CENTURY succession model

FIGURE 7 Changes in aboveground plant carbon density on three landscapes at the La Copita from 1950 to 1990 (Archer and Boutton, unpublished). Patch/soil-specific field estimates of plant carbon density (Northup et al, 1996, McMurtry, Nelson and Archer, unpublished) were multiplied by patch area as measured in aerial photographs to generate whole-landscape estimates. Dashed lines denote predictions from linked CENTURY-succession model (Hibbard, 1995). See Figure 4 for changes in woody cover on the three landscapes. 

For about 95% of the history of modern science, since Bacon s work in the seventeenth century, the general idea of how to explain natural phenomena consisted of a clear course collection of the facts, systemization of them into empirical laws, the invention of a number of alternative and competing intuitive models by which the facts could be qualitatively understood, and, finally, mathematical expression of the more qualitatively successful models to obtain sometimes more and sometimes less numerical agreement with the experimental values. The models that matched best were judged to describe a particular phenomenon better than the other models. 

The classical approach appropriately known as molecular mechanics has been used with conspicuous success to predict molecular geometries, chemical reactivities and even magnetic, electronic and spectral properties of molecular systems. Molecular mechanics functions with no intention or pretence to elucidate the essential nature of molecules it applies concepts that pertain to the nineteenth-century classical model of the molecule, i.e, bond length, bond order, force constant, torsional rigidity and steric congestion. Transferable numerical values are empirically... 

Nevertheless, chemists have been planning their reactions for more than a century now, and each day they run hundreds of thousands of reactions with high degrees of selectivity and yield. The secret to success lies in the fact that chemists can build on a vast body of experience accumulated over more than a hundred years of performing millions of chemical reactions under carefully controlled conditions. Series of experiments were analyzed for the essential features determining the course of a reaction, and models were built to order the observations into a conceptual framework that could be used to make predictions by analogy. Furthermore, careful experiments were planned to analyze the individual steps of a reaction so as to elucidate its mechanism. 

The Mills-Nixon hypothesis that small ring annelation on benzene would induce bond fixation (bond alternation) by trapping out one Kekul6 tautomer is a casualty of early twentieth century structural chemistry. Due to a lack of direct methods for analyzing molecular structure, structural postulates of that time were often supported by an analysis of product distributions. An experimental observable such as product selectivity or isomer count was correlated to an unobservable structural feature derived on the basis of a chemical model. Classical successes of this method are van t Hoff s proof of the tetrahedral carbon atom and Fischer s proof for the configuration of sugars. In the case of Mills and Nixon, however, the paradigm broke down. 

After over half a century of chemotherapy research, cancer remains one of the most difficult life-threatening diseases to treat, a consequence of factors that include limitations of animal models, tiunour diversity, drug resistance and the side effects of therapy. Although there have been successes, most notably in treatment of testicular cancer [1], chemotherapy can currently still offer only a modest increase in survival time in the majority of advanced disease cases [2], The incidence of cancer is increasing due to ageing populations in most countries, and it has been estimated that in 20 years time there will be 20 million new cancer patients worldwide each year [3]. An optimistic view, however, is that in the coming decades advances in prevention, detection and treatment will see cancer becoming considered not as a fatal but as a chronic disease [3]. 

The reductionist approach to science has been extremely successful for several centuries. Its goal was the postulation of a hypothesis, later of a model, and ultimately of a theory, from experimental data (induction) or the postulation of a model with subsequent experimental verification (deduction). Parallel to the availability of a hyper-exponentially growing amount of data, a complementary approach is taking shape, termed a data-driven or systems approach. 

The two-filament model of the sarcomere was proposed half a century ago (Huxley and Hanson, 1954 Huxley and Niedergerke, 1954) and has been proved to be highly successful in explaining many features of contracting muscle. However, it was realized early that the model is unable to... 

A clonal model places all the discriminating action at the very bottom of the evolutionary events and that proposal, in turn, leads to the uniformity argument. Major development occurs early on when the chemical system is at maximum plasticity, and that is not only the source of basic uniformity but also the major source of emotional resistance to the new model within the scientific community. The proposal that chemistry worldwide would either give rise to the same mode of life or to no life at all seems an assault on common sense, the same common sense that has been so successfully assaulted by all the pioneers in science early in the past century. 

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