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Lancelet
The lancelets ( ), also known as amphioxi (: amphioxus ), consist of 32 described species of somewhat fish-like benthic filter feeding chordates in the subphylum Cephalochordata, class Leptocardii, and family Branchiostomatidae. Lancelets diverged from other chordates during or prior to the Cambrian period. A number of fossil chordates have been suggested to be closely related to lancelets, including ''Pikaia'' and ''Cathaymyrus'' from the Cambrian and ''Palaeobranchiostoma'' from the Permian, but their close relationship to lancelets has been doubted by other authors. Molecular clock analysis suggests that modern lancelets probably diversified much more recently, during the Cretaceous or Cenozoic. They are of interest to List of authors of names published under the ICZN, Zoologists as lancelets contain many organs and organ systems that are Homology (biology), homologous to those of modern fish. Therefore, they provide a number of examples of possible evolutionary exaptation. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Chordate
A chordate ( ) is a bilaterian animal belonging to the phylum Chordata ( ). All chordates possess, at some point during their larval or adult stages, five distinctive physical characteristics ( synapomorphies) that distinguish them from other taxa. These five synapomorphies are a notochord, a hollow dorsal nerve cord, an endostyle or thyroid, pharyngeal slits, and a post- anal tail. In addition to the morphological characteristics used to define chordates, analysis of genome sequences has identified two conserved signature indels (CSIs) in their proteins: cyclophilin-like protein and inner mitochondrial membrane protease ATP23, which are exclusively shared by all vertebrates, tunicates and cephalochordates. These CSIs provide molecular means to reliably distinguish chordates from all other animals. Chordates are divided into three subphyla: Vertebrata (fish, amphibians, reptiles, birds and mammals), whose notochords are replaced by a cartilaginous/ bony axia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Asymmetron
''Asymmetron'' is one of the few living genera of lancelets ( order Amphioxiformes). It is the type genus of family Branchiostomatidae. ''Asymmetron'' can grow to 60 mm. The species of this genus are found in world oceans The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian, Antarctic/Southern, and .... The genus ''Asymmetron'' currently contains only two species: *'' Asymmetron inferum'' *'' Asymmetron lucayanum'' References {{Taxonbar, from=Q9635660 Cephalochordata ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cambrian
The Cambrian ( ) is the first geological period of the Paleozoic Era, and the Phanerozoic Eon. The Cambrian lasted 51.95 million years from the end of the preceding Ediacaran period 538.8 Ma (million years ago) to the beginning of the Ordovician Period 486.85 Ma. Most of the continents lay in the southern hemisphere surrounded by the vast Panthalassa Ocean. The assembly of Gondwana during the Ediacaran and early Cambrian led to the development of new convergent plate boundaries and continental-margin arc magmatism along its margins that helped drive up global temperatures. Laurentia lay across the equator, separated from Gondwana by the opening Iapetus Ocean. The Cambrian marked a profound change in life on Earth; prior to the Period, the majority of living organisms were small, unicellular and poorly preserved. Complex, multicellular organisms gradually became more common during the Ediacaran, but it was not until the Cambrian that fossil diversity seems to rapidly ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homology (biology)
In biology, homology is similarity in anatomical structures or genes between organisms of different taxa due to shared ancestry, ''regardless'' of current functional differences. Evolutionary biology explains homologous structures as retained heredity from a common descent, common ancestor after having been subjected to adaptation (biology), adaptive modifications for different purposes as the result of natural selection. The term was first applied to biology in a non-evolutionary context by the anatomist Richard Owen in 1843. Homology was later explained by Charles Darwin's theory of evolution in 1859, but had been observed before this from Aristotle's biology onwards, and it was explicitly analysed by Pierre Belon in 1555. A common example of homologous structures is the forelimbs of vertebrates, where the bat wing development, wings of bats and origin of avian flight, birds, the arms of primates, the front flipper (anatomy), flippers of whales, and the forelegs of quadrupedalis ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fertilisation
Fertilisation or fertilization (see spelling differences), also known as generative fertilisation, syngamy and impregnation, is the fusion of gametes to give rise to a zygote and initiate its development into a new individual organism or offspring. While processes such as insemination or pollination, which happen before the fusion of gametes, are also sometimes informally referred to as fertilisation, these are technically separate processes. The cycle of fertilisation and development of new individuals is called sexual reproduction. During double fertilisation in angiosperms, the haploid male gamete combines with two haploid polar nuclei to form a triploid primary endosperm nucleus by the process of vegetative fertilisation. History In antiquity, Aristotle conceived the formation of new individuals through fusion of male and female fluids, with form and function emerging gradually, in a mode called by him as epigenetic. In 1784, Spallanzani established the need of in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gonochorism
In biology, gonochorism is a sexual system where there are two Sex, sexes and each individual organism is either male or female. The term gonochorism is usually applied in animal species, the vast majority of which are gonochoric. Gonochorism contrasts with simultaneous hermaphroditism but it may be hard to tell if a species is gonochoric or Sequential hermaphroditism, sequentially hermaphroditic e.g. parrotfish, ''Patella ferruginea''. However, in gonochoric species individuals remain either male or female throughout their lives. Species that reproduce by Thelytokous, thelytokous parthenogenesis and do not have males can still be classified as gonochoric. Terminology The term is derived from Greek language, Greek ''gone'' 'generation' + ''chorizein'' 'to separate'. The term gonochorism originally came from German ''Gonochorismus''. Gonochorism is also referred to as unisexualism or gonochory. Evolution Gonochorism has Convergent evolution, evolved independently multiple ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plankton
