Symmetry in biology
Symmetry in biology is the balanced distribution of duplicate body parts or shapes within the body of an organism. In nature and biology, symmetry is always approximate. For example, plant leaves – while considered symmetrical – match up when folded in half. Symmetry creates a class of patterns in nature, where the near-repetition of the pattern element is by reflection or rotation; the body plans of most multicellular organisms exhibit some form of symmetry, whether radial, bilateral, or spherical. A small minority, notably among the sponges, exhibit no symmetry. Symmetry was once important in animal taxonomy. Radially symmetric organisms resemble a pie where several cutting planes produce identical pieces; such an organism exhibits no right sides. They have a front and a back. Symmetry has been important in the taxonomy of animals. Most radially symmetric animals are symmetrical about an axis extending from the center of the oral surface, which contains the mouth, to the center of the opposite, end.
Radial symmetry is suitable for sessile animals such as the sea anemone, floating animals such as jellyfish, slow moving organisms such as starfish. Animals in the phyla Cnidaria and Echinodermata are radially symmetric, although many sea anemones and some corals have bilateral symmetry defined by a single structure, the siphonoglyph. Many flowers are radially actinomorphic. Identical flower parts – petals and stamens – occur at regular intervals around the axis of the flower, the female part, with the carpel and stigma. Many viruses have radial symmetries, their coats being composed of a small number of protein molecules arranged in a regular pattern to form polyhedrons, spheres, or ovoids. Most are icosahedrons. Tetramerism is a variant of radial symmetry found in jellyfish, which have four canals in an otherwise radial body plan. Pentamerism means. Among animals, only the echinoderms such as sea stars, sea urchins, sea lilies are pentamerous as adults, with five arms arranged around the mouth.
Being bilaterian animals, they develop with mirror symmetry as larvae gain pentaradial symmetry later. Flowering plants show fivefold symmetry in various fruits; this is well seen in the arrangement of the five carpels in an apple cut transversely. Hexamerism is found in the corals and sea anemones which are divided into two groups based on their symmetry; the most common corals in the subclass Hexacorallia have a hexameric body plan. Octamerism is found in corals of the subclass Octocorallia; these have polyps with octameric radial symmetry. The octopus, has bilateral symmetry, despite its eight arms. Spherical symmetry occurs in an organism if it is able to be cut into two identical halves through any cut that runs through the organism's center. Organisms which show approximate spherical symmetry include the freshwater green alga Volvox. In bilateral symmetry, only one plane, called the sagittal plane, divides an organism into mirror image halves, thus there is approximate reflection symmetry. Internal organs are however not symmetric.
Animals that are bilaterally symmetric have mirror symmetry in the sagittal plane, which divides the body vertically into left and right halves, with one of each sense organ and limb group on either side. At least 99% of animals are bilaterally symmetric, including humans, where facial symmetry influences people's judgements of attractiveness; when an organism moves in one direction, it has a front or head end. This end encounters the environment before the rest of the body as the organism moves along, so sensory organs such as eyes tend to be clustered there, it is the site for a mouth as food is encountered. A distinct head, with sense organs connected to a central nervous system, therefore tends to develop. Given a direction of travel which creates a front/back difference, gravity which creates a dorsal/ventral difference and right are unavoidably distinguished, so a bilaterally symmetric body plan is widespread and found in most animal phyla. Bilateral symmetry permits streamlining to reduce drag, on a traditional view in zoology facilitates locomotion.
However, in the Cnidaria, different symmetries exist, bilateral symmetry is not aligned with the direction of locomotion, so another mechanism such as internal transport may be needed to explain the origin of bilateral symmetry in animals. The phylum Echinodermata, which includes starfish, sea urchins and sand dollars, is unique among animals in having bilateral symmetry at the larval stage, but pentamerism as adults. Bilateral symmetry is not broken. In experiments using the fruit fly, Drosophila, in contrast to other traits, right- or left-sidedness in eye size, or eye facet number, wing-folding behavior show a lack of response. Females of some species select for symmetry, presumed by biologists to be a ma
Australia the Commonwealth of Australia, is a sovereign country comprising the mainland of the Australian continent, the island of Tasmania and numerous smaller islands. It is the world's sixth-largest country by total area; the neighbouring countries are Papua New Guinea and East Timor to the north. The population of 25 million is urbanised and concentrated on the eastern seaboard. Australia's capital is Canberra, its largest city is Sydney; the country's other major metropolitan areas are Melbourne, Brisbane and Adelaide. Australia was inhabited by indigenous Australians for about 60,000 years before the first British settlement in the late 18th century, it is documented. After the European exploration of the continent by Dutch explorers in 1606, who named it New Holland, Australia's eastern half was claimed by Great Britain in 1770 and settled through penal transportation to the colony of New South Wales from 26 January 1788, a date which became Australia's national day; the population grew in subsequent decades, by the 1850s most of the continent had been explored and an additional five self-governing crown colonies established.
