Richard Bradley's understanding of biological productivity: A study of eighteenth-century ecological ideas

Conclusions Bradley succeeded in conceptualizing biological productivity in terms—monetary investment vs. profit—that could be applied to organisms as different in form and habitat as trees, grapevines, and crayfish.⁴¹ This form of measurement was not precise enough to have served as a basis for actual comparisons of production rate. His way of thinking, however, could have been applied with other terms of measurement once the usefulness of such measurements had been realized. The realization that production rate is an important factor is implicit in his discussions, but for his purposes, yearly yields were generally sufficiently precise determinations.Although Bradley drew substantially upon the contributions of others, his writings represent a significant beginning for productivity ecology. All of the kinds of investigations that he reported could have been extended, rendered more precise, and formed the basis of ecological generalizations during the eighteenth century.There were, however, certain conceptual limitations imposed by a lack of relevant knowledge in physiology and in physical science. A good understanding of productivity ultimately depends upon an understanding of metabolism, which in turn depends upon an understanding of photosynthesis, respiration, biochemistry, and the first and second laws of thermodynamics. The essential knowledge of these subjects would not be available until decades after Bradley's time.     

课堂教学中的生物学概念及其表述方式

生物学教学的任务之一是知识的教学,其关键是概念教学。不同的生物学教师对概念的理解不同,而这样的理解又对课堂教学的要求、方式和结果产生影响。依据国内外近年来的研究成果,阐述了什么是生物学概念及如果在教学中准确表述概念。     

Chemical approaches to understanding biological mechanisms

A report on work with small-molecule inhibitors of cellular processes presented at the 39th Annual Meeting of the American Society for Cell Bilogy, Washington DC, December 11-15, 1999     

Translating genome sequences into biological understanding

A report on the Genomics, Proteomics and Bioinformatics Thematic Meeting during the 2003 American Society for Biochemistry and Molecular Biology (ASBMB) Annual Meeting, San Diego, USA, 11-15 April 2003.     

Botswana1 children's understanding of biological inheritance

This paper reports the findings of an investigation which probed Batswana students' understanding of inheritance. A sample of students (aged 12 to 16+) responded to a pencil and paper questionnaire, which presented them with a variety of situations which they were asked to explain. Half of the sample were presented with English questions, and the other half with questions in Setswana (the vernacular language of the students). In both cases, they were asked to respond in the same language as the questions. Analysis of the responses revealed a variety of ‘alternative frameworks’, including a widespread belief in the inheritance of acquired characteristics. These are reported and discussed and their implications for teaching are explored. The language of the questions and responses and the gender of the students appeared to have little effect on the nature of the ideas revealed.     

A review of the applications of solid state physics concepts to biological systems

The evidence for solid state physical processes in diverse biological systems is reviewed. Semiconduction of electrons across the enzyme particles as the rate-limiting process in cytochrome oxidase is evidenced by the peculiar kinetic patterns of this enzyme and by microwave Hall effect measurements. PN junction conduction of electrons is suggested by kinetics of photobiological free radicals in eye and photosynthesis. Superconduction at physiological temperatures may be involved in growth and nerve. Phonons and polarons seem likely to be involved in mitochondrial phosphorylation. Piezoelectricity and pyroelectricity may be involved in growth and nerve. Infrared electromagnetic waves may transmit energy in lipid bilayers of nerve and mitochondria. Complexed sodium and potassium ions in structured cell water may be analogous to valence band electrons in a semiconductor, and the free cations may be considered analogous to conduction band electrons. Ionic processes in cell water therefore resemble electronic conduction processes in solid semiconductors, which leads to kinetic predictions in agreement with experiment. The future of solid state biology depends on the development of new experimental methods able to measure solid state physical properties in biological materials which are non-crystalline, impure, particulate, and wet.     

Towards an ecological understanding of biological nitrogen fixation

Biogeochemistry - N limitation to primary production and other ecosystem processes is widespread. To understand the causes and distribution of N limitation, we must understand the controls of...     

