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SPECIES RADIATION.   Term Paper ID:26317 Click to get this paper

Essay Subject: Causes & effects of evolutionary abundance in certain geographical areas in certain eras. Specialization, adaptation, variations, theories.... More...

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Paper Abstract: Causes & effects of evolutionary abundance in certain geographical areas in certain eras. Specialization, adaptation, variations, theories. Paper Introduction: Evolution is a process of change and development as organisms adapt to their environment and to changing circumstance through time. A variety of mechanisms have been identified as being involved in the process of evolution. This process does not take place in a steady and even manner, and eras of massive change have been identified in the fossil record during which a process called radiation has taken place, producing many new species and so many changes in a given population. Such a sudden and massive expansion of species has been identified in different parts of the world, such as the rapid growth in diversity of cichild fish in Lake Victoria in eastern Africa, where more than 500 species have evolved over the last 12,000 years. Scientists have sought to discover why such radiations occur. Darwin explained the process of specialization and related Text of the Paper: The entire text of the paper is shown below. However, the text is somewhat scrambled. We want to give you as much information as we possibly can about our papers and essays, but we cannot give them away for free. In the text below you will find that while disordered, many of the phrases are essentially intact. From this text you will be able to get a solid sense of the writing style, the concepts addressed, and the sources used in the research paper. A species is ableto adapt when it has sufficient genetic variance to have what amount to alot of "choices" so that some adaptations will be successful and will bepassed on to subsequent generations. Major periods of radiation have puzzled researchers, such as theCambrian explosion or the Ordovician radiation of marine species around 45 million years ago. . Species radiation has been observed in different species in differentenvironments on earth, and attempts have been made to replicate radiationto show what forces are at work in the process. Theincrease in mountain building was largely due to the closing of the lapetusSea, causing continents to collide, at which time mountains were pushed up,including those that would evolve into the Appalachians. Scientists have sought to discover why suchradiations occur. The relative isolation of areas such as Australia are one reason forthe adaptive radiations that take place there, but such radiations takeplace in large and small environments, isolated and otherwise. However, research with the island lizards shows that such factors do notalways lead to disparate outcomes. Darwin explained the idea ofspecialization by examining the facts as observed and developing theoriesto explain those facts. At a meeting in 1997 of the EuropeanSociety for Evolutionary Biology, researchers described how microbesliving in a vial full of nutrient broth formed a rainforest in miniaturewhile quickly diversifying into a range of new forms. This still raised the question of why, and Miller believes thaterosion from mountains may pump nutrients into the sea to fuel booms inmarine plankton and to increase the food supply for creatures higher up thefood chain. This process does not take place in a steady and even manner,and eras of massive change have been identified in the fossil record duringwhich a process called radiation has taken place, producing many newspecies and so many changes in a given population. . The reason for this is that certain factorswhich cause taxa to respond to similar selective factors in different wayscombine with unique historical events and subtle environmental differences. This was accomplished by Paul Rainey of OxfordUniversity and his colleague Michael Travisano. Eldredge asks how it is possible to test this issue, but tests of thegeneral principle have been devised. (1985). Adaptive radiation can also be found among plant species, and withinmost large plant families there has been radiation into trees, shrubs,lianas, and various types of herbs, including aquatic species. Cracraft and Eldredge once described four basicmacroevolutionary patterns--trends, adaptive radiation, arrested evolution,and steady state. On the origin of species. An extraordinary amount of modification implies an unusually large and long-continued amount of variability, which has continually been accumulated by natural selection for the benefit of the species (Darwin, 1964, 153). Thisis counter to the theory of historical contingency, which proposes thatunique events in the past have a large influence on subsequent evolutionand that repeated occurrences of an evolutionary event would result inradically different outcomes. The result is that organisms with more food are more likely tothrive and diversify into different species and genera ("Origins ofdiversity," 1995, 28). Ehrlich, P.R., Holm, R.W., & Parnell, D.R. Losos, J.B., Jackman, T.R., Larson, A., de Queiroz, K., & Rodriguez-Schettino, L. It wasnoted that the recurring evolution of ecologically and morphologicallysimilar species suggested that adaptation rather than constraint is thereason for the predictable evolutionary responses shown in this experiment(Losos, Jackman, Larson, de Queiroz, and Rodriguez-Schettino, 1998, 2115-2117). Evolution is a process of change and development as organisms adaptto their environment and to changing circumstance through time. Discover Magazine 16, 28.----------------------- 9 (1974). (1998, March 27). Darwin explained the process of specialization and related it toadaptation. Adaptive radiations are described as rathergeneral sorts of phenomena which can be broken down into certain trends andsome "status quo" patterns (Eldredge, 1985, 176-177). In addition, theseplants support many times more species of bird, insect, and mammal than canbe found on an equivalent piece of temperate land. Such variations as are produced through these processes occur all thetime, but the explosions in species that occur from time to time must havesome other force causing the process of selection to take place at a higherrate. Morell, V. "Origins of diversity" (1995, June 1). Such a sudden andmassive expansion of species has been identified in different parts of theworld, such as the rapid growth in diversity of cichild fish in LakeVictoria in eastern Africa, where more than 5 species have evolved overthe last 12, years. "Biodiversity in a vial of sugarwater." Science. One reason for this belief is that faunasand floras that have evolved in similar environment often show moredifferences than similarities. New York: Simon and Schuster. Inaddition, poisonous snakes of the