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Eccentric Sand Dollar
''Dendraster excentricus'', also known as the eccentric sand dollar, sea-cake, biscuit-urchin, western sand dollar, or Pacific sand dollar, is a species of sand dollar in the family Dendrasteridae. It is a flattened, burrowing sea urchin found in the north-eastern Pacific Ocean from Alaska to Baja California. General information ''Dendraster excentricus'' is an irregular echinoid that is flattened and burrows into the sand, unlike the regular echinoids, or sea urchins. It can be found living in the Pacific Ocean from Alaska to Baja California. The range for ''Dendraster excentricus'' is larger and includes the range of the other two extant species of Dendraster: '' D. vizcainoensis'' and '' D. terminalis''. The flower pattern in this species is off-center, giving it the species name ''excentricus''. Its test (skeleton) is compared to that of a sea urchin below. Description They are colored gray, brown, black or shades of purple. Their size is variable, averaging 76 mm with ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ganges Harbour
Ganges, British Columbia is an unincorporated community on Salt Spring Island in the province of British Columbia, Canada. History Ganges Harbour, from which Ganges takes its name, was originally called Admiralty Bay but was renamed by George Henry Richards, Captain Richards in 1859 after , and indirectly after the Ganges river in South Asia. The ship was at the Pacific Station from 1857 to 1860 under the command of Captain John Fulford as flagship of Robert Lambert Baynes, Rear Admiral Robert L. Baynes. ''Ganges'' was the last sailing line-of-battle ship in foreign service. The first house on Salt Spring Island was built here in 1859 by the first group of 20 settlers that arrived on the island that summer. On 4 July 1860 the harbour was the scene of the killing of eight Heiltsuk, Bella Bella (Heiltsuk) people and the capture of three women and two boys for slaves by the Cowichan Tribes, Cowichans. A few days later, two Cowichans were beheaded, by a band from Kwakwaka'wakw, Fort ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Diatom
A diatom (Neo-Latin ''diatoma''), "a cutting through, a severance", from el, διάτομος, diátomos, "cut in half, divided equally" from el, διατέμνω, diatémno, "to cut in twain". is any member of a large group comprising several genera of algae, specifically microalgae, found in the oceans, waterways and soils of the world. Living diatoms make up a significant portion of the Earth's biomass: they generate about 20 to 50 percent of the oxygen produced on the planet each year, take in over 6.7 billion metric tons of silicon each year from the waters in which they live, and constitute nearly half of the organic material found in the oceans. The shells of dead diatoms can reach as much as a half-mile (800 m) deep on the ocean floor, and the entire Amazon basin is fertilized annually by 27 million tons of diatom shell dust transported by transatlantic winds from the African Sahara, much of it from the Bodélé Depression, which was once made up of a system of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pisaster Brevispinus
''Pisaster brevispinus'', commonly called the pink sea star, giant pink sea star, or short-spined sea star, is a species of sea star in the northeast Pacific Ocean. It was first described to science by William Stimson in 1857. The type specimen was collected on a sandy bottom, deep, near the mouth of San Francisco Bay. Description The pink sea star has five thick arms and a large central disc. It is one of the largest sea stars in the world. While typically having a diameter of , monsters up to have been found. The largest animals may weigh . The upper, arboral, surface of this star is generally pink, sometimes with shadings of gray. The radius of the arms is 2.8 to 5.0 times the radius of the central disc. The central disc contains an obvious madreporite on its upper surface. This structure filters water used by the animal. The mouth of the animal is found on the underside of the central disc. There are short, spines on the upper surface of the star. While a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Benthos
Benthos (), also known as benthon, is the community of organisms that live on, in, or near the bottom of a sea, river, lake, or stream, also known as the benthic zone.Benthos from the Census of Antarctic Marine Life website This community lives in or near marine or freshwater sedimentary environments, from s along the , out to the , and t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nektonic
Nekton or necton (from the ) refers to the actively swimming aquatic organisms in a body of water. The term was proposed by German biologist Ernst Haeckel to differentiate between the active swimmers in a body of water, and the passive organisms that were carried along by the current, the plankton. As a guideline, nektonic organisms have a high Reynolds number (greater than 1000) and planktonic organisms a low one (less than 10). However, some organisms can begin life as plankton and transition to nekton later on in life, sometimes making distinction difficult when attempting to classify certain plankton-to-nekton species as one or the other. For this reason, some biologists choose not to use this term. History The term was first proposed and used by the German biologist Ernst Haeckel in 1891 in his article ''Plankton-Studien'' where he contrasted it with plankton, the aggregate of passively floating, drifting, or somewhat motile organisms present in a body of water, primarily t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Egg Jelly
