Taxaceae called the yew family, is a coniferous family which includes seven genera and about 30 species of plants, or in older interpretations three genera and 7 to 12 species. They are many-branched, small shrubs; the leaves are evergreen, spirally arranged twisted at the base to appear 2-ranked. They are linear to lanceolate, have pale green or white stomatal bands on the undersides; the plants are dioecious monoecious. The male cones are 2–5 millimetres long, shed pollen in the early spring; the female cones are reduced, with just one ovuliferous scale and one seed. As the seed matures, the ovuliferous scale develops into a fleshy aril enclosing the seed; the mature aril is brightly coloured, soft and sweet, is eaten by birds which disperse the hard seed undamaged in their droppings. However, the seeds are poisonous to humans, containing the poisons taxine and taxol. Taxaceae is now included with all other conifers in the order Pinales, as DNA analysis has shown that the yews are monophyletic with the other families in the Pinales, a conclusion supported by micromorphology studies.
They were treated as distinct from other conifers by placing them in a separate order Taxales. Ernest Henry Wilson referred to Taxaceae as taxad in his book ”1916, Conifers and taxads of Japan"; some studies in the early 2000s suggested the genera Torreya and Amentotaxus were better transferred to Cephalotaxaceae, as genetic tests showed they are more related to Cephalotaxus than to Taxus. More recent studies have included, with Cephalotaxus, in a broader interpretation of Taxaceae as a single larger family. In this sense, the Taxaceae includes about 30 species; the differences suggested between Taxaceae and Cephalotaxaceae were based on the morphology of the seeds, with Taxaceae having smaller mature seeds growing to 5–8 millimetres in 6–8 months and not being enclosed by the aril. Cephalotaxaceae seeds show a longer maturation period, ranging from 18–20 months, with the mature seeds enclosed in the aril and ranging from 12–40 millimetres. A few botanists have transferred Austrotaxus to its own family, the Austrotaxaceae, suggesting it may be closer to the Podocarpaceae than to the other Taxaceae, but genetic evidence does not support this transfer.
Anderson, E. & Owens, J. N.. Analysing the reproductive biology of Taxus: should it be included in Coniferales? Acta Hort. 615: 233-234. Chase, M. W. et al.. Phylogenetics of seed plants, an analysis of nucleotide sequences from the plastid gene rbcL. Ann. Missouri Bot. Gard. 80: 528-580. Price, R. A.. Generic and familial relationships of the Taxaceae from rbcL and matK sequence comparisons. Acta Hort. 615: 235-237
Melanesia is a subregion of Oceania extending from New Guinea island in the southwestern Pacific Ocean to the Arafura Sea, eastward to Fiji. The region includes the four independent countries of Vanuatu, Solomon Islands and Papua New Guinea, as well as the French special collectivity of New Caledonia, the Indonesian region of Western New Guinea. Most of the region is in the Southern Hemisphere, with a few small northwestern islands of Western New Guinea in the Northern Hemisphere; the name Melanesia was first used by Jules Dumont d'Urville in 1832 to denote an ethnic and geographical grouping of islands whose inhabitants he thought were distinct from those of Micronesia and Polynesia. The name Melanesia, from Greek μέλας, νῆσος, etymologically means "islands of black ", in reference to the dark skin of the inhabitants; the concept among Europeans of Melanesia as a distinct region evolved over time as their expeditions mapped and explored the Pacific. Early European explorers noted the physical differences among groups of Pacific Islanders.
In 1756 Charles de Brosses theorized that there was an "old black race" in the Pacific who were conquered or defeated by the peoples of what is now called Polynesia, whom he distinguished as having lighter skin. In the first half of the nineteenth century Jean Baptiste Bory de Saint-Vincent and Jules Dumont d'Urville identified Melanesians as a distinct racial group. Over time, Europeans viewed Melanesia as a distinct cultural, rather than racial, area. Scholars and other commentators disagreed on its boundaries. In the nineteenth century Robert Codrington, a British missionary, produced a series of monographs on "the Melanesians" based on his long-time residence in the region. In works including The Melanesian Languages and The Melanesians: Studies in Their Anthropology and Folk-lore, Codrington defined Melanesia as including Vanuatu, Solomon Islands, New Caledonia, Fiji, he did not include the islands of New Guinea. Like Bory de Saint-Vincent, he excluded Australia from Melanesia, it was in these works.
