A polyphyletic group is a set of organisms, or other evolving elements, that have been grouped together but do not share an immediate common ancestor. The term is applied to groups that share characteristics that appear to be similar but have not been inherited from common ancestors; the arrangement of the members of a polyphyletic group is called a polyphyly. Alternatively, polyphyletic is used to describe a group whose members come from multiple ancestral sources, regardless of similarity of characteristics. For example, the biological characteristic of warm-bloodedness evolved separately in the ancestors of mammals and the ancestors of birds. Other polyphyletic groups are for example algae, C4 photosynthetic plants, edentates. Many biologists aim to avoid homoplasies in grouping taxa together and therefore it is a goal to eliminate groups that are found to be polyphyletic; this is the stimulus for major revisions of the classification schemes. Researchers concerned more with ecology than with systematics may take polyphyletic groups as legitimate subject matter.
The term polyphyly, or polyphyletic, derives from the two ancient greek words πολύς, meaning "many, a lot of", φῦλον, meaning "genus, species", refers to the fact that a polyphyletic group includes organisms arising from multiple ancestral sources. Conversely, the term monophyly, or monophyletic, builds on the ancient greek prefix μόνος, meaning "alone, unique", refers to the fact that a monophyletic group includes organisms consisting of all the descendants of a unique common ancestor. By comparison, the term paraphyly, or paraphyletic, uses the ancient greek prefix παρά, meaning "beside, near", refers to the situation in which one or several monophyletic subgroups are left apart from all other descendants of a unique common ancestor. In many schools of taxonomy, the existence of polyphyletic groups in a classification is discouraged. Monophyletic groups are considered by these schools of thought to be the most important grouping of organisms. One reason for this view is that some clades are simple to define in purely phylogenetic terms without reference to clades introduced: a node-based clade definition, for example, could be "All descendants of the last common ancestor of species X and Y".
On the other hand, polyphyletic groups can be delimited in terms of clades, for example "the flying vertebrates consist of the bat and pterosaur clades". Because polyphyletic groups can be defined as a sum of clades, they are considered less fundamental than monophyletic clades. A stronger reason is that grouping species monophyletically facilitates prediction far more than does polyphyletic grouping. For example, classifying a newly discovered grass in the monophyletic family Poaceae, the true grasses results in numerous predictions about its structure and its developmental and reproductive characteristics, inherited from the common ancestor of this family. In contrast, Linnaeus' assignment of plants with two stamens to the polyphyletic class Diandria, while practical for identification, turns out to be useless for prediction, since the presence of two stamens has developed convergently in many groups. Predictive success is the touchstone. Species have a special status in systematics as being an observable feature of nature itself and as the basic unit of classification.
It is implicitly assumed that species are monophyletic. However hybrid speciation arguably leads to polyphyletic species. Hybrid species are a common phenomenon in nature in plants where polyploidy allows for rapid speciation. Convergent evolution Tudge, Colin; the Variety of Life. Oxford University Press. ISBN 0198604262. "Evolution - A-Z - Polyphyletic group". Www.blackwellpublishing.com. Retrieved 2018-02-24. Funk, D. J. and Omland, K. E.. "Species-level paraphyly and polyphyly: Frequency and consequences, with insights from animal mitochondrial DNA" Annu. Rev. Ecol. Evol. Syst. 34: 397–423. At ftp://220.127.116.11/users/bhhanser/Subspecies%20general%20literature/FunkEtal2003AnnuRevEcolEvolV34pp397-423.pdf
Senecio haworthii known as Woolly senecio is a perennial dwarf shrub of the Senecio genus that grows in South Africa between the altitudes of 900 and 1200 meters. Its first description was written by Adrian Hardy Haworth, in Miscellanea naturalia, 1803, p. 189, with the name of Cacalia tomentosa. Haworth stated that he had received the plant, introduced eight years before, from the Stockwell Botanical Garden of his friend Benjamin Robertson; the leaves are remarkably densely felted, so much so that the felt can be stripped off and used as tinder. The plant is accordingly called "tontelbos" in Afrikaans; the word means "tinder bush". Though its flowers are nothing special to look at, the plant is striking grown, attractive. Like most Richtersveld plants it does not do well in wet soil, but is not in general a demanding garden subject. Like in nature, Senecio haworthii needs rare water and full sun. Media related to Caputia tomentosa at Wikimedia Commons
