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Winteraceae

Winteraceae

Belliolum
Bubbia
Drimys
Exospermum
Pseudowintera
Takhtajania
Tasmannia
Tetrathalamus
Zygogynum The Winteraceae are a family of flowering plants. The family includes 120 species of trees and shrubs in 9 genera. The Winteraceae are a mostly southern-hemisphere family associated with the Antarctic flora, found in tropical to temperate climate regions of Malesia, Oceania, eastern Australia, New Zealand, Madagascar and the Neotropic. Many members of the family are fragrant, and are used to produce essential oils. Most of the genera are concentrated in Australasia and Malesia. Drimys is found in the Neotropic ecozone, from southern Mexico to the subarctic forests of southern South America. Takhtajania includes a single species, T. perrieri, endemic to Madagascar. The family disappeared from the African fossil record roughly 24 million years ago. The Winteraceae are characteristic of the Antarctic flora, which has its origins in the southern portion of the ancient supercontinent of Gondwana, and is generally found in humid temperate and subtropical regions of the southern hemisphere, and at higher elevations in the humid tropics. Winter's Bark (Drimys winteri), a slender tree native to the Magellanic and Valdivian temperate rain forests of Chile and Argentina, is grown as a garden plant for its handsome and fragrant mahogany-red bark and bright-green leaves, and its clusters of creamy white jasmine-scented flowers. Tasmannia lanceolata, known as Tasmanian pepper, is grown as an ornamental shrub, and is increasingly being used as a condiment.

Reference

Feild, Taylor S., Brodribb, Tim, Holbrook, N. Michele. (2002). Hardly a Relict: Freezing and the Evolution of Vesselless Wood in Winteraceae. Evolution 2002 56: 464-478. Category:Canellales Category:Plant families

Drimys

D. andina
D. brasiliensis
D. confertifolia
D. winteri Drimys is a genus of woody evergreen flowering plants, part of family Winteraceae. The species of Drimys are native to the Neotropic, ranging from southern Mexico to the southern tip of South America. The Winteraceae are primitive dicots, associated with the humid temperate Antarctic flora of the southern hemisphere, which evolved millions of years ago on the ancient supercontinent of Gondwana. Members of the family generally have aromatic bark and leaves, and some are used to extract essential oils. Genus Drimys formerly included a number of species from Australasia, including Tasmanian Pepper (D. lanceolata). Recent botanical studies have led to a growing consensus of botanists to split the genus into two, with the Neotropical species remaining in genus Drimys, and the Australasian species classified in genus Tasmannia. Winter's Bark (Drimys winteri), a slender tree native to the Magellanic and Valdivian temperate rain forests of Chile and Argentina, where it forms an dominant tree in the coastal evergreen forests. It is also grown as a garden plant for its handsome and fragrant mahogany-red bark and bright-green leaves, and its clusters of creamy white jasmine-scented flowers. D. winteri was the first commercial source of vitamin C. D. andina is also native to Chile, and was until recently considered a subspecies of D. winteri. D. confertifolia is endemic to the Juan Fernández Islands 670 km off the Chilean coast, where they form a dominant tree in the tall lowland forests and lower montane forests of the islands. D. brasiliensis ranges from southern Brazil to southern Mexico.

Reference

- Doust, Andrew N. and Drinnan, Andrew N. 2004. Floral development and molecular phylogeny support the generic status of Tasmannia (Winteraceae). American Journal of Botany 91: 321-331.

External links

- [http://www.chilebosque.cl/tree/dwint.html Drimys winteri pictures in Chilebosque]
- [http://www.chilebosque.cl/shrb/dandi.html Drimys andina pictures in Chilebosque] Category:Canellales Category:Flora of Chile

Pseudowintera

P. axillaris
P. colorata
P. traversii Pseudowintera is a genus of woody evergreen flowering trees and shrubs, part of family Winteraceae. The species of Pseudowintera are native to New Zealand. The Winteraceae are primitive dicots, associated with the humid Antarctic flora of the southern hemisphere.
- P. axillaris is known as the lowland horopito. It is a shrub or small tree reaching up to 8 meters in height. It is distributed in lowland and lower montane forests from 35º to 42º south latitude. On the South Island it grows west of the divide.
- P. colorata is an evergreen shrub or small tree commonly known as the Pepperwood or mountain horopito, 1 to 2.5 meters high, with yellow and green leaves blotched with red, and bright red new leaves in the spring. It is widespread across New Zealand, from lowland forests to higher montane forests, and from 36º 30' south latitude southward to Stewart Island.
- P. traversii is a compact shrub, to 1 meter in height. Its distribution is limited to the northwest corner of the South Island, from Collingwood to Westport. Category:Canellales Category:New Zealand plants

Takhtajania

Takhtajania is a genus of primitive flowering plants of the family Winteraceae, which contains a single species, T. perrieri. It is native to the Southern Hemisphere. Takhtajania is native to the highlands of Madagascar, where it is found in a small area of the Madagascar subhumid forests. It is a small evergreen tree or shrub, with shiny green lance-shaped leaves and reddish-pink flowers. The first known specimen of the plant was collected in 1909 on the Manongarivo Massif of central Madagascar at an elevation of 1700 meters. In 1963, the French botanist Capuron examined the unidentifed plant sample, which he identified as a new species, which he named Bubbia perrieri, after the French botanist Henri Perrier de la Bâthie, classifying it in the Australasian Winteraceae genus Bubbia. In 1978, the botanists Baranova and J. F. Leroy reclassified the plant into its own genus, Takhtajania, after the Russian botanist Armen Takhtajan. In 1994 Malagasy plant collector Fanja Rasoavimbahoaka collected a specimen in Anjahanaribe-Sud Special Reserve 150 km from the location at which the 1909 specimen was collected, which George E. Schatz identified in May 1997 as Takhtajania. A subsequent expedition discovered a large grove of the species at the spot where the second sample was collected. Takhtajania lacks water-conducting cells, called vessels, which allow plants to withstand drought, and must have remained in moist conditions for millions of years.

External link

[http://www.mobot.org/MOBOT/Madagasc/winterac.html Images of Winteraceae in Madagascar (Missouri Botanic Garden)] Category:Canellales

Family

:This article is about the human domestic group. For other uses, see Family (disambiguation). Family (disambiguation) in 1997]] A family is a domestic group of people, or a number of domestic groups, typically affiliated by birth or marriage, or by comparable legal relationships including domestic partnership, adoption, surname and in some cases ownership (as was the case in the Roman Empire). Although many people (including social scientists) have understood familial relationships in terms of "blood," many anthropologists have argued that the notion of "blood" must be understood metaphorically, and in that in many societies family is understood through other concepts rather than "blood." Article 16(3) of the Universal Declaration of Human Rights says, "The family is the natural and fundamental group unit of society and is entitled to protection by society and the State".

Family cross-culturally

According to sociology and anthropology, the primary function of the family is to reproduce society, either biologically, socially, or both. Thus, one's experience of one's family shifts over time. From the perspective of children, the family is a family of orientation: the family serves to locate children socially, and plays a major role in their enculturation and socialization. From the point of view of the parent(s), the family is a family of procreation the goal of which is to produce and enculturate and socialize children. However, producing children is not the only function of the family. In societies with a sexual division of labor, marriage, and the resulting relationship between a husband and wife, is necessary for the formation of an economically productive household. In modern societies marriage entails particular rights and privilege that encourage the formation of new families even when there is no intention of having children. The structure of families traditionally hinges on relations between parents and children, between spouses, or both. Consequently, there are four major types of family: patrifocal, matrifocal, consanguineal and conjugal. (Note: these are ideal families. In all societies there are acceptable deviations from the ideal or statistical norm, owing either to incidental circumstances, such as the death of a member of the family, infertility or personal preferences). A patrifocal family consists of a father and his children and is found in societies where men take multiple wives (polygamy or polygyny)and/or remain involved with each for a relatively short time. This type of family is rare from a worldwide perspective but occurs in Islamic states with considerable frequency. In some emirates the laws encourage this structure by allowing a maximum of four wives per man at any given time, and automatic deflection of custody rights to the father in the case of a divorce. In these societies a man will often take a wife and may conceive a child with her, but after a relatively short time put her out of his harem so he can take another woman without exceeding the quota of 4. The man then keeps his child and thus a patrifocal structure emerges. Even without the expulsion of the mother, the structure may be patrifocal because the children (often as infants) are removed from the harem structure and placed into the father's family. A matrifocal family consists of a mother and her children. Generally, these children are her biological offspring, although adoption of children is a practice in nearly every society. This kind of family is common where women have the resources to rear their children by themselves, or where men are more mobile than women. A consanguineal family consists of a mother and her children, and other people — usually the family of the mother. This kind of family is common where mothers do not have the resources to rear their children on their own, and especially where property is inherited. When important property is owned by men, consanguineal families commonly consist of a husband and wife, their children and other members of the husband's family. A conjugal family consists of one or more mothers and their children, and/or one or more spouses (usually husbands). This kind of family is common where there is a division of labor requiring the participation of both men and women, and where families are relatively mobile. A notable subset of this family type is the nuclear family, in which one woman has one husband and they raise their children together.

