869 resultados para life-history
Resumo:
Drought events are projected to increase in frequency and magnitude, which may alter the composition of ecological communities. Using a functional community metric that describes abundance, life history traits and conservation status, based upon Grime’s CSR (Competitive-Stress tolerant-Ruderal)¬ scheme, we investigated how British butterfly communities changed during an extreme drought in 1995. Throughout Britain, the total abundance of these insects had a significant tendency to increase, accompanied by substantial changes in community composition, particularly in more northerly, wetter sites. Communities tended to shift away from specialist, vulnerable species, and towards generalist, widespread species and, in the year following, communities had yet to return to equilibrium. Importantly, heterogeneity in surrounding landscapes mediated community responses to the drought event. Contrary to expectation, however, community shifts were more extreme in areas of greater topographic diversity, whilst land-cover diversity buffered community changes and limited declines in vulnerable specialist butterflies.
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Although previous studies have addressed the question of why large brains evolved, we have limited understanding of potential beneficial or detrimental effects of enlarged brain size in the face of current threats. Using novel phylogenetic path analysis, we evaluated how brain size directly and indirectly, via its effects on life-history and ecology, influences vulnerability to extinction across 474 mammalian species. We found that larger brains, controlling for body size, indirectly increase vulnerability to extinction by extending the gestation period, increasing weaning age, and limiting litter sizes. However, we found no evidence of direct, beneficial or detrimental, effects of brain size on vulnerability to extinction, even when we explicitly considered the different types of threats that lead to vulnerability. Order-specific analyses revealed qualitatively similar patterns for Carnivora and Artiodactyla. Interestingly, for Primates, we found that larger brain size was directly (and indirectly) associated with increased vulnerability to extinction. Our results indicate that under current conditions the constraints on life-history imposed by large brains outweigh the potential benefits, undermining the resilience of the studied mammals. Contrary to the selective forces that have favoured increased brain size throughout evolutionary history, at present, larger brains have become a burden for mammals.
Resumo:
Species of Gracilaria are some of the most useful algae in the world for the production of agar. As a consequence of its economic importance, the genus has been the subject of many studies worldwide. Color variants of Gracilaria birdiae have been found in the natural population on the Brazilian coast, and they have also been isolated from plants cultivated in laboratory. These findings raised new questions regarding intraspecific variation and the prospects of cultivating such variants for their agar production. Therefore, this work aimed to determine the mode of color inheritance for two G. birdiae strains: a greenish-brown strain (gb) found in a natural population and a green strain (gr) which had arisen as a spontaneous mutation in a red plant cultured in the laboratory. The pigment contents of these strains, as well as the red wildtype (rd), were also characterized. Crosses between female and male plants of the same color (rd, gr, or gb) and between different colors were performed. Crosses between plants of the same color showed tetrasporophytic and gametophytic descendents of the parental color. Recessive nuclear inheritance was found in the greenish-brown strain, and cytoplasmic maternal inheritance was found in the green strain; both had lower phycoerythrin and higher concentrations of allophycocyanin and phycocyanin than the wild-type. Chlorophyll a contents were similar among all strains. Taken together, our results contribute to knowledge about the variability of this important red algae. In addition, since greenish-brown and green strains showed stability of color, both could be selected and tested in experimental sea cultivation to evaluate if mutants have advantageous performance when compared with red strain.
Resumo:
Most amphibian species have biphasic life histories and undergo an ontogenetic shift from aquatic to terrestrial habitats. In deforested landscapes, streams and forest fragments are frequently disjunct, jeopardizing the life cycle of forest-associated amphibians with aquatic larvae. We tested the impact of habitat split-defined as human-induced disconnection between habitats used by different life-history stages of a species-on four forest-associated amphibian species in a severely fragmented landscape of the Brazilian Atlantic Forest. We surveyed amphibians in forest fragments with and without streams (referred to as wet and dry fragments, respectively), including the adjacent grass-field matrix. Our comparison of capture rates in dry fragments and nearby streams in the matrix allowed us to evaluate the number of individuals that engaged in high-risk migrations through nonforested habitats. Adult amphibians moved from dry fragments to matrix streams at the beginning of the rainy season, reproduced, and returned at the end of the breeding period. Juveniles of the year moved to dry fragments along with adults. These risky reproductive migrations through nonforested habitats that expose individuals to dehydration, predation, and other hazards may cause population declines in dry fragments. Indeed, capture rates were significantly lower in dry fragments compared with wet fragments. Declining amphibians would strongly benefit from investments in the conservation and restoration of riparian vegetation and corridors linking breeding and nonbreeding areas.