Jacobaea vulgaris, syn. Senecio jacobaea, is a common wild flower in the family Asteraceae, native to northern Eurasia in dry, open places, has been distributed as a weed elsewhere. Common names include ragwort, common ragwort, stinking willie, tansy ragwort, benweed, St. James-wort, stinking nanny/ninny/willy, dog standard, stammerwort. In the western United States it is known as tansy ragwort, or tansy, though its resemblance to the true tansy is superficial. Although the plant is unwanted by landowners because it is considered a weed by many, it provides a great deal of nectar for pollinators, it was rated in the top 10 for most nectar production in a UK plants survey conducted by the AgriLand project, supported by the UK Insect Pollinators Initiative. It was the top producer of nectar sugar in another study in Britain, with a production per floral unit of; the plant is considered to be biennial but it has the tendency to exhibit perennial properties under certain cultural conditions. The stems are erect, have no or few hairs, reach a height of 0.3–2.0 metres.
The leaves are pinnately lobed and the end lobe is blunt. The many names that include the word "stinking" arise because of the unpleasant smell of the leaves; the hermaphrodite flower heads are 1.5–2.5 centimetres diameter, are borne in dense, flat-topped clusters. It has a long flowering period lasting from June to November. Pollination is by a wide range of bees and moths and butterflies. Over a season, one plant may produce 2,000 to 2,500 yellow flowers in 20- to 60-headed, flat-topped corymbs; the number of seeds produced may be as large as 75,000 to 120,000, although in its native range in Eurasia few of these would grow into new plants and research has shown that most seeds do not travel a great distance from the parent plant. Two subspecies are accepted: Jacobaea vulgaris ssp. vulgaris - the typical plant, with ray florets present. Jacobaea vulgaris ssp. dunensis - the ray florets are missing. Ragwort is abundant in waste land and grazing pastures, it can be found along road sides, grows in all cool and high rainfall areas.
Ragwort is native to the Eurasian continent. In Europe it is spread, from Scandinavia to the Mediterranean. In Britain and Ireland it is listed as a weed. In the United States it has been introduced, is present in the northwest and northeast: California, Illinois, Massachusetts, Montana, New Jersey, New York, Oregon and Washington. In South America it grows in Argentina, in Africa in the north, on the Asian continent in India and Siberia, it is a widespread weed in New Australia. In many Australian states ragwort has been declared a noxious weed; this status requires landholders to remove it by law. The same applies to New Zealand, where farmers sometimes bring in helicopters to spray their farms if the ragwort is too widespread. Ragwort is a food plant for the larvae of Cochylis atricapitana, Phycitodes maritima, Phycitodes saxicolais. Ragwort is best known as the food of caterpillars of the cinnabar moth Tyria jacobaeae, they absorb alkaloids from the plant and become distasteful to predators, a fact advertised by the black and yellow warning colours.
The red and black, day-flying adult moth is distasteful to many potential predators. The moth is used as a control for ragwort in countries in which it has been introduced and become a problem, like New Zealand and the western United States; as both larvae and adults are distinctly colored and marked, identification of cinnabars is easy outside of their natural range, grounds and range keepers can recognize them. In both countries, the tansy ragwort flea beetle has been introduced to combat the plant. Another beetle, Longitarsus ganglbaueri feeds on ragwort, but will feed on other plants as well, making it an unsuitable biological control; the biological control of ragwort was used in the 1930s. In the United Kingdom, where the plant is native, ragwort provides a home and food source to at least 77 insect species. Thirty of these species of invertebrate use ragwort as their food source and there are another 22 species where ragwort forms a significant part of their diet. Furthermore, English Nature identifies a further 117 species that use ragwort as a nectar source whilst travelling between feeding and breeding sites, or between metapopulations.
