An Oak is a tree A tree is a perennial woody plant. It is most often defined as a woody plant that has many secondary branches supported clear of the ground on a single main stem or trunk with clear apical dominance. A minimum height specification at maturity is cited by some authors, varying from 3 m to 6 m; some authors set a minimum of 10 cm trunk diameter or shrub A shrub or bush is distinguished from a tree by its multiple stems and lower height, usually less than 5–6 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 in the genus In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin" Quercus (pronounced /ˈkwɜrkəs/;[1] Latin Latin or sometimes Roman is an Italic language originally spoken in Latium and Ancient Rome. Although often considered a dead language, in view of the fact that it has no native speakers, a small number of scholars can fluently speak it and it continues to be taught in schools and universities and has been, and currently is, used in the process of "oak tree"), of which about 600 species This is an incomplete list of Quercus species. The genus contains about 400 species exist on earth. "Oak" may also appear in the names of species in related genera, notably Lithocarpus Lithocarpus is a genus in the beech family Fagaceae, differing from Quercus in the erect male spikes. The World Checklist accepts 334 species, though some other texts suggest as few as 100 species. About 100 Asian species of the genus were formerly treated in the genus Pasania. All but one are native to east and southeast Asia; the single. The genus is native to the northern hemisphere The Northern Hemisphere is the half of a planet that is north of equator—the word hemisphere literally means 'half sphere'. It is also that half of the celestial sphere north of the celestial equator. Earth's northern hemisphere contains most of its land area and most of its human population, and includes deciduous Deciduous means falling off at maturity or tending to fall off and is typically used in reference to trees or shrubs that lose their leaves seasonally and to the shedding of other plant structures such as petals after flowering or fruit when ripe. In a more specific sense deciduous means the dropping of a part that is no longer needed, or falling and evergreen In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during winter species extending from cold latitudes to tropical The tropics is a region of the Earth by the Equator. It is limited in latitude by the Tropic of Cancer in the northern hemisphere at approximately 23° 26′ 16″ N and the Tropic of Capricorn in the southern hemisphere at 23° 26′ 16″ ( or 23.438° ) S. The tropics are also referred to as the tropical zone and the torrid zone (see Asia Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.6% of the Earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population. During the 20th century Asia's population nearly quadrupled and the Americas The Americas, or America, are lands in the Western hemisphere, also known as the New World, comprising the continents of North America and South America with their associated islands and regions. The plural form the Americas is often used in English, as the singular America is ambiguous: America is more commonly used to refer to the United States.
Oaks have spirally In mathematics, a spiral is a curve which emanates from a central point, getting progressively farther away as it revolves around the point arranged leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide at the expense of water loss. In the Devonian period, when carbon, with a lobed margin in many species; some have serrated leaves In botany, a leaf is an above-ground plant organ specialized for photosynthesis. For this purpose, a leaf is typically flat and thin. As an evolutionary trait, the flatness of leaves works to expose the chloroplasts to more light and to increase the absorption of carbon dioxide at the expense of water loss. In the Devonian period, when carbon or entire leaves with a smooth margin. The flowers A flower, sometimes known as a bloom or blossom, is the reproductive structure found in flowering plants . The biological function of a flower is to mediate the union of male sperm with female ovum in order to produce seeds. The process begins with pollination, is followed by fertilization, leading to the formation and dispersal of the seeds. For are catkins A catkin or ament is a slim, cylindrical flower cluster, with inconspicuous or no petals, usually wind-pollinated but sometimes insect pollinated (as in Salix). They contain many, usually unisexual flowers, arranged closely along a central stem which is often drooping. They are found in many plant families, including Betulaceae, Fagaceae, Moraceae,, produced in spring Spring is one of the four temperate seasons, the transition period between winter and summer. Spring and "springtime" refer to the season, and broadly to ideas of rebirth, renewal and regrowth. The specific definition of "spring" as a season differs, however, among scientific disciplines such as astronomy and meterorology, and. The fruit The term has different meanings dependent on context. In non-technical usage, such as food preparation, fruit normally means the fleshy seed-associated structures of certain plants that are sweet and edible in the raw state, such as apples, oranges, grapes, strawberries, juniper berries and bananas. Seed-associated structures that do not fit these is a nut Nut is a hard shelled fruit of some plants that has an indehiscent seed. While a wide variety of dried seeds and fruits are called nuts in English, only a certain number of them are considered by biologists to be true nuts. Nuts are an important source of nutrients for both humans and wildlife called an acorn The acorn, or oak nut, is the nut of the oaks and their close relatives . It usually contains a single seed (rarely two seeds), enclosed in a tough, leathery shell, and borne in a cup-shaped cupule. Acorns vary from 1–6 cm long and 0.8–4 cm broad. Acorns take between about 6 or 24 months (depending on the species) to mature; see List of, borne in a cup-like structure known as a cupule The calybium and the cupule make up the accessory fruit of flowering plants in the family Fagaceae. These two parts derive from different flower components; each acorn contains one seed (rarely two or three) and takes 6–18 months to mature, depending on species. The live oaks Live oak or evergreen oak is a general term for a number of unrelated oaks in several different sections of the genus Quercus that happen to share the characteristic of evergreen foliage are distinguished for being evergreen In botany, an evergreen plant is a plant that has leaves in all seasons. This contrasts with deciduous plants, which completely lose their foliage during winter, but are not actually a distinct group and instead are dispersed across the genus.