The relative effectiveness of teaching methods on pupils' understanding of the classification of living organisms at two levels of intelligence

A classification task, involving the sorting of pictures of plants and animals into major orders and classes, and a standardised test of general intelligence, were administered to randomly selected groups of 12 year old pupils drawn from four comprehensive schools. Sub-samples were selected at random of pupils of above and below average intelligence who had been taught classification either by the “Nuffield” approach or by a “traditional” method. Analysis of variance of the scores obtained showed that although the achievement of the upper intelligence group was superior (1 %level) to that of the lower intelligence group, there was a significant interaction (5 % level) between the method of teaching that had been received and intellectual level. Pupils of above average intelligence generally obtained higher scores when they had been taught by the “Nuffield” method, whereas the achievement of pupils of below average intelligence was generally much greater when they had been taught by a “traditional” method.     

Physicochemical and biological study of selected hydrophobic polyethylenimine-based polycationic liposomes and their complexes with DNA

Non-viral gene therapy is based on the development of efficient and safe gene carrier systems able to transfer DNA into cells. Polyethylenimine (PEI), the most promising non-viral vector, with its high cationic-charge-density potential is able (1) to compact DNA in complexes (polyplexes) smaller than those formed by liposomes (lipoplexes) and (2) to destabilize the endosomal membrane by a 'proton sponge' effect. Several PEI's hydrophobic modifications were reported in the last several years but in some cases a reduced transfection efficiency was observed. The mechanism underlying this phenomenon is not well understood so far. In order to extensively investigate these mechanisms, we reported a physicochemical and biological study of selected hydrophobic PEI's derivatives grafted with chains of different length and percentages of substitution able to form vesicles (polycationic liposomes) and to bind DNA. Their properties were studied by means of dynamic light scattering, freeze-fracture microscopy, potentiometric titrations, gel retardation assays, polyanion exchange reactions, toxicity assays, in vitro transfections, and fluorescence microscopy. Our results indicate that even if polyplexes are able to pass through the cellular membrane, the stability of PEI's hydrophobic polyplexes likely explain their different transfection efficiency in vitro.     

Towards new concepts for a biological neuroscience of consciousness

In the search for a sound model of consciousness, we aim at introducing new concepts: closure, compositionality, biobranes and autobranes. This is important to overcome reductionism and to bring life back into the neuroscience of consciousness. Using these definitions, we conjecture that consciousness co-arises with the non-trivial composition of biological closure in the form of biobranes and autobranes: conscious processes generate closed activity at various levels and are, in turn, themselves, supported by biobranes and autobranes. This approach leads to a non-reductionist biological and simultaneously phenomenological theory of conscious experience, giving new perspectives for a science of consciousness. Future works will implement experimental definitions and computational simulations to characterize these dynamical biobranes interacting.     

Unifying concepts of biological function from molecules to ecosystems

The concept of function arises at all levels of biological study and is often loosely and variously defined, especially within ecology. This has led to ambiguity, obscuring the common structure that unites levels of biological organisation, from molecules to ecosystems. Here we build on already successful ideas from molecular biology and complexity theory to create a precise definition of biological function which spans levels of biological organisation and can be quantified in the unifying currency of biomass, enabling comparisons of functional effectiveness (irrespective of the specific function) across the field of ecology. We give precise definitions of ecological and ecosystem function that bring clarity and precision to studies of biodiversity– ecosystem function relationships and questions of ecological redundancy. To illustrate the new concepts and their unifying power, we construct a simple community‐level model with nutrient cycling and animal‐plant mutualism, emphasising the importance of its network structure in determining overall functioning. This type of network structure is that of an autocatalytic set of functional relationships, which also appears at biochemical, cellular and organism levels of organisation, creating a nested hierarchy. This enables a common and unifying concept of function to apply from molecular interaction networks up to the global ecosystem.