Glossary of leaf morphology
The following is a defined list of terms which are used to describe leaf morphology in the description and taxonomy of plants. Leaves may compound; the edge of the leaf may be smooth or bearing hair, bristles or spines. For more terms describing other aspects of leaves besides their overall morphology see the leaf article. Leaves of most plants include a flat structure called the blade or lamina, but not all leaves are flat, some are cylindrical. Leaves may be simple, with compound, with several leaflets. In flowering plants, as well as the blade of the leaf, there may be a stipules. Leaf structure is described by several terms that include: Being one of the more visible features, leaf shape is used for plant identification. Similar terms are used for other plant parts, such as petals and bracts. Leaf margins are used in visual plant identification because they are consistent within a species or group of species, are an easy characteristic to observe. Edge and margin are interchangeable in the sense that they both refer to the outside perimeter of a leaf.
Leaves may be folded or rolled in various ways. If the leaves are folded in the bud, but unrolls is its called vernation, ptyxis is the folding of an individual leaf in a bud; the Latin word for'leaf', folium, is neuter. In descriptions of a single leaf, the neuter singular ending of the adjective is used, e.g. folium lanceolatum'lanceolate leaf', folium lineare'linear leaf'. In descriptions of multiple leaves, the neuter plural is used, e.g. folia linearia'linear leaves'. Descriptions refer to the plant using the ablative singular or plural, e.g. foliis ovatis'with ovate leaves'. Glossary of botanical terms Glossary of plant morphology Cladophylls are leaf-like petioles Leaf size Sinus Leaflet and Rachis Petiole and Plant stem Phylloclades are flattened stems that resemble leaves Pinnation Plant morphology Taxonomy The Description of Leaves, University of Rochester Fairchild Tropical Botanic Garden Vplants Botany 115 The seed site
In biology, a mutation is the permanent alteration of the nucleotide sequence of the genome of an organism, virus, or extrachromosomal DNA or other genetic elements. Mutations result from errors during DNA replication or other types of damage to DNA, which may undergo error-prone repair, or cause an error during other forms of repair, or else may cause an error during replication. Mutations may result from insertion or deletion of segments of DNA due to mobile genetic elements. Mutations may or may not produce discernible changes in the observable characteristics of an organism. Mutations play a part in both normal and abnormal biological processes including: evolution and the development of the immune system, including junctional diversity; the genomes of RNA viruses are based on RNA rather than DNA. The RNA viral genome can be double single stranded. In some of these viruses replication occurs and there are no mechanisms to check the genome for accuracy; this error-prone process results in mutations.
Mutation can result in many different types of change in sequences. Mutations in genes can either have no effect, alter the product of a gene, or prevent the gene from functioning properly or completely. Mutations can occur in nongenic regions. One study on genetic variations between different species of Drosophila suggests that, if a mutation changes a protein produced by a gene, the result is to be harmful, with an estimated 70 percent of amino acid polymorphisms that have damaging effects, the remainder being either neutral or marginally beneficial. Due to the damaging effects that mutations can have on genes, organisms have mechanisms such as DNA repair to prevent or correct mutations by reverting the mutated sequence back to its original state. Mutations can involve the duplication of large sections of DNA through genetic recombination; these duplications are a major source of raw material for evolving new genes, with tens to hundreds of genes duplicated in animal genomes every million years.
Most genes belong to larger gene families of shared ancestry. Novel genes are produced by several methods through the duplication and mutation of an ancestral gene, or by recombining parts of different genes to form new combinations with new functions. Here, protein domains act as modules, each with a particular and independent function, that can be mixed together to produce genes encoding new proteins with novel properties. For example, the human eye uses four genes to make structures that sense light: three for cone cell or color vision and one for rod cell or night vision. Another advantage of duplicating a gene is. Other types of mutation create new genes from noncoding DNA. Changes in chromosome number may involve larger mutations, where segments of the DNA within chromosomes break and rearrange. For example, in the Homininae, two chromosomes fused to produce human chromosome 2. In evolution, the most important role of such chromosomal rearrangements may be to accelerate the divergence of a population into new species by making populations less to interbreed, thereby preserving genetic differences between these populations.
Sequences of DNA that can move about the genome, such as transposons, make up a major fraction of the genetic material of plants and animals, may have been important in the evolution of genomes. For example, more than a million copies of the Alu sequence are present in the human genome, these sequences have now been recruited to perform functions such as regulating gene expression. Another effect of these mobile DNA sequences is that when they move within a genome, they can mutate or delete existing genes and thereby produce genetic diversity. Nonlethal mutations increase the amount of genetic variation; the abundance of some genetic changes within the gene pool can be reduced by natural selection, while other "more favorable" mutations may accumulate and result in adaptive changes. For example, a butterfly may produce offspring with new mutations; the majority of these mutations will have no effect. If this color change is advantageous, the chances of this butterfly's surviving and producing its own offspring are a little better, over time the number of butterflies with this mutation may form a larger percentage of the population.
Neutral mutations are defined as mutations whose effects do not influence the fitness of an individual. These can increase in frequency over time due to genetic drift, it is believed that the overwhelming majority of mutations have no significant effect on an organism's fitness. DNA repair mechanisms are able to mend most changes before they become permanent mutations, many organisms have mechanisms for eliminating otherwise-permanently mutated somatic cells. Beneficial mutations can improve reproductive success. Mutationism is one of several alternatives to evolution by natural selection that have existed both before and after the publication of Charles Darwin's 1859 book, On the Origin of Species. In the theory, mutation was the source of novelty
In archaeology and archaeological stratification a cut or truncation is a context that represents a moment in time when other archaeological deposits were removed for the creation of some feature such as a ditch or pit. In layman's terms, a cut can be thought of a hole, dug in the past, though cut applies to other parts of the archaeological record such as horizontal truncations like terraced ground. A cut context is sometimes referred to as a "negative context" as opposed to a "positive context"; the term denotes that a cut has removed material from the archaeological record or natural at the time of its creation as opposed to a positive context which adds material to the archaeological record. A cut has zero thickness and no material properties of its own and is defined by the limits of other contexts. Cuts are seen in the record by virtue of the difference between the material it was cut through and the material that back fills it; this difference is seen as an "edge" by the archaeologists on site.