Family in the West

polygyny middle American "nuclear" family.]] The preceding types of families are found in a wide variety of settings, and their specific functions and meanings depend largely on their relationship to other social institutions. Sociologists are especially interested in the function and status of these forms in stratified, especially capitalist, societies. Non-scholars, especially in the United States and Europe, use the term "nuclear family" to refer to conjugal families. Sociologists distinguish between conjugal families that are relatively independent of the kindreds of the parents and of other families in general, and nuclear families which maintain relatively close ties with their kindreds. Non-scholars, especially in the United States and Europe, also use the term "extended family". This term has two distinct meanings. First, it is used synonymously with consanguinal family. Second, in societies dominated by the conjugal family, it is used to refer to kindred (an egocentric network of relatives that extends beyond the domestic group) who do not belong to the conjugal family. These types refer to ideal or normative structures found in particular societies. In any society there is some variation in the actual composition and conception of families. Much sociological, historical and anthropological research is dedicated to understanding this variation, and changes over time in the family form. Thus, some speak of the bourgeois family, a family structure arising out of 16th and 17th century European households, in which the center of the family is a marriage between a man and woman, with strictly defined gender roles. The man typically is responsible for income and support, the woman for home and family matters. In contemporary Europe and the United States, people academic, political and civil sectors have called attention to single-father-headed households, and families headed by same-sex couples, although academics point out that these forms exist in other societies.

Economic function of the family

In traditional society the family is often supposed to have been the primary economic unit. This role has gradually diminished in modern times and in societies like the United States is much smaller except for certain sectors such as agriculture and a few upper class families. In China the family as an economic unit still plays a strong role in the countryside. However, the relations between the economic role of the family, its socio-economic mode of production and cultural values are highly complex. Chinaern U.S. family of Danish/German extraction]]

Kinship terminology

A kinship terminology is a specific system of familial relationships. The now rather dated anthropologist Louis Henry Morgan argued that kinship terminologies reflect different sets of distinctions. For example, most kinship terminologies distinguish between sexes (this is the difference between a brother and a sister) and between generation (this is the difference between a child and a parent). Moreover, he argued, kinship terminologies distinguish between relatives by blood and marriage (although recently some anthropologists have argued that many societies define kinship in terms other than "blood"). But Morgan also observed that different languages (and thus, societies) organize these distinctions differently. He thus proposed to describe kin terms and terminologies as either descriptive or classificatory. "Descriptive" terms refer to only one type of relationship, while "classificatory" terms refer to many types of relationships. Most kinship terminologies include both descriptive and classificatory terms. For example, in Western societies there is only one way to be related to one's brother (brother = parents' son); thus, in Western society, brother is a descriptive term. But there are many ways to be related to one's cousin (cousin = mother's brother's son, mother's sister's son, father's brother's son, father's sister's son, and so on); thus, in Western society, "cousin" is a classificatory term. Morgan discovered that what may be a descriptive term in one society can be a classificatory term in another society. For example, in some societies there are many different people that one would call "mother" (the woman of whom one was born, as well as her sister and husband's sister, and also one's father's sister). Moreover, some societies do not lump together relatives that the West classifies together (in other words, in some languages there is no word for cousin because mother's sister's children and father's sister's children are referred to in different terms). Armed with these different terms, Morgan identified six basic patterns of kinship terminologies:
- Hawaiian: the most classificatory; only distinguishes between sex and generation.
- Sudanese: the most descriptive; no two relatives are referred to by the same term.
- Eskimo: has both classificatory and descriptive terms; in addition to sex and generation, also distinguishes between lineal relatives (who are related directly by a line of descent) and collateral relatives (who are related by blood, but not directly in the line of descent). Lineal relatives have highly descriptive terms, collateral relatives have highly classificatory terms.
- Iroquois: has both classificatory and descriptive terms; in addition to sex and generation, also distinguishes between siblings of opposite sexes in the parental generation. Siblings of the same sex are considered blood relatives, but siblings of the opposite sex are considered relatives by marriage. Thus, one's mother's sister is also called mother, and one's father's brother is also called father; however, one's mother's brother is called father-in-law, and one's father's sister is called mother-in-law.
- Crow: like Iroquois, but further distinguishes between mother's side and father's side. Relatives on the mother's side of the family have more descriptive terms, and relatives on the father's side have more classificatory terms.
- Omaha: like Iroquois, but further distinguishes between mother's side and father's side. Relatives on the mother's side of the family have more classificatory terms, and relatives on the father's side have more descriptive terms. Societies in different parts of the world and using different languages may share the same basic terminology; in such cases it is very easy to translate the kinship terms of one language into another, although connatations may vary. But it is usually impossible to translate directly the kinship terms of a society that uses one system into the language of a society that uses a different system. Some languages, such as Chinese, Japanese, and Hungarian, add another dimension to some relations: relative age. There are, e.g., different words for "older brother" and "younger brother." Thus, although Westerners may naturally agree with Morgan that "brother" is descriptive rather than classificatory, speakers of these languages might disagree.

English kinship terminology

Most Western societies employ English kinship terminology. This kinship terminology is common in societies based on conjugal (or nuclear) families, where nuclear families must be relatively mobile. Members of the nuclear family use descriptive kinship terms:
- Mother: the female parent
- Father: the male parent
- Son: the males born of the mother; sired by the father
- Daughter: the females born of the mother; sired by the father
- Brother: a male born of the same mother; sired by the same father
- Sister: a female born of the same mother; sired by the same father It is generally assumed that the mother's husband is also the genitor. In some families, a woman may have children with more than one man or a man may have children with more than one woman. Children who share one parent but not another are called "half-brothers" or "half-sisters." Children who do not share parents, but whose parents are married, are called "step-brothers" or "step-sisters." If a person is married to the parent of a child, but is not the parent of the child themselves, then they are the "step-parent" of the child, either the "stepmother" or "stepfather". Children who are adopted into a family are generally called by the same terms as children born into the family. Typically, societies with conjugal families also favor neolocal residence; thus upon marriage a person separates from the nuclear family of their childhood (family of orientation) and forms a new nuclear family (family of procreation). This practice means that members of one's own nuclear family were once members of another nuclear family, or may one day become members of another nuclear family. Members of the nuclear families of members of one's own nuclear family may be lineal or collateral. When they are lineal, they are referred to in terms that build on the terms used within the nuclear family:
- Grandfather: a parent's father
- Grandmother: a parent's mother
- Grandson: a child's son
- Granddaughter: a child's daughter When they are collateral, they are referred to in more classificatory terms that do not build on the terms used within the nuclear family:
- Uncle: father's brother, father's sister's husband, mother's brother, mother's sister's husband
- Aunt: father's sister, father's brother's wife, mother's sister, mother's brother's wife
- Nephew: sister's sons, brother's sons
- Niece: sister's daughters, brother's daughters When separated by additional generations (in other words, when one's collateral relatives belong to the same generation as one's grandparents or grandchildren), these terms are modified by the prefix "great". Most collateral relatives were never members of the nuclear family of the members of one's own nuclear family.
- Cousin: the most classificatory term; the children of aunts or uncles. Cousins may be further distinguished by degree of collaterality and generation. Two persons of the same generation who share a grandparent are "first cousins" (one degree of collaterality); if they share a great-grandparent they are "second cousins" (two degrees of collaterality) and so on. If the shared ancestor is the grandparent of one individual and the great-grandparent of the other, the individuals are said to be "first cousins once removed" (removed by one generation); if the shared ancestor is the grandparent of one individual and the great-great-grandparent of the other, the individuals are said to be "first cousins twice removed" (removed by two generations), and so on. Similarly, if the shared ancestor is the great-grandparent of one person and the great-great-grandparent of the other, the individuals are said to be "second cousins once removed." Distant cousins of an older generation (in other words, one's parents' first cousins) are technically first cousins once removed, but are often classified with "aunts" and "uncles". Similarly, a person may refer to close friends of one's parents as "aunt" or "uncle," or may refer to close friends as "brother" or "sister". This practice is called fictive kinship. Relationships by marriage, except for wife/husband, are qualified by the term "-in-law". The mother and father of one's spouse are one's mother-in-law and father-in-law; the spouse of one's son or daughter is one's son-in-law or daughter-in-law. The term "sister-in-law" refers to three essentially different relationships, either the wife of one's brother, or the sister of one's spouse, or the wife of one's spouse's sibling. "Brother-in-law" is similarly ambiguous. There are no special terms for the rest of one's spouse's family. Specific distinctions vary among Western societies. For instance, in French, the prefix beau- or belle- is used for both "-in-law" and "step-"; in other words, one's belle-soeur could be the sister of one's spouse, the wife of one's sibling, the wife of one's spouse's sibling, or the daughter of one's parent's spouse. In Spanish, each of the roles that English creates with the suffix "-in-law" has a different word (suegros- parents-in-law, yerno-son-in-law, nuera-daughter-in-law, cuñados-siblings-in-law), but there is a suffix -astro or -astra that is equivalent to "step-". In Swedish, terms for grandparents differ on the side of the parents, i.e., "farfar" and "farmor" (father-father, father-mother) vs. "mormor" and "morfar" (mother-mother, mother-father). There is also a term, "half-sibling" (and -brother, -sister) for siblings with whom one shares only one parent.