These consist of solitary bees, hoverflies and butterflies such as the small copper butterfly. Pollen is collected by solitary bees. Besides the fact that ragwort is attractive to such a vast array of insects, some of these are rare indeed. Of the 30 species that feed on ragwort alone, seven are deemed Nationally Scarce. A further three species are on the IUCN Red List. In short, ragwort is an exclusive food source for ten rare or threatened insect species, including the Cinnabar moth, the Picture Winged Fly, the Scarce Clouded Knot Horn moth, the Sussex Emerald moth; the Sussex Emerald has been labelled a Priority Species in the United Kingdom Biodiversity Action Plan. A Priority Species is one, scarce and declining; the remainder of the ten threatened species include three species of Leaf Beetle, another Picture-Winged Fly, three micro moths. All of these species are Nationally Scarce B, with one Leaf Beetle catego
Synapomorphy and apomorphy
In phylogenetics and synapomorphy refer to derived characters of a clade: characters or traits that are derived from ancestral characters over evolutionary history. An apomorphy is a character, different from the form found in an ancestor, i.e. an innovation, that sets the clade apart from other clades. A synapomorphy is a shared apomorphy. In other words, it is an apomorphy shared by members of a monophyletic group, thus assumed to be present in their most recent common ancestor. An apomorphy is a character, different from the form found in an ancestor, i.e. an innovation, that sets the clade apart from other clades. A synapomorphy is a shared apomorphy. In other words, it is an apomorphy shared by members of a monophyletic group, thus assumed to be present in their most recent common ancestor. In most groups of mammals, the vertebral column is conserved, with the same number of vertebrae found in the neck of a giraffe, for example, as in mammals with shorter necks. However, in the Afrotheria clade, which includes elephant shrews, golden moles and elephants, there is an increase in the number of thoracolumbar vertebrae.
This is a synapomorphy of the clade: a shared feature considered to be derived from a common ancestor. The word synapomorphy—coined by German entomologist Willi Hennig—is derived from the Greek words σύν, syn = shared; these phylogenetic terms are used to describe different patterns of ancestral and derived character or trait states as stated in the above diagram in association with synapomorphies. Symplesiomorphy – an ancestral trait shared by two or more taxa. Plesiomorphy – a symplesiomorphy discussed in reference to a more derived state. Pseudoplesiomorphy – is a trait that cannot be identified as neither a plesiomorphy nor an apomorphy, a reversal. Reversal – is a loss of derived trait present in ancestor and the reestablishment of a plesiomorphic trait. Convergence – independent evolution of a similar trait in two or more taxa. Apomorphy – a derived trait. Apomorphy shared by two or more taxa and inherited from a common ancestor is synapomorphy. Apomorphy unique to a given taxon is autapomorphy.
Synapomorphy/Homology – a derived trait, found in some or all terminal groups of a clade, inherited from a common ancestor, for which it was an autapomorphy. Underlying synapomorphy – a synapomorphy, lost again in many members of the clade. If lost in all but one, it can be hard to distinguish from an autapomorphy. Autapomorphy – a distinctive derived trait, unique to a given taxon or group. Homoplasy in biological systematics is when a trait has been gained or lost independently in separate lineages during evolution; this convergent evolution leads to species independently sharing a trait, different from the trait inferred to have been present in their common ancestor. Parallel Homoplasy – derived trait present in two groups or species without a common ancestor due to convergent evolution. Reverse Homoplasy – trait present in an ancestor but not in direct descendants that reappears in descendants. Hemiplasy A new method of measuring phylogenetic characteristics is the use of Relative Apparent Synapomorphy Analysis.