family Elapidae (cobras and theirrelatives) also show adaptive radiation in Australia so that they haveproduced forms that superficially resemble the vipers or pit vipers. Naturalistshave long been fascinated by the diversity found in the Amazon region. Theadaptation can be singular and minor or can involve the entire organism asit changes from one function or environment to another. Cambridge,Massachusetts: Harvard University Press. This was seen as arepresentation of certain macroevolutionary events and enabled evolutionarybiologists to study such miniature adaptive radiations for clues to whatdrives them in nature. References Darwin, C. The region has anabsence of placental mammals, so marsupials developed grazing forms(certain kangaroos), burrowing forms (marsupial moles), forms resemblingfree and flying squirrels (phalangers), rabbit-like forms (hare wallabies),wolf-like carnivores (Tasmanian wolves), badger-like carnivores (Tasmaniandevil), and-eating carnivores (banded anteater), and arboreal forms whichhave no obvious placental equivalent (koalas, tree kangaroos). The process ofevolution. The attainment of true flight serves tobring advantages in terms of escape, dispersal, and food seeking, leadingto the rapid proliferation of the group, a proliferation called adaptiveradiation. A comparison of events on differentislands showed the repeated evolution of the same ecomorph types. The levels of orogenic activity, or mountainbuilding, during the Paleozoic era increased in the Ordovician. (1997, April 1). It was found that the diversity increased inforeland basins at a rate more than twice that of the carbonate platforms,suggesting that proximity to budding mountains was a spur to marinediversity. A varietyof mechanisms have been identified as being involved in the process ofevolution. Entomologists gatheringspecimens in one day at one site in the Amazon acquired 44 species ofbutterfly, more than can be found in the entire eastern United States.Scientists still argue over the reason for this biodiversity, with someclaiming climate is the reason, while others note that climatic change inthe Amazon has been greater than believed in the past (Morell, 1997, 56).Adaptive radiation is the process involved in much of this diversity, butwhat contributes to its action is still under discussion. Recently Arnold Miller of the University of Cincinnatihas proposed a reason for the Ordovician radiation, seeing in thecontemporaneous era of mountain-building a force that could explain theincrease in biodiversity. Time frames. Ehrlich, Holm, and Parnell (1974) cite the development of birds as acase of adaptive radiation in the early stages as they split from thearchosaurian reptiles of the Mesozoic and apparently perfected flightthrough selection for increased flight range and agility in a group ofclimbing and gliding reptiles. They notedthat this vial offered a variety of environments, all differing in theamount of available oxygen because oxygen varied with depth in the broth.After five days, the original ancestor had undergone rapid morphologicalchange and had given rise to numerous new forms, each one presumablyadapted to a specific niche in the vial (Morell, 1997). He isexplaining differences which can be observed, showing that the way adifference develops is based on the way the species responds to itsenvironment: When a part has been developed in an extraordinary manner in any one species, compared with the other species of the same genus, we may conclude that this part has undergone an extraordinary amount of modification, since the period when the species branched off from the common progenitor of the genus . (1997, October 17). Eldredge, N. Specialization is the adaptation of a body part to aparticular function or of a whole organism to a particular environment, andmuch of the diversity of life is expressed through specialization.Organisms are specialized in order to perform certain tasks in response toenvironmental conditions. Inmore temperate climes, forests typically support no more than 5 to 6 species of tree. "On the origin of (Amazonian) species."Discover Magazine 18, 56-64. That original ancestor occupied a singleecological niche. In the world today, a major example of adaptive radiation isfound in the diversity of marsupials in Australia. The fossil recordshowed an increase in over 6,5 organisms--trilobites, brachiopods, andmollusks, for example. A recent report on theadaptive radiations of island lizards in the Greater Antilles suggests thatadaptive radiation may have similar results in similar environments. Morell, V. Adaptive radiations are described as a rapid and erratic series ofbursts in species development, with a proliferation of changes from asingle common ancestor. Somefamilies have also independently produced saprophytic and insectivorousderivatives, and specialized types of adaptive radiation are found forparticular mechanisms in plants, such as the series of pollination systemsthat can be found within the phlox family (Ehrlich, Holm, and Parnell,1974, 292). Those organisms able to adapt to changingconditions and to develop a new functional use for an organ or body partwill survive better than those that do not make such adaptation. New York: McGraw-Hill. He observes domestic animals and the developmentof a breed over time and determines that the way human beings have useddomestic animals has strengthened some parts of those animals anddiminished the use of others, producing modifications that were theninherited by subsequent generations. He then extrapolates from this tonature in general, always acknowledging limitations in his method: Under free nature, we can have no standard of comparison, by which to judge of the effects of long-continued use or disuse, for we know not the parent-forms; but many animals have structures which can be explained by the effects of disuse (Darwin, 1964, 134).Darwin's method is to examine changes based on relationships between onegeneration and the next or one species and related species. They placed Pseudomonasfluorescens, a common aerobic bacterium that thrives in the soil as well ason plants, in the unfamiliar habitat of a broth-filled vial. Eldredge (1985) later stated that the possibilitiescould have been simplified in that some of these are only forms of others.He notes that trends seem always to result from the differential productionand survival of the ever-more-specialized within lineages of creatures in arelatively narrow niche. Othergood examples of adaptive radiation are found in the Galapagos finches andAfrican lake cichlids (Ehrlich, Holm, and Parnell, 1974, 292). The Amazon, on the other hand, is far more lavish and hastwice as many species of tree within an acre or two. "Contingency and determinism in replicatedadaptive radiations of island lizards." Science, 2115-2118. (1964). If this paper is not what you are looking for, you can search again: Search for: or Click here to request an essay written just for you.