References

- American Kinship, David Schneider
- A Natural History of Families, Scott Forbes, Princeton University Press, 2005, ISBN 0691094829
- More Than Kin and Less Than Kind, Douglas W. Mock, Belknap Press, 2004, ISBN 0674012852

External links

- [http://wikitree.org WikiTree.org] - freely-edited family tree of all human beings.
- Online Dictionary of the Social Sciences: http://bitbucket.icaap.org/
- Cousins: http://www.tedpack.org/cousins.html
- [http://www.islamimatrimonials.com/muslim_matrimonials_family.htm Muslim Matrimonial] and Muslim Family
- Grandparent Connection: http://www.thegrandparentconnection.org
- The Good Enough Family: http://samvak.tripod.com/family.html
- Cousin marriages: http://www.cousincouples.com/
- Family Court: http://www.stephenbaskerville.net/
- [http://www.unh.edu/frl/ Family Research Laboratory]
- Wiktionary entries for Western kinship terminology providing multilingual translations
- mother, father, son, daughter, brother, sister
- grandmother grandfather grandson granddaughter
- uncle aunt nephew niece
- cousin Category:Family Category:Divorce Category:Human development Category:Kinship and descent Category:Marriage ms:Keluarga ja:家族 simple:Family

Species

In biology, a species is the basic unit of biodiversity. In scientific classification, a species is assigned a two-part name in Latin. The genus is listed first (and capitalized), followed by a specific epithet. For example, humans belong to the genus Homo, and are in the species Homo sapiens. The name of the species is the whole binomial not just the second term (the specific epithet). The binomial, and most other purely formal aspects of the biological codes of nomenclature, were formalized by Carolus Linnaeus in the 1700's and as a result are called the "Linnaean system". At that time, species were thought to represent independent acts of creation by God, and were therefore considered objectively real and immutable. Since the advent of the theory of evolution, the conception of species has undergone vast changes in biology, however no consensus on the definition of the word has yet been reached. The most commonly cited definition of "species" was first coined by Ernst Mayr. By this definition, called the biological species concept or isolation species concept, species are "groups of actually or potentially interbreeding natural populations which are reproductively isolated from other such groups". However, many other species concepts are also used (see other definitions of species below). The scientific name of a species is properly typeset in italics. When an unknown species is being referred to this may be done by using the abbreviation "sp." in the singular or "spp." in the plural in the place of the second part of the scientific name. Note that the word "specie" is not the singular of "species". It refers to coined money.

Definitions of species

The definition of a species given above as taken from Mayr, is somewhat idealistic. Since it assumes sexual reproduction, it leaves the term undefined for a large class of organisms that reproduce asexually. Biologists frequently do not know whether two morphologically similar groups of organisms are "potentially" capable of interbreeding. Further, there is considerable variation in the degree to which hybridization may succeed under natural and experimental conditions, or even in the degree to which some organisms use sexual reproduction between individuals to breed. Consequently, several lines of thought in the definition of species exist: ; Typological species : A group of organisms in which individuals are members of the species if they sufficiently conform to certain fixed properties. The clusters of variations or phenotypes within specimens (ie: longer and shorter tails) would differentiate the species. This method was used as a "classical" method of determining species, such as with Linnaeus early in evolutionary theory. However, we now know that different phenotypes do not always constitute different species (e.g.: a 4-winged Drosophila born to a 2-winged mother is not a different species). Species named in this manner are called morphospecies. ; Morphological species : A population or group of populations that differs morphologically from other populations. For example, we can distinguish between a chicken and a duck because they have different shaped bills and the duck has webbed feet. Species have been defined in this way since well before the beginning of recorded history. This species concept is much criticised because more recent genetic data reveals that genetically distinct populations may look very similar and, contrarily, large morphological differences sometimes exist between very closely-related populations. Nonetheless, most species known have been described solely from morphology. ; Biological / Isolation species : A set of actually or potentially interbreeding populations. This is generally the most useful formulation for scientists working with living examples of the higher taxa like mammals, fish, and birds, but meaningless for organisms that do not reproduce sexually. It does not distinguish between the theoretical possibility of interbreeding and the actual likelihood of gene flow between populations and is thus impractical in instances of allopatric (geographically isolated) populations. The results of breeding experiments done in artificial conditions may or may not reflect what would happen if the same organisms encountered each other in the wild, making it difficult to gauge whether or not the results of such experiments are meaningful in reference to natural populations. ; Mate-recognition species : A group of organisms that are known to recognise one another as potential mates. Like the isolation species concept above, it applies only to organisms that reproduce sexually. Unlike the isolation species concept, it focuses specifically on pre-mating reproductive isolation. ; Phylogenetic / Evolutionary / Darwinian species : A group of organisms that shares an ancestor; a lineage that maintains its integrity with respect to other lineages through both time and space. At some point in the progress of such a group, members may diverge from one another: when such a divergence becomes sufficiently clear, the two populations are regarded as separate species. ; Microspecies : Species that reproduce without meiosis or mitosis so that each generation is genetically identical to the previous generation. See also apomixis. In practice, these definitions often coincide, and the differences between them are more a matter of emphasis than of outright contradiction. Nevertheless, no species concept yet proposed is entirely objective, or can be applied in all cases without resorting to judgement. Given the complexity of life, some have argued that such an objective definition is in all likelihood impossible, and biologists should settle for the most practical definition. For most vertebrates, this is the biological species concept, and to a lesser extent (or for different purposes) the phylogenetic species concept. Many BSC subspecies are considered species under the PSC; the difference between the BSC and the PSC can be summed up insofar as that the BSC defines a species as a consequence of manifest evolutionary history, while the PSC defines a species as a consequence of manifest evolutionary potential. Thus, a PSC species is "made" as soon as an evolutionary lineage has started to separate, while a BSC species starts to exist only when the lineage separation is complete.

Importance in biological classification

The idea of species has a long history. It is one of the most important levels of classification, for several reasons:
- It often corresponds to what lay people treat as the different basic kinds of organism - dogs are one species, cats another.
- It is the standard binomial nomenclature (or trinomial nomenclature) by which scientists typically refer to organisms.
- It is the only taxonomic level which has empirical content, in the sense that asserting that two animals are of different species is saying something more than classificatory about them. After thousands of years of use, the concept remains central to biology and a host of related fields, and yet also remains at times ill-defined and controversial.