On 1 January 1901, the six colonies federated. Australia has since maintained a stable liberal democratic political system that functions as a federal parliamentary constitutional monarchy, comprising six states and ten territories. Being the oldest and driest inhabited continent, with the least fertile soils, Australia has a landmass of 7,617,930 square kilometres. A megadiverse country, its size gives it a wide variety of landscapes, with deserts in the centre, tropical rainforests in the north-east and mountain ranges in the south-east. A gold rush began in Australia in the early 1850s, its population density, 2.8 inhabitants per square kilometre, remains among the lowest in the world. Australia generates its income from various sources including mining-related exports, telecommunications and manufacturing. Indigenous Australian rock art is the oldest and richest in the world, dating as far back as 60,000 years and spread across hundreds of thousands of sites. Australia is a developed country, with the world's 14th-largest economy.
It has a high-income economy, with the world's tenth-highest per capita income. It is a regional power, has the world's 13th-highest military expenditure. Australia has the world's ninth-largest immigrant population, with immigrants accounting for 26% of the population. Having the third-highest human development index and the eighth-highest ranked democracy globally, the country ranks in quality of life, education, economic freedom, civil liberties and political rights, with all its major cities faring well in global comparative livability surveys. Australia is a member of the United Nations, G20, Commonwealth of Nations, ANZUS, Organisation for Economic Co-operation and Development, World Trade Organization, Asia-Pacific Economic Cooperation, Pacific Islands Forum and the ASEAN Plus Six mechanism; the name Australia is derived from the Latin Terra Australis, a name used for a hypothetical continent in the Southern Hemisphere since ancient times. When Europeans first began visiting and mapping Australia in the 17th century, the name Terra Australis was applied to the new territories.
Until the early 19th century, Australia was best known as "New Holland", a name first applied by the Dutch explorer Abel Tasman in 1644 and subsequently anglicised. Terra Australis still saw occasional usage, such as in scientific texts; the name Australia was popularised by the explorer Matthew Flinders, who said it was "more agreeable to the ear, an assimilation to the names of the other great portions of the earth". The first time that Australia appears to have been used was in April 1817, when Governor Lachlan Macquarie acknowledged the receipt of Flinders' charts of Australia from Lord Bathurst. In December 1817, Macquarie recommended to the Colonial Office. In 1824, the Admiralty agreed that the continent should be known by that name; the first official published use of the new name came with the publication in 1830 of The Australia Directory by the Hydrographic Office. Colloquial names for Australia include "Oz" and "the Land Down Under". Other epithets include "the Great Southern Land", "the Lucky Country", "the Sunburnt Country", "the Wide Brown Land".