The objective of analysis is to determine if a given characteristic is common between taxa as a result of either shared ancestors or the process of convergence. This method allows for several advantages such as computational efficiency and it administers an unbiased and reliable measure of phylogenetic signal; the concept of synapomorphy is relative to a given clade in the tree of life. What counts as a synapomorphy for one clade may well be a primitive character or plesiomorphy at a less inclusive or nested clade. For example, the presence of mammary glands is a synapomorphy for mammals in relation to tetrapods but is a symplesiomorphy for mammals in relation to one another—rodents and primates, for example. So the concept can be understood as well in terms of "a character newer than" and "a character older than" the apomorphy: mammary glands are evolutionarily newer than vertebral column, so mammary glands are an autapomorphy if vertebral column is an apomorphy, but if mammary glands are the apomorphy being considered vertebral column is a plesiomorphy.
Cladograms are diagrams. These illustrations are accurate predictive device in modern genetics, they are depicted in either tree or ladder form. Synapomorphies create evidence for historical relationships and their associated hierarchical structure. Evolutionarily, a synapomorphy is the marker for the most recent common ancestor of the monophyletic group consisting of a set of taxa in a cladogram. Cladistics, Berkeley
Plants are multicellular, predominantly photosynthetic eukaryotes of the kingdom Plantae. Plants were treated as one of two kingdoms including all living things that were not animals, all algae and fungi were treated as plants. However, all current definitions of Plantae exclude the fungi and some algae, as well as the prokaryotes. By one definition, plants form the clade Viridiplantae, a group that includes the flowering plants and other gymnosperms and their allies, liverworts and the green algae, but excludes the red and brown algae. Green plants obtain most of their energy from sunlight via photosynthesis by primary chloroplasts that are derived from endosymbiosis with cyanobacteria, their chloroplasts contain b, which gives them their green color. Some plants are parasitic or mycotrophic and have lost the ability to produce normal amounts of chlorophyll or to photosynthesize. Plants are characterized by sexual reproduction and alternation of generations, although asexual reproduction is common.
There are about 320 thousand species of plants, of which the great majority, some 260–290 thousand, are seed plants. Green plants provide a substantial proportion of the world's molecular oxygen and are the basis of most of Earth's ecosystems on land. Plants that produce grain and vegetables form humankind's basic foods, have been domesticated for millennia. Plants have many cultural and other uses, as ornaments, building materials, writing material and, in great variety, they have been the source of medicines and psychoactive drugs; the scientific study of plants is known as a branch of biology. All living things were traditionally placed into one of two groups and animals; this classification may date from Aristotle, who made the distincton between plants, which do not move, animals, which are mobile to catch their food. Much when Linnaeus created the basis of the modern system of scientific classification, these two groups became the kingdoms Vegetabilia and Animalia. Since it has become clear that the plant kingdom as defined included several unrelated groups, the fungi and several groups of algae were removed to new kingdoms.
However, these organisms are still considered plants in popular contexts. The term "plant" implies the possession of the following traits multicellularity, possession of cell walls containing cellulose and the ability to carry out photosynthesis with primary chloroplasts; when the name Plantae or plant is applied to a specific group of organisms or taxon, it refers to one of four concepts. From least to most inclusive, these four groupings are: Another way of looking at the relationships between the different groups that have been called "plants" is through a cladogram, which shows their evolutionary relationships; these are not yet settled, but one accepted relationship between the three groups described above is shown below. Those which have been called "plants" are in bold; the way in which the groups of green algae are combined and named varies between authors. Algae comprise several different groups of organisms which produce food by photosynthesis and thus have traditionally been included in the plant kingdom.
