Investigando as concepções de força em situações do cotidiano ao longo do ciclo da experiência Kellyana

This research explored the construction process of the scientific concept of force among pupils at High School, who were engaged in a didactic sequence organized according to the five phases of Kellyan Cycle of experience: Anticipation, Investment, Encounter, Confirmation or Disconfirmation and Constructive Revision. It also intended to identify conceptions of force applied to everyday life situations. The results of this research showed that pupils, during the Anticipation phase, possessed intuitive conceptions as well as difficulties in differentiating the concepts of orientation and direction of a force. The activities developed during the Cycle aroused pupils´ attention, impelling them to develop hypotheses, to reflect and to establish relationships between experienced situations and the theme under study. This enabled the evolution of their concepts.http://dx.doi.org/10.5007/2175-7941.2008v25n2p287Esta pesquisa teve como objetivo investigar o processo de construção do conceito científico de força entre alunos do 1º ano do Ensino Médio, que participaram de uma seqüência didática organizada de acordo com as cinco fases do Ciclo da Experiência Kellyana: Antecipação; Investimento; Encontro; Confirmação ou Desconfirmação e Revisão Construtiva. Procurou-se identificar as concepções sobre força em situações do cotidiano. Os resultados desta pesquisa mostraram que os alunos, na fase da Antecipação, possuíam conceitos intuitivos, bem como tinham dificuldades de entender os conceitos de direção e sentido de uma força. As atividades desenvolvidas durante o Ciclo despertaram a atenção dos alunos, impulsionando-os a levantar hipóteses, refletir e estabelecer relações das situações vivenciadas com o tema em estudo, o que oportunizou uma contribuição de forma relevante para a evolução dos seus conceitos

Maturation trends indicative of rapid evolution preceded the collapse of northern cod

Northern cod, comprising populations of Atlantic cod (Gadus morhua) off southern Labrador and eastern Newfoundland, supported major fisheries for hundreds of years. But in the late 1980s and early 1990s, northern cod underwent one of the worst collapses in the history of fisheries. The Canadian government closed the directed fishing for northern cod in July 1992, but even after a decade-long offshore moratorium, population sizes remain historically low. Here we show that, up until the moratorium, the life history of northern cod continually shifted towards maturation at earlier ages and smaller sizes. Because confounding effects of mortality changes and growth-mediated phenotypic plasticity are accounted for in our analyses, this finding strongly suggests fisheries-induced evolution of maturation patterns in the direction predicted by theory. We propose that fisheries managers could use the method described here as a tool to provide warning signals about changes in life history before more overt evidence of population decline becomes manifest

Directional Bilateral Asymmetry in Fish Otolith: A Potential Tool to Evaluate Stock Boundaries?

The otolith, found in both inner ears of bony fish, has mainly been used to estimate fish age. Another application that has been developing significantly in recent years, however, is the use of otolith shape as a tool for stock identification. Often, studies have directly used the shape asymmetry between the right and left otoliths. We tested the magnitude of directional asymmetry between the sagittal otoliths (left vs. right) of 2991 individuals according to their catch locations, and we selected species to evaluate whether directional asymmetry may itself be a tool to evaluate stock boundaries. Elliptical Fourier descriptors were used to describe the otolith shape. We used a flatfish, the common sole (Solea solea, n = 2431), from the eastern English Channel and the southern North Sea as well as a roundfish, the bogue (Boops boops, n = 560), from the Mediterranean Sea. Both species showed significant levels of directional asymmetry between the testing locations. The bogue otoliths showed significant asymmetry for only 5 out of 11 locations, with substantial separation between two large areas: the Algerian coast and the western part of the Italian coast. The sole otoliths showed significant asymmetry in the shape analysis (3.84–6.57%), suggesting a substantial separation between two large areas: the English and French parts of the English Channel and the southern North Sea. Consequently, directional bilateral asymmetry in otolith shape is a potential new method for stock identification.Postprin

Limited evolutionary responses to harvesting regime in the intensive production of algae

Plastic changes in the growth and productivity of algae in response to environment and stocking density are well established. In contrast, the capacity for such changes to persist once environmental differences cease, potentially signalling an evolutionary response, have rarely been tested for algae in intensive production systems. We tested whether continuous differences in harvesting regime (a high stocking density/low-yield regime versus low stocking density/high-yield regime) generated changes in biomass productivity and other growth metrics within several strains of the clonal macroalga Oedogonium (Chlorophyta, Oedogoniales) and whether such changes persisted once differential harvesting yields ceased. We found considerable plasticity in growth rate and biomass productivity over a 12-week period of active selection (i.e. repeated high-yield and low-yield harvesting of clonal lineages within strains) and that strains responded differently to this selection pressure over time. While small, but significant, differences in growth rates of clonal lineages exposed to high-yield vs low-yield harvesting regimes were maintained after prolonged culture under a common selection regime (i.e. medium-yield harvesting), differences in biomass productivity were not. There was no evidence for positive or negative effects of maintaining multiple strains in polyculture on growth and biomass productivity. Overall, we detected limited potential for evolutionary responses to harvesting regime in the main commercial trait of interest—biomass productivity. This outcome is important for commercial cultivation in intensive production systems, since it identifies a low risk that harvesting practices will impact negatively on biomass productivity in the longer term