The latter two both derive from Dorothea Mackellar's 1908 poem "My Country". Human habitation of the Australian continent is estimated to have begun around 65,000 to 70,000 years ago, with the migration of people by land bridges and short sea-crossings from what is now Southeast Asia; these first inhabitants were the ancestors of modern Indigenous Australians. Aboriginal Australian culture is one of the oldest continual civilisations on earth. At the time of first European contact, most Indigenous Australians were hunter-gatherers with complex economies and societies. Recent archaeological finds suggest. Indigenous Australians have an oral culture with spiritual values based on reverence for the land and a belief in the Dreamtime; the Torres Strait Islanders, ethnically Melanesian, obtained their livelihood from seasonal horticulture and the resources of their reefs and seas. The northern coasts and waters of Australia were visited s
Enkianthus is a genus of shrubs or small trees in the heath family. Its native range is in Asia, as far west as the eastern Himalayas, as far south as Indochina, as far north and east as China and Japan; this genus is considered cladistically the most basal member of the Ericaceae, that is, the descendant of the common ancestor of that Ericaceae that branched earliest from the rest of that family. It is classified as the sole member of the subfamily Enkianthoideae. Twelve to 15 species are included in the genus by various authors. Species include: Several species are found in cultivation, notably E. campanulatus, E. cernuus and E. perulatus. E. cernuus f. rubens has gained the Royal Horticultural Society’s Award of Garden Merit
Calluna vulgaris is the sole species in the genus Calluna in the flowering plant family Ericaceae. It is a low-growing perennial shrub growing to 20 to 50 centimetres tall, or to 1 metre and taller, is found in Europe and Asia Minor on acidic soils in open sunny situations and in moderate shade, it is the dominant plant in most heathland and moorland in Europe, in some bog vegetation and acidic pine and oak woodland. It is tolerant of grazing and regenerates following occasional burning, is managed in nature reserves and grouse moors by sheep or cattle grazing, by light burning. Calluna was separated from the related genus Erica by Richard Anthony Salisbury, who devised the generic name Calluna from the Greek Kallyno, "beautify, sweep clean", in reference to its traditional use in besoms; the specific epithet vulgaris is Latin for'common'. Calluna is differentiated from Erica by its corolla and calyx each being in four parts instead of five. Calluna has small scale-leaves borne in opposite and decussate pairs, whereas those of Erica are larger and in whorls of 3-4, sometimes 5.
The flowers emerge in late summer. They are terminal in racemes with sepal-like bracts at the base with a superior ovary, the fruit a capsule. Unlike Erica, Calluna sometimes sports double flowers. Calluna is sometimes referred to as Summer heather to distinguish it from winter or spring flowering species of Erica. Calluna is native to Europe, the Faroe Islands, the Azores, it has been introduced into many other places worldwide with suitable climates, including North America, New Zealand and the Falkland Islands. Despised until the 19th century for its associations with the most rugged rural poverty, heather's growth in popularity may be paralleled with the vogue for alpine plants, it is a popular ornamental plant in gardens and for landscaping, in lime-free areas where it will thrive, but has defeated many a gardener on less acid soil. There are many named cultivars, selected for variation in flower colour and for different foliage colour and growing habits. Different cultivars have flower colours ranging from white, through pink and a wide range of purples, including reds.
The flowering season with different cultivars extends from late July to November in the northern hemisphere. The flowers may turn brown but still remain on the plants over winter, this can lead to interesting decorative effects. Cultivars with ornamental foliage are selected for reddish and golden leaf colour. A few forms can be silvery grey. Many of the ornamental foliage forms change colour with the onset of winter weather increasing in intensity of colour; some forms are grown for distinctive young spring foliage. Cultivars include ‘Beoley Crimson’, ‘Boskoop’, ‘Cuprea’,'Firefly',‘Long White’; the following cultivars have gained the Royal Horticultural Society's Award of Garden Merit: Heather is an important food source for various sheep and deer which can graze the tips of the plants when snow covers low-growing vegetation. Willow grouse and red grouse feed on the young seeds of this plant. Both adult and larva of the heather beetle feed on it, can cause extensive mortality in some instances.
The larvae of a number of Lepidoptera species feed on the plant, notably the small emperor moth Saturnia pavonia. Heather was used to dye wool yellow and to tan leather. With malt, heather is an ingredient in gruit, a mixture of flavourings used in the brewing of heather-beer during the Middle Ages before the use of hops. Thomas Pennant wrote in A Tour in Scotland that on the Scottish island of Islay "ale is made of the young tops of heath, mixing two thirds of that plant with one of malt, sometimes adding hops". From time immemorial heather has been used for making besoms, a practice recorded in "Buy Broom Buzzems" a song written by William Purvis from Newcastle-upon-Tyne, England. Heather honey is a valued product in moorland and heathland areas, with many beehives being moved there in late summer. Not always as valued as it is today, it was dismissed as mel improbum by Dioscurides. Heather honey has a characteristic strong taste, an unusual texture, for it is thixotropic, being a jelly until stirred, when it becomes a syrup like other honey, but sets again to a jelly.
