Ziziphus spina-christi, known as the Christ's thorn jujube, is an evergreen tree or plant native to northern and tropical Africa and Western Asia. It is native to East Africa and some tropical countries. In the Levant, it grows in valleys up to an elevation of 500 m; the ripe fruits are edible. The seed, contained within a small, oblong woody pit, is opened and eaten by local fauna, including the rock hyrax. In the Levant, a hundred years ago, it was called sidr and was common in the Jordan Valley and around Jerusalem. There were some folklore traditions that said the trees were protected by benevolent spirits or dead saints. By some traditions, it was the tree. Matthew George Easton argues that the spina-christi is too brittle to be bent into a crown, suggests another local plant which he says is called "nabk"; the oldest known Ziziphus is located south of Jerusalem, in Israel. It is estimated to be about 2000 years old, it is believed locally to be the tree from which Jesus' crown of thorns was made.
Ziziphus spina-christi in West African plants – A Photo Guide. The ethnobotany of Christ's Thorn Jujube in Israel Thorns of Ziziphus spina-christi Flowers in Israel - Ziziphus spina-christi
Asia is Earth's largest and most populous continent, located in the Eastern and Northern Hemispheres. It shares the continental landmass of Eurasia with the continent of Europe and the continental landmass of Afro-Eurasia with both Europe and Africa. Asia covers an area of 44,579,000 square kilometres, about 30% of Earth's total land area and 8.7% of the Earth's total surface area. The continent, which has long been home to the majority of the human population, was the site of many of the first civilizations. Asia is notable for not only its overall large size and population, but dense and large settlements, as well as vast populated regions, its 4.5 billion people constitute 60% of the world's population. In general terms, Asia is bounded on the east by the Pacific Ocean, on the south by the Indian Ocean, on the north by the Arctic Ocean; the border of Asia with Europe is a historical and cultural construct, as there is no clear physical and geographical separation between them. It has moved since its first conception in classical antiquity.
The division of Eurasia into two continents reflects East–West cultural and ethnic differences, some of which vary on a spectrum rather than with a sharp dividing line. The most accepted boundaries place Asia to the east of the Suez Canal separating it from Africa. China and India alternated in being the largest economies in the world from 1 to 1800 CE. China was a major economic power and attracted many to the east, for many the legendary wealth and prosperity of the ancient culture of India personified Asia, attracting European commerce and colonialism; the accidental discovery of a trans-Atlantic route from Europe to America by Columbus while in search for a route to India demonstrates this deep fascination. The Silk Road became the main east–west trading route in the Asian hinterlands while the Straits of Malacca stood as a major sea route. Asia has exhibited economic dynamism as well as robust population growth during the 20th century, but overall population growth has since fallen. Asia was the birthplace of most of the world's mainstream religions including Hinduism, Judaism, Buddhism, Taoism, Islam, Sikhism, as well as many other religions.
Given its size and diversity, the concept of Asia—a name dating back to classical antiquity—may have more to do with human geography than physical geography. Asia varies across and within its regions with regard to ethnic groups, environments, historical ties and government systems, it has a mix of many different climates ranging from the equatorial south via the hot desert in the Middle East, temperate areas in the east and the continental centre to vast subarctic and polar areas in Siberia. The boundary between Asia and Africa is the Red Sea, the Gulf of Suez, the Suez Canal; this makes Egypt a transcontinental country, with the Sinai peninsula in Asia and the remainder of the country in Africa. The border between Asia and Europe was defined by European academics; the Don River became unsatisfactory to northern Europeans when Peter the Great, king of the Tsardom of Russia, defeating rival claims of Sweden and the Ottoman Empire to the eastern lands, armed resistance by the tribes of Siberia, synthesized a new Russian Empire extending to the Ural Mountains and beyond, founded in 1721.
The major geographical theorist of the empire was a former Swedish prisoner-of-war, taken at the Battle of Poltava in 1709 and assigned to Tobolsk, where he associated with Peter's Siberian official, Vasily Tatishchev, was allowed freedom to conduct geographical and anthropological studies in preparation for a future book. In Sweden, five years after Peter's death, in 1730 Philip Johan von Strahlenberg published a new atlas proposing the Urals as the border of Asia. Tatishchev announced; the latter had suggested the Emba River as the lower boundary. Over the next century various proposals were made until the Ural River prevailed in the mid-19th century; the border had been moved perforce from the Black Sea to the Caspian Sea into which the Ural River projects. The border between the Black Sea and the Caspian is placed along the crest of the Caucasus Mountains, although it is sometimes placed further north; the border between Asia and the region of Oceania is placed somewhere in the Malay Archipelago.
