997 resultados para Division of Biological Sciences


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In accordance with the plan for joint Anglo-Soviet scientific and technical collaboration on environmental problems, the comparative evaluation of systems of hydrobiological analysis of the surface water quality started in 1977 at the Regional Laboratory of the Severn-Trent Water Authority in Nottingham were continued in the spring of 1978. The investigations were carried out under the auspices of the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR. Hydrobiological and hydrochemical samples were collected by Soviet and British specialists from the Kiev reservoir and the rivers Dnieper, Sozh, Desna and Snov. The samples were processed on the expedition ships and in the Laboratory for the Hydrobiology of Small Water Bodies of the Institute of Hydrobiology of the Academy of Sciences of the Ukrainian SSR. The possible approved methods to be adopted were evaluated from the samples using the phytoperiphyton, phytoplankton, zooplankton and zoobenthos against a background of hydrochemical characteristics. The study concludes that weather conditions complicated the work on testing the systems of biological indication of water quality and made it inadvisable to use those methods of comparison which were used when similar work was carried out in Nottingham.

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Under nitrogen-limiting conditions Rhizobium meliloti can establish symbiosis with Medicago plants to form nitrogen-fixing root nodules. Nodule organogenesis starts with the dedifferentiation and division of root cortical cells. In these cells the early nodulin gene enod40, which encodes an unusually small peptide (12 or 13 amino acids), is induced from the beginning of this process. Herein we show that enod40 expression evokes root nodule initiation. (i) Nitrogen-deprived transgenic Medicago truncatula plants overexpressing enod40 exhibit extensive cortical cell division in their roots in the absence of Rhizobium. (ii) Bombardment of Medicago roots with an enod40-expressing DNA cassette induces dedifferentiation and division of cortical cells and the expression of another early nodulin gene, Msenod12A. Moreover, transient expression of either the enod40 region spanning the oligopeptide sequence or only the downstream region without this sequence induces these responses. Our results suggest that the cell-specific growth response elicited by enod40 is involved in the initiation of root nodule organogenesis.

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We report the isolation and expression of the Hox gene, Cnox-2, in Hydractinia symbiolongicarpus, a hydrozoan displaying division of labor. We found different patterns of aboral-to-oral Cnox-2 expression among polyp polymorphs, and we show that experimental conversion of one polyp type to another is accompanied by concordant alteration in Cnox-2 expression. Our results are consistent with the suggestion that polyp polymorphism, characteristic of hydractiniid hydroids, arose via evolutionary modification of proportioning of head to body column.

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This bibliography contains 807 selected references on techniques for the use of radioactive and stable isotopes in biological sciences. These references were taken from the 1948-1956 open literature. A list of the journals from which they were selected and an author index are also included.

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Includes indexes.

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At head of title: U.S. Atomic Energy Commission.

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Within cooperative societies, group members share in caring for offspring. Although division of labour among group members has been relatively well studied in insects, less is known about vertebrates. Most studies of avian helping focus solely on the extent to which helpers provision the offspring, however, helpers can participate in everything from nest building to predator defence. Bad provisioners may, for example, not be as 'uncooperative' as they appear. if they are good defenders. Thus, the distribution of helping tasks between group members should have important implications for our interpretation of group dynamics. Here, we compare two distinct forms of helping behaviour in the cooperatively breeding noisy miner (Manorina melanocephala): chick provisioning and mobbing nest predators. We show that the way in which individual helpers invest in these two helping behaviours varies enormously across individuals and among social groups. Good provisioners often contributed relatively little to mobbing and vice versa. Indeed, (18%) of helpers only mobbed, 22% just provisioned, whereas 60% of helpers performed both forms of helping. Across nests, provisioning was significantly negatively correlated with mobbing effort. We suggest that small differences in the costs or benefits of different aspects of helping (due to differences in age, relatedness or social status) have a big impact on the division of labour within a group. Consequently, social groups can be made up from individuals who often specialise in one helping behaviour, and/or helpers who perform a number of behaviours to differing degrees. Division of labour within social groups will, therefore, have important consequences for the maintenance of cooperatively breeding in vertebrates.

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In recent decades the importance of structuring sciences such as botany or phytosociology faced a declining attention from the scientific community. This was accompanied by a growing interest in theoretical ecology. For such scenario greatly contributed an hypothetical exhaustion of research topics in these areas, but especially the introduction of new technologies that have provided powerful tools for data analysis. This allowed, for example, to make predictions about the impacts of climate change on species and plant communities and the consequent recognition of theoretical ecology, as one of the most prestigious pieces of current biological sciences. However, theoretical ecology has been facing serious knoledge gaps that greatly compromise their results, putting again the spotligth on structuring sciences. For example there are enourmous gaps in knowledge and data on dispersal, species and communities chorology and abundace, as well as in biological interactions. These data is essential, since they will determine ecological behavior of species. Its omission always limits the understanding and proper execution of the models generated by theoretical ecology. In this conference we will present a review on the gaps in knowledge and data in flora and vegetation fields in order to identify situations where geobotanical knowledge can make their major contribution. Furthermore, we will emphasize the need to reformulate objectives in geobotanical sciences in order to give it the deserved scientific recognition, considering the relationship between different scientific knowledges.

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This research recognizes the cognitive contributions to the students participating in the Third Costa Rican Biological Sciences Olympics that will define the advancement and strengthening in the construction of its conceptual dimension in the scientific literacy.  This paper is based, mainly, on qualitative approach techniques (ethnographic design:  case study); however, some data are interpreted through quantitative methodologies (descriptive design with an explanatory and exploratory touch) for the analysis of a sample of 54 high school students, finalists in the category A of the Olympics, through the use of tools such as a documentary study and a survey, in July 2009.  The information generated was analyzed using elements of inferential and descriptive statistics, figures and histograms.  It was proved that there is a better cognitive management in the topics assessed, an increase in the students’ academic performance as the tests are applied, a commitment for the academic update supported by the development of several tasks for previous preparation, curriculum contributions unprecedented based on our sample, a consent to optimize student’s knowledge about Biology, which will allow the application of scientific notions to diversify and renew the knowledge, according to what is established in the principles of scientific literacy.