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River Barrier Hypothesis
The river barrier hypothesis is a hypothesis seeking to partially explain the high biodiversity, species diversity in the Amazon Basin, first presented by Alfred Russel Wallace in his 1852 paper ''On Monkeys of the Amazon''.Wallace, A. R. (1854). On the monkeys of the Amazon. ''Journal of Natural History'', 14(84), 451-454. It argues that the formation and movement of the Amazon River, Amazon and some of its tributaries presented a significant enough barrier to movement for wildlife populations to precipitate allopatric speciation. Facing different selection pressures and genetic drift, the divided populations diverged into separate species. There are several observable qualities that should be present if speciation has resulted from a river barrier. Divergence of species on either side of the river should increase with the size of the river, expressing weakly or not at all in the headwaters and more strongly in the wider, deeper channels further downriver. Organisms endemic to ter ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Amazon Basin
The Amazon basin is the part of South America drained by the Amazon River and its tributaries. The Amazon drainage basin covers an area of about , or about 35.5 percent of the South American continent. It is located in the countries of Bolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, and Venezuela. Most of the basin is covered by the Amazon rainforest, also known as Amazonia. With a area of dense tropical forest, this is the largest rainforest in the world. Geography The Amazon River begins in the Andes Mountains at the west of the basin with its main tributary the Marañón River and Apurimac River in Peru. The highest point in the watershed of the Amazon is the second biggest peak of Yerupajá at . With a length of about before it drains into the Atlantic Ocean, it is one of the two longest rivers in the world. A team of scientists has claimed that the Amazon is longer than the Nile, but debate about its exact length continues. The Amazon s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Landform Evolution
A landform is a natural or anthropogenic land feature on the solid surface of the Earth or other planetary body. Landforms together make up a given terrain, and their arrangement in the landscape is known as topography. Landforms include hills, mountains, canyons, and valleys, as well as shoreline features such as bays, peninsulas, and seas, including submerged features such as mid-ocean ridges, volcanoes, and the great ocean basins. Physical characteristics Landforms are categorized by characteristic physical attributes such as elevation, slope, orientation, stratification, rock exposure and soil type. Gross physical features or landforms include intuitive elements such as berms, mounds, hills, ridges, cliffs, valleys, rivers, peninsulas, volcanoes, and numerous other structural and size-scaled (e.g. ponds vs. lakes, hills vs. mountains) elements including various kinds of inland and oceanic waterbodies and sub-surface features. Mountains, hills, plateaux, and plains are the fou ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ridge Hypothesis
A ridge or a mountain ridge is a geographical feature consisting of a chain of mountains or hills that form a continuous elevated crest for an extended distance. The sides of the ridge slope away from the narrow top on either side. The lines along the crest formed by the highest points, with the terrain dropping down on either side, are called the ridgelines. Ridges are usually termed hills or mountains as well, depending on size. Smaller ridges, especially those leaving a larger ridge, are often referred to as spurs. Types There are several main types of ridges: ;Dendritic ridge: In typical dissected plateau terrain, the stream drainage valleys will leave intervening ridges. These are by far the most common ridges. These ridges usually represent slightly more erosion resistant rock, but not always – they often remain because there were more joints where the valleys formed or other chance occurrences. This type of ridge is generally somewhat random in orientation, often ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Poison Dart Frog
Poison dart frog (also known as dart-poison frog, poison frog or formerly known as poison arrow frog) is the common name of a group of frogs in the family Dendrobatidae which are native to tropical Central and South America. These species are diurnal and often have brightly colored bodies. This bright coloration is correlated with the toxicity of the species, making them aposematic. Some species of the family Dendrobatidae exhibit extremely bright coloration along with high toxicity, while others have cryptic coloration with minimal to no amount of observed toxicity. The species that have great toxicity derive this feature from their diet of ants, mites and termites. However, other species that exhibit cryptic coloration, and low to no amounts of toxicity, eat a much larger variety of prey. Many species of this family are threatened due to human infrastructure encroaching on their habitats. These amphibians are often called "dart frogs" due to the Native Americans' use of the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gene Flow
In population genetics, gene flow (also known as gene migration or geneflow and allele flow) is the transfer of genetic material from one population to another. If the rate of gene flow is high enough, then two populations will have equivalent allele frequencies and therefore can be considered a single effective population. It has been shown that it takes only "one migrant per generation" to prevent populations from diverging due to drift. Populations can diverge due to selection even when they are exchanging alleles, if the selection pressure is strong enough. Gene flow is an important mechanism for transferring genetic diversity among populations. Migrants change the distribution of genetic diversity among populations, by modifying allele frequencies (the proportion of members carrying a particular variant of a gene). High rates of gene flow can reduce the genetic differentiation between the two groups, increasing homogeneity. For this reason, gene flow has been thought to c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dendrobatid Frog, Peru, 02-02