Resumo:
A relatively large amount of variation occurs in the reproductive ecology of tropical snakes, and this variation is generally regarded as being a consequence of seasonality in climate and prey availability. In some groups, even closely related species may differ in their reproductive ecology; however, in others it seems to be very conservative. Here we explore whether characters related to reproduction are phylogenetically constrained in a monophyletic group of snakes, the subfamily Dipsadinae, which ranges from Mexico to southern South America. We provide original data on reproduction for Leptodeira annulata, Imantodes cenchoa, and three species of Sibynomorphus from southern, southeastern and central Brazil, and data from literature for other species and populations of dipsadines. Follicular cycles were seasonal in Atractus reticulatus, Dipsa, albifrons, Hypsiglena torquata, Leptodeira maculata, L. punctata, Sibynomorphus spp. and Sibon sanniola from areas where climate is seasonal. In contrast, extended or continuous follicular cycles were recorded in Dipsas catesbyi, D. neivai, Imantodes cenchoa, Leptodeira annulata, and Ninia maculata from areas with seasonal and aseasonal climates. Testicular cycles also varied from seasonal (in H. torquiata) to continuous (in Dipsa,5 spp., Leptodeira annulata, L. maculata, N. maculata, and Sibynomorphus spp.). Most dipsadines are small (less than 500 rum SVL), and females attain sexual maturity with similar relative body size than males. Sexual dimorphism occurred in terms of SVL and tail length in most species, and clutch size tended to be small (less than five eggs). Combat behavior occurs in Imantodes cenchoa, which did not show sexual size dimorphism. Reproductive timing, for both females and males, varied among species but in general there were no differences between the tribes of Dipsadinae in most of the reproductive characteristics, such as mean body size, relative size at sexual maturity, sexual size and tail dimorphism, duration of vitellogenesis or egg-carrying in oviducts.
Resumo:
Limited financial sources and the difficulty in performing complete surveys, allied to the speed of habitat fragmentation and the urgent necessity in select conservation areas, create the necessity of using some methodologies which bypass these problems. One possibility is the use of surrogate taxa that might be used as indicator of others groups richness and even total richness of an area. We investigated if the use of surrogate taxon is useful among seven mammal orders in Amazon. We tested through Pearson`s correlation (Bonferroni`s adjusted) if (1) there was a correlation between richness of total species and some order; (2) there was a significant pair wise correlation between species richness of each order; and (3) the combination of two orders would give better results as a surrogate for the total richness. The correlations found, in general, were positive. It means that the increase in the richness of an order was followed by its increase in another order, as well as in the total species richness. Only Didelphimorphia was significantly correlated with the total species richness. In the pair wise analyses only one assembly, Primates and Artiodactyla, was significantly correlated with total richness. Since indicator species are more effective within taxonomic groups (life-history characteristics are likely to be more different among than within major taxonomic groups), we suggest that an indicator group might be chosen for each one. In this case, for mammals from Amazon, it would be Didelphimorphia. (C) 2008 Elsevier Ltd. All rights reserved.
Resumo:
The sexual system of the symbiotic shrimp Thor amboinensis is described, along with observations on sex ratio and host-use pattern of different populations. We used a comprehensive approach to elucidate the previously unknown sexual system of this shrimp. Dissections, scanning electron microscopy, size-frequency distribution analysis, and laboratory observations demonstrated that T amboinensis is a protandric hermaphrodite: shrimp first mature as males and change into females later in life. Thor amboinensis inhabited the large and structurally heterogeneous sea anemone Stichoclactyla helianthus in large groups (up to 11 individuals) more frequently than expected by chance alone. Groups exhibited no particularly complex social structure and showed male-biased sex ratios more frequently than expected by chance alone. The adult sex ratio was male-biased in the four separate populations studied, one of them being thousands of kilometers apart from the others. This study supports predictions central to theories of resource monopolization and sex allocation. Dissections demonstrated that unusually large males were parasitized by an undescribed species of isopod (family Entoniscidae). Infestation rates were similarly low in both sexes (approximate to 11%-12%). The available information suggests that T. amboinensis uses pure search promiscuity as a mating system. This hypothesis needs to be formally tested with mating behavior observations and field measurements on the movement pattern of both sexes of the species. Further detailed studies on the lifestyle and sexual system of all the species within this genus and the development of a molecular phylogeny are necessary to elucidate the evolutionary history of gender expression in the genus Thor.
