation Reports'', the journal has a 2020 impact factor The impact factor (IF) or journal impact factor (JIF) of an academic journal is a type of journal ranking. Journals with higher impact factor values are considered more prestigious or important within their field. The Impa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Science Advances
''Science Advances'' is a peer-reviewed multidisciplinary open-access scientific journal established in early 2015 and published by the American Association for the Advancement of Science. The journal's scope includes all areas of science. History The journal was announced by the American Association for the Advancement of Science in February 2014, and the first articles were published in early 2015. In 2019, ''Science Advances'' surpassed '' Science Magazine'' in the number of monthly submissions, becoming the largest member in the Science family of journals. It is the only member of that family where all papers are gold open access. Editorial structure and journal scope The journal's scope includes all areas of science, including life sciences, public health, neurosciences, physical sciences, social sciences, computer sciences, environmental sciences, and space sciences. Editorial decisions are made by the editorial board. The board is divided into topical areas, eac ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
PBS Digital Studios
PBS Digital Studios is a non-profit organization through which PBS distributes original educational web video content. Based in Arlington, Virginia, it comprises both original series and partnerships with existing YouTube YouTube is an American social media and online video sharing platform owned by Google. YouTube was founded on February 14, 2005, by Steve Chen, Chad Hurley, and Jawed Karim who were three former employees of PayPal. Headquartered in ... channels. Most of the series are about science, popular culture, art, food, news, and music. History PBS Digital Studios was founded by Jason Seiken in June 2012.Looking Back On A Year Of PBS Digital Studios July 18, 2013. They had their first viral hit with a "remix" of [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morphology (biology)
Morphology (from Ancient Greek μορφή (morphḗ) "form", and λόγος (lógos) "word, study, research") is the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, color, pattern, size), as well as the form and structure of internal parts like bones and organs, i.e., anatomy. This is in contrast to physiology, which deals primarily with function. Morphology is a branch of life science dealing with the study of the overall structure of an organism or taxon and its component parts. History The etymology of the word "morphology" is from the Ancient Greek (), meaning "form", and (), meaning "word, study, research". While the concept of form in biology, opposed to function, dates back to Aristotle (see Aristotle's biology), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Fried ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