Implications of assignment of species status

The naming of a particular species should be regarded as a hypothesis about the evolutionary relationships and distinguishability of that group of organisms. As further information comes to hand, the hypothesis may be confirmed or refuted. Sometimes, especially in the past when communication was more difficult, taxonomists working in isolation have given two distinct names to individual organisms later identified as the same species. When two named species are discovered to be of the same species, the older species name is usually retained, and the newer species name dropped, a process called synonymization, or convivially, as lumping. Dividing a taxon into multiple, often new, taxons is called splitting. Taxonomists are often referred to as "lumpers" or "splitters" by their colleagues, depending on their personal approach to recognizing differences or commonalities between organisms (see lumpers and splitters). Traditionally, researchers relied on observations of anatomical differences, and on observations of whether different populations were able to interbreed successfully, to distinguish species; both anatomy and breeding behavior are still important to assigning species status. As a result of the revolutionary (and still ongoing) advance in microbiological research techniques, including DNA analysis, in the last few decades, a great deal of additional knowledge about the differences and similarities between species has become available. Many populations which were formerly regarded as separate species are now considered to be a single taxon, and many formerly grouped populations have been split. Any taxonomic level (species, genus, family, etc.) can be synonymized or split, and at higher taxonomic levels, these revisions have been still more profound. From a taxonomical point of view, groups within a species can be defined as being of a taxon hierarchically lower than a species. In zoology only the subspecies is used, while in botany the variety, subvariety, and form are used as well.

The isolation species concept in more detail

In general, for large, complex, organisms that reproduce sexually (such as mammals and birds), one of several variations on the isolation or biological species concept is employed. Often, the distinction between different species, even quite closely related ones, is simple. Horses (Equus caballus) and donkeys (Equus asinus) are easily told apart even without study or training, and yet are so closely related that they can interbreed after a fashion. Because the result, a mule or hinny, is not usually fertile, they are clearly separate species. But many cases are more difficult to decide. This is where the isolation species concept diverges from the evolutionary species concept. Both agree that a species is a lineage that maintains its integrity over time, that is diagnosably different to other lineages (else we could not recognise it), is reproductively isolated (else the lineage would merge into others, given the chance to do so), and has a working intra-species recognition system (without which it could not continue). In practice, both also agree that a species must have its own independent evolutionary history—otherwise the characteristics just mentioned would not apply. The species concepts differ in that the evolutionary species concept does not make predictions about the future of the population: it simply records that which is already known. In contrast, the isolation species concept refuses to assign the rank of species to populations that, in the best judgement of the researcher, would recombine with other populations if given the chance to do so.

The isolation question

There are, essentially, two questions to resolve. First, is the proposed species consistently and reliably distinguishable from other species? Secondly, is it likely to remain so in the future? To take the second question first, there are several broad geographic possibilities.
- The proposed species are sympatric—they occupy the same habitat. Observation of many species over the years has failed to establish even a single instance of two diagnostically different populations that exist in sympatry and have then merged to form one united population. Without reproductive isolation, population differences cannot develop, and given reproductive isolation, gene flow between the populations cannot merge the differences. This is not to say that cross breeding does not take place at all, simply that it has become negligible. Generally, the hybrid individuals are less capable of successful breeding than pure-bred individuals of either species.
- The proposed species are allopatric—they occupy different geographical areas. Obviously, it is not possible to observe reproductive isolation in allopatric groups directly. Often it is not possible to achieve certainty by experimental means either: even if the two proposed species interbreed in captivity, this does not demonstrate that they would freely interbreed in the wild, nor does it always provide much information about the evolutionary fitness of hybrid individuals. A certain amount can be inferred from other experimental methods: for example, do the members of population A respond appropriately to playback of the recorded mating calls of population B? Sometimes, experiments can provide firm answers. For example, there are seven pairs of apparently almost identical marine snapping shrimp (Altheus) populations on either side of the Isthmus of Panama, which did not exist until about 3 million years ago. Until then, it is assumed, they were members of the same seven species. But when males and females from opposite sides of the isthmus are placed together, they fight instead of mating. Even if the isthmus were to sink under the waves again, the populations would remain genetically isolated: therefore they are now different species. In many cases, however, neither observation nor experiment can produce certain answers, and the determination of species rank must be made on a 'best guess' basis from a general knowledge of other related organisms.
- The proposed species are parapatric—they have breeding ranges that abut but do not overlap. This is fairly rare, particularly in temperate regions. The dividing line is often a sudden change in habitat (an ecotone) like the edge of a forest or the snow line on a mountain, but can sometimes be remarkably trivial. The parapatry itself indicates that the two populations occupy such similar ecological roles that they cannot coexist in the same area. Because they do not crossbreed, it is safe to assume that there is a mechanism, often behavioral, that is preventing gene flow between the populations, and that therefore they should be classified as separate species.
- There is a hybrid zone where the two populations mix. Typically, the hybrid zone will include representatives of one or both of the 'pure' populations, plus first-generation and back-crossing hybrids. The strength of the barrier to genetic transmission between the two pure groups can be assessed by the width of the hybrid zone relative to the typical dispersal distance of the organisms in question. The dispersal distance of oaks, for example, is the distance that a bird or squirrel can be expected to carry an acorn; the dispersal distance of Numbats is about 15 kilometres, as this is as far as young Numbats will normally travel in search of vacant territory to occupy after leaving the nest. The narrower the hybrid zone relative to the dispersal distance, the less gene flow there is between the population groups, and the more likely it is that they will continue on separate evolutionary paths. Nevertheless, it can be very difficult to predict the future course of a hybrid zone; the decision to define the two hybridizing populations as either the same species or as separate species is difficult and potentially controversial.
- The variation in the population is clinal; at either extreme of the population's geographic distribution, typical individuals are clearly different, but the transition between them is seamless and gradual. For example, the Koalas of northern Australia are clearly smaller and lighter in colour than those of the south, but there is no particular dividing line: the further south an individual Koala is found, the larger and darker it is likely to be; Koalas in intermediate regions are intermediate in weight and colour. In contrast, over the same geographic range, black-backed (northern) and white-backed (southern) Australian Magpies do not blend from one type to another: northern populations have black backs, southern populations white backs, and there is an extensive hybrid zone where both 'pure' types are common, as are crossbreeds. The variation in Koalas is clinal (a smooth transition from north to south, with populations in any given small area having a uniform appearance), but the variation in magpies is not clinal. In both cases, there is some uncertainty regarding correct classification, but the consensus view is that species rank is not justified in either. The gene flow between northern and southern magpie populations is judged to be sufficiently restricted to justify terming them subspecies (not full species); but the seamless way that local Koala populations blend one into another shows that there is substantial gene flow between north and south. As a result, experts tend to reject even subspecies rank in this case.

The difference question

Obviously, when defining a species, the geographic circumstances become meaningful only if the populations groups in question are clearly different: if they are not consistently and reliably distinguishable from one another, then we have no grounds for believing that they might be different species. The key question in this context, is "how different is different?" and the answer is usually "it all depends". In theory, it would be possible to recognise even the tiniest of differences as sufficient to delineate a separate species, provided only that the difference is clear and consistent (and that other criteria are met). There is no universal rule to state the smallest allowable difference between two species, but in general, very trivial differences are ignored on the twin grounds of simple practicality, and genetic similarity: if two population groups are so close that the distinction between them rests on an obscure and microscopic difference in morphology, or a single base substitution in a DNA sequence, then a demonstration of restricted gene flow between the populations will probably be difficult in any case. More typically, one or other of the following requirements must be met:
- It is possible to reliably measure a quantitative difference between the two groups that does not overlap. A population has, for example, thicker fur, rougher bark, longer ears, or larger seeds than another population, and although this characteristic may vary within each population, the two do not grade into one another, and given a reasonably large sample size, there is a definite discontinuity between them. Note that this applies to populations, not individual organisms, and that a small number of exceptional individuals within a population may 'break the rule' without invalidating it. The less a quantitative difference varies within a population and the more it varies between populations, the better the case for making a distinction. Nevertheless, borderline situations can only be resolved by making a 'best-guess' judgement.
- It is possible to distinguish a qualitative difference between the populations; a feature that does not vary continuously but is either entirely present or entirely absent. This might be a distinctively shaped seed pod, an extra primary feather, a particular courting behaviour, or a clearly different DNA sequence. Sometimes it is not possible to isolate a single difference between species, and several factors must be taken in combination. This is often the case with plants in particular. In eucalypts, for example, Corymbia ficifolia cannot be reliably distinguished from its close relative Corymbia calophylla by any single measure (and sometimes individual trees cannot be definitely assigned to either species), but populations of Corymbia can be clearly told apart by comparing the colour of flowers, bark, and buds, number of flowers for a given size of tree, and the shape of the leaves and fruit. When using a combination of characteristics to distinguish between populations, it is necessary to use a reasonably small number of factors (if more than a handful are needed, the genetic difference between the populations is likely to be insignificant and is unlikely to endure into the future), and to choose factors that are functionally independent (height and weight, for example, should usually be considered as one factor, not two).

