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Taxonomy Of Liliaceae
The taxonomy of the plant family Liliaceae has had a complex history since its first description in the mid-eighteenth century. Originally, the Liliaceae were defined as having a " ''calix''" (perianth) of six equal-coloured parts, six stamens, a single style, and a superior, three-chambered (trilocular) ovary turning into a capsule fruit at maturity. The taxonomic circumscription of the family Liliaceae progressively expanded until it became the largest plant family and also extremely diverse, being somewhat arbitrarily defined as all species of plants with six tepals and a superior ovary. It eventually came to encompass about 300 genera and 4,500 species, and was thus a " catch-all" and hence paraphyletic. Only since the more modern taxonomic systems developed by the Angiosperm Phylogeny Group (APG) and based on phylogenetic principles, has it been possible to identify the many separate taxonomic groupings within the original family and redistribute them, leaving a relativel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Late Cretaceous
The Late Cretaceous (100.5–66 Ma) is the younger of two epochs into which the Cretaceous Period is divided in the geologic time scale. Rock strata from this epoch form the Upper Cretaceous Series. The Cretaceous is named after ''creta'', the Latin word for the white limestone known as chalk. The chalk of northern France and the white cliffs of south-eastern England date from the Cretaceous Period. Climate During the Late Cretaceous, the climate was warmer than present, although throughout the period a cooling trend is evident. The tropics became restricted to equatorial regions and northern latitudes experienced markedly more seasonal climatic conditions. Geography Due to plate tectonics, the Americas were gradually moving westward, causing the Atlantic Ocean to expand. The Western Interior Seaway divided North America into eastern and western halves; Appalachia and Laramidia. India maintained a northward course towards Asia. In the Southern Hemisphere, Australia and Ant ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumscription (taxonomy)
In biological taxonomy, circumscription is the content of a taxon, that is, the delimitation of which subordinate taxa are parts of that taxon. If we determine that species X, Y, and Z belong in Genus A, and species T, U, V, and W belong in Genus B, those are our circumscriptions of those two genera. Another systematist might determine that T, U, V, W, X, Y, and Z all belong in genus A. Agreement on circumscriptions is not governed by the Codes of Zoological or Botanical Nomenclature, and must be reached by scientific consensus. A goal of biological taxonomy is to achieve a stable circumscription for every taxon. This goal conflicts, at times, with the goal of achieving a natural classification that reflects the evolutionary history of divergence of groups of organisms. Balancing these two goals is a work in progress, and the circumscriptions of many taxa that had been regarded as stable for decades are in upheaval in the light of rapid developments in molecular phylogenetics ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Eurasia
Eurasia (, ) is the largest continental area on Earth, comprising all of Europe and Asia. Primarily in the Northern and Eastern Hemispheres, it spans from the British Isles and the Iberian Peninsula in the west to the Japanese archipelago and the Russian Far East to the east. The continental landmass is bordered by the Atlantic Ocean and Africa to the west, the Pacific Ocean to the east, the Arctic Ocean to the north, and by Africa, the Mediterranean Sea, and the Indian Ocean to the south. The division between Europe and Asia as two continents is a historical social construct, as many of their borders are over land; thus, in some parts of the world, Eurasia is recognized as the largest of the six, five, or four continents on Earth. In geology, Eurasia is often considered as a single rigid megablock. However, the rigidity of Eurasia is debated based on paleomagnetic data. Eurasia covers around , or around 36.2% of the Earth's total land area. It is also home to the largest ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Clades
A clade (), also known as a monophyletic group or natural group, is a group of organisms that are monophyletic – that is, composed of a common ancestor and all its lineal descendants – on a phylogenetic tree. Rather than the English term, the equivalent Latin term ''cladus'' (plural ''cladi'') is often used in taxonomical literature. The common ancestor may be an individual, a population, or a species (extinct or extant). Clades are nested, one in another, as each branch in turn splits into smaller branches. These splits reflect evolutionary history as populations diverged and evolved independently. Clades are termed monophyletic (Greek: "one clan") groups. Over the last few decades, the cladistic approach has revolutionized biological classification and revealed surprising evolutionary relationships among organisms. Increasingly, taxonomists try to avoid naming taxa that are not clades; that is, taxa that are not monophyletic. Some of the relationships between organisms t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genetic Divergence
Genetic divergence is the process in which two or more populations of an ancestral species accumulate independent genetic changes (mutations) through time, often leading to reproductive isolation and continued mutation even after the populations have become Reproductive isolation, reproductively isolated for some period of time, as there isn’t genetic exchange anymore. In some cases, subpopulations living in ecologically distinct peripheral environments can exhibit genetic divergence from the remainder of a population, especially where the range of a population is very large (see parapatric speciation). The genetic differences among divergent populations can involve silent mutations (that have no effect on the phenotype) or give rise to significant Morphology (biology), morphological and/or physiology, physiological changes. Genetic divergence will always accompany reproductive isolation, either due to novel adaptations via selection and/or due to genetic drift, and is the principal ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mya (unit)