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Classification
Oak trees are flowering plants. The genus is divided into two subgenera In biology, a subgenus is a taxonomic rank directly below genus. See rank and rank (zoology) and a number of sections In botany, a section is a low-level taxonomic rank directly below subgenus. See rank and rank (zoology). It is typically used to help organize very large genera, which may have hundreds of species:
Subgenus Quercus
See also: List of Quercus species This is an incomplete list of Quercus species. The genus contains about 400 speciesThe Subgenus Quercus is divided into the following sections:
- Sect. Quercus (synonyms Lepidobalanus and Leucobalanus), the white oaks This is an incomplete list of Quercus species. The genus contains about 400 species of Europe Europe is one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally divided from Asia to its east by the water divide of the Ural Mountains, the Ural River, the Caspian Sea, the Caucasus region (Specification of borders) and the Black Sea to the southeast. Europe is bordered by the Arctic Ocean and, Asia Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.6% of the Earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population. During the 20th century Asia's population nearly quadrupled and North America North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific Ocean; South America lies to the southeast. Styles are short; acorns mature in 6 months and taste sweet or slightly bitter; the inside of acorn shell is hairless. The leaves mostly lack a bristle on their lobe tips, which are usually rounded.
- Sect. Mesobalanus, Hungarian oak and its relatives This is an incomplete list of Quercus species. The genus contains about 400 species of Europe and Asia. Styles long; acorns mature in about 6 months and taste bitter; the inside of acorn shell is hairless. The section Mesobalanus is closely related to section Quercus and sometimes included in it.
- Sect. Cerris, the Turkey oak and its relatives This is an incomplete list of Quercus species. The genus contains about 400 species of Europe and Asia. Styles long; acorns mature in 18 months and taste very bitter. The inside of the acorn shell is hairless. Its leaves typically have sharp lobe tips, with bristles at the lobe tip.
- Sect. Protobalanus, the Canyon live oak and its relatives This is an incomplete list of Quercus species. The genus contains about 400 species, in southwest United States ^ b. English is the de facto language of American government and the sole language spoken at home by 80% of Americans age five and older. Spanish is the second most commonly spoken language and northwest Mexico In Pre-Columbian Mesoamerica many cultures matured into advanced civilizations such as the Olmec, the Toltec, the Teotihuacan, the Zapotec, the Maya and the Aztec before the first contact with Europeans. In 1521, Spain conquered and colonized the territory, which was administered as the viceroyalty of New Spain which would eventually become Mexico. Styles short, acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. Leaves typically have sharp lobe tips, with bristles at the lobe tip.
- Sect. Lobatae (synonym Erythrobalanus), the red oaks This is an incomplete list of Quercus species. The genus contains about 400 species of North America, Central America Central America is the central geographic region of the Americas. It is the southernmost, isthmian portion of the North American continent, which connects with South America on the southeast. Central America is considered to be part of the Mesoamerican biodiversity hotspot, excluding the southern portions of Panama and northern South America South America is the southern continent of America, situated in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. It is bordered on the west by the Pacific Ocean and on the north and east by the Atlantic Ocean; North America and the Caribbean Sea lie to the northwest. Styles long, acorns mature in 18 months and taste very bitter. The inside of the acorn shell appears woolly. The actual nut is encased in a thin, clinging, papery skin. Leaves typically have sharp lobe tips, with spiny bristles at the lobe.