Historical development of the species concept

In the earliest works of science, a species was simply an individual organism that represented a group of similar or nearly identical organisms. No other relationships beyond that group were implied. Aristotle used the words genus and species to mean generic and specific categories. Aristotle and other pre-Darwinian scientists took the species to be distinct and unchanging, with an "essence", like the chemical elements. When early observers began to develop systems of organization for living things, they began to place formerly isolated species into a context. To the modern mind, many of the schemes delineated are whimsical at best, such as those that determined consanguinity based on color (all plants with yellow flowers) or behavior (snakes, scorpions and certain biting ants). In the 18th century Carolus Linnaeus classified organisms according to differences in the form of reproductive apparatus. Although his system of classification sorts organisms according to degrees of similarity, it made no claims about the relationship between similar species. At the time, it was still widely believed that there is no organic connection between species, no matter how similar they appear; every species was individually created by God, a view today called creationism. This approach also suggested a type of idealism: the notion that each species exists as an "ideal form". Although there are always differences (although sometimes minute) between individual organisms, Linnaeus considered such variation problematic. He strove to identify individual organisms that were exemplary of the species, and considered other non-exemplary organisms to be deviant and imperfect. By the 19th century most naturalists understood that species could change form over time, and that the history of the planet provided enough time for major changes. As such, the new emphasis was on determining how a species could change over time. Jean-Baptiste Lamarck suggested that an organism could pass on an acquired trait to its offspring, i.e., the giraffe's long neck was attributed to generations of giraffes stretching to reach the leaves of higher treetops (this well-known and simplistic example, however, does not do justice to the breadth and subtlety of Lamarck's ideas). Lamarck's most important insight may have been that species can be extraordinarily fluid; his 1809 Zoological Philosophy contained one of the first logical refutations of creationism. With the acceptance of the work of Charles Darwin in the 1860s, Lamarck's view of evolution was quickly eclipsed. It was not until the late 20th century that his work began to be reexamined, and took its place as a fundamental stepping stone to the modern theory of adaptive mutation. Lamarck's long-discarded ideas of the goal-oriented evolution of species, also known the teleological process, have also received renewed attention, particularly by proponents of artificial selection. Charles Darwin and Alfred Wallace provided what scientists now consider the most powerful and compelling theory of evolution. Basically, Darwin argued that it is populations that evolve, not individuals. His argument relies on a radical shift in perspective from Linnaeus: rather than defining species in ideal terms (and searching for an ideal representative and rejecting deviations), Darwin considered variation among individuals to be natural. He further argued that variation, far from being problematic, actually provides the explanation for the existence of distinct species. Darwin's work drew on Thomas Malthus' insight that the rate of growth of a biological population will always outpace the rate of growth of the resources in the environment, such as the food supply. As a result, Darwin argued, not all the members of a population will be able to survive and reproduce. Those that did will, on average, be the ones possessing variations—however slight—that make them slightly better adapted to the environment. If these variable traits are heritable, then the offspring of the survivors will also possess them. Thus, over many generations, adaptive variations will accumulate in the population, while counter-adaptive will be eliminated. It should be emphasized that whether a variation is adaptive or non-adaptive depends on the environment: different environments favor different traits. Since the environment effectively selects which organisms live to reproduce, it is the environment (the "fight for existence") that selects the traits to be passed on. This is the theory of evolution by natural selection. In this model, the length of a giraffe's neck would be explained by positing that proto-giraffes with longer necks would have had a significant reproductive advantage to those with shorter necks. Over many generations, the entire population would be a species of long-necked animals. In 1859, when Darwin published his theory of natural selection, the mechanism behind the inheritance of individual traits was unknown. Although Darwin made some speculations on how traits are inherited (pangenesis), his theory relies only on the fact that inheritable traits exist, and are variable (which makes his accomplishment even more remarkable.) Although Gregor Mendel's paper on genetics was published in 1866, its significance was not recognized. It was not until 1900 that his work was rediscovered by Hugo de Vries, Carl Correns and Erich von Tschermak, who realised that the "inheritable traits" in Darwin's theory are genes. The theory of the evolution of species through natural selection has two important implications for discussions of species -- consequences that fundamentally challenge the assumptions behind Linnaeus' taxonomy. First, it suggests that species are not just similar, they may actually be related. Some students of Darwin argue that all species are descended from a common ancestor. Second, it supposes that "species" are not homogeneous, fixed, permanent things; members of a species are all different, and over time species change. This suggests that species do not have any clear boundaries but are rather momentary statistical effects of constantly changing gene-frequencies. One may still use Linnaeus' taxonomy to identify individual plants and animals, but one can no longer think of species as independent and immutable. The rise of a new species from a parental line is called speciation. There is no clear line demarcating the ancestral species from the descendant species. Although the current scientific understanding of species suggests there is no rigorous and comprehensive way to distinguish between different species in all cases, biologists continue to seek concrete ways to operationalize the idea. One of the most popular biological definitions of species is in terms of reproductive isolation; if two creatures cannot reproduce to produce fertile offspring, then they are in different species. This definition captures a number of intuitive species boundaries, but nonetheless has some problems, however. It has nothing to say about species that reproduce asexually, for example, and it is very difficult to apply to extinct species. Moreover, boundaries between species are often fuzzy: there are examples where members of one population can produce fertile offspring with a second population, and members of the second population can produce fertile offspring with members of a third population, but members of the first and third population cannot produces fertile offspring. Consequently, some people reject this notion of species. In recent years we have witnessed the drastic reduction in the size of breeding populations and the geographical range of many physically large mammals. In earlier times it was assumed that every species existed in at least a few thousand living individuals, except very rare relic, isolated groups. In the present, many well know mammal & bird species are so stressed by habitat loss, and other effects of the modern world, that only a very few breeding males may contribute the genetic material to a small number of breeding females. In these highly stressed conditions, the likelihood of change is very much greater. Mammals may become smaller, have darker fur, more stripes, more cautious behavior, even over time learn to co-exist with the human world. Very likely, evolution is radically accelerated, and we are only beginning to notice it. Species in transition before our eyes. It is possible that this severe stress is essential to the creation of new species, and may have been a prime factor throughout biological history, from other population reducing influences. Richard Dawkins defines two organisms as conspecific if and only if they have the same number of chromosomes and, for each chromosome, both organisms have the same number of nucleotides (The Blind Watchmaker, p. 118). However, most if not all taxonomists would strongly disagree. For example, in many amphibians, most notably in New Zealand's Leiopelma frogs, the genome consists of "core" chromosomes which are mostly invariable and accessory chromosomes, of which exist a number of possible combinations. Even though the chromosome numbers are highly variable between populations, these can interbreed successfully and form a single evolutionary unit. In plants, polyploidy is extremely commonplace with few restrictions on interbreeding; as individuals with an odd number of chromosome sets are usually sterile, depending on the actual number of chromosome sets present, this results in the odd situation where some individuals of the same evolutionary unit can interbreed with certain others and some cannot, with all populations being eventually linked as to form a common gene pool. The classification of species has been profoundly affected by technological advances that have allowed researchers to determine relatedness based on molecular markers, starting with the comparatively crude blood plasma precipitation assays in the mid-20th century and coming into full swing with Charles Sibley's ground-breaking DNA-DNA hybridisation studies in the 1970s. The results of the technique caused revolutionary changes in the higher taxonomic categories (such as phyla and classes), resulting in the reordering of many branches of the phylogenetic tree (see also: molecular phylogeny). For taxonomic categories below genera, the results have been mixed so far; the pace of evolutionary change on the molecular level is rather slow, yielding clear differences only after considerable periods of reproductive separation. Instances of hybridization can result in misleading molecular data, the Pomarine Skua - Great Skua phenomenon being a famous example. Turtles have been determined to evolve with just one-eighth of the speed of other reptiles on the molecular level, and the rate of molecular evolution in albatrosses is half of what is found in the rather closely related storm-petrels. The hybridization technique is however no longer considered a good technique and more reliable computational techniques for sequence comparison are now used for. Molecular taxonomy does not directly measure the evolutionary processes, but rather the overall change brought upon by these processes. The processes that lead to the generation and maintenance of variation such as mutation, crossover and selection are not uniform (see also molecular clock). DNA is only extremely rarely a direct target of natural selection rather than changes in the DNA sequence enduring over generations being a result of the latter; for example, silent transition-transversion combinations would alter the melting point of the DNA sequence, but not the sequence of the encoded proteins and thus are a possible example where, for example in microorganisms, a mutation confers a change in fitness all by itself.