Uncertainty about the delineation and definition of the region continues. The scholarly consensus now includes New Guinea within Melanesia. Ann Chowning wrote in her 1977 textbook on Melanesia that there is no general agreement among anthropologists about the geographical boundaries of Melanesia. Many apply the term only to the smaller islands, excluding New Guinea. In 1998 Paul Sillitoe wrote of Melanesia: "it is not easy to define on geographical, biological, or any other grounds, where Melanesia ends and the neighbouring regions... begins". He concludes that the region is a historical category which evolved in the nineteenth century from the discoveries made in the Pacific and has been legitimated by use and further research in the region, it covers populations that have a certain linguistic and cultural affinity – a certain ill-defined sameness, which shades off at its margins into difference. Both Sillitoe and Chowning include the island of New Guinea in the definition of Melanesia, both exclude Australia.
Most of the peoples in Melanesia have established independent countries, are administered by France or have active independence movements. Many have taken up the term'Melanesia' as a source of identity and "empowerment". Stephanie Lawson writes that the term "moved from a term of denigration to one of affirmation, providing a positive basis for contemporary subregional identity as well as a formal organisation". For instance, the author Bernard Narokobi wrote about the "Melanesian Way" as a distinct form of culture that could empower the people of this region; the concept is used in geopolitics. For instance, the Melanesian Spearhead Group preferential trade agreement is a regional trade treaty among Vanuatu, Solomon Islands, Papua New Guinea, Fiji; the people of Melanesia have a distinctive ancestry. Along with the aboriginal inhabitants of Australia, the Southern Dispersal theory indicates they emigrated from Africa between 50,000 and 100,000 years ago and dispersed along the southern edge of Asia.
The limit of this ancient migration was Sahul, the continent formed when Australia and New Guinea were united by a land bridge as a result of low sea levels. The first migration into Sahul came over 40,000 years ago. A further expansion into the eastern islands of Melanesia came much probably between 4000 B. C. and 3000 B. C. Along the north coast of New Guinea and in the islands north and east of New Guinea, the Austronesian people, who had migrated into the area somewhat more than 3,000 years ago, came into contact with these pre-existing populations of Papuan-speaking peoples. In the late 20th century, some scholars theorized a long period of interaction, which resulted in many complex changes in genetics and culture among the peoples; this Polynesian theory, however, is somewhat contradicted by the findings of a genetic study published by Temple University in 2008. It found that neither Micronesians have much genetic relation to Melanesians, it appeared that, having developed their sailing outrigger canoes, the ancestors of the Polynesians migrated from East Asia, moved through the Melanesian area on their way, kept going to eastern areas, where they settled.
They left little genetic evidence in Melanesia and "only intermixed to
Hedera called ivy, is a genus of 12–15 species of evergreen climbing or ground-creeping woody plants in the family Araliaceae, native to western and southern Europe, northwestern Africa and across central-southern Asia east to Japan and Taiwan. On level ground they remain creeping, not exceeding 5–20 cm height, but on suitable surfaces for climbing, including trees, natural rock outcrops or man-made structures such as quarry rock faces or built masonry and wooden structures, they can climb to at least 30 m above the ground. Ivies have two leaf types, with palmately lobed juvenile leaves on creeping and climbing stems and unlobed cordate adult leaves on fertile flowering stems exposed to full sun high in the crowns of trees or the tops of rock faces, from 2 m or more above ground; the juvenile and adult shoots differ, the former being slender and scrambling or climbing with small aerial roots to affix the shoot to the substrate, the latter thicker, self-supporting and without roots. The flowers are greenish-yellow with five small petals.