Subgenus Cyclobalanopsis
- The ring-cupped oaks This is an incomplete list of Quercus species. The genus contains about 400 species of eastern and southeastern Asia Asia is the world's largest and most populous continent, located primarily in the eastern and northern hemispheres. It covers 8.6% of the Earth's total surface area and with approximately 4 billion people, it hosts 60% of the world's current human population. During the 20th century Asia's population nearly quadrupled. Evergreen trees growing 10–40 m tall. They are distinct from subgenus Quercus in that they have acorns with distinctive cups bearing concrescent rings of scales; they commonly also have densely clustered acorns, though this does not apply to all of the species. The Flora of China treats Cyclobalanopsis as a distinct genus In biology, a genus is a low-level taxonomic rank (a taxon) used in the classification of living and fossil organisms, which is an example of definition by genus and differentia. The term comes from Latin genus "descent, family, type, gender", cognate with Greek: γένος – genos, "race, stock, kin", but most taxonomists consider it a subgenus In biology, a subgenus is a taxonomic rank directly below genus. See rank and rank (zoology) of Quercus. It contains about 150 species.
Hybridization
Interspecific hybridisation In biology and specifically genetics, hybrid has several meanings, all referring to the offspring of sexual reproduction is quite common among oaks, but usually only between species within the same section and most common in the white oak group (subgenus Quercus, section Quercus; see List of Quercus species This is an incomplete list of Quercus species. The genus contains about 400 species). Inter-section hybrids, except between species of sections Quercus and Mesobalanus, are unknown. Recent systematic studies appear to confirm a high tendency of Quercus species to hybridize because of a combination of factors. White oaks are unable to discriminate against pollination by other species in the same section because they are wind pollinated Anemophily or wind pollination is a form of pollination whereby pollen is distributed by wind. Anemophilous plants may be either gymnosperms or angiosperms (flower-producing). However, flowering anemophilous species do not develop scented flowers, nor do they produce nectar. This distinguishes them from entomophilous and zoophilous species (whose and they have weak internal barriers to hybridisation, hybridization produces functional seeds and fertile hybrid offspring.[2] Ecological stresses, especially near habitat margins, can also cause a breakdown of mate recognition as well as a reduction of male function (pollen quantity and quality) in one parent species.[2][3]
Frequent hybridisation among oaks has consequences for oak populations around the world; most notably, hybridization has produced large populations of hybrids with copious amounts of introgression Introgression, also known as introgressive hybridization, in genetics , is the movement of a gene (gene flow) from one species into the gene pool of another by repeated backcrossing an interspecific hybrid with one of its parent species. Introgression is a long-term process; it may take many hybrid generations before the backcrossing occurs, and the evolution of new species.[4] Frequent hybridisation and high levels of introgression have caused different species in the same populations to share up to 50% of their genetic information.[5] The high rates of hybridisation and introgression, produces genetic data that often does not differentiate between two clearly morphologically distinct species, but instead differentiates populations.[6] Numerous hypotheses have been proposed to explain how oak species are able to remain morphologically and ecologically distinct with such high levels of gene flow In population genetics, gene flow is the transfer of alleles of genes from one population to another, but the problem is still largely a mystery to botanists.
The Fagaceae The family Fagaceae, or beech family, comprises about 900 species of both evergreen and deciduous trees and shrubs, which are characterized by alternate simple leaves with pinnate venation, unisexual flowers in the form of catkins, and fruit in the form of cup-like nuts. Fagaceous leaves are often lobed and both petioles and stipules are generally, or oak family, is a very slowly evolving clade compared to other angiosperms,[7][8] and the hybridisation patterns in Quercus pose a great challenge to the concept of a species.[citation needed] A species is often defined as a group of “actually or potentially interbreeding populations which are reproductively isolated from other such groups.”[9] By this definition, many species of Quercus would be lumped together according to their geographic and ecological habitat, despite clear distinctions in morphology and, to a large extent, genetic data.
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Sat, 22 May 2010 20:28:37 GM
Michael Amonett, president, Old . Oak. Cliff Conservation League, Dallas . NIMBY strikes again.
