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Insular Dwarfism
Insular dwarfism, a form of phyletic dwarfism, is the process and condition of large animals evolving or having a reduced body size when their population's range is limited to a small environment, primarily islands. This natural process is distinct from the intentional creation of dwarf breeds, called dwarfing. This process has occurred many times throughout evolutionary history, with examples including dinosaurs, like '' Europasaurus'' and ''Magyarosaurus dacus'', and modern animals such as elephants and their relatives. This process, and other "island genetics" artifacts, can occur not only on islands, but also in other situations where an ecosystem is isolated from external resources and breeding. This can include caves, desert oases, isolated valleys and isolated mountains ("sky islands"). Insular dwarfism is one aspect of the more general "island effect" or "Foster's rule", which posits that when mainland animals colonize islands, small species tend to evolve larger bodies ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Elephas Falconeri 4
''Elephas'' is one of two surviving genera in the family of elephants, Elephantidae, with one surviving species, the Asian elephant, ''Elephas maximus''. Several extinct species have been identified as belonging to the genus, extending back to the Pliocene era. While formerly assigned to this genus, ''Elephas recki'', the straight-tusked elephant ''E. antiquus'' and the dwarf elephants '' E. falconeri'' and '' E. cypriotes'' are now placed in the separate genus ''Palaeoloxodon''. The genus is very closely related to the genus ''Mammuthus''. Taxonomy The scientific name ''Elephas'' was proposed by Carl Linnaeus in 1758 who described the genus and an elephant from Ceylon. The genus is assigned to the proboscidean family Elephantidae and is made up of one living and seven extinct species:Maglio, V.J. (1973). "Origin and evolution of the Elephantidae". ''Transactions of the American Philosophical Society, Philadelphia Volume 63''. American Philosophical Society, Philadelphia, pp. 14 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Morphology (biology)
Morphology is a branch of biology dealing with the study of the form and structure of organisms and their specific structural features. This includes aspects of the outward appearance (shape, structure, colour, pattern, size), i.e. external morphology (or eidonomy), as well as the form and structure of the internal parts like bones and organs, i.e. internal morphology (or anatomy). This is in contrast to physiology, which deals primarily with function. Morphology is a branch of life science dealing with the study of gross structure of an organism or taxon and its component parts. History The etymology of the word "morphology" is from the Ancient Greek (), meaning "form", and (), meaning "word, study, research". While the concept of form in biology, opposed to function, dates back to Aristotle (see Aristotle's biology), the field of morphology was developed by Johann Wolfgang von Goethe (1790) and independently by the German anatomist and physiologist Karl Friedrich Burdach ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Stegodont
''Stegodon'' ("roofed tooth" from the Ancient Greek words , , 'to cover', + , , 'tooth' because of the distinctive ridges on the animal's molars) is an extinct genus of proboscidean, related to elephants. It was originally assigned to the family Elephantidae along with modern elephants but is now placed in the extinct family Stegodontidae. Like elephants, ''Stegodon'' had teeth with plate-like lophs that are different from those of more primitive proboscideans like gomphotheres and mastodons. The oldest fossils of the genus are found in Late Miocene strata in Asia, likely originating from the more archaic ''Stegolophodon,'' shortly afterwards migrating into Africa. While the genus became extinct in Africa during the Pliocene, ''Stegodon'' remained widespread in Asia until the end of the Pleistocene. Morphology Size Some species of ''Stegodon'' were amongst the largest proboscideans. ''S. zdanskyi'' is known from an old male (50-plus years old) from the Yellow River that is tall ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Homo Floresiensis
''Homo floresiensis'' also known as "Flores Man"; nicknamed "Hobbit") is an extinct species of small archaic human that inhabited the island of Flores, Indonesia, until the arrival of modern humans about 50,000 years ago. The remains of an individual who would have stood about in height were discovered in 2003 at Liang Bua on the island of Flores in Indonesia. Partial skeletons of at least nine individuals have been recovered, including one complete skull, referred to as "LB1". These remains have been the subject of intense research to determine whether they were diseased modern humans or a separate species; a 2017 study concludes by phylogenetic analysis that ''H. floresiensis'' is an early species of ''Homo'', a sister species of ''Homo habilis''. This hominin was at first considered remarkable for its survival until relatively recent times, initially thought to be only 12,000 years ago. However, more extensive stratigraphic and chronological work has pushed the dating of ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Papagomys
''Papagomys'' is a genus of very large rats in the tribe Rattini of the subfamily Murinae. It contains two species, which are known only from the Indonesian island of Flores:Musser and Carleton, 2005; Zijlstra et al., 2008; Aplin and Helgen, 2010 *Flores giant rat ''Papagomys armandvillei'' *Verhoeven's giant tree rat Verhoeven's giant tree rat (''Papagomys theodorverhoeveni'') is an extinct rat of subfamily Murinae that lived on Flores in Indonesia Indonesia, officially the Republic of Indonesia, is a country in Southeast Asia and Oceania between the ... ''Papagomys theodorverhoeveni'' (extinct) References Literature cited *Aplin, K.P. and Helgen, K.M. 2010. Quaternary murid rodents of Timor. Part I: New material of ''Coryphomys buehleri'' Schaub, 1937, and description of a second species of the genus. Bulletin of the American Museum of Natural History 341:1–80. * *Zijlstra, J.S., Hoek Ostende, L.W. van den and Due, R.A. 2008Verhoeven's giant rat of Flores (''Pap ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pigeon
