The technique of allometry investigates the effects of size on such variables as food intake, energy requirements, growth rates and age at first reproduction. This book brings together much of what is known about the consequences of size and provides a new and mathematically rigorous framework within which many quantitative predictions are made and tested using published and unpublished data. Explanations are proposed for many previously unexplained phenomena such as why in some species females are thousands of times heavier than males, whereas in no species are males more than about eight times heavier than females. The models presented afford a synthesis of the effects of size and open up pathways for further theoretical investigation and experimental testing. Care has been taken to give verbal presentations of all the mathematical conclusions to ensure that the text is widely intelligible.

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We report here on the first of two evaluations of a national project (Getting Practical: Improving Practical Work in Science-IPWiS) designed to improve the effectiveness of practical work in both primary and secondary schools in England. This first baseline evaluation of the effectiveness of practical work is based on a study of a diverse range of 30 practical lessons undertaken in non-selective primary (n = 10) and secondary (n = 20) schools prior to the teachers undertaking a training intervention designed to improve their effective use of practical work. A multi-site case study approach employing a condensed fieldwork strategy was used in which data were collected, using audiotape-recorded discussions, interviews and observational field notes. The analysis, based on work by Millar et al. and Tiberghien, considers what students do and think relative to what their teacher intended them to do and think. In both primary and secondary schools the widespread use of highly structured 'recipe' style tasks meant that practical work was highly effective in enabling students (n = 857) to do what the teacher intended. Whilst tasks in primary schools tended to be shorter than in secondary schools, with more time devoted to helping students understand the meaning of new scientific words, neither primary nor secondary teachers' lesson plans incorporated explicit strategies to assist students in making links between their observations and scientific ideas. As such, tasks were less effective in enabling students to use the intended scientific ideas to understand their actions and reflect upon the data they collected. These findings suggest that practical work might be made more effective, in terms of developing students' conceptual understanding-an aim of the IPWiS project-if teachers adopted a more 'hands-on' and 'minds-on' approach and explicitly planned how students were to link these two essential components of practical work.

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This paper investigates the factors that influence 15 year-old students' intentions to study physics post-16, when it is no longer compulsory. The analysis is based on the year 10 (age 15 years) responses of 5034 students from 137 England schools as learners of physics during the academic year 2008-09. Factor analyses uncovered a range of physicsspecific constructs, seven of which were statistically significantly associated with intention to study physics post-16 in our final multi-level model; in descending order of effect size these are extrinsic material gain motivation, intrinsic value of physics, home support for achievement in physics, emotional response to physics lessons, perceptions of physics lessons, physics self-concept and advice-pressure to study physics. A further analysis using individual items from the survey rather than constructs (aggregates of items) supported the finding that extrinsic motivation in physics was the most important factor associated with intended participation. In addition, this item-level analysis indicated that within the advicepressure to study physics construct the encouragement individual students receive from their teachers is the key factor that encourages them to intend to continue with physics post-16.

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In order to name an animal they see, children use their existing mental models to provide the animal with a name. In this study, pupils of a range of ages (4, 8, 11, and 14 years old) were presented with preserved specimens of six different animals and asked a series of questions about them. The results indicate that pupils of all ages main ly recognize and use anatomical features when naming the animals and explaining why they are what they are. However, older pupils are more likely to also use behavioural and habitat attributes. For both girls and boys, the home and direct observation are more important as sources of knowledge than school or books, although books seem more important for boys than for girls. As pupils age, their reasons for grouping animals become more com plicated: in addition to relying on shared anatomical features, they begin to show evidence of an embedded taxonomic knowledge, knowing, for instance, what a mammal is and using this knowledge to group animals.

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