This is shown in the picture above, where a half sectioned Saxon pit has had half its backfill removed and we can see a difference between the ground the pit was cut into and the material filling the pit. Sometimes these differences are not clear and an archaeologist must rely on experience and insight to discover cuts. Re-cuts are cuts made within the confines or near confines of other cuts to regain the function of the original cut or harvest material from the original fill. Re-cuts are considered quite valuable as a source of information because they can shed insight on function and attitude over time. An example of re-cutting would be a roadside ditch being re-cut and emptied of silt and detritus as a form of maintenance. Conversely, a roadside ditch, never re-cut gives a certain impression about the attitude towards the investment in infrastructure the road represents. Re-cuts by their nature are hard to discern because the re-cut can truncate the original cut in part and be in the confines of the original fill in other parts.
They can be absent from the record. Cutting is the reason why not all past activity on a site leaves traces of its existence in the sequence. Fig 2 shows, it is possible that numerous other re-cuts took place and were truncated out of the archaeological record by one or more of the re-cuts that has survived. Alignment Archaeological association Archaeological context Archaeological plan Archaeological section Cut Feature Fill Harris matrix Relationship Single context recording The MoLAS archaeological site manual MoLAS, London 1994. ISBN 0-904818-40-3. Rb 128pp. Bl/wh
Cheque truncation is a cheque clearance system that involves the digitalisation of a physical paper cheque into a substitute electronic form for transmission to the paying bank. The process of cheque clearance, involving data matching and verification, is done using digital images instead of paper copies. Cheque truncation reduces or eliminates the physical movement of paper cheques and reduces the time and cost of cheque clearance. Cheque truncation offers the potential reduction in settlement periods with the electronic processing of the cheque payment system. For cheque clearance, a cheque has to be presented to the drawee bank for payment; this was done by taking the cheque to the drawee bank, but as cheque usage increased this became cumbersome and banks arranged to meet each day at a central location to exchange cheques and receive payment in money. This became known as central clearing. Bank customers who received cheques could deposit them at their own bank, who would arrange for the cheque to be forwarded to the drawee bank and the money credited to and debited from the appropriate accounts.
If a cheque was dishonoured it would be physically returned to the original bank marked as such. This process would take several days, as the cheques had to be transported to the central clearing location, from where they were taken to the payee bank. If the cheque was dishonoured, it would be sent back to the bank; this is known as the clearing cycle. Cheques had to be examined by hand at each stage. In the 1960s, machine readable codes were added to the bottom of cheques in MICR format, which speeded up the clearing and sorting process. However, the law in most countries still required cheques to be delivered to the payee bank, so physical movement of the paper continued. Starting in the mid-1990s, some countries started to change their laws to allow "truncation": cheques would be imaged and a digital representation of the cheque would be transmitted to the drawee bank, the original cheques destroyed; the MICR codes and cheque details are encoded as text in addition to the image. The bank where the cheque was deposited would do the truncation and this decreased the time it took to clear a cheque.
In some cases, large retailers that received large volumes of cheques would do the truncation. Once the cheque has been turned into a digital document, it can be processed through the banking system just like any other electronic payment. Although technology needed to exist to enable cheque truncation, the laws related to cheques were the main impediment to its introduction. New Zealand was one of the first countries to introduce truncation and imaging of cheques, when in 1995 the Cheques Act 1960 was amended to provide for the electronic presentation of cheques. A number of other countries adopted the system over the next few years, but progress was mixed due to the decline in the use of cheques in favour of electronic payment systems; some countries decided that the effort to implement truncation could not be justified for a declining payment method, instead phased out the use of cheques altogether. In 2004, the United States enacted the Check 21 Act to authorize cheque truncation by the conversion of an original paper check into an electronic image for presentation through the clearing process.
The law enacted the recognition and acceptance of a “substitute check" created by a financial institution in lieu of the original paper check. Any bank that receives the original paper check can remove or "truncate" the paper check from the clearing process. New laws needed to address ways to make sure that the digital image was a true and accurate copy of the original cheque, as well as a mechanism to enable the process to be audited to protect consumers, it needed to address the process for dishonoured cheques, as paper cheques could no longer be returned. A typical solution, as defined by the Monetary Authority of Singapore for the Singapore cheque truncation system, was that a special'Image Return Document' was created and sent back to the bank that had truncated the cheque. Security related to imaging and creating an electronic cheque is defined and the cheque clearing process adjusted to accommodate electronic cheques. Banks and financial institutions use cheque truncation systems as part of this process.
These systems deal with two main processes, outward clearing and inward clearing: outward clearing takes place at the branch level, where deposited cheques are scanned and an operator performs amount entry, account entry, verification and bundling. The cheques are sent to a service branch.inward clearing takes place in the service branch, where cheques received from branches are processed and an operator performs amount entry, account entry, verification and bundling of the cheques. Once verification is complete, the cheques are sent to the clearing house; those cheques that failed validation due to discrepancies are sent back to the originating branch to be corrected. Some banks have built proprietary system to handle truncation. There are a number of software companies that provide commercial solutions and services, including: Substitute check in United States Cheque truncation system - India Substitute check French check processing fee controversy of 2010