The seaweeds range from large multicellular algae to single-celled organisms and are classified into three groups, the green algae, red algae and brown algae. There is good evidence that the brown algae evolved independently from the others, from non-photosynthetic ancestors that formed endosymbiotic relationships with red algae rather than from cyanobacteria, they are no longer classified as plants as defined here; the Viridiplantae, the green plants – green algae and land plants – form a clade, a group consisting of all the descendants of a common ancestor. With a few exceptions, the green plants have the following features in common, they undergo closed mitosis without centrioles, have mitochondria with flat cristae. The chloroplasts of green plants are surrounded by two membranes, suggesting they originated directly from endosymbiotic cyanobacteria. Two additional groups, the Rhodophyta and Glaucophyta have primary chloroplasts that appear to be derived directly from endosymbiotic cyanobacteria, although they differ from Viridiplantae in the pigments which are used in photosynthesis and so are different in colour.
These groups differ from green plants in that the storage polysaccharide is floridean starch and is stored in the cytoplasm rather than in the plastids. They appear to have had a common origin with Viridiplantae and the three groups form the clade Archaeplastida, whose name implies that their chloroplasts were derived from a single ancient endosymbiotic event; this is the broadest modern definition of the term'plant'. In contrast, most other algae not only have different pigments but have chloroplasts with three or four surrounding membranes, they are not close relatives of the Archaeplastida having acquired chloroplasts separately from ingested or symbiotic green and red algae. They are thus not included in the broadest modern definition of the plant kingdom, although they were in the past; the green plants or Viridiplantae were traditionally divided into the green algae (including
In biology, a species is the basic unit of classification and a taxonomic rank of an organism, as well as a unit of biodiversity. A species is defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring by sexual reproduction. Other ways of defining species include their karyotype, DNA sequence, behaviour or ecological niche. In addition, paleontologists use the concept of the chronospecies since fossil reproduction cannot be examined. While these definitions may seem adequate, when looked at more they represent problematic species concepts. For example, the boundaries between related species become unclear with hybridisation, in a species complex of hundreds of similar microspecies, in a ring species. Among organisms that reproduce only asexually, the concept of a reproductive species breaks down, each clone is a microspecies. All species are given a two-part name, a "binomial"; the first part of a binomial is the genus.
The second part is called the specific epithet. For example, Boa constrictor is one of four species of the genus Boa. None of these is satisfactory definitions, but scientists and conservationists need a species definition which allows them to work, regardless of the theoretical difficulties. If species were fixed and distinct from one another, there would be no problem, but evolutionary processes cause species to change continually, to grade into one another. Species were seen from the time of Aristotle until the 18th century as fixed kinds that could be arranged in a hierarchy, the great chain of being. In the 19th century, biologists grasped. Charles Darwin's 1859 book The Origin of Species explained how species could arise by natural selection; that understanding was extended in the 20th century through genetics and population ecology. Genetic variability arises from mutations and recombination, while organisms themselves are mobile, leading to geographical isolation and genetic drift with varying selection pressures.
Genes can sometimes be exchanged between species by horizontal gene transfer. Viruses are a special case, driven by a balance of mutation and selection, can be treated as quasispecies. Biologists and taxonomists have made many attempts to define species, beginning from morphology and moving towards genetics. Early taxonomists such as Linnaeus had no option but to describe what they saw: this was formalised as the typological or morphological species concept. Ernst Mayr emphasised reproductive isolation, but this, like other species concepts, is hard or impossible to test. Biologists have tried to refine Mayr's definition with the recognition and cohesion concepts, among others. Many of the concepts are quite similar or overlap, so they are not easy to count: the biologist R. L. Mayden recorded about 24 concepts, the philosopher of science John Wilkins counted 26. Wilkins further grouped the species concepts into seven basic kinds of concepts: agamospecies for asexual organisms biospecies for reproductively isolated sexual organisms ecospecies based on ecological niches evolutionary species based on lineage genetic species based on gene pool morphospecies based on form or phenotype and taxonomic species, a species as determined by a taxonomist.