External links

- http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/S/Speciation.html
- [http://www.sciencedaily.com/releases/2003/12/031231082553.htm 2003-12-31, ScienceDaily: Working On The 'Porsche Of Its Time': New Model For Species Determination Offered] Quote: "...two species of dinosaur that are members of the same genera varied from each other by just 2.2 percent. Translation of the percentage into an actual number results in an average of just three skeletal differences out of the total 338 bones in the body. Amazingly, 58 percent of these differences occurred in the skull alone. "This is a lot less variation than I'd expected", said Novak..."
- [http://www.sciencedaily.com/releases/2003/08/030808081854.htm 2003-08-08, ScienceDaily: Cross-species Mating May Be Evolutionarily Important And Lead To Rapid Change, Say Indiana University Researchers] Quote: "...the sudden mixing of closely related species may occasionally provide the energy to impel rapid evolutionary change..."
- [http://www.sciencedaily.com/releases/2004/01/040109064407.htm 2004-01-09 ScienceDaily: Mayo Researchers Observe Genetic Fusion Of Human, Animal Cells; May Help Explain Origin Of AIDS] Quote: "...The researchers have discovered conditions in which pig cells and human cells can fuse together in the body to yield hybrid cells that contain genetic material from both species... "What we found was completely unexpected", says Jeffrey Platt, M.D."
- [http://www.sciencedaily.com/releases/2000/09/000913211733.htm 2000-09-18, ScienceDaily: Scientists Unravel Ancient Evolutionary History Of Photosynthesis] Quote: "...gene-swapping was common among ancient bacteria early in evolution..."
- [http://plato.stanford.edu/entries/species/ Stanford Encyclopedia of Philosophy entry]
- [http://www.barcodinglife.org/ Barcoding of species] rank22 rank22 ms:Spesies ja:種 (生物) th:สปีชีส์

Tree

, the tallest tree species on earth]] A tree can be defined as a large, perennial, woody plant. Though there is no set definition regarding minimum size, the term generally applies to plants at least 6 m (20 ft) high at maturity and, more importantly, having secondary branches supported on a single main stem or trunk (see shrub for comparison). Compared with most other plant forms, trees are long-lived. A few species of trees grow to 100 m tall, and some can live for several thousand years. Trees are important components of the natural landscape and significant elements in landscaping, and in agriculture supplying orchard crops (such as apples). Trees also play an important role in many of the world's mythologies (see Tree (mythology)).

Classifications

Tree (mythology)]] A tree is a plant form and trees occur in many different orders and families of plants. Trees thus show a wide variety of growth form, leaf type and shape, bark characteristics, reproductive structures, etc. The earliest trees were tree ferns and horsetails, which grew in vast forests in the Carboniferous Period; tree ferns still survive, but the only surviving horsetails are not of tree form. Later, in the Triassic Period, conifers, ginkgos, cycads and other gymnosperms appeared, and subsequently flowering plants in the Cretaceous Period. Most species of trees today are flowering plants and conifers. The listing below gives examples of many well-known trees and how they are typically classified. A small group of trees growing together is called a grove or copse, and a landscape covered by a dense growth of trees is called a forest. Several biotopes are defined largely by the trees that inhabit them; examples are rainforest and taiga (see ecozones). A landscape of trees scattered or spaced across grassland (usually grazed or burned over periodically) is called a savanna.

Morphology

The basic parts of a tree are the roots, trunk(s), branches, twigs and leaves. Tree stems consist mainly of support and transport tissues (xylem and phloem). Wood consists of xylem cells, and bark is made of phloem and other tissues external to the vascular cambium. Trees may be broadly grouped into exogenous and endogenous trees according to the way in which their stem diameter increases. Exogenous trees, which comprise the great majority of modern trees (all conifers, and all broadleaf trees), grow by the addition of new wood outwards, immediately under the bark. Endogenous trees, mainly in the monocotyledons (e.g. palms), grow by addition of new material inwards. As an exogenous tree grows, it creates growth rings. In temperate climates, these are commonly visible due to changes in the rate of growth with temperature variation over an annual cycle. These rings can be counted to determine the age of the tree, and used to date cores or even wood taken from trees in the past; this practice is known as the science of dendrochronology. In some tropical regions with constant year-round climate, growth is continuous and distinct rings are not formed, so age determination is impossible. Age determination is also impossible in endogenous trees. dendrochronology, Chile]] The roots of a tree are generally embedded in earth, providing anchorage for the above-ground biomass and absorbing water and nutrients from the soil. Above ground, the trunk gives height to the leaf-bearing branches, aiding in competition with other plant species for sunlight. In many trees, the arrangement of the branches optimizes exposure of the leaves to sunlight. Not all trees have all the plant organs or parts mentioned above. For example, most palm trees are not branched, the saguaro cactus of North America has no functional leaves, tree ferns do not produce bark, etc. Based on their general shape and size, all of these are nonetheless generally regarded as trees. Indeed, sometimes size is the more important consideration. A plant form that is similar to a tree, but generally having smaller, multiple trunks and/or branches that arise near the ground, is called a shrub. However, no sharp differentiation between shrubs and trees is possible. Given their small size, bonsai plants would not technically be 'trees', but one should not confuse reference to the form of a species with the size or shape of individual specimens. A spruce seedling does not fit the definition of a tree, but all spruces are trees. Bamboos by contrast, do show most of the characteristics of trees, yet are rarely called trees.

