|
Common Periwinkle
The common periwinkle or winkle (''Littorina littorea'') is a species of small edible whelk or sea snail, a marine gastropod mollusc that has gills and an operculum, and is classified within the family Littorinidae, the periwinkles. This is a robust intertidal species with a dark and sometimes banded shell. It is native to the rocky shores of the northeastern, and introduced to the northwestern, Atlantic Ocean. Description The shell is broadly ovate, thick, and sharply pointed except when eroded. The shell contains six to seven whorls with some fine threads and wrinkles. The color varies from grayish to gray-brown, often with dark spiral bands. The base of the columella is white. The shell lacks an umbilicus. The white outer lip is sometimes checkered with brown patches. The inside of the shell is chocolate brown. The width of the shell ranges from at maturity, with an average length of . Shell height can reach up to , [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sweden
Sweden, formally the Kingdom of Sweden, is a Nordic countries, Nordic country located on the Scandinavian Peninsula in Northern Europe. It borders Norway to the west and north, and Finland to the east. At , Sweden is the largest Nordic country by both area and population, and is the List of European countries by area, fifth-largest country in Europe. Its capital and largest city is Stockholm. Sweden has a population of 10.6 million, and a low population density of ; 88% of Swedes reside in urban areas. They are mostly in the central and southern half of the country. Sweden's urban areas together cover 1.5% of its land area. Sweden has a diverse Climate of Sweden, climate owing to the length of the country, which ranges from 55th parallel north, 55°N to 69th parallel north, 69°N. Sweden has been inhabited since Prehistoric Sweden, prehistoric times around 12,000 BC. The inhabitants emerged as the Geats () and Swedes (tribe), Swedes (), who formed part of the sea-faring peopl ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Littorina Littorea 02
''Littorina'' is a genus of small sea snails, marine gastropod molluscs in the family Littorinidae, the winkles or periwinkles.WoRMS (2011). Littorina Férussac, 1822. Accessed through: World Register of Marine Species at http://www.marinespecies.org/aphia.php?p=taxdetails&id=138135 on 2011-04-15 These small snails live in the tidal zone of rocky shores. Overview In Europe there are about nine species in this genus, one of which is the rough periwinkle, ''Littorina saxatilis'' (Olivi, 1792). Another closely related (supposed) species ''Littorina tenebrosa'' (Montagu 1802) was thought to be distinct because of its different ecological requirements, but current studies have shown that it is not at all clear whether the two are indeed separate species or whether ''L. tenebrosa'' is perhaps merely an ecotype (an ecological form) of ''L. saxatilis''.Gosling, E.M. (2002). ''The periwinkle as a model in biodiversity studies: a geneticist's view.'' in Marine Biodiversity in Ireland ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blackwater Estuary
The Blackwater Estuary is the estuary of the River Blackwater between Maldon and West Mersea in Essex. It is a 5,538 hectare biological Site of Special Scientific Interest (SSSI). An area of 4,395 hectares is also designated a Ramsar Wetland of International Importance, and a Special Protection Area 1,099 hectares is a National Nature Reserve. Tollesbury Wick and part of Abbotts Hall Farm, both nature reserve managed by the Essex Wildlife Trust, are in the SSSI. Oysters have been harvested from the estuary for more than a thousand years and there are remains of fish weirs from the Anglo-Saxon era. At the head of the estuary is the town of Maldon, which is a centre of salt production. The other major settlement is the town West Mersea, of Mersea Island, on the northern seaward side. Numerous other villages are on its banks. Within the estuary is Northey Island which was the location for the first experiments in the UK in 'managed retreat', i.e. creating saltmarsh by s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plymouth Sound
Plymouth Sound, or locally just The Sound, is a deep inlet or sound in the English Channel near Plymouth in England. Description Its southwest and southeast corners are Penlee Point in Cornwall and Wembury Point in Devon, a distance of about 3 nautical miles (6 km). Its northern limit is Plymouth Hoe giving a north–south distance of nearly 3 nautical miles (6 km). The Sound has three water entrances. The marine entrance is from the English Channel to the south, with a deep-water channel to the west of the Plymouth Breakwater. There are two freshwater inlets: one, from the northwest, is from the River Tamar via the Hamoaze and Devonport Dockyard, the largest naval dockyard in western Europe. The other, at northeast, is from the River Plym disgorging into its narrow estuary, Cattewater harbour between Mount Batten and the Royal Citadel. In the centre of the Sound, midway between Bovisand Bay and Cawsand Bay, is Plymouth Breakwater, which creates a harbou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Larva
A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase of their life cycle. A larva's appearance is generally very different from the adult form (''e.g.'' caterpillars and butterflies) including different unique structures and organs that do not occur in the adult form. Their diet may also be considerably different. In the case of smaller primitive arachnids, the larval stage differs by having three instead of four pairs of legs. Larvae are frequently adapted to different environments than adults. For example, some larvae such as tadpoles live almost exclusively in aquatic environments but can live outside water as adult frogs. By living in a distinct environment, larvae may be given shelter from predators and reduce competition for resources with the adult population. Animals in the lar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Corneous