The fruit is a greenish-black, dark purple or yellow berry 5–10 mm diameter with one to five seeds, ripening in late winter to mid-spring. The seeds are dispersed by birds; the species differ in detail of the leaf shape and size and in the structure of the leaf trichomes, in the size and, to a lesser extent, the colour of the flowers and fruit. The chromosome number differs between species; the basic diploid number is 48, while some are tetraploid with 96, others hexaploid with 144 and octaploid with 192 chromosomes. Ivies are natives of Eurasia and North Africa but have been introduced to North America and Australia, they invade disturbed forest areas in North America. Ivy seeds are spread by birds. Ivies are of major ecological importance for their nectar and fruit production, both produced at times of the year when few other nectar or fruit sources are available; the ivy bee Colletes hederae is dependent on ivy flowers, timing its entire life cycle around ivy flowering. The fruit are eaten by a range of birds, including thrushes and woodpigeons.
The leaves are eaten by the larvae of some species of Lepidoptera such as angle shades, lesser broad-bordered yellow underwing, scalloped hazel, small angle shades, small dusty wave, swallow-tailed moth and willow beauty. A wide range of invertebrates shelter and overwinter in the dense woody tangle of ivy. Birds and small mammals nest in ivy, it serves to increase the surface complexity of woodland environments. The following species are accepted. Algeria, Tunisia. Hedera canariensis Willd. – Canaries ivy. Canary Islands. Hedera colchica K. Koch – Persian ivy. Alborz, Turkey. Hedera cypria McAllister – Cyprus ivy. Cyprus Hedera iberica Ackerfield & J. Wen – Iberian ivy. SW Iberian coasts. Hedera maderensis – Madeiran ivy. Madeira. Hedera maroccana McAllister – Moroccan ivy. Morocco. Hedera nepalensis K. Koch – Himalayan ivy. Himalaya, SW China. Hedera pastuchovii G. Woronow – Pastuchov's ivy. Caucasus, Alborz. Hedera rhombea Siebold ex Bean – Japanese ivy. Japan, Taiwan. Trichomes stellate Hedera azorica Carrière – Azores ivy.
Azores. Hedera helix L. – Common ivy. Europe, widespread. Hedera hibernica Bean – Atlantic ivy. Atlantic western Europe; the species of ivy are allopatric and related, many have on occasion been treated as varieties or subspecies of H. helix, the first species described. Several additional species have been described in the southern parts of the former Soviet Union, but are not regarded as distinct by most botanists; the only verified hybrid involving ivies is the intergeneric hybrid × Fatshedera lizei, a cross between Fatsia japonica and Hedera hibernica. This hybrid was produced once in a garden in France in 1910 and never repeated, the hybrid being maintained in cultivation by vegetative propagation. Despite the close relationship between Hedera helix and H. hibernica, no hybrids between them have yet been found. Hybridisation may however have played a part in the evolution of some species in the genus. Ivies are popular in cultivation within their native range and compatible climates elsewhere, for their evergreen foliage, attracting wildlife, for adaptable design uses in narrow planting spaces and on tall or wide walls for aesthetic addition, or to hide unsightly walls and tree stumps.
Numerous cultivars with variegated foliage and/or unusual leaf shapes have been selected for horticultural use. Much discussion has involved. In Europe, the harm is minor although there can be competition for soil nutrients and water, senescent trees supporting heavy ivy growth can be liable to windthrow damage. Harm and problems are more significant in North America, where ivy is without the natural pests and diseases that control its vigour in its native continents.
Vascular plants known as tracheophytes, form a large group of plants that are defined as those land plants that have lignified tissues for conducting water and minerals throughout the plant. They have a specialized non-lignified tissue to conduct products of photosynthesis. Vascular plants include the clubmosses, ferns and angiosperms. Scientific names for the group include Tracheophyta and Equisetopsida sensu lato; the term higher plants should be avoided as a synonym for vascular plants as it is a remnant of the abandoned concept of the great chain of being. Vascular plants are defined by three primary characteristics: Vascular plants have vascular tissues which distribute resources through the plant; this feature allows vascular plants to evolve to a larger size than non-vascular plants, which lack these specialized conducting tissues and are thereby restricted to small sizes. In vascular plants, the principal generation phase is the sporophyte, which produce spores and is diploid. By contrast, the principal generation phase in non-vascular plants is the gametophyte, which produces gametes and is haploid.
