In botanical nomenclature, a form is one of the "secondary" taxonomic ranks, below that of variety, which in turn is below that of species. If more than three ranks are listed in describing a taxon, the "classification" is being specified, but only three parts make up the "name" of the taxon: a genus name, a specific epithet, an infraspecific epithet; the abbreviation "f." or the full "forma" should be put before the infraspecific epithet to indicate the rank. It is not italicised. For example: Acanthocalycium spiniflorum f. klimpelianum or Acanthocalycium spiniflorum forma klimpelianum Donald Crataegus aestivalis Torr. & A. Gray var. cerasoides Sarg. f. luculenta Sarg. is a classification of a plant whose name is: Crataegus aestivalis Torr. & A. Gray f. luculenta Sarg. A form designates a group with a noticeable morphological deviation; the usual taxonomic practice is that the individuals classified within the form are not known to be related. For instance, white-flowered plants of species that have coloured flowers can be grouped and named.
Formae apomicticae are sometimes named among plants. There are theoretically countless numbers of forms based on minor genetic differences, only a few that have particular significance are to be named. Form Forma specialis, an informal rank used for a parasitic form adapted to a particular host Trinomial nomenclature Variety Subvariety Plant variety Cultivar Hybrid Race
International Code of Nomenclature for algae, fungi, and plants
The International Code of Nomenclature for algae and plants is the set of rules and recommendations dealing with the formal botanical names that are given to plants, fungi and a few other groups of organisms, all those "traditionally treated as algae, fungi, or plants". It was called the International Code of Botanical Nomenclature; the current version of the code is the Shenzhen Code adopted by the International Botanical Congress held in Shenzhen, China, in July 2017. As with previous codes, it took effect as soon as it was ratified by the congress, but the documentation of the code in its final form was not published until 26 June 2018; the name of the Code is capitalized and not. The lower-case for "algae and plants" indicates that these terms are not formal names of clades, but indicate groups of organisms that were known by these names and traditionally studied by phycologists and botanists; this includes blue-green algae. There are special provisions in the ICN for some of these groups.
The ICN can only be changed by an International Botanical Congress, with the International Association for Plant Taxonomy providing the supporting infrastructure. Each new edition supersedes the earlier editions and is retroactive back to 1753, except where different starting dates are specified. For the naming of cultivated plants there is a separate code, the International Code of Nomenclature for Cultivated Plants, which gives rules and recommendations that supplement the ICN. Botanical nomenclature is independent of zoological and viral nomenclature. A botanical name is fixed to a taxon by a type; this is invariably dried plant material and is deposited and preserved in a herbarium, although it may be an image or a preserved culture. Some type collections can be viewed online at the websites of the herbaria in question. A guiding principle in botanical nomenclature is priority, the first publication of a name for a taxon; the formal starting date for purposes of priority is 1 May 1753, the publication of Species Plantarum by Linnaeus.
However, to avoid undesirable effects of strict enforcement of priority, conservation of family and species names is possible. The intent of the Code is that each taxonomic group of plants has only one correct name, accepted worldwide, provided that it has the same circumscription and rank; the value of a scientific name is. Names of taxa are treated as Latin; the rules of nomenclature are retroactive unless there is an explicit statement that this does not apply. The rules governing botanical nomenclature have a long and tumultuous history, dating back to dissatisfaction with rules that were established in 1843 to govern zoological nomenclature; the first set of international rules was the Lois de la nomenclature botanique, adopted as the "best guide to follow for botanical nomenclature" at an "International Botanical Congress" convened in Paris in 1867. Unlike modern codes, it was not enforced, it was organized as six sections with 68 articles in total. Multiple attempts to bring more "expedient" or more equitable practice to botanical nomenclature resulted in several competing codes, which reached a compromise with the 1930 congress.
In the meantime, the second edition of the international rules followed the Vienna congress in 1905. These rules were published as the Règles internationales de la Nomenclature botanique adoptées par le Congrès International de Botanique de Vienne 1905. Informally they are referred to as the Vienna Rules; some but not all subsequent meetings of the International Botanical Congress have produced revised versions of these Rules called the International Code of Botanical Nomenclature, International Code of Nomenclature for algae and plants. The Nomenclature Section of the 18th International Botanical Congress in Melbourne, Australia made major changes: The Code now permits electronic-only publication of names of new taxa; the requirement for a Latin validating diagnosis or description was changed to allow either English or Latin for these essential components of the publication of a new name. "One fungus, one name" and "one fossil, one name" are important changes. As an experiment with "registration of names", new fungal descriptions require the use of an identifier from "a recognized repository".