Champion trees

The world's champion trees can be considered on several factors; height, trunk diameter or girth, total size, and age. It is significant that in each case, the top position is always held by a conifer, though a different species in each case; in most measures, the second to fourth places are also held by conifers. ;Tallest trees The heights of the tallest trees in the world have been the subject of considerable dispute and much (often wild) exaggeration. Modern verified measurement with laser rangefinders combined with tape drop measurements made by tree climbers, carried out by the [http://www.uark.edu/misc/ents/home.htm U.S. Eastern Native Tree Society] has shown that most older measuring methods and measurements are unreliable, often producing exaggerations of 5% to 15% above the real height. Historical claims of trees of 114 m, 117 m, 130 m, and even 150 m, are now largely disregarded as unreliable, fantasy or outright fraud. The following are now accepted as the top five tallest reliably measured species: # Coast Redwood Sequoia sempervirens: 112.83 m, Humboldt Redwoods State Park, California ([http://www.conifers.org/cu/se/index.htm Gymnosperm Database]) # Coast Douglas-fir Pseudotsuga menziesii: 100.3 m, Brummit Creek, Coos County, Oregon ([http://www.conifers.org/pi/ps/menziesii2.htm Gymnosperm Database]) # Sitka Spruce Picea sitchensis: 96.7 m, Prairie Creek Redwoods State Park, California ([http://www.conifers.org/pi/pic/sitchensis.htm Gymnosperm Database]) # Giant Sequoia Sequoiadendron giganteum: 93.6 m, Redwood Mountain Grove, California ([http://www.conifers.org/cu/se2/index.htm Gymnosperm Database]) # Australian Mountain-ash Eucalyptus regnans: 92.0 m, Styx Valley, Tasmania ([http://www.forestrytas.com.au/forestrytas/tasfor/tasforests_12/tasfor_12_09.pdf Forestry Tasmania] [pdf file]) ;Stoutest trees The girth (circumference) of a tree is – or at least should be – much easier to measure than the height, as it is a simple matter of stretching a tape round the trunk, and pulling it taut to find the circumference. Despite this, U.K. tree author Alan Mitchell made the following comment about measurements of yew trees in the British Isles: :"The aberrations of past measurements of yews are beyond belief. For example, the tree at Tisbury has a well-defined, clean, if irregular bole at least 1.5 m long. It has been found to have a girth which has dilated and shrunk in the following way: 11.28 m (1834 Loudon), 9.3 m (1892 Lowe), 10.67 m (1903 Elwes and Henry), 9.0 m (1924 E. Swanton), 9.45 m (1959 Mitchell) .... Earlier measurements have therefore been omitted". As a general standard, tree girth is taken at 'breast height'; this is defined differently in different situations, with most foresters measuring girth at 1.3 m above ground, while ornamental tree measurers usually measure at 1.5 m above ground; in most cases this makes little difference to the measured girth. On sloping ground, the "above ground" reference point is usually taken as the highest point on the ground touching the trunk, but some use the average between the highest and lowest points of ground. Some of the inflated old measurements may have been taken at ground level. Some past exaggerated measurements also result from measuring the complete next-to-bark measurement, pushing the tape in and out over every crevice and buttress. Modern trends are to cite the tree's diameter rather than the circumference; this is obtained by dividing the measured circumference by π; it assumes the trunk is circular in cross-section (an oval or irregular cross-section would result in a mean diameter slightly greater than the assumed circle). This is cited as dbh (diameter at breast height) in tree literature. A further problem with measuring baobabs Adansonia is that these trees store large amounts of water in the very soft wood in their trunks. This leads to marked variation in their girth over the year, swelling to a maximum at the end of the rainy season, minimum at the end of the dry season. Although baobabs have some of the highest girth measurements of any trees, no accurate measurements are currently available, but probably do not exceed 10-11 m diameter. The stoutest species in diameter, excluding baobabs, are: # Montezuma Cypress Taxodium mucronatum: 11.42 m, Árbol del Tule, Santa Maria del Tule, Oaxaca, Mexico (A. F. Mitchell, International Dendrology Society Year Book 1983: 93, 1984). # Giant Sequoia Sequoiadendron giganteum: 8.85 m, General Grant tree, Grant Grove, California ([http://www.conifers.org/cu/se2/index.htm Gymnosperm Database]) # Coast Redwood Sequoia sempervirens: 7.44 m, Prairie Creek Redwoods State Park, California ([http://www.conifers.org/cu/se/index.htm Gymnosperm Database]) ;Largest trees The largest trees in total volume are those which are both tall and of large diameter, and in particular, which hold a large diameter high up the trunk. Measurement is very complex, particularly if branch volume is to be included as well as the trunk volume, so measurements have only been made for a small number of trees, and generally only for the trunk. No attempt has ever been made to include root volume. The top four species measured so far are ([http://www.conifers.org/topics/biggest.htm Gymnosperm Database]): # Giant Sequoia Sequoiadendron giganteum: 1489 m³, General Sherman tree # Coast Redwood Sequoia sempervirens: 1045 m³, Del Norte Titan tree # Western Redcedar Thuja plicata: 500 m³, Quinault Lake Redcedar # Kauri Agathis australis: 400 m³, Tane Mahuta tree (total volume, including branches, 516.7 m³)
However, the Alerce Fitzroya cupressoides, as yet un-measured, may well slot in at third or fourth place, and Montezuma Cypress Taxodium mucronatum is also likely to be high in the list. The largest angiosperm tree is a Australian Mountain-ash, the 'El Grande' tree of about 380 m³ in Tasmania. ;Oldest trees The oldest trees are determined by growth ring counts in cores taken from the edge to the centre of the tree or from entire cross-sections. Accurate determination is only possible for trees which produce growth rings, generally those which occur in seasonal climates; trees in uniform non-seasonal tropical climates grow continuously and do not have distinct growth rings. It is also only possible for trees which are solid to the centre of the tree; many very old trees become hollow as the dead heartwood decays away. For some of these species, age estimates have been made on the basis of extrapolating current growth rates, but the results are usually little better than guesswork or wild speculation. The verified oldest measured ages are ([http://www.conifers.org/topics/oldest.htm Gymnosperm Database]): # Great Basin Bristlecone Pine Pinus longaeva: 4844 years # Alerce Fitzroya cupressoides: 3622 years # Giant Sequoia Sequoia sempervirens: 3266 years # Huon-pine Lagarostrobos franklinii: 2500 years # Rocky Mountains Bristlecone Pine Pinus aristata: 2435 years Other species suspected of reaching exceptional age include European Yew Taxus baccata (probably over 3000 years) and Western Redcedar Thuja plicata. The oldest verified age for an angiosperm tree is 2293 years for the Sri Maha Bodhi Sacred Fig (Ficus religiosa) planted in 288 BC at Anuradhapura, Sri Lanka; this is also the oldest human-planted tree with a known planting date.

Major tree genera

Flowering plants (Magnoliophyta; angiosperms)

Dicotyledons (Magnoliopsida; broadleaf or hardwood trees)

- Anacardiaceae (Cashew family)
- Cashew, Anacardium occidentale
- Mango, Mangifera indica
- Pistachio, Pistacia vera
- Sumac, Rhus species
- Lacquer tree, Toxicodendron verniciflua
- Annonaceae (Custard apple family)
- Cherimoya Annona cherimola
- Custard apple Annona reticulata
- Pawpaw Asimina triloba
- Soursop Annona muricata
- Apocynaceae (Dogbane family)
- Pachypodium Pachypodium species
- Aquifoliaceae (Holly family)
- Holly, Ilex species
- Araliaceae (Ivy family)
- Kalopanax, Kalopanax pictus Kalopanax tree (background) in fall]]
- Betulaceae (Birch family)
- Alder, Alnus species
- Birch, Betula species
- Hornbeam, Carpinus species
- Hazel, Corylus species
- Bignoniaceae (family)
- Catalpa, Catalpa species
- Cactaceae (Cactus family)
- Saguaro, Carnegiea gigantea
- Cannabaceae (Cannabis family)
- Hackberry, Celtis species
- Cornaceae (Dogwood family)
- Dogwood, Cornus species
- Dipterocarpaceae family
- Garjan Dipterocarpus species
- Sal Shorea species
- Ericaceae (Heath family)
- Arbutus, Arbutus species
- Eucommiaceae (Eucommia family)
- Eucommia Eucommia ulmoides
- Fabaceae (Pea family)
- Acacia, Acacia species
- Honey locust, Gleditsia triacanthos
- Black locust, Robinia pseudoacacia
- Laburnum, Laburnum species
- Pau Brasil, Brazilwood, Caesalpinia echinata
- Fagaceae (Beech family )
- Chestnut, Castanea species
- Beech, Fagus species
- Southern beech, Nothofagus species
- Tanoak, Lithocarpus densiflorus
- Oak, Quercus species
- Fouquieriaceae (Boojum family)
- Boojum, Fouquieria columnaris
- Hamamelidaceae (Witch-hazel family)
- Sweetgum, Liquidambar species
- Persian Ironwood, Parrotia persica
- Juglandaceae (Walnut family)
- Walnut, Juglans species
- Hickory, Carya species
- Wingnut, Pterocarya species
- Lauraceae (Laurel family)
- Cinnamon Cinnamomum zeylanicum
- Bay Laurel Laurus nobilis
- Avocado Persea americana
- Lecythidaceae (Paradise nut family)
- Brazil Nut Bertholletia excelsa
- Lythraceae Loosestrife family
- Crape-myrtle Lagerstroemia species
- Magnoliaceae (Magnolia family)
- Tulip tree, Liriodendron species
- Magnolia, Magnolia species
- Malvaceae (Mallow family; including Tiliaceae and Bombacaceae) Bombacaceae
- Baobab, Adansonia species
- Silk-cotton tree, Bombax species
- Bottletrees, Brachychiton species
- Kapok, Ceiba pentandra
- Durian, Durio zibethinus
- Balsa, Ochroma lagopus
- Cacao (cocoa), Theobroma cacao
- Linden (Basswood, Lime), Tilia species
- Meliaceae (Mahogany family)
- Neem, Azadirachta indica
- Bead tree, Melia azedarach
- Mahogany, Swietenia mahagoni
- Moraceae (Mulberry family)
- Fig, Ficus species
- Mulberry, Morus species
- Myristicaceae (Nutmeg family)
- Nutmeg, Mysristica fragrans
- Myrtaceae (Myrtle family)
- Eucalyptus, Eucalyptus species
- Myrtle, Myrtus species
- Guava, Psidium guajavaGuava in flower]]
- Nyssaceae (Tupelo family; sometimes included in Cornaceae)
- Tupelo, Nyssa species
- Dove tree, Davidia involucrata
- Oleaceae (Olive family)
- Olive, Olea europaea
- Ash, Fraxinus species
- Paulowniaceae (Paulownia family)
- Foxglove Tree, Paulownia species
- Platanaceae (Plane family)
- Plane, Platanus species
- Rhizophoraceae (Mangrove family)
- Red Mangrove, Rhizophora mangle
- Rosaceae (Rose family)
- Rowans, Whitebeams, Service Trees Sorbus species
- Hawthorn, Crataegus species
- Pear, Pyrus species
- Apple, Malus species
- Almond, Prunus dulcis
- Peach, Prunus persica
- Plum, Prunus domestica
- Cherry, Prunus species
- Rubiaceae (Bedstraw family)
- Coffee, Coffea species
- Rutaceae (Rue family)
- Citrus, Citrus species
- Cork-tree, Phellodendron species
- Euodia, Tetradium species
- Salicaceae (Willow family)
- Aspen, Populus species
- Poplar, Populus species
- Willow, Salix species Willow
- Sapindaceae (including Aceraceae, Hippocastanaceae) (Soapberry family)
- Maple, Acer species
- Buckeye, Horse-chestnut, Aesculus species
- Mexican Buckeye, Ungnadia speciosa
- Lychee, Litchi sinensis
- Golden rain tree, Koelreuteria paniculata
- Sapotaceae (Sapodilla family)
- Gutta-percha, Palaquium species
- Tambalacoque, or "dodo tree", Sideroxylon grandiflorum, previously Calvaria major
- Simaroubaceae family
- Tree of heaven, Ailanthus species
- Theaceae (Camellia family)
- Gordonia, Gordonia species
- Stuartia, Stuartia species
- Thymelaeaceae (Thymelaea family)
- Ramin, Gonystylus species
- Ulmaceae (Elm family)
- Elm, Ulmus species
- Zelkova, Zelkova species
- Verbenaceae family
- Teak, Tectona species