Resumo:
The overall aim of this study is to analyse history teachers’ understanding of the school subject history. The aim have also been to uncover what factors the history teachers say have affected their understanding of the school subject. Based on survey and interview methods, the question that this study deals with is: in the light of which general understanding of the school subject history, do the teachers make didactic choices on a daily basis? The first theme is biographical. The teachers’ life-history is taken into consideration and several factors in the teachers’ background and the school environment have been identified. It also seems as if the teachers’ understanding of the school subject goes from an elementary and searching approach to one that is more complex and convinced. The second theme is a more structural approach. The results shows three major orientations among the teachers’ general understanding namely, educational (bildung) orientation, critical orientation and identity orientation. Even though a main orientation can be seen among the teachers, an important result is also that the orientation is overall complex. At the most general level some patterns can be seen. First the connection between the teachers’ biography and their general understanding of the school subject. In the understanding of the school subject, it is also notable that teachers relate in different ways to history as science, history as identity and history from an ideological viewpoint. It is also possible to note some signs of change in the school subject history that follows a lager historiographical context.
Resumo:
Este trabalho pretende analisar os principais centros de pós-graduação e de pesquisa em economia localizados em São Paulo e no Rio de Janeiro, a partir do levantamento de documentos, programas, regulamentos e publicações de seus principais expoentes. Também pretendemos utilizar depoimentos desses expoentes para entender como os processos decisórios foram analisados de "dentro" da instituição. A história da vida do entrevistado permite que entremos no mundo das emoções, nos limites da racionalidade do ator histórico. Ao quebrarmos o esquematismo simplista, podemos desvendar as relações entre o indivíduo e a rede histórica. A memória, com suas falhas, distorções e inversões, torna-se um elemento de análise para explicar o presente, a partir da compreensão do passado sob a ótica de quem vivenciou os fatos.
Resumo:
Essa pesquisa procurou investigar o processo de composição narrativa pela dupla estagiário-terapeuta/paciente, em uma situação de psicoterapia psicanalítica, a partir do contexto de uma prática supervisionada de estágio em Psicologia Clínica. Participaram da pesquisa duas acadêmicas de Psicologia que realizaram o estágio em um abrigo municipal. O trabalho clínico desenvolvido pelas estagiárias foi acompanhado pela supervisão acadêmica, cuja responsável na época era a pesquisadora. Também participaram dessa pesquisa três meninas de seis, nove e dez anos de idade, acolhidas temporariamente na instituição e em acompanhamento psicoterapêutico pelas estagiárias. Os atendimentos foram realizados uma vez por semana, individualmente, na própria instituição. As estagiárias relataram cada entrevista preliminar realizada com as crianças sob a forma escrita de entrevista dialogada, cujo objetivo é a memorização do desenvolvimento da entrevista. Essa memorização associada às reflexões acerca do estágio produzidas no espaço de supervisão acadêmica formaram as fontes dos dados. Para atingir o objetivo dessa pesquisa, três estudos foram realizados e, em cada um deles, três casos, constituídos por diferentes duplas terapêuticas, foram analisados. Os resultados dos três estudos demonstram, inicialmente, que o discurso elaborado pelas duplas terapêuticas, em cada entrevista preliminar isoladamente, estrutura-se narrativamente porque esse discurso apresenta os dois princípios da narrativa, que são a sucessão e a transformação, como propõe Tzvetan Todorov. A análise conjunta dessas entrevistas denota, entretanto, que as narrativas constituídas nesse processo não podem ser reduzidas a uma lógica de sucessão linear como formula esse autor. A seqüência narrativa é regida pela lógica de causalidade semântica, que é de natureza polifônica, como propõe Paul Ricoeur. As intervenções das estagiárias sob a forma de construções, conforme conceito estabelecido por Freud, mesmo que guiadas pelo princípio da associação livre, são demarcadas, em sua maioria, pela repetição de uma versão já conhecida da história da vida de seu paciente, geralmente àquela que versa sobre o motivo do abrigamento. Assim, essas intervenções, cujo efeito possível seria que o paciente pudesse desconstruir os sentidos dados a priori, reconstruindo novas versões para os acontecimentos de sua vida e, com isso, ocupasse o lugar de autor de sua história, acabam insistindo no trauma. Dessa forma, fica explicitado um dos paradoxos do processo de formação da escuta clínica: o estagiário, ao procurar abrir os sentidos para o seu paciente, construindo junto com ele uma versão possível para a sua história, acaba, muitas vezes, fechando o sentido, construindo uma única versão para os eventos narrados pelo paciente.