The Maluku Islands in Indonesia are considered to lie on the border of southeast Asia, with New Guinea, to the east of the islands, being wholly part of Oceania. The terms Southeast Asia and Oceania, devised in the 19th century, have had several vastly different geographic meanings since their inception; the chief factor in determining which islands of the Malay Archipelago are Asian has been the location of the colonial possessions of the various empires there. Lewis and Wigen assert, "The narrowing of'Southeast Asia' to its present boundaries was thus a gradual process." Geographical Asia is a cultural artifact of European conceptions of the world, beginning with the Ancient Greeks, being imposed onto other cultures, an imprecise concept causing endemic contention about what it means. Asia does not correspond to the cultural borders of its various types of constituents. From the time of Herodotus a minority of geographers have rejected the three-continent system on the grounds that there is no substantial physical separation between
The eudicots, Eudicotidae or eudicotyledons are a clade of flowering plants, called tricolpates or non-magnoliid dicots by previous authors. The botanical terms were introduced in 1991 by evolutionary botanist James A. Doyle and paleobotanist Carol L. Hotton to emphasize the evolutionary divergence of tricolpate dicots from earlier, less specialized, dicots; the close relationships among flowering plants with tricolpate pollen grains was seen in morphological studies of shared derived characters. These plants have a distinct trait in their pollen grains of exhibiting three colpi or grooves paralleling the polar axis. Molecular evidence confirmed the genetic basis for the evolutionary relationships among flowering plants with tricolpate pollen grains and dicotyledonous traits; the term means "true dicotyledons", as it contains the majority of plants that have been considered dicots and have characteristics of the dicots. The term "eudicots" has subsequently been adopted in botany to refer to one of the two largest clades of angiosperms, monocots being the other.
The remaining angiosperms include magnoliids and what are sometimes referred to as basal angiosperms or paleodicots, but these terms have not been or adopted, as they do not refer to a monophyletic group. The other name for the eudicots is tricolpates, a name which refers to the grooved structure of the pollen. Members of the group have tricolpate pollen; these pollens have three or more pores set in furrows called colpi. In contrast, most of the other seed plants produce monosulcate pollen, with a single pore set in a differently oriented groove called the sulcus; the name "tricolpates" is preferred by some botanists to avoid confusion with the dicots, a nonmonophyletic group. Numerous familiar plants are eudicots, including many common food plants and ornamentals; some common and familiar eudicots include members of the sunflower family such as the common dandelion, the forget-me-not and other members of its family, buttercup and macadamia. Most leafy trees of midlatitudes belong to eudicots, with notable exceptions being magnolias and tulip trees which belong to magnoliids, Ginkgo biloba, not an angiosperm.
The name "eudicots" is used in the APG system, of 1998, APG II system, of 2003, for classification of angiosperms. It is applied to a monophyletic group, which includes most of the dicots. "Tricolpate" is a synonym for the "Eudicot" monophyletic group, the "true dicotyledons". The number of pollen grain furrows or pores helps classify the flowering plants, with eudicots having three colpi, other groups having one sulcus. Pollen apertures are any modification of the wall of the pollen grain; these modifications include thinning and pores, they serve as an exit for the pollen contents and allow shrinking and swelling of the grain caused by changes in moisture content. The elongated apertures/ furrows in the pollen grain are called colpi, along with pores, are a chief criterion for identifying the pollen classes; the eudicots can be divided into two groups: the basal eudicots and the core eudicots. Basal eudicot is an informal name for a paraphyletic group; the core eudicots are a monophyletic group.