Corneous is a biological and medical term meaning horny, in other words made out of a substance similar to that of horns and hooves in some mammals. The word is generally used to describe natural or pathological anatomical structures made out of a hard layer of protein. In mammals this protein would usually be keratin. The word corneous is also often used to describe the operculum of a snail, a gastropod mollusc. Not all gastropods have opercula, but in the great majority of those that do have one, the operculum is corneous. (However in several genera within a few families including the marine Naticidae and the terrestrial Pomatiidae, the operculum is primarily calcareous, in other words mostly made of calcium carbonate Calcium carbonate is a chemical compound with the chemical formula . It is a common substance found in Rock (geology), rocks as the minerals calcite and aragonite, most notably in chalk and limestone, eggshells, gastropod shells, shellfish skel ....) Co ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg (biology)
An egg is an organic vessel grown by an animal to carry a possibly fertilization, fertilized egg cell (a zygote) and to egg incubation, incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the animal hatches. Most arthropods, vertebrates (excluding live-bearing mammals), and Mollusca, mollusks lay eggs, although some, such as scorpions, do not. Reptile eggs, bird eggs, and monotreme eggs are laid out of water and are surrounded by a protective eggshell, shell, either flexible or inflexible. Eggs laid on land or in nests are usually kept within a warm and favorable temperature range while the embryo grows. When the embryo is adequately developed it hatches, i.e., breaks out of the egg's shell. Some embryos have a temporary egg tooth they use to crack, pip, or break the eggshell or covering. The largest recorded egg is from a whale shark and was in size. Whale shark eggs typically hatch within the m ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Oviparous
Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings known as hatchlings with little or no embryonic development within the mother. This is the reproductive method used by most animal species, as opposed to viviparous animals that develop the embryos internally and metabolically dependent on the maternal circulation, until the mother gives birth to live juveniles. Ovoviviparity is a special form of oviparity where the eggs are retained inside the mother (but still metabolically independent), and are carried internally until they hatch and eventually emerge outside as well-developed juveniles similar to viviparous animals. Modes of reproduction The traditional modes of reproduction include oviparity, taken to be the ancestral condition, traditionally where either unfertilised oocytes or ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolutionary Biology
Evolutionary biology is the subfield of biology that studies the evolutionary processes such as natural selection, common descent, and speciation that produced the diversity of life on Earth. In the 1930s, the discipline of evolutionary biology emerged through what Julian Huxley called the Modern synthesis (20th century), modern synthesis of understanding, from previously unrelated fields of biological research, such as genetics and ecology, systematics, and paleontology. The investigational range of current research has widened to encompass the genetic architecture of adaptation, molecular evolution, and the different forces that contribute to evolution, such as sexual selection, genetic drift, and biogeography. The newer field of evolutionary developmental biology ("evo-devo") investigates how embryogenesis is controlled, thus yielding a wider synthesis that integrates developmental biology with the fields of study covered by the earlier evolutionary synthesis. Subfields ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Speciation
Speciation is the evolutionary process by which populations evolve to become distinct species. The biologist Orator F. Cook coined the term in 1906 for cladogenesis, the splitting of lineages, as opposed to anagenesis, phyletic evolution within lineages. Charles Darwin was the first to describe the role of natural selection in speciation in his 1859 book ''On the Origin of Species''. He also identified sexual selection as a likely mechanism, but found it problematic. There are four geographic modes of speciation in nature, based on the extent to which speciating populations are isolated from one another: allopatric speciation, allopatric, peripatric speciation, peripatric, parapatric speciation, parapatric, and sympatric speciation, sympatric. Whether genetic drift is a minor or major contributor to speciation is the subject of much ongoing discussion. Rapid sympatric speciation can take place through polyploidy, such as by doubling of chromosome number; the result is progeny wh ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phenotype
In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological properties, and its behavior. An organism's phenotype results from two basic factors: the expression of an organism's genetic code (its genotype) and the influence of environmental factors. Both factors may interact, further affecting the phenotype. When two or more clearly different phenotypes exist in the same population of a species, the species is called polymorphic. A well-documented example of polymorphism is Labrador Retriever coloring; while the coat color depends on many genes, it is clearly seen in the environment as yellow, black, and brown. Richard Dawkins in 1978 and again in his 1982 book '' The Extended Phenotype'' suggested that one can regard bird nests and other built structures such as caddisfly larva cases and beaver dams ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