They have true roots and stems if one or more of these traits are secondarily lost in some groups. The formal definition of the division Tracheophyta encompasses both these characteristics in the Latin phrase "facies diploida xylem et phloem instructa". One possible mechanism for the presumed switch from emphasis on the haploid generation to emphasis on the diploid generation is the greater efficiency in spore dispersal with more complex diploid structures. In other words, elaboration of the spore stalk enabled the production of more spores, enabled the development of the ability to release them higher and to broadcast them farther; such developments may include more photosynthetic area for the spore-bearing structure, the ability to grow independent roots, woody structure for support, more branching. A proposed phylogeny of the vascular plants after Kenrick and Crane is as follows, with modification to the gymnosperms from Christenhusz et al. Pteridophyta from Smith et al. and lycophytes and ferns by Christenhusz et al.
This phylogeny is supported by several molecular studies. Other researchers state that taking fossils into account leads to different conclusions, for example that the ferns are not monophyletic. Water and nutrients in the form of inorganic solutes are drawn up from the soil by the roots and transported throughout the plant by the xylem. Organic compounds such as sucrose produced by photosynthesis in leaves are distributed by the phloem sieve tube elements; the xylem consists of vessels in flowering plants and tracheids in other vascular plants, which are dead hard-walled hollow cells arranged to form files of tubes that function in water transport. A tracheid cell wall contains the polymer lignin; the phloem however consists of living cells called sieve-tube members. Between the sieve-tube members are sieve plates, which have pores to allow molecules to pass through. Sieve-tube members lack such organs as nuclei or ribosomes, but cells next to them, the companion cells, function to keep the sieve-tube members alive.
The most abundant compound in all plants, as in all cellular organisms, is water which serves an important structural role and a vital role in plant metabolism. Transpiration is the main process of water movement within plant tissues. Water is transpired from the plant through its stomata to the atmosphere and replaced by soil water taken up by the roots; the movement of water out of the leaf stomata creates a transpiration pull or tension in the water column in the xylem vessels or tracheids. The pull is the result of water surface tension within the cell walls of the mesophyll cells, from the surfaces of which evaporation takes place when the stomata are open. Hydrogen bonds exist between water molecules; the draw of water upwards may be passive and can be assisted by the movement of water into the roots via osmosis. Transpiration requires little energy to be used by the plant. Transpiration assists the plant in absorbing nutrients from the soil as soluble salts. Living root cells passively absorb water in the absence of transpiration pull via osmosis creating root pressure.
It is possible for there to be no evapotranspiration and therefore no pull of water towards the shoots and leaves. This is due to high temperatures, high humidity, darkness or drought. Xylem and phloem tissues are involved in the conduction processes within plants. Sugars are conducted throughout the plant in the phloem and other nutrients through the xylem. Conduction occurs from a source to a sink for each separate nutrient. Sugars are produced in the leaves by photosynthesis and transported to the growing shoots and roots for use in growth, cellular respiration or storage. Minerals are transported to the shoots to allow cell division and growth. Fern allies Non-vascular plant “Higher plants” or “vascular plants”
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
Micronesia is a subregion of Oceania, composed of thousands of small islands in the western Pacific Ocean. It has a shared cultural history with two other island regions: Polynesia to the east and Melanesia to the south; the region is part of the Oceania ecozone. There are four main archipelagos along with numerous outlying islands. Micronesia is divided politically among several sovereign countries. One of these is the Federated States of Micronesia, called "Micronesia" for short and is not to be confused with the overall region; the Micronesia region encompasses five sovereign, independent nations—the Federated States of Micronesia, Kiribati, the Marshall Islands and Nauru—as well as three U. S. territories in the northern part: Northern Mariana Islands and Wake Island. Micronesia began to be settled several millennia ago, although there are competing theories about the origin and arrival of the first settlers; the earliest known contact with Europeans occurred in 1521. The coinage of the term "Micronesia" is attributed to Jules Dumont d'Urville's usage in 1832.