A 2010 study suggested the core eudicots can be divided into two clades, Gunnerales and a clade called "Pentapetalae", comprising all the remaining core eudicots. The Pentapetalae can be divided into three clades: Dilleniales superrosids consisting of Saxifragales and rosids superasterids consisting of Santalales, Berberidopsidales and asteridsThis division of the eudicots is shown in the following cladogram: The following is a more detailed breakdown according to APG IV, showing within each clade and orders: clade Eudicots order Ranunculales order Proteales order Trochodendrales order Buxales clade Core eudicots order Gunnerales order Dilleniales clade Superrosids order Saxifragales clade Rosids order Vitales clade Fabids order Fabales order Rosales order Fagales order Cucurbitales order Oxalidales order Malpighiales order Celastrales order Zygophyllales clade Malvids order Geraniales order Myrtales order Crossosomatales order Picramniales order Malvales order Brassicales order Huerteales order Sapindales clade Superasterids order Berberidopsidales order Santalales order Caryophyllales clade Asterids order Cornales order Ericales clade Campanulids order Aquifoliales order Asterales order Escalloniales order Bruniales order Apiales order Dipsacales order Paracryphiales clade Lamiids order Solanales order Lamiales order Vahliales order Gentianales order Boraginales order Garryales order Metteniusales order Icacinales Eudicots at the Encyclopedia of Life Eudicots, Tree of Life Web Project Dicots Plant Life Forms
In botany, a tree is a perennial plant with an elongated stem, or trunk, supporting branches and leaves in most species. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are usable as lumber or plants above a specified height. Trees are not a taxonomic group but include a variety of plant species that have independently evolved a woody trunk and branches as a way to tower above other plants to compete for sunlight. Trees tend to be long-lived, some reaching several thousand years old. In wider definitions, the taller palms, tree ferns and bamboos are trees. Trees have been in existence for 370 million years, it is estimated. A tree has many secondary branches supported clear of the ground by the trunk; this trunk contains woody tissue for strength, vascular tissue to carry materials from one part of the tree to another. For most trees it is surrounded by a layer of bark. Below the ground, the roots spread out widely. Above ground, the branches divide into smaller shoots.
The shoots bear leaves, which capture light energy and convert it into sugars by photosynthesis, providing the food for the tree's growth and development. Trees reproduce using seeds. Flowers and fruit may be present, but some trees, such as conifers, instead have pollen cones and seed cones. Palms and bamboos produce seeds, but tree ferns produce spores instead. Trees play a significant role in moderating the climate, they remove carbon dioxide from the atmosphere and store large quantities of carbon in their tissues. Trees and forests provide a habitat for many species of plants. Tropical rainforests are among the most biodiverse habitats in the world. Trees provide shade and shelter, timber for construction, fuel for cooking and heating, fruit for food as well as having many other uses. In parts of the world, forests are shrinking as trees are cleared to increase the amount of land available for agriculture; because of their longevity and usefulness, trees have always been revered, with sacred groves in various cultures, they play a role in many of the world's mythologies.
Although "tree" is a term of common parlance, there is no universally recognised precise definition of what a tree is, either botanically or in common language. In its broadest sense, a tree is any plant with the general form of an elongated stem, or trunk, which supports the photosynthetic leaves or branches at some distance above the ground. Trees are typically defined by height, with smaller plants from 0.5 to 10 m being called shrubs, so the minimum height of a tree is only loosely defined. Large herbaceous plants such as papaya and bananas are trees in this broad sense. A applied narrower definition is that a tree has a woody trunk formed by secondary growth, meaning that the trunk thickens each year by growing outwards, in addition to the primary upwards growth from the growing tip. Under such a definition, herbaceous plants such as palms and papayas are not considered trees regardless of their height, growth form or stem girth. Certain monocots may be considered trees under a looser definition.
Aside from structural definitions, trees are defined by use. The tree growth habit is an evolutionary adaptation found in different groups of plants: by growing taller, trees are able to compete better for sunlight. Trees tend some reaching several thousand years old. Several trees are among the oldest organisms now living. Trees have modified structures such as thicker stems composed of specialised cells that add structural strength and durability, allowing them to grow taller than many other plants and to spread out their foliage, they differ from shrubs, which have a similar growth form, by growing larger and having a single main stem. The tree form has evolved separately in unrelated classes of plants in response to similar environmental challenges, making it a classic example of parallel evolution. With an estimated 60,000-100,000 species, the number of trees worldwide might total twenty-five per cent of all living plant species; the greatest number of these grow in tropical regions and many of these areas have not yet been surveyed by botanists, making tree diversity and ranges poorly known.
The majority of tree species are angiosperms. There are about 1000 species of gymnosperm trees, including conifers, cycads and gnetales. Most angiosperm trees are eudicots, the "true dicotyledons", so named because the seeds contain two cotyledons or seed leaves. There are some trees among the old lineages of flowering plants called basal angiosperms or paleodicots. Wood gives structural strength to the trunk of most types of tree; the vascular system of trees allows water and other chemicals to be di
Biological dispersal refers to both the movement of individuals from their birth site to their breeding site, as well as the movement from one breeding site to another. Dispersal is used to describe the movement of propagules such as seeds and spores. Technically, dispersal is defined as any movement; the act of dispersal involves three phases: departure, transfer and there are different fitness costs and benefits associated with each of these phases. Through moving from one habitat patch to another, the dispersal of an individual has consequences not only for individual fitness, but for population dynamics, population genetics, species distribution. Understanding dispersal and the consequences both for evolutionary strategies at a species level, for processes at an ecosystem level, requires understanding on the type of dispersal, the dispersal range of a given species, the dispersal mechanisms involved. Biological dispersal may be contrasted with geodispersal, the mixing of isolated populations following the erosion of geographic barriers to dispersal or gene flow.
