|
Odobenus
The walrus (''Odobenus rosmarus'') is a large pinniped marine mammal with discontinuous distribution about the North Pole in the Arctic Ocean and subarctic seas of the Northern Hemisphere. It is the only extant species in the family Odobenidae and genus ''Odobenus''. This species is subdivided into two subspecies: the Atlantic walrus (''O. r. rosmarus''), which lives in the Atlantic Ocean, and the Pacific walrus (''O. r. divergens''), which lives in the Pacific Ocean. Adult walrus are characterised by prominent tusks and whiskers, and considerable bulk: adult males in the Pacific can weigh more than and, among pinnipeds, are exceeded in size only by the two species of elephant seals. Walrus live mostly in shallow waters above the continental shelves, spending significant amounts of their lives on the sea ice looking for benthic bivalve molluscs. Walruses are relatively long-lived, social animals, and are considered to be a "keystone species" in the Arctic marine regions. The ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Odobenidae
Odobenidae is a family of pinnipeds, of which the only extant species is the walrus (''Odobenus rosmarus''). In the past, however, the group was much more diverse, and includes more than a dozen fossil genera. Taxonomy All genera, except '' Odobenus'', are extinct. *†'' Archaeodobenus'' *†'' Prototaria'' *†'' Proneotherium'' *†'' Nanodobenus'' *†'' Neotherium'' *†'' Imagotaria'' *†'' Kamtschatarctos'' *†''Pelagiarctos'' *†''Pontolis'' *†'' Pseudotaria'' *†'' Titanotaria'' *Clade Neodobenia **†'' Gomphotaria'' **Subfamily Dusignathinae ***†'' Dusignathus'' **Subfamily Odobeninae ***†'' Aivukus'' ***†''Ontocetus ''Ontocetus'' is an extinct genus of walrus, an aquatic carnivoran of the family Odobenidae, endemic to coastal regions of the southern North Sea and the southeastern coastal regions of the U.S. during the Miocene-Pleistocene. It lived from 1 ...'' ***†'' Pliopedia'' ***†'' Protodobenus'' ***†'' Valenictus'' ***'' Odobenus'' In r ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pinniped
Pinnipeds (pronounced ), commonly known as seals, are a widely range (biology), distributed and diverse clade of carnivorous, fin-footed, semiaquatic, mostly marine mammals. They comprise the extant taxon, extant families Odobenidae (whose only living member is the walrus), Otariidae (the eared seals: sea lions and fur seals), and Phocidae (the earless seals, or true seals), with 34 extant species and more than 50 extinct species described from fossils. While seals were historically thought to have descended from two ancestral lines, molecular phylogenetics, molecular evidence supports them as a monophyletic group (descended from one ancestor). Pinnipeds belong to the suborder Caniformia of the order Carnivora; their closest living relatives are musteloids (Mustelidae, weasels, Procyonidae, raccoons, skunks and red pandas), having diverged about 50 million years ago. Seals range in size from the and Baikal seal to the and southern elephant seal. Several species exhibit ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tusk
Tusks are elongated, continuously growing front teeth that protrude well beyond the mouth of certain mammal species. They are most commonly canine tooth, canine teeth, as with Narwhal, narwhals, chevrotains, musk deer, water deer, muntjac, pigs, peccary, peccaries, hippopotamuses and walruses, or, in the case of elephants, elongated incisors. Tusks share common features such as extra-oral position, growth pattern, composition and structure, and lack of contribution to ingestion. Tusks are thought to have adapted to the extra-oral environments, like dry or aquatic or arctic. In most tusked species both the males and the females have tusks although the males' are larger. Most mammals with tusks have a pair of them growing out from either side of the mouth. Tusks are generally curved and have a smooth, continuous surface. The male narwhal's straight single Helix, helical tusk, which usually grows out from the left of the mouth, is an exception to the typical features of tusks describ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Bivalvia
Bivalvia () or bivalves, in previous centuries referred to as the Lamellibranchiata and Pelecypoda, is a class (biology), class of aquatic animal, aquatic molluscs (marine and freshwater) that have laterally compressed soft bodies enclosed by a calcified exoskeleton consisting of a hinged pair of half-bivalve shell, shells known as valve (mollusc), valves. As a group, bivalves have no head and lack some typical molluscan organs such as the radula and the odontophore. Their gills have evolved into ctenidium (mollusc), ctenidia, specialised organs for feeding and breathing. Common bivalves include clams, oysters, Cockle (bivalve), cockles, mussels, scallops, and numerous other family (biology), families that live in saltwater, as well as a number of families that live in freshwater. Majority of the class are benthic filter feeders that bury themselves in sediment, where they are relatively safe from predation. Others lie on the sea floor or attach themselves to rocks or other h ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elephant Seal
Elephant seals or sea elephants are very large, oceangoing earless seals in the genus ''Mirounga''. Both species, the northern elephant seal (''M. angustirostris'') and the southern elephant seal (''M. leonina''), were hunted to the brink of extinction for lamp oil by the end of the 19th century, but their numbers have since recovered. They can weigh up to . Despite their name, elephant seals are not closely related to elephants, and the large proboscis or trunk that males of the species possess is an example of convergent evolution. The northern elephant seal, somewhat smaller than its southern relative, ranges over the Pacific coast of the U.S., Canada and Mexico. The most northerly breeding location on the Pacific Coast is at Race Rocks Marine Protected Area, at the southern tip of Vancouver Island in the Strait of Juan de Fuca. The southern elephant seal is found in the Southern Hemisphere on islands such as South Georgia and Macquarie Island, and on the coasts of New Z ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Germanic Language