Mya may refer to: Brands and product names * Mya (program), an intelligent personal assistant created by Motorola * Mya (TV channel), an Italian Television channel * Midwest Young Artists, a comprehensive youth music program Codes * Burmese language, ISO 639-3 code is * Moruya Airport's IATA code * The IOC, license plate, and UNDP country code for Myanmar ("MYA") People * Mya (given name) * Mya (singer) (Mya Marie Harrison, born 1979), an American R&B singer-songwriter and actress * Bo Mya (1927–2006), nom de guerre of a Myanmar rebel leader, chief rapist of the Karen National Union Other uses * ''Mýa'' (album), a 1998 album by Mýa * ''Mya'' (bivalve), a genus of soft-shell clams * MYA (unit) for "million years ago", a science-related unit of time used in astronomy, geology and biology See also * A (motor yacht) (M/Y A), a superyacht * Maia (other) * Maya (other) Maya may refer to: Civilizations * Maya peoples, of southern Mexico and norther ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sister Clade
In phylogenetics, a sister group or sister taxon, also called an adelphotaxon, comprises the closest relative(s) of another given unit in an evolutionary tree. Definition The expression is most easily illustrated by a cladogram: Taxon A and taxon B are sister groups to each other. Taxa A and B, together with any other extant or extinct descendants of their most recent common ancestor (MRCA), form a monophyletic group, the clade AB. Clade AB and taxon C are also sister groups. Taxa A, B, and C, together with all other descendants of their MRCA form the clade ABC. The whole clade ABC is itself a subtree of a larger tree which offers yet more sister group relationships, both among the leaves and among larger, more deeply rooted clades. The tree structure shown connects through its root to the rest of the universal tree of life. In cladistic standards, taxa A, B, and C may represent specimens, species, genera, or any other taxonomic units. If A and B are at the same taxonomi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Liliales
Liliales is an order of monocotyledonous flowering plants in the Angiosperm Phylogeny Group and Angiosperm Phylogeny Web system, within the lilioid monocots. This order of necessity includes the family Liliaceae. The APG III system (2009) places this order in the monocot clade. In APG III, the family Luzuriagaceae is combined with the family Alstroemeriaceae and the family Petermanniaceae is recognized. Both the order Lililiales and the family Liliaceae have had a widely disputed history, with the circumscription varying greatly from one taxonomist to another. Previous members of this order, which at one stage included most monocots with conspicuous tepals and lacking starch in the endosperm are now distributed over three orders, Liliales, Dioscoreales and Asparagales, using predominantly molecular phylogenetics. The newly delimited Liliales is monophyletic, with ten families. Well known plants from the order include ''Lilium'' (lily), tulip, the North American wildflower ''Tri ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phylogenetic
In biology, phylogenetics (; from Greek φυλή/ φῦλον [] "tribe, clan, race", and wikt:γενετικός, γενετικός [] "origin, source, birth") is the study of the evolutionary history and relationships among or within groups of organisms. These relationships are determined by Computational phylogenetics, phylogenetic inference methods that focus on observed heritable traits, such as DNA sequences, protein amino acid sequences, or morphology. The result of such an analysis is a phylogenetic tree—a diagram containing a hypothesis of relationships that reflects the evolutionary history of a group of organisms. The tips of a phylogenetic tree can be living taxa or fossils, and represent the "end" or the present time in an evolutionary lineage. A phylogenetic diagram can be rooted or unrooted. A rooted tree diagram indicates the hypothetical common ancestor of the tree. An unrooted tree diagram (a network) makes no assumption about the ancestral line, and does ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Angiosperm Phylogeny Group
The Angiosperm Phylogeny Group (APG) is an informal international group of systematic botanists who collaborate to establish a consensus on the taxonomy of flowering plants (angiosperms) that reflects new knowledge about plant relationships discovered through phylogenetic studies. , four incremental versions of a classification system have resulted from this collaboration, published in 1998, 2003, 2009 and 2016. An important motivation for the group was what they considered deficiencies in prior angiosperm classifications since they were not based on monophyletic groups (i.e., groups that include all the descendants of a common ancestor). APG publications are increasingly influential, with a number of major herbaria changing the arrangement of their collections to match the latest APG system. Angiosperm classification and the APG In the past, classification systems were typically produced by an individual botanist or by a small group. The result was a large number of systems ( ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Paraphyletic
In taxonomy (general), taxonomy, a group is paraphyletic if it consists of the group's most recent common ancestor, last common ancestor and most of its descendants, excluding a few Monophyly, monophyletic subgroups. The group is said to be paraphyletic ''with respect to'' the excluded subgroups. In contrast, a monophyletic group (a clade) includes a common ancestor and ''all'' of its descendants. The terms are commonly used in phylogenetics (a subfield of biology) and in the tree model of historical linguistics. Paraphyletic groups are identified by a combination of Synapomorphy and apomorphy, synapomorphies and symplesiomorphy, symplesiomorphies. If many subgroups are missing from the named group, it is said to be polyparaphyletic. The term was coined by Willi Hennig to apply to well-known taxa like Reptilia (reptiles) which, as commonly named and traditionally defined, is paraphyletic with respect to mammals and birds. Reptilia contains the last common ancestor of reptiles a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Catch-all Taxon
Wastebasket taxon (also called a wastebin taxon, dustbin taxon or catch-all taxon) is a term used by some taxonomists to refer to a taxon that has the sole purpose of classifying organisms that do not fit anywhere else. They are typically defined by either their designated members' often superficial similarity to each other, or their ''lack'' of one or more distinct character states or by their ''not'' belonging to one or more other taxa. Wastebasket taxa are by definition either paraphyletic or polyphyletic, and are therefore not considered valid taxa under strict cladistic rules of taxonomy. The name of a wastebasket taxon may in some cases be retained as the designation of an evolutionary grade, however. The term was coined in a 1985 essay by Steven Jay Gould. Examples There are many examples of paraphyletic groups, but true "wastebasket" taxa are those that are known not to, and perhaps not intended to, represent natural groups, but are nevertheless used as convenient groups ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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