This makes the extraction of the honey from the comb difficult, it is therefore sold as comb honey. White heather is regarded in Scotland as being lucky, a tradition brought from Balmoral to England by Queen Victoria and sprigs of it are sold as a charm and worked into bridal bouquets. Heather stalks are used by a small industry in Scotland as a raw material for sentimental jewellery; the stalks are stripped of bark, dyed in bright colours and compressed with resin. Calluna vulgaris herb has been used in the traditional Austrian medicine internally as tea for treatment of disorders of the kidneys and urinary tract; the plant was introduced to New Zealand and has become an invasive weed in some areas, notably the Tongariro National Park in the North Island and the Wilderness Reserve in the South Island, overgrowing native plants. Heather beetles have been released to stop the heather, with preliminary trials successful to date; the shoots of Calluna vulgaris contain the phenolic compounds chlorogenic acid, its 3-O-glucoside, 3-O-galactoside and 3-O-arabinoside.
Heather is seen as iconic of Scotland. When poems like
Blueberries are perennial flowering plants with blue– or purple–colored berries. They are classified in the section Cyanococcus within the genus Vaccinium. Vaccinium includes cranberries and huckleberries. Commercial "blueberries" – including both wild and cultivated blueberries – are all native to North America; the highbush blueberry varieties were introduced into Europe during the 1930s. Blueberries are prostrate shrubs that can vary in size from 10 centimeters to 4 meters in height. In commercial production of blueberries, the species with small, pea–size berries growing on low–level bushes are known as "lowbush blueberries", while the species with larger berries growing on taller cultivated bushes are known as "highbush blueberries"; the leaves can be either deciduous or evergreen, ovate to lanceolate, 1–8 cm long and 0.5–3.5 cm broad. The flowers are bell-shaped, pale pink or red, sometimes tinged greenish; the fruit is a berry 5–16 millimeters in diameter with a flared crown at the end. They are covered in a protective coating of powdery epicuticular wax, colloquially known as the "bloom".
They have a sweet taste, with variable acidity. Blueberry bushes bear fruit in the middle of the growing season: fruiting times are affected by local conditions such as altitude and latitude, so the peak of the crop, in the northern hemisphere, can vary from May to August; the genus Vaccinium has a circumpolar distribution, with species being present in North America and Asia. Many commercially sold species with English common names including "blueberry" are from North America. Many North American native species of blueberries are grown commercially in the Southern Hemisphere in Australia, New Zealand and South American nations. Several other wild shrubs of the genus Vaccinium produce eaten blue berries, such as the predominantly European Vaccinium myrtillus and other bilberries, which in many languages have a name that translates to "blueberry" in English. See the Identification section for more information. Note: habitat and range summaries are from the Flora of New Brunswick, published in 1986 by Harold R. Hinds, Plants of the Pacific Northwest coast, published in 1994 by Pojar and MacKinnon.
Some other blue-fruited species of Vaccinium: Vaccinium koreanum Vaccinium myrtillus Vaccinium uliginosum Commercially offered blueberries are from species that occur only in eastern and north-central North America. Other sections in the genus, native to other parts of the world, including the Pacific Northwest and southern United States, South America and Asia, include other wild shrubs producing similar-looking edible berries, such as huckleberries and whortleberries and bilberries; these species are sometimes sold as blueberry jam or other products. The names of blueberries in languages other than English translate as "blueberry", e.g. Scots blaeberry and Norwegian blåbær. Blaeberry, blåbær and French myrtilles refer to the European native bilberry, while bleuets refers to the North American blueberry. Russian голубика does not refer to blueberries, which are non-native and nearly unknown in Russia, but rather to their close relatives, bog bilberries. Cyanococcus blueberries can be distinguished from the nearly identical-looking bilberries by their flesh color when cut in half.
Ripe blueberries have light green flesh, while bilberries and huckleberries are red or purple throughout. Blueberries are sold fresh or are processed as individually quick frozen fruit, purée, juice, or dried or infused berries; these may be used in a variety of consumer goods, such as jellies, blueberry pies, snack foods, or as an additive to breakfast cereals. Blueberry jam is made from blueberries, sugar and fruit pectin. Blueberry sauce is a sweet sauce prepared using blueberries as a primary ingredient. Blueberry wine is made from the flesh and skin of the berry, fermented and matured. Blueberries consist of 84 % water, they contain only negligible amounts of micronutrients, with moderate levels of the essential dietary mineral manganese, vitamin C, vitamin K and dietary fiber. Nutrient contents of blueberries are a low percentage of the DV. One serving provides a low caloric value of 57 kcal per 100 g serving and glycemic load score of 6 out of 100 per day. Blueberries contain anthocyanins, other polyphenols and various phytochemicals under preliminary research for their potential role in the human body.