A typological species is a group of organisms in which individuals conform to certain fixed properties, so that pre-literate people recognise the same taxon as do modern taxonomists. The clusters of variations or phenotypes within specimens would differentiate the species; this method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, different phenotypes are not different species. Species named in this manner are called morphospecies. In the 1970s, Robert R. Sokal, Theodore J. Crovello and Peter Sneath proposed a variation on this, a phenetic species, defined as a set of organisms with a similar phenotype to each other, but a different phenotype from other sets of organisms, it differs from the morphological species concept in including a numerical measure of distance or similarity to cluster entities based on multivariate comparisons of a reasonably large number of phenotypic traits. A mate-recognition species is a group of sexually reproducing organisms that recognize one another as potential mates.
Expanding on this to allow for post-mating isolation, a cohesion species is the most inclusive population of individuals having the potential for phenotypic cohesion through intrinsic cohesion mechanisms. A further development of the recognition concept is provided by the biosemiotic concept of species. In microbiology, genes can move even between distantly related bacteria extending to the whole bacterial domain; as a rule of thumb, microbiologists have assumed that kinds of Bacteria or Archaea with 16S ribosomal RNA gene sequences more similar than 97% to each other need to be checked by DNA-DNA hybridisation to decide if they belong to the same species or not. This concept was narrowed in 2006 to a similarity of 98.7%. DNA-DNA hybri
An annual plant is a plant that completes its life cycle, from germination to the production of seeds, within one year, dies. Summer mature by autumn of the same year. Winter annuals germinate during the autumn and mature during the spring or summer of the following calendar year. One seed-to-seed life cycle for an annual can occur in as little as a month in some species, though most last several months. Oilseed rapa can go from seed-to-seed in about five weeks under a bank of fluorescent lamps; this style of growing is used in classrooms for education. Many desert annuals are therophytes, because their seed-to-seed life cycle is only weeks and they spend most of the year as seeds to survive dry conditions. In cultivation, many food plants are, or are grown as, including all domesticated grains; some perennials and biennials are grown in gardens as annuals for convenience if they are not considered cold hardy for the local climate. Carrot and parsley are true biennials that are grown as annual crops for their edible roots and leaves, respectively.
Tomato, sweet potato and bell pepper are tender perennials grown as annuals. Ornamental perennials grown as annuals are impatiens, wax begonia, pelargonium and petunia. Examples of true annuals include corn, rice, peas, beans and marigold. Summer annuals sprout, produce seed, die, during the warmer months of the year; the lawn weed crabgrass is a summer annual. Winter annuals germinate in autumn or winter, live through the winter bloom in winter or spring; the plants grow and bloom during the cool season when most other plants are dormant or other annuals are in seed form waiting for warmer weather to germinate. Winter annuals die after setting seed; the seeds germinate in the winter when the soil temperature is cool. Winter annuals grow low to the ground, where they are sheltered from the coldest nights by snow cover, make use of warm periods in winter for growth when the snow melts; some common winter annuals include henbit, deadnettle and winter cress. Winter annuals are important ecologically, as they provide vegetative cover that prevents soil erosion during winter and early spring when no other cover exists and they provide fresh vegetation for animals and birds that feed on them.
Although they are considered to be weeds in gardens, this viewpoint is not always necessary, as most of them die when the soil temperature warms up again in early to late spring when other plants are still dormant and have not yet leafed out. Though they do not compete directly with cultivated plants, sometimes winter annuals are considered a pest in commercial agriculture, because they can be hosts for insect pests or fungal diseases which attack crops being cultivated; the property that they prevent the soil from drying out can be problematic for commercial agriculture. In 2008, it was discovered that the inactivation of only two genes in one species of annual plant leads to the conversion into a perennial plant. Researchers deactivated the SOC1 and FUL genes in Arabidopsis thaliana, which control flowering time; this switch established phenotypes common in perennial plants, such as wood formation. Biennial plant – Flowering plant that takes two years to complete its biological lifecycle. Perennial plant – Plant that lives for more than two years