Plankton are the diverse collection of organisms that drift in Hydrosphere, water (or atmosphere, air) but are unable to actively propel themselves against ocean current, currents (or wind). The individual organisms constituting plankton are called plankters. In the ocean, they provide a crucial source of food to many small and large aquatic organisms, such as bivalves, fish, and baleen whales. Marine plankton include bacteria, archaea, algae, protozoa, microscopic fungi, and drifting or floating animals that inhabit the saltwater of oceans and the brackish waters of estuaries. fresh water, Freshwater plankton are similar to marine plankton, but are found in lakes and rivers. Mostly, plankton just drift where currents take them, though some, like jellyfish, swim slowly but not fast enough to generally overcome the influence of currents. Although plankton are usually thought of as inhabiting water, there are also airborne versions that live part of their lives drifting in the at ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tampa Bay
Tampa Bay is a large natural harbor and shallow estuary connected to the Gulf of Mexico on the west-central coast of Florida, comprising Hillsborough Bay, McKay Bay, Old Tampa Bay, Middle Tampa Bay, and Lower Tampa Bay. The largest freshwater inflow into the bay is the Hillsborough River, which flows into Hillsborough Bay in downtown Tampa. Many other smaller rivers and streams also flow into Tampa Bay, resulting in a large watershed area. The shores of Tampa Bay were home to the Weeden Island Culture and then the Safety Harbor culture for thousands of years. These cultures relied heavily on Tampa Bay for food, and the waters were rich enough that they were one of the few Native American cultures that did not have to farm. The Tocobaga was likely the dominant chiefdom in the area when Spanish explorers arrived in the early 1500s, but there were likely smaller chiefdoms on the eastern side of the bay which were not well documented. The indigenous population had been decimat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maghreb
The Maghreb (; ), also known as the Arab Maghreb () and Northwest Africa, is the western part of the Arab world. The region comprises western and central North Africa, including Algeria, Libya, Mauritania, Morocco, and Tunisia. The Maghreb also includes the territorial dispute, disputed territory of Western Sahara. As of 2018, the region had a population of over 100 million people. The Maghreb is usually defined as encompassing much of the northern part of Africa, including a large portion of the Sahara Desert, but excluding Egypt and the Sudan, which are considered to be located in the Mashriq — the eastern part of the Arab world. The traditional definition of the Maghreb — which restricted its scope to the Atlas Mountains and the coastal plains of Morocco, Algeria, Tunisia and Libya — was expanded in modern times to include Mauritania and the disputed territory of Western Sahara. During the era of al-Andalus on the Iberian Peninsula (711–1492), the Maghreb's inhabita ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Continental Shelf
A continental shelf is a portion of a continent that is submerged under an area of relatively shallow water, known as a shelf sea. Much of these shelves were exposed by drops in sea level during glacial periods. The shelf surrounding an island is known as an "''insular shelf''." The continental margin, between the continental shelf and the abyssal plain, comprises a steep continental slope, surrounded by the flatter continental rise, in which sediment from the continent above cascades down the slope and accumulates as a pile of sediment at the base of the slope. Extending as far as 500 km (310 mi) from the slope, it consists of thick sediments deposited by turbidity currents from the shelf and slope. The continental rise's gradient is intermediate between the gradients of the slope and the shelf. Under the United Nations Convention on the Law of the Sea, the name continental shelf was given a legal definition as the stretch of the seabed adjacent to the shores ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Mississippi Sound
The Mississippi Sound is a sound along the Gulf Coast of the United States. It runs east-west along the southern coasts of Mississippi and Alabama, from the mouth of the Pearl River at the Mississippi-Louisiana state border to the Dauphin Island Bridge, a distance of about . The sound is separated from the Gulf on its southern side by the Mississippi–Alabama barrier islands: Cat, Ship, Horn, West Petit Bois (formerly known as Sand Island), Petit Bois, and Dauphin. Ship, Horn, West Petit Bois and Petit Bois Islands are part of the National Park Service's Gulf Islands National Seashore. Those islands separate the sound from the Gulf of Mexico. The sediment of the islands was created partly by the ancient Mississippi River when the St. Bernard Lobe of the Mississippi Delta was active over two thousand years ago. The expansion of the St. Bernard subdelta slowly isolated the Mississippi Sound from ocean dynamics of the open Gulf of Mexico. Traditional seafood harvests, part ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution
Evolution is the change in the heritable Phenotypic trait, characteristics of biological populations over successive generations. It occurs when evolutionary processes such as natural selection and genetic drift act on genetic variation, resulting in certain characteristics becoming more or less common within a population over successive generations. The process of evolution has given rise to biodiversity at every level of biological organisation. The scientific theory of evolution by natural selection was conceived independently by two British naturalists, Charles Darwin and Alfred Russel Wallace, in the mid-19th century as an explanation for why organisms are adapted to their physical and biological environments. The theory was first set out in detail in Darwin's book ''On the Origin of Species''. Evolution by natural selection is established by observable facts about living organisms: (1) more offspring are often produced than can possibly survive; (2) phenotypic variatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