Some important versions are listed below. Specific to botany Author citation Botanical name Botanical nomenclature International Association for Plant Taxonomy International Code of Nomenclature for Cultivated Plants International Plant Names Index Correct name Infraspecific name Hybrid name More general Glossary of scientific naming Binomial nomenclature Nomenclature codes Scientific classification Undescribed species
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
Life is a characteristic that distinguishes physical entities that have biological processes, such as signaling and self-sustaining processes, from those that do not, either because such functions have ceased, or because they never had such functions and are classified as inanimate. Various forms of life exist, such as plants, fungi, protists and bacteria; the criteria can at times be ambiguous and may or may not define viruses, viroids, or potential synthetic life as "living". Biology is the science concerned with the study of life. There is no consensus regarding the definition of life. One popular definition is that organisms are open systems that maintain homeostasis, are composed of cells, have a life cycle, undergo metabolism, can grow, adapt to their environment, respond to stimuli and evolve. However, several other definitions have been proposed, there are some borderline cases of life, such as viruses or viroids. Abiogenesis attempts to describe the natural process of life arising from non-living matter, such as simple organic compounds.
The prevailing scientific hypothesis is that the transition from non-living to living entities was not a single event, but a gradual process of increasing complexity. Life on Earth first appeared as early as 4.28 billion years ago, soon after ocean formation 4.41 billion years ago, not long after the formation of the Earth 4.54 billion years ago. The earliest known life forms are microfossils of bacteria. Earth's current life may have descended from an RNA world, although RNA-based life may not have been the first; the mechanism by which life began on Earth is unknown, though many hypotheses have been formulated and are based on the Miller–Urey experiment. Since its primordial beginnings, life on Earth has changed its environment on a geologic time scale, but it has adapted to survive in most ecosystems and conditions; some microorganisms, called extremophiles, thrive in physically or geochemically extreme environments that are detrimental to most other life on Earth. The cell is considered the functional unit of life.
There are two kinds of cells and eukaryotic, both of which consist of cytoplasm enclosed within a membrane and contain many biomolecules such as proteins and nucleic acids. Cells reproduce through a process of cell division, in which the parent cell divides into two or more daughter cells. In the past, there have been many attempts to define what is meant by "life" through obsolete concepts such as odic force, spontaneous generation and vitalism, that have now been disproved by biological discoveries. Aristotle was the first person to classify organisms. Carl Linnaeus introduced his system of binomial nomenclature for the classification of species. New groups and categories of life were discovered, such as cells and microorganisms, forcing dramatic revisions of the structure of relationships between living organisms. Though only known on Earth, life need not be restricted to it, many scientists speculate in the existence of extraterrestrial life. Artificial life is a computer simulation or man-made reconstruction of any aspect of life, used to examine systems related to natural life.
Death is the permanent termination of all biological functions which sustain an organism, as such, is the end of its life. Extinction is the term describing the dying out of a group or taxon a species. Fossils are the preserved traces of organisms; the definition of life has long been a challenge for scientists and philosophers, with many varied definitions put forward. This is because life is a process, not a substance; this is complicated by a lack of knowledge of the characteristics of living entities, if any, that may have developed outside of Earth. Philosophical definitions of life have been put forward, with similar difficulties on how to distinguish living things from the non-living. Legal definitions of life have been described and debated, though these focus on the decision to declare a human dead, the legal ramifications of this decision. Since there is no unequivocal definition of life, most current definitions in biology are descriptive. Life is considered a characteristic of something that preserves, furthers or reinforces its existence in the given environment.
This characteristic exhibits all or most of the following traits: Homeostasis: regulation of the internal environment to maintain a constant state. Living things require energy to maintain internal organization and to produce the other phenomena associated with life. Growth: maintenance of a higher rate of anabolism than catabolism. A growing organism increases in size in all of its parts, rather than accumulating matter. Adaptation: the ability to change over time in response to the environment; this ability is fundamental to the process of evolution and is determined by the organism's heredity and external factors. Response to stimuli: a response can take many forms, from the contraction of a unicellular organism to external chemicals, to complex reactions involving all the senses of multicellular organisms. A response is expressed by motion. Reproduction: the ability to produce new individual organisms, either asexually from a single parent organism or sexually from two parent organisms; these complex processes, called physiological functions, have under