Egg jelly (extracellular layer'', ''jelly coat) is a gelatinous layer that surrounds the oocytes of many organisms and releases species-specific chemoattractants that activate and guide sperm to the oocyte. The release of chemoattractants is species dependent. For example, sperm in '' Lytechinus variegatus'', the green sea urchin, are not chemotactically attracted to the jelly or the egg. The egg jelly is located immediately surrounding the vitelline envelope and consists primarily of a network of short peptides and sulfated fucan glycoproteins. These short peptides diffuse into the surrounding area and stimulate respiration and movement of the sperm to the egg. An example of such a peptide is resact, which has been studied as the primary means of attracting and orientating sperm to the eggs in sea urchins. The sulfated fucan glycoproteins play an important role in binding to sperm receptors and triggering the acrosomal reaction. Many other functions for the egg jelly have been pr ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Genital Papilla
The genital papilla is an anatomical feature of the external genitalia of some animals. In mammals In mammals, the genital papilla is a part of female external genitalia not present in humans, which appears as a small, fleshy flab of tissue. The papilla covers the opening of the vagina In mammals, the vagina is the elastic, muscular part of the female genital tract. In humans, it extends from the vestibule to the cervix. The outer vaginal opening is normally partly covered by a thin layer of mucosal tissue called the hymen ....Laboratory Manual for General Biology 5th Edition In fish In fish, the genital papilla is a small, fleshy tube behind the anus present in some fishes, from which the sperm or eggs are released; the sex of a fish often can be determined by the shape of its papilla. References Mammal anatomy Mammal reproductive system Fish anatomy {{mammal-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gonopore
A gonopore, sometimes called a gonadopore, is a genital pore in many invertebrates. Hexapods, including insects have a single common gonopore, except mayflies, which have a pair of gonopores. More specifically, in the unmodified female it is the opening of the common oviduct, and in the male, it is the opening of the ejaculatory duct. The position of the gonopore varies considerably between groups, but is generally constant within groups, allowing its position to be used as a "segmental marker". In Malacostraca, it is on the sixth thoracic segment; in Symphyla it is on the fourth trunk segment; in arachnids, it is on the second segment of the opisthosoma. In insects and centipedes, the gonopores are close to the animal's tail, while in millipedes they are on the third body segment behind the head, near the second pair of legs. See also * Gonopod * Gonopodium Fins are distinctive anatomical features composed of bony spines or rays protruding from the body of a fish. They ar ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Sand Dollar Embryos
Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of soil or soil type; i.e., a soil containing more than 85 percent sand-sized particles by mass. The composition of sand varies, depending on the local rock sources and conditions, but the most common constituent of sand in inland continental settings and non-tropical coastal settings is silica (silicon dioxide, or SiO2), usually in the form of quartz. Calcium carbonate is the second most common type of sand, for example, aragonite, which has mostly been created, over the past 500million years, by various forms of life, like coral and shellfish. For example, it is the primary form of sand apparent in areas where reefs have dominated the ecosystem for millions of years like the Caribbean. Somewhat more rarely, sand may be composed of calc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hydrofoil
A hydrofoil is a lifting surface, or foil, that operates in water. They are similar in appearance and purpose to aerofoils used by aeroplanes. Boats that use hydrofoil technology are also simply termed hydrofoils. As a hydrofoil craft gains speed, the hydrofoils lift the boat's hull out of the water, decreasing drag and allowing greater speeds. Description The hydrofoil usually consists of a winglike structure mounted on struts below the hull, or across the keels of a catamaran in a variety of boats (see illustration). As a hydrofoil-equipped watercraft increases in speed, the hydrofoil elements below the hull(s) develop enough lift to raise the hull out of the water, which greatly reduces hull drag. This provides a corresponding increase in speed and fuel efficiency. Wider adoption of hydrofoils is prevented by the increased complexity of building and maintaining them. Hydrofoils are generally prohibitively more expensive than conventional watercraft above a certain disp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aristotle
Aristotle (; grc-gre, Ἀριστοτέλης ''Aristotélēs'', ; 384–322 BC) was a Greek philosopher and polymath during the Classical period in Ancient Greece. Taught by Plato, he was the founder of the Peripatetic school of philosophy within the Lyceum and the wider Aristotelian tradition. His writings cover many subjects including physics, biology, zoology, metaphysics, logic, ethics, aesthetics, poetry, theatre, music, rhetoric, psychology, linguistics, economics, politics, meteorology, geology, and government. Aristotle provided a complex synthesis of the various philosophies existing prior to him. It was above all from his teachings that the West inherited its intellectual lexicon, as well as problems and methods of inquiry. As a result, his philosophy has exerted a unique influence on almost every form of knowledge in the West and it continues to be a subject of contemporary philosophical discussion. Little is known about his life. Aristotle was born in th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