Most polyphenol studies have been conducted using the highbush cultivar of blueberries, while content of polyphenols and anthocyanins in lowbush blueberries exceeds values found in highbush cultivars. Blueberries may be cultivated. In North America, the most common cultivated species is V. corymbosum, the northern highbush blueberry. Hybrids of this with other Vaccinium species adapted to southern U. S. climates are known collectively as southern highbush blueberries. So-called "wild" blueberries, smaller than cultivated highbush ones, have intense color; the lowbush blueberry, V. angustifolium, is found from the Atlantic provinces westward to Quebec and southward to Michigan and West Virginia. In some areas, it produces natural
Sympetalae Rchb. Meaning “with fused petals”, is a descriptive botanical name used in the Eichler and Wettstein systems for a group in the flowering plants. In this group the flowers have a separate calyx and corolla with the petals fused, at least at the base of the corolla, a condition known as sympetaly. Prior to the phylogenic classifications of August Eichler and his successors this group corresponds to the Gamopetalae of Bentham and Hooker In Eichler's Bluthendiagramme, Sympetalae classified as Metachlamydeae, was listed as a subclass of the class Dicotyleae, in contrast to the Choripetalae. Adolf Engler and Karl Prantl listed Sympetalae as a division of the class Dicotyledoneae in their system, Die Naturlichen Pflanzenfamilien, with Sympetalae being composed of gamopetalous families Alfred Rendle Sympetalae originated from dicots, divided Sympetalae into Pentacyclicae and Tetracyclicae in accordance with the number of flower parts in each group. According to Engler and Prantl, Sympetalae includes the following orders: Diapensiales, Primulales, Ebenales, Tubiflorae, Rubiales and Campanulatae.
This group corresponds to the Asteridae in the Cronquist system and to the asterids in the APG II-system. Asteridae Asterids
In botany, stipule is a term coined by Linnaeus which refers to outgrowths borne on either side of the base of a leafstalk. A pair of stipules is considered part of the anatomy of the leaf of a typical flowering plant, although in many species the stipules are inconspicuous or absent. In some older botanical writing, the term "stipule" was used more to refer to any small leaves or leaf-parts, notably prophylls; the position of stipules on a plant varies from species to species, though they are located near the base of a leaf. Stipules are most common on dicotyledons; some monocotyledon plants only display one per leaf. A relationship exists between the anatomy of the stem node and the presence or absence of stipules: most plants with trilacunar nodes have stipules. Stipules are morphologically variable and might appear as glands, hairs, spines, or laminar structures. If a single stipule goes all the way around the stem, it is known as an ochrea; the three types of stipules according to duration are caducous and persistent.
Caducous stipules fall off before the leaf unfolds, while deciduous stipules fall off after the leaf unfolds. Persistent stipules remain attached to the plant. Stipules can be considered free lateral, interpetiolar, ochreate, bud scales, tendrillar or spiny. A stipule can be fused to the other stipule from the same node. A stipule is "adnate" if it's fused together on part of the petiole length, but the anterior is still free. A stipule is "interpetiolar" if it is located in between the petioles, as opposed to being attached to the petioles, one stipule from each leaf is fused together, so it appears that there's just one stipule between each leaf. A stipule is "intrapetiolar" if it is located in the angle that's between a petiole. In this case, the two stipules form together and appear to be one stipule. A stipule is "ochreate" if a single stipule appears to be a solid tube that goes all the way around the stem. A stipule is "foliaceous"; these are used to photosynthesize. A stipule protects leaf buds as they form.
These fall off as soon as the leaf unfolds. A stipule is considered "tendrillar" if they are long thin tendrils, are used by climbing plants. A stipule is considered "spiny" if they are pointy; these are used to deter animals. A stipule is considered to be "abaxial", "counter" or "leaf opposed" if it's located on the opposite side to where the leaf meets the stem. Stipules have various functions; some stipules may be vestigial. It is known. Sometimes stipules protect the next leaf or bud as it grows in falls off after the leaf unfolds, as with Tulip Poplars. Stipules can be used as climbing tendrils by climbing plants. Spiny stipules can be used to help protect the plant from animals. Esau, K. 1953. Plant Anatomy. Second Edition. John Wiley & Sons, Inc. New York, Sidney. 767 pp. Stipules and stipels