Dispersal can be distinguished from animal migration, although within the population genetics literature, the terms'migration' and'dispersal' are used interchangeably. Some organisms are motile throughout their lives, but others are adapted to move or be moved at precise, limited phases of their life cycles; this is called the dispersive phase of the life cycle. The strategies of organisms' entire life cycles are predicated on the nature and circumstances of their dispersive phases. In general there are two basic types of dispersal: Density-independent dispersal Organisms have evolved adaptations for dispersal that take advantage of various forms of kinetic energy occurring in the environment; this is referred to as density independent or passive dispersal and operates on many groups of organisms that depend on animal vectors, gravity or current for dispersal. Density-dependent dispersal Density dependent or active dispersal for many animals depends on factors such as local population size, resource competition, habitat quality, habitat size.
Due to population density, dispersal may relieve pressure for resources in an ecosystem, competition for these resources may be a selection factor for dispersal mechanisms. Dispersal of organisms is a critical process for understanding both geographic isolation in evolution through gene flow and the broad patterns of current geographic distributions. A distinction is made between natal dispersal where an individual moves away from the place it was born, breeding dispersal where an individual moves away from one breeding location to breed elsewhere. In the broadest sense, dispersal occurs. There are a number of benefits to dispersal such as locating new resources, escaping unfavorable conditions, avoiding competing with siblings, avoiding breeding with related individuals which could lead to inbreeding depression. There are a number of costs associated with dispersal, which can be thought of in terms of four main currencies: energy, risk and opportunity. Energetic costs include the extra energy required to move as well as energetic investment in movement machinery.
Risks include increased injury and mortality during dispersal and the possibility of settling in an unfavorable environment. Time spent dispersing is time that cannot be spent on other activities such as growth and reproduction. Dispersal can lead to outbreeding depression if an individual is better adapted to its natal environment than the one it ends up in. In social animals a dispersing individual must find and join a new group, which can lead to loss of social rank. "Dispersal range" refers to the distance a species can move from an existing population or the parent organism. An ecosystem depends critically on the ability of individuals and populations to disperse from one habitat patch to another. Therefore, biological dispersal is critical to the stability of ecosystems. Few species are evenly or randomly distributed within or across landscapes. In general, species vary across the landscape in association with environmental features that influence their reproductive success and population persistence.
Spatial patterns in environmental features permit individuals to escape unfavorable conditions and seek out new locations. This allows the organism to "test" new environments for their suitability, provided they are within animal's geographic range. In addition, the ability of a species to disperse over a changing environment could enable a population to survive extreme conditions.. As the climate changes and predators have to adapt to survive; this poses a problem for example the Southern Rockhopper Penguins. These penguins are able to live and thrive in a variety of climates due to the penguins' phenotypic plasticity. However, they are predicted to respond by dispersal, not adaptation this time; this is explained due to slow microevolution. Penguins in the subantarctic have different foraging behavior than the subtropical waters, it would be hard to survive and keep up with the fast changing climate because these behaviors took years to shape. A dispersal barrier may mean that the dispersal
The subtropics are geographic and climate zones located between the tropics at latitude 23.5° and temperate zones north and south of the Equator. Subtropical climates are characterized by warm to hot summers and cool to mild winters with infrequent frost. Most subtropical climates fall into two basic types: humid subtropical, where rainfall is concentrated in the warmest months, dry summer climate or, where seasonal rainfall is concentrated in the cooler months. Subtropical climates can occur at high elevations within the tropics, such as in the southern end of the Mexican Plateau and in Vietnam and Taiwan. Six climate classifications use the term to help define the various temperature and precipitation regimes for the planet Earth. A great portion of the world's deserts are located within the subtropics, due to the development of the subtropical ridge. Within savanna regimes in the subtropics, a wet season is seen annually during the summer, when most of the yearly rainfall falls. Within Mediterranean climate regimes, the wet season occurs during the winter.