Columbidae () is a bird family consisting of doves and pigeons. It is the only family in the order Columbiformes. These are stout-bodied birds with short necks and short slender bills that in some species feature fleshy ceres. They primarily feed on seeds, fruits, and plants. The family occurs worldwide, but the greatest variety is in the Indomalayan and Australasian realms. The family contains 344 species divided into 50 genera. Thirteen of the species are extinct. In English, the smaller species tend to be called "doves" and the larger ones "pigeons". However, the distinction is not consistent, and does not exist in most other languages. Historically, the common names for these birds involve a great deal of variation between the terms. The bird most commonly referred to as just "pigeon" is the domestic pigeon, which is common in many cities as the feral pigeon. Doves and pigeons build relatively flimsy nests, often using sticks and other debris, which may be placed on bra ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dodo
The dodo (''Raphus cucullatus'') is an extinct flightless bird that was endemic to the island of Mauritius, which is east of Madagascar in the Indian Ocean. The dodo's closest genetic relative was the also-extinct Rodrigues solitaire. The two formed the subfamily Raphinae, a clade of extinct flightless birds that were a part of the family which includes pigeons and doves. The closest living relative of the dodo is the Nicobar pigeon. A white dodo was once thought to have existed on the nearby island of Réunion, but it is now believed that this assumption was merely confusion based on the also-extinct Réunion ibis and paintings of white dodos. Subfossil remains show the dodo was about tall and may have weighed in the wild. The dodo's appearance in life is evidenced only by drawings, paintings, and written accounts from the 17th century. Since these portraits vary considerably, and since only some of the illustrations are known to have been drawn from live specimens, ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Thermoregulation
Thermoregulation is the ability of an organism to keep its body temperature within certain boundaries, even when the surrounding temperature is very different. A thermoconforming organism, by contrast, simply adopts the surrounding temperature as its own body temperature, thus avoiding the need for internal thermoregulation. The internal thermoregulation process is one aspect of homeostasis: a state of dynamic stability in an organism's internal conditions, maintained far from thermal equilibrium with its environment (the study of such processes in zoology has been called physiological ecology). If the body is unable to maintain a normal temperature and it increases significantly above normal, a condition known as hyperthermia occurs. Humans may also experience lethal hyperthermia when the wet bulb temperature is sustained above for six hours. The opposite condition, when body temperature decreases below normal levels, is known as hypothermia. It results when the homeostatic c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Generation Time
In population biology and demography, generation time is the average time between two consecutive generations in the lineages of a population. In human populations, generation time typically ranges from 22 to 33 years. Historians sometimes use this to date events, by converting generations into years to obtain rough estimates of time. Definitions and corresponding formulas The existing definitions of generation time fall into two categories: those that treat generation time as a renewal time of the population, and those that focus on the distance between individuals of one generation and the next. Below are the three most commonly used definitions: The time it takes for the population to grow by a factor of its net reproductive rate The net reproductive rate \textstyle R_0 is the number of offspring an individual is expected to produce during its lifetime (a net reproductive rate of 1 means that the population is at its demographic equilibrium). This definition envisions the ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gestation Period
In mammals, pregnancy is the period of reproduction during which a female carries one or more live offspring from implantation in the uterus through gestation. It begins when a fertilized zygote implants in the female's uterus, and ends once it leaves the uterus. Fertilization and implantation During copulation, the male inseminates the female. The spermatozoon fertilizes an ovum or various ova in the uterus or fallopian tubes, and this results in one or multiple zygotes. Sometimes, a zygote can be created by humans outside of the animal's body in the artificial process of in-vitro fertilization. After fertilization, the newly formed zygote then begins to divide through mitosis, forming an embryo, which implants in the female's endometrium. At this time, the embryo usually consists of 50 cells. Development After implantation A blastocele is a small cavity on the center of the embryo, and the developing embryonary cells will grow around it. Then, a flat layer cell forms on ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Evolution (journal)
''Evolution: International Journal of Organic Evolution'', is a monthly scientific journal that publishes significant new results of empirical or theoretical investigations concerning facts, processes, mechanics, or concepts of evolutionary phenomena and events. ''Evolution'' is published by the Society for the Study of Evolution. Its current editor-in-chief is Tracey Chapman. Former editors-in-chief The journal was founded soon after the Second World War. Its first editor was the evolutionary geneticist Ernst Mayr. * Ruth Geyer Shaw, July 2013 – 2017 * Daphne Fairbairn Daphne (; ; el, Δάφνη, , ), a minor figure in Greek mythology, is a naiad, a variety of female nymph associated with fountains, wells, springs, streams, brooks and other bodies of freshwater. There are several versions of the myth in whi ..., 2010- June 2013 References External linksOfficial website Evolutionary biology journals Publications established in 1947 Academic journals published by l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
