BackgroundThe rate and fitness effects of mutations are key in understanding the evolution of every species. Traditionally, these parameters are estimated in mutation accumulation experiments where replicate lines are propagated in conditions that allow mutations to randomly accumulate without the purging effect of natural selection. These experiments have been performed with many model organisms but we still lack empirical estimates of the rate and effects of mutation in the protists.ResultsWe performed a mutation accumulation (MA) experiment in Tetrahymena thermophila, a species that can reproduce sexually and asexually in nature, and measured both the mean decline and variance increase in fitness of 20 lines. The results obtained with T. thermophila were compared with T. pyriformis that is an obligate asexual species. We show that MA lines of T. thermophila go to extinction at a rate of 1.25 clonal extinctions per bottleneck. In contrast, populations of T. pyriformis show a much higher resistance to extinction. Variation in gene copy number is likely to be a key factor in explaining these results, and indeed we show that T. pyriformis has a higher mean copy number per cell than T. thermophila. From fitness measurements during the MA experiment, we infer a rate of mutation to copy number variation of 0.0333 per haploid MAC genome of T. thermophila and a mean effect against copy number variation of 0.16. A strong effect of population size in the rate of fitness decline was also found, consistent with the increased power of natural selection.ConclusionsThe rate of clonal extinction measured for T. thermophila is characteristic of a mutational degradation and suggests that this species must undergo sexual reproduction to avoid the deleterious effects detected in the laboratory experiments. We also suggest that an increase in chromosomal copy number associated with the phenotypic assortment of amitotic divisions can provide an alternative mechanism to escape the deleterious effect of random chromosomal copy number variation in species like T. pyriformis that lack the resetting mechanism of sexual reproduction. Our results are relevant to the understanding of cell line longevity and senescence in ciliates.

The purpose of the study was to investigate how young students engage in an inquirybased project driven by real-life contexts. Elementary school children were engaged in a small inquiry project centred on marine biodiversity and species adaptations. All activities included the exploration of an out-of-school setting as a learning context. A total of 49 students and 2 teachers were involved in the activities. The research methods included observation, document analysis and content analysis of the answers to a questionnaire and an interview. The results revealed that most of the students acquired scientific knowledge related to biological diversity and adaptations to habitat. Moreover, students progressively demonstrate greater autonomy, argumentative ability and decision-making. One implication of the present study is that elementary science curriculum could be better managed with inquiry projectbased activities that explore different types of resources and out-of-school settings.

This study aims to analyse the potentialities of using Personal Meaning Maps to assess school children's learning in a visit to a Planetarium. A total of 123 primary students were involved. They were asked to create a PMM, and a drawing, before and after the visit. The results suggest that the visit enhanced the degree to which students generate words and conceptual categories to describe their understanding of the suggested concepts. PMMs seemed to be a good tool to evaluate the impact of the activities on students' ideas about the thematic explored. Drawings helped to understand the main misconceptions.

In this paper we present an evaluation of an App for mobile devices, ‘Roteiro dos Descobrimentos’, as an educational digital resource for primary school students. The study involved the participation of 131 students and eight teachers. Data were collected from participant observation, students’ questionnaires and interviews to students and teachers. According to students, they learned new things, related with the topics explored, in an easy and funny way. Students also emphasized as positive aspects the fact that they had to face different challenges and the need to mobilize their knowledge to solve them. Teachers referred that students showed great interest and enthusiasm during the activities. As main gains, teachers stressed that the application fosters the relationship of students with the city, facilitates collaboration, and promotes students’ autonomy. In resume, it seems that the playful and interactive dimension of the App promoted the development of important skills such as the ability to interact with the environment, collaborative work, autonomy, and reading and interpretation skills. As a conclusion, there is a great receptivity to integrate mobile technologies in the teaching and learning process, but the role of the teacher can’t be dismissed, as a mediator and educator.