Micronesia is a region that includes 2100 islands, with a total land area of 2,700 km2, the largest of, Guam, which covers 582 km2. The total ocean area within the perimeter of the islands is 7,400,000 km2. There are four main island groups in Micronesia: the Caroline Islands the Gilbert Islands the Mariana Islands the Marshall IslandsPlus the island country of Nauru; the Caroline Islands are a scattered archipelago consisting of about 500 small coral islands, north of New Guinea and east of the Philippines. The Carolines consist of two states: the Federated States of Micronesia, consisting of 600 islands on the eastern side of the chain with Kosrae being the most eastern and Palau consisting of 250 islands on the western side; the Gilbert Islands are a chain of sixteen atolls and coral islands, arranged in an approximate north-to-south line. In a geographical sense, the equator serves as the dividing line between the northern Gilbert Islands and the southern Gilbert Islands; the Republic of Kiribati contains all of the Gilberts, as well as the island of Tarawa, the site of the country's capital.
The Mariana Islands are an arc-shaped archipelago made up by the summits of fifteen volcanic mountains. The island chain arises as a result of the western edge of the Pacific Plate moving westward and plunging downward below the Mariana plate, a region, the most volcanically active convergent plate boundary on Earth; the Marianas were politically divided in 1898, when the United States acquired title to Guam under the Treaty of Paris, 1898, which ended the Spanish–American War. Spain sold the remaining northerly islands to Germany in 1899. Germany lost all of her colonies at the end of World War I and the Northern Mariana Islands became a League of Nations Mandate, with Japan as the mandatory. After World War II, the islands were transferred into the United Nations Trust Territory System, with the United States as Trustee. In 1976, the Northern Mariana Islands and the United States entered into a covenant of political union under which commonwealth status was granted the Northern Mariana Islands and its residents received United States citizenship.
The Marshall Islands are located north of Nauru and Kiribati, east of the Federated States of Micronesia and south of the U. S. territory of Wake Island. The islands consist of 29 low-lying atolls and 5 isolated islands, comprising 1,156 individual islands and islets; the atolls and islands form two groups: the Ratak Chain and the Ralik Chain. All the islands in the chain are part of the Republic of the Marshall Islands, a presidential republic in free association with the United States. Having few natural resources, the islands' wealth is based on a service economy, as well as some fishing and agriculture. Of the 29 atolls, 24 of them are inhabited. Bikini Atoll is an atoll in the Marshall Islands. There are 23 islands in the Bikini Atoll; the islands of Bokonijien and Nam were vaporized during nuclear tests that occurred there. The islands are composed of sand; the average elevation is only about 2.1 metres above low tide level. Nauru is an oval-shaped island country in the southwestern Pacific Ocean, 42 km south of the Equator, listed as the world's smallest republic, covering just 21 km2.
With 11,347 residents, it is the second least-populated country, after Vatican City. The island is surrounded by a coral reef, exposed at low tide and dotted with pinnacles; the presence of the reef has prevented the establishment of a seaport, although channels in the reef allow small boats access to the island. A fertile coastal strip 150 to 300 m wide lies inland from the beach. Wake Island is a coral atoll with a coastline of 19 km just north of the Marshall Islands, it is an unincorporated territory of the United States. Access to the island is restricted and all activities on the island are managed by the United States Air Force; the majority of the islands in the area are part of a coral atoll. Coral atolls begin as coral reefs; when the volcano sinks back down into the sea, the coral continues to grow, keeping the reef at or above water level. One exception is Pohnpei in the Federated States of Micronesia, which still has the central volcano and coral reefs around it