The Germanic languages are a branch of the Indo-European language family spoken natively by a population of about 515 million people mainly in Europe, North America, Oceania, and Southern Africa. The most widely spoken Germanic language, English, is also the world's most widely spoken language with an estimated 2 billion speakers. All Germanic languages are derived from Proto-Germanic, spoken in Iron Age Scandinavia, Iron Age Northern Germany and along the North Sea and Baltic coasts. The West Germanic languages include the three most widely spoken Germanic languages: English with around 360–400 million native speakers; German, with over 100 million native speakers; and Dutch, with 24 million native speakers. Other West Germanic languages include Afrikaans, an offshoot of Dutch originating from the Afrikaners of South Africa, with over 7.1 million native speakers; Low German, considered a separate collection of unstandardized dialects, with roughly 4.35–7.15 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Walrus Ivory
Walrus ivory, also known as morse, comes from two modified upper canines of a walrus. The tusks grow throughout life and may, in the Pacific walrus, attain a length of one metre. Walrus teeth are commercially carved and traded; the average walrus tooth has a rounded, irregular peg shape and is approximately 5 cm in length. The tip of a walrus tusk has a tooth enamel coating which is worn away during the animal's youth. Fine longitudinal cracks, which appear as radial cracks in cross-section, originate in the cementum and penetrate the dentine. These cracks can be seen throughout the length of the tusk. Whole cross-sections of walrus tusks are generally oval with widely spaced indentations. The dentine is composed of two types: primary dentine and secondary (often called osteodentine). Primary dentine has a classical ivory appearance. Secondary dentine is marble or oatmeal-like. Carving Walrus-ivory carving and engraving has been an important folk art for people of the A ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Blubber
Blubber is a thick layer of Blood vessel, vascularized adipose tissue under the skin of all cetaceans, pinnipeds, penguins, and sirenians. It was present in many marine reptiles, such as Ichthyosauria, ichthyosaurs and plesiosaurs. Description Lipid-rich, collagen fiber-laced blubber comprises the Subcutaneous tissue, hypodermis and covers the whole body, except for parts of the appendages. It is strongly attached to the musculature and skeleton by highly organized, fan-shaped networks of tendons and ligaments, can comprise up to 50 per cent of the body mass of some marine mammals during some points in their lives, and can range from thick in dolphins and smaller whales, to more than thick in some bigger whales, such as Right whale, right and bowhead whales. However, this is not indicative of larger whales' ability to retain heat better, as the thickness of a whale's blubber does not significantly affect heat loss. More indicative of a whale's ability to retain heat is the wat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Circumpolar Peoples
Circumpolar peoples and Arctic peoples are umbrella terms for the various indigenous peoples of the Arctic region. Approximately four million people are resident in the Arctic, among which 10 percent are indigenous peoples belonging to a vast number of distinct communities. They represent a minority with the exception of Greenland of which 90 percent of its population is composed of Inuit. It is difficult to find an exact number of the indigenous peoples in the Arctic as states have a tendency to downplay the numbers. Moreover, each state has its own different methods to count its indigenous population. For instance, Russia excludes from the official status of "small peoples of the North" ( or ) every community that exceeds 50,000 people. They are therefore excluding from the definition certain numerically large indigenous communities like the Komi peoples, Karelians or Yakuts. Prehistory The earliest inhabitants of North America's central and eastern Arctic are referred to as t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Keystone Species
A keystone species is a species that has a disproportionately large effect on its natural environment relative to its abundance. The concept was introduced in 1969 by the zoologist Robert T. Paine. Keystone species play a critical role in maintaining the structure of an ecological community, affecting many other organisms in an ecosystem and helping to determine the types and numbers of various other species in the community. Without keystone species, the ecosystem would be dramatically different or cease to exist altogether. Some keystone species, such as the wolf and lion, are also apex predators. The role that a keystone species plays in its ecosystem is analogous to the role of a keystone in an arch. While the keystone is under the least pressure of any of the stones in an arch, the arch still collapses without it. Similarly, an ecosystem may experience a dramatic shift if a keystone species is removed, even though that species was a small part of the ecosystem by measur ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mollusca
Mollusca is a phylum of protostome, protostomic invertebrate animals, whose members are known as molluscs or mollusks (). Around 76,000 extant taxon, extant species of molluscs are recognized, making it the second-largest animal phylum after Arthropoda. The number of additional fossil species is estimated between 60,000 and 100,000, and the proportion of undescribed species is very high. Many taxa remain poorly studied. Molluscs are the largest marine biology, marine phylum, comprising about 23% of all the named marine organisms. They are highly diverse, not just in size and anatomical structure, but also in behaviour and habitat, as numerous groups are freshwater mollusc, freshwater and even terrestrial molluscs, terrestrial species. The phylum is typically divided into 7 or 8 taxonomy (biology), taxonomic class (biology), classes, of which two are entirely extinct. Cephalopod molluscs, such as squid, cuttlefish, and octopuses, are among the most neurobiology, neurologi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