Resumo:
Este trabalhe tem cerne objetivo investigar e universo psicossocial de um grupo de mulheres idosas de classe socioeconômica baixa. Inicialmente, são analisadas as problemáticas da mulher e de idoso a partir de uma revisão crítica da literatura, compreendendo estudes teóricos e pesquisas empíricas realizadas no Brasil. Também são focalizados os conceitos de identidade e de marginalidade, cem frequência referidos no percurso de trabalho. A seguir, é relatada uma pesquisa de campo em que se utiliza e método de história de vida. Foram entrevistadas 20 mulheres cem idade acima de 60 anos, de baixa renda, residentes em uma cidade de médio porte de Estado de Espirite Santo. Apresenta-se uma caracterização prévia da população e posteriormente uma análise das entrevistas. Nesta análise observam-se algumas convergências básicas nas condições objetivas de vida e nas representações construídas pele grupo das entrevistadas acerca de suas vivências, no que se refere especialmente às suas condições de trabalho, às suas inserções nos contextos familiar e público, às imagens das figuras masculina e feminina elaboradas e à situação. vivencial de envelhecimento. Destacam-se entre essas convergências: o exercício de atividades laborais informais não-especializadas; a referência frequente ao contexto familiar; a construção de uma auto imagem fragilizada ou ambígua que não se coaduna com as experiências de sustentáculo familiar relatadas; e uma adequação/inadequação ao modelo vigente de velhice, denotando, frequentemente, uma defasagem entre a idade cronológica e o sentimento subjetivo do envelhecimento. Finalmente, a conclusão procura integrar os aspectos mais significativos observados nos relatos, delineando-se o perfil psicossocial do grupo estudado.
Resumo:
O presente trabalho pretende ser o primeiro no campo da psicologia da mulher, a enfocar o tema amamentação numa perspectiva sócio-cultural. Trata-se de uma pesquisa de campo não experimental realizada entre mulheres que amamentaram seus filhos. O método utilizado para coleta de dados foi a história de vida. A população estudada consta de trinta nutrizes, a saber: dez de classe média, dez de classe baixa e dez avós. Foi feita uma análise comparativa da experiência de amamentação das mulheres dos três grupos estudados. Com base nesses dados pode-se concluir, que a amamentação longe de ser apenas um fato biológico singular, é uma construção social, instrumento ideológico de opressão da mulher.
Resumo:
O objetivo desta pesquisa foi investigar a vida cotidiana de mulheres rotuladas como deficientes mentais, através de seus relatos biográficos pessoais. As entrevistadas descreveram sua rotina em casa e na instituição, falaram sobre suas famílias, relacionamentos, dificuldades em integração social, e sobre seus problemas físicos e de aprendizagem. Ficou clara no discurso deste grupo a dicotomia entre o mundo “de dentro", compreendendo os espaços protegidos da casa e da instituição, e o mundo ameaçador e violento “de fora", representado pela rua. Seus relacionamentos sociais restringem-se aos personagens do mundo “de dentro": a família, os profissionais, e os colegas da instituição, e muitas entrevistadas disseram se· sentir discriminadas pelas pessoas “de fora". Embora várias mulheres tenham exprimido o desejo de ser independentes (trabalhar fora, sair sozinhas, etc), na prática mantém urna relação de extrema dependência familiar. A pesar de dois terços das entrevistadas terem mais de 20 anos, elas não parecem ter nenhuma perspectiva concreta de morar sozinhas, casar, ou vir a formar sua própria família. Um dos pressupostos deste estudo era de que o estigma da deficiência mental, seria o terna central nas histórias de vida. Entretanto, mais da metade dos sujeitos não abordou esta questão, e muito poucas se autodenominaram deficientes. Foi postulado que os efeitos do estigma talvez sejam minimizados neste grupo devido à superproteção familiar e institucional por um lado, e a evitação do mundo "de fora" (onde esta condição seria denunciada mais abertamente) por outro. Assim sendo, em sua prática diária, a maioria dessas mulheres têm poucas oportunidades de se confrontar com a situação de marginalização. Deficiência mental foi analisada como um fenômeno socialmente construído, e acredita-se que estas pessoas funcionem em um nível mais dependente do que sua condição orgânica exigiria, por terem sido reforçadas por representar o papel social de deficientes. Apesar das características comuns, cada história de vida provou ser original e única, mostrando o erro em se considerar as pessoas portadoras de deficiência mental como um grupo homogêneo e bem definido. Além disso, a não ser pela dependência familiar, falta de participação autônoma e integrada na comunidade, e relacionamento amoroso e sexual restrito, a ideia dessas mulheres não é qualitativamente diferente do resto da população.
Resumo:
This dissertation aimed to identify the factors that conduct the women of today to decide for or against motherhood, as well as to identify her feelings about the subject. An exploratory field research was conducted using the life-history technique. Thirty one middle class working women, with no children, and in hers thirties, were Interviewed and offered statements about their decisions on procreate or note from the analysis of the statements we found that the degree of anxiety to make a choice seems to vary according to the extension of inner conflicts. These conflicts seems to derive from two sources: a) the degree of Interior disposability to become a mother; b) the degree of support from external sources. Emotional questions were clearly the more Influential actor to come to a resolution on the matter. The woman of today, although more acting socially. seems to fear that eventual renunciation to the maternal status may, In the future be sensed as a vacuum. This study made manifest that In the long run - with the Increment of the inner psychological pressure to make a decision -the women tend to be well-inclined toward motherhood.