Areas bordering warm oceans are prone to locally heavy rainfall from tropical cyclones, which can contribute a significant percentage of the annual rainfall. Plants such as palms, mango, pistachio and avocado are grown within the subtropics; the tropics have been defined as lying between the Tropic of Cancer and Tropic of Capricorn, located at latitudes 23.45° north and south, respectively. According to the American Meteorological Society, the poleward fringe of the subtropics is located at latitudes 35° north and south, respectively. Several methods have been used to define the subtropical climate. In the Trewartha climate classification, a subtropical region should have at least eight months with a mean temperature greater than 10 °C and at least one month with a mean temperature under 18 °C. German climatologists Carl Troll and Karlheinz Paffen defined Warm temperate zones as plain and hilly lands having an average temperature of the coldest month between 2 °C and 13 °C in the Northern Hemisphere and between 6 °C and 13 °C in the Southern Hemisphere, excluding oceanic and continental climates.
According to the Troll-Paffen climate classification, there exists one large subtropical zone named the warm-temperate subtropical zone, subdivided into seven smaller areas. According to the E. Neef climate classification, the subtropical zone is divided into two parts: Rainy winters of the west sides and Eastern subtropical climate. According to the Wilhelm Lauer & Peter Frankenberg climate classification, the subtropical zone is divided into three parts: high-continental and maritime. According to the Siegmund/Frankenberg climate classification, subtropical is one of six climate zones in the world. Heating of the earth near the equator leads to large amounts of upward motion and convection along the monsoon trough or intertropical convergence zone; the upper-level divergence over the near-equatorial trough leads to air rising and moving away from the equator aloft. As the air moves towards the mid-latitudes, it cools and sinks, which leads to subsidence near the 30th parallel of both hemispheres.
This circulation leads to the formation of the subtropical ridge. Many of the world's deserts are caused by these climatological high-pressure areas, located within the subtropics; this regime is known as an arid subtropical climate, located in areas adjacent to powerful cold ocean currents. Examples of this climate are the coastal areas of southern Africa, the south of the Canary Islands and the coasts of Peru and Chile; the humid subtropical climate is located on the western side of the subtropical high. Here, unstable tropical airmasses in summer bring convective overturning and frequent tropical downpours, summer is the season of peak annual rainfall. In the winter the monsoon retreats, the drier trade winds bring more stable airmass and dry weather, frequent sunny skies. Areas that have this type of subtropical climate include Australia, Southeast Asia, parts of South America, the deep south of the United States. In areas bounded by warm ocean like the southeastern United States and East Asia, tropical cyclones can contribute to local rainfall within the subtropics.
Japan receives over half of its rainfall from typhoons. The Mediterranean climate is a subtropical climate with a wet season in winter and a dry season in the summer. Regions with this type of climate include the rim lands of the Mediterranean Sea, southwestern Australia around the Perth area, parts of the west coast of South American around Santiago, the coastal areas of western Mexico, coastal California in the United States; these climates do not see hard frosts or snow, which allows plants such as palms and citrus to flourish. As one moves toward the tropical side the slight winter cool season disappears, while at the poleward threshold of the subtropics the winters become cooler; some crops which have been traditionally farmed in tropical climates, such as mango and avocado, are cultivated in the subtropics. Pest control of the crops is less difficult than within the tropics, due to the cooler winters. Tree ferns are grown within subtropical areas within the subtropics and within topography within the tropics.
Dracaena and yucca can grow within the subtropics. Tre
A shrub or bush is a small- to medium-sized woody plant. Unlike herbaceous plants, shrubs have persistent woody, they are distinguished from trees by their multiple stems and shorter height, are under 6 m tall. Plants of many species may grow either depending on their growing conditions. Small, low shrubs less than 2 m tall, such as lavender and most small garden varieties of rose, are termed "subshrubs". An area of cultivated shrubs in a park or a garden is known as a shrubbery; when clipped as topiary, suitable species or varieties of shrubs develop 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 character. Shrubs in common garden practice are considered broad-leaved plants, though some smaller conifers such as mountain pine and common juniper are shrubby in structure. Species that grow into a shrubby habit may be either evergreen.
In botany and ecology, a shrub is more used to describe the particular physical structural or plant life-form of woody plants which are less than 8 metres high and have many stems arising at or near the base. For example, a descriptive system adopted in Australia is based on structural characteristics based on life-form, plus the height and amount of foliage cover of the tallest layer or dominant species. For shrubs 2–8 metres high the following structural forms are categorized: dense foliage cover — closed-shrub mid-dense foliage cover — open-shrub sparse foliage cover — tall shrubland sparse foliage cover — tall open shrublandFor shrubs less than 2 metres high the following structural forms are categorized: dense foliage cover — closed-heath or closed low shrubland— mid-dense foliage cover — open-heath or mid-dense low shrubland— sparse foliage cover — low shrubland sparse foliage cover — low open shrubland Those marked with * can develop into tree form