Poison dart frog (also known as dart-poison frog, poison frog or formerly known as poison arrow frog) is the common name of a group of frogs in the family Dendrobatidae which are native to tropical Central and South America. These species are diurnal and often have brightly colored bodies. This bright coloration is correlated with the toxicity of the species, making them aposematic. Some species of the family Dendrobatidae exhibit extremely bright coloration along with high toxicity, while others have cryptic coloration with minimal to no amount of observed toxicity. The species that have great toxicity derive this feature from their diet of ants, mites and termites. However, other species that exhibit cryptic coloration, and low to no amounts of toxicity, eat a much larger variety of prey. Many species of this family are threatened due to human infrastructure encroaching on their habitats. These amphibians are often called "dart frogs" due to the Native Americans' use of thei ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Manakin
The manakins are a family, Pipridae, of small suboscine passerine birds. The group contains some 54 species distributed through the American tropics. The name is from Middle Dutch ''mannekijn'' "little man" (also the source of the different bird name '' mannikin''). Description Manakins range in size from and in weight from . Species in the genus ''Tyranneutes'' are the smallest manakins, those in the genus '' Antilophia'' are believed to be the largest (since the genus '' Schiffornis'' are no longer considered manakins). They are compact stubby birds with short tails, broad and rounded wings, and big heads. The bill is short and has a wide gap. Females and first-year males have dull green plumage; most species are sexually dichromatic in their plumage, the males being mostly black with striking colours in patches, and in some species having long, decorative tail or crown feathers or erectile throat feathers. In some species, males from two to four years old have a distinctive su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tamarin
The tamarins are squirrel-sized New World monkeys from the family Callitrichidae in the genus ''Saguinus''. They are the first offshoot in the Callitrichidae tree, and therefore are the sister group of a clade formed by the lion tamarins, Goeldi's monkeys and marmosets. Taxonomy and evolutionary history Hershkovitz (1977) recognised ten species in the genus ''Saguinus'', further divided into 33 morphotypes based on facial pelage. A later classification into two clades was based on variations in dental measurements. A taxonomic review (Rylands et al., 2016) showed the tamarins are a sister group to all other callitrichids, branching off 15–13 million years ago. Within this clade, six species groups are historically recognised, ''nigricollis'', ''mystax'', ''midas'', ''inustus'', ''bicolor'' and ''oedipus'', five of which were shown to be valid with ''Sanguinus inustus'' placed within the ''midas'' group. The review noted that the smaller-bodied ''nigricollis'' group began div ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Aripuanã River
Aripuanã River ( pt, Rio Aripuanã) is a river in the Mato Grosso and Amazonas states in north-western Brazil. It is a tributary of the Madeira River in the Amazon Basin. The town of Novo Aripuanã is located on its banks where it merges into the Madeira River. The town of Aripuanã is also on its banks, but on the upper (southern) section of the river. The Aripuanã is a clearwater river. Course In Mato Grosso to the south of the border with Amazonas the river defines the western boundary of the Igarapés do Juruena State Park, created in 2002. To the north of the Amazonas border it flows through the Aripuanã Sustainable Development Reserve, created in 2005. Further north in Amazonas the Trans-Amazonian Highway (BR-230) crosses the Aripuanã. North of the highway the river flows through the Aripuanã National Forest, a sustainable development unit created in 2016 in the last week before the provisional removal of president Dilma Rousseff. It then flows through the J ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Ji-Paraná River
The Ji-Paraná River (Machado River), sometimes spelled Jiparaná, is a river in Rondônia state in western Brazil. It is a tributary of the Madeira River in the Amazon Basin. For much of its length it runs roughly parallel with the northeastern state border of Rondônia. The city of Ji-Paraná is divided by the river. Part of the river's basin is covered by the Jacundá National Forest, a sustainable use conservation unit. Part of the basin is in the Jaru Biological Reserve, a fully protected conservation unit created in 1984. The river forms the southern boundary in Rondônia of the Campos Amazônicos National Park, a protected area created in 2006 that holds an unusual enclave of cerrado vegetation in the Amazon rainforest. See also *List of rivers of Rondônia ReferencesBrazilian Ministry of Transport River A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Madeira River
The Madeira River ( pt, Rio Madeira, link=no ) is a major waterway in South America. It is estimated to be in length, while the Madeira-Mamoré is estimated near or in length depending on the measuring party and their methods. The Madeira is the biggest tributary of the Amazon, accounting for about 15% of the water in the basin. A map from Emanuel Bowen in 1747, held by the David Rumsey Map Collection, refers to the Madeira by the pre-colonial, indigenous name Cuyari. The River of Cuyari, called by the Portuguese Madeira or the Wood River, is formed by two great rivers, which join near its mouth. It was by this River, that the Nation of Topinambes passed into the River Amazon. Climate The mean inter-annual precipitations on the great basins vary from , the entire upper Madeira basin receiving . The greatest extremes of rainfall are between . Even just below the confluence that forms it, the Madeira is one of the largest rivers of the world, with a mean inter-annual discharg ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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