Monocotyledons (Liliopsida)

Monocotyledon
- Agavaceae (Agave family)
- Cabbage tree, Cordyline australis
- Dragon tree, Dracaena draco
- Joshua tree, Yucca brevifolia
- Arecaceae (Palmae) (Palm family)
- Areca Nut, Areca catechu
- Coconut Cocos nucifera
- Date Palm, Phoenix dactylifera
- Chusan Palm, Trachycarpus fortunei
- Poaceae (grass family)
- Bamboos Poaceae subfamily Bambusoideae
- Note that banana 'trees' are not actually trees; they are not woody nor is the stalk perennial.

Conifers (Pinophyta; softwood trees)

- Araucariaceae (Araucaria family)
- Araucaria, Araucaria species
- Kauri, Agathis species
- Cupressaceae (Cypress family)
- Cypress, Cupressus species
- Cypress, Chamaecyparis species
- Juniper, Juniperus species
- Alerce or Patagonian cypress, Fitzroya cupressoides
- Sugi, Cryptomeria japonica
- Coast Redwood, Sequoia sempervirens
- Giant Sequoia, Sequoiadendron giganteum
- Dawn Redwood, Metasequoia glyptostroboides
- Bald Cypress, Taxodium distichum
- Pinaceae (Pine family)
- White pine, Pinus species
- Pinyon pine, Pinus species
- Pine, Pinus species
- Spruce, Picea species
- Larch, Larix species
- Douglas-fir, Pseudotsuga species
- Fir, Abies species
- Cedar, Cedrus species
- Podocarpaceae (Yellowwood family)
- African Yellowwood, Afrocarpus falcatus
- Totara, Podocarpus totara
- Sciadopityaceae
- Kusamaki, Sciadopitys species
- Taxaceae (Yew family)
- Yew, Taxus species

Ginkgos (Ginkgophyta)

- Ginkgoaceae (Ginkgo family)
- Ginkgo, Ginkgo biloba

Cycads (Cycadophyta)

- Cycadaceae family
- Ngathu cycad, Cycas angulata
- Zamiaceae family
- Wunu cycad, Lepidozamia hopei

Ferns (Pterophyta)

- Cyatheaceae and Dicksoniaceae families
- Tree ferns, Cyathea, Alsophila, Dicksonia (not a monophyletic group)

Life stages

The life cycles of trees, especially conifers, are divided into the following stages in forestry for survey and documentation purposes: # Seed # Seedling: the above ground part of the embryo that sprout from the seed # Sapling: After the seedling reaches 1m tall, and until it reaches 7cm in stem diameter # Pole: young trees from 7-30cm diameter # Mature tree: over 30cm diameter, reproductive years begin # Old tree: dominate old growth forest; height growth slows greatly, with majority of productivity in seed production # Overmature: dieback and decay become common # Snag: standing dead wood # Log/debris: fallen dead wood Tree diameters are measured at height of between 1.3-1.5m above the highest point on the ground at its base. The 7cm diameter definition is economically based, from the smallest saleable stem size (for paper production, etc), and the 30cm diameter is the smallest base diameter for sawlogs. Each stage may be uniquely perceptive to different pathogens and suitable for especially adapted arboreal animals.

External links

- [http://www.globaltrees.org/default.asp GLOBAL TREES .org] Campaigning to save the world's most threatened trees
- [http://www.fssca.net/romero/ Romero Memorial Tree Project] Plant a tree in El Salvador

Bibliography

- Pakenham, T. (2002). Remarkable Trees of the World. ISBN 0297843001
- Pakenham, T. (1996). Meetings with Remarkable Trees. ISBN 0297832557 Category:Plants
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- Category:Botany Category: plant morphology ms:Pokok ja:木 simple:Tree th:ต้นไม้

Shrub

:"Shrub" is also a derogatory nickname for United States President George W Bush. George W Bush A shrub or bush is a horticultural rather than strictly botanical category of woody plant, distinguished from a tree by its multiple stems and lower height, usually less than 6 m tall. A large number of plants can be either shrubs or trees, depending on the growing conditions they experience. Small, low shrubs such as lavender, periwinkle and thyme are often termed subshrubs. A natural plant community dominated by shrubs is called a shrubland. The word bush can also refer to a type of plant community, as in the Australian bush. This is often characterised by scrubby, open woodland and is a generic term for Eucalyptus dominated woodland in particular. An area of cultivated shrubs in a park or garden is known as a shrubbery. When clipped as topiary, shrubs generally have dense foliage and many small leafy branches growing close together. Many shrubs respond well to renewal pruning, in which hard cutting back to a 'stool' results in long new stems known as "canes". Other shrubs respond better to selective pruning to reveal their structure and character. Shrubs in common garden practice are generally broad-leaved plants, though some smaller conifers such as Mountain Pine and Common Juniper are also shrubby in structure. Shrubs can be either deciduous or evergreen.

List of Shrubs

Incomplete! Those marked
- can also develop into tree form. ;A
- Abelia (Abelia)
- Actinidia (Actinidia)
- Aralia (Angelica Tree, Hercules' Club)
-
- Arctostaphylos (Bearberry, Manzanita)
-
- Aronia (Chokeberry)
- Artemisia (Sagebrush)
- Aucuba (Aucuba) ;B
- Berberis (Barberry)
- Buddleja (Butterfly bush)
- Buxus (Box)
- ;C
- Calia (Mescalbean)
- Callicarpa (Beautyberry)
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- Callistemon (Bottlebrush)
-
- Calluna (Heather)
- Calycanthus (Sweetshrub)
- Camellia (Camellia, Tea)
-
- Caragana (Pea-tree)
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- Carpenteria (Carpenteria)
- Caryopteris (Blue Spiraea