Theoretical Biology Forum最新文献

Nowadays, the idea that life affects the development of the planetary environment, and can, in turn, affect the future evolution of itself (in a coevolutionary way) is well-accepted. However, since the proposal of the Gaia hypothesis, there has been widespread criticism. Most of it is related to teleology, the absence of natural selection at a universal scale, and the lack of planetary reproduction. Some of the problems concerning the 'internal' logic of the idea have been resolved. Nevertheless, it is not sure whether Earth can be considered a unit of selection and (therefore) Gaia can adapt according to Darwinian evolution. After Lovelock and Margulis, Gaia has been considered a symbiotic planet composed of biotic (the biosphere) and abiotic (the geosphere-atmosphere) interacting with and coevolving elements. Here I propose why and suggest how a Gaian system should be considered alive in any evolutionary sense. I take into consideration the three principal criticisms and I analyse them following a logic-inductive reasoning. I use thought experiments and analogical arguments to analyse the rationale and the mechanisms by which Gaia evolves and may reproduce. This reasoning could allow rejecting the aforementioned criticisms as outdated and insufficient to discredit the main idea. I argue that without invoking teleology - so without any foresight or planning - a Gaian planet can be considered a coevolutionary system analogous to a multicellular body: a super-unit of selection. I describe different situations according to which Gaia is able to reproduce and transfer her planetary genome to other uninhabited or inhabited planets. Then I suggest that Gaia can face exclusion- competition-coexistence states depending on the fitness of her biota compared to those of the other reproducing biospheres. This demonstrates that Gaia can reproduce and evolve in competition-cooperation with other planets. Some deep implications arise from this evidence, also in light of the recent discovery of a new solar system with Earth-like planets by NASA.

The dawn of photosynthesis, characterized by the research of Priestley, Ingen- Housz and Senebier, culminated in 1804 with a historical essay of Théodore De Saussure. According to the historians, during the first half of the nineteenth century in which the genesis of the cell theory started off, the research on photosynthesis met a phase of stagnation. Indeed, the literature review of the period does not report particular innovation; however, several scientists (botanists, physiologists, and chemists) supported the thesis of De Saussure with a series of analyses that, in our opinion, deserve to be known. Mirbel, De Candolle, Raspail, Berzelius, Payen, Dutrochet, von Mohl, and other scholars attempted to expand knowledge on photosynthesis but were not able to arrive at a theory that was consistent with a functional mechanism, nor with a suitable chemical model to explain the transformation of the water and carbon dioxide into sugars. A classic case of such inadequacy concerns the discovery of chlorophyll. This compound, isolated in 1818 by Pelletier and Caventou, remained an enigma for many years and was never put in relation with the synthesis of starch. The accurate research of von Mohl led this scientist to believe that the granules of chlorophyll were entirely independent of starch granules, although in many cases these latter were observable inside the granules of chlorophyll. Only in the early forties, Justus von Liebig realized that the assimilation of carbon and hydrogen required a series of chemical reactions that, starting from some organic acids, ended in the formation of sugar. In conclusion, our analysis does not lead to define this period as stagnation but rather as transition, in which the concept of photosynthesis was clear, even though difficult to treat under physiological and chemical views. From the sixties, the researches of Julius von Sachs will open a new road, thanks also to the research carried out in the transition period.

This essay responds to Peter T. Saunders's call to go Beyond the neo-Darwinist Paradigm. While there is much to commend in his analysis, especially his suggestion that the extended evolutionary synthesis (EES) may not go far enough, he leaves the question of whether this should involve mere revision or total replacement open. A historiographical review reveals significant problems stemming from certain positivist assumptions and commitments within neo-Darwinian orthodoxy and the EES over and above any scientific considerations. As such, mere tweaking of the existing paradigm or its extension will do little to remedy the intellectual prejudices currently plaguing it. A complete overhaul is suggested by applying the López Ontological Demarcation Design (LODD) principle with biology in a multidisciplinary, non-reductionist philosophical framework. Building on the concept of Organismic-Systems Biology (OSB), a component of General Systems Theory (GTS) associated with polymathic biologist Ludwig von Bertalanffy (1901-1972), and cosmic evolution (CE) proposed by UCLA philosopher John Elof Boodin (1869-1950), the outline of a new evolutionary synthesis is offered as a prolegomenon to further study and evaluation.

Intimate partner violence (IPV) has been a well-studied problem in the past psychological literature, especially through its classical methodology such as qualitative, quantitative and mixed methods. This article introduces two basic stochastic models as an alternative approach to simulate the short and long-term dynamics of a couple at risk of IPV. In both models, the members of the couple may assume a finite number of states, updating them in a probabilistic way at discrete time steps. After defining the transition probabilities, we first analyze the evolution of the couple in isolation and then we consider the case in which the individuals modify their behavior depending on the perceived violence from other couples in their environment or based on the perceived informal social support. While high perceived violence in other couples may converge toward the own presence of IPV by means a gender-specific transmission, the gender differences fade-out in the case of received informal social support. Despite the simplicity of the two stochastic models, they generate results which compare well with past experimental studies about IPV and they give important practical implications for prevention intervention in this field.

Description: The understanding of the factors governing the enzyme catalysis is one of the most important goals of biochemistry and biophysics. In this context the contribution of theoretical research might be of high relevance. However, despite the huge amount of proposed approaches, the modelling of enzyme reactions still represents a very difficult task and a definitive and conclusive theoretical-computational strategy is still far from being available. In this study, after a presentation of the main difficulties associated to a coherent and possibly rigorous modelling of these processes, we present a computational theoretical method specifically designed for addressing complex molecular systems eventually applied to a benchmark reaction: the initial proton transfer in Triosephosphate Isomerase. This latter species, termed as the 'perfect enzyme' because of its exceptional ability as catalyst, provides an excellent test for evaluating the different environmental and intrinsic determinants at the basis of enzyme activity.

Description: Ever since Darwin, there have been challenges to the claim that the natural selection of small random variations is a sufficient explanation of evolution. Even mainstream evolutionists are now beginning to accept that something more is required. The question is whether this will be merely a few add-ons that leave the paradigm unaltered, or whether the whole framework of explanation, including its application to other disciplines, will be changed.

Description: A number of common features can be observed in the earliest developing embryos of all animal phyla. A simple extant model of morphogenesis is outlined here, with the aim of giving a model of the relatively rapid appearance of Cambrian animals, 541-515 mya. Developmental patterning, elucidated by a simple linear model with only short-range diffusion of ligands, is given as the origin of the most primitive animals. The key aspect of the model involves the interaction between the emergence of the Wnt and Hedgehog (Hh) signaling pathways. The non-canonical Wnt pathway is crucial in first establishing a sphere of cells, by way of cell-cell connection fi bers. A mutation in the Wnt pathway at the dawn of multicellular organisms is argued to have given rise to the early Hh pathway, and their interaction gives two spatially separate gene determination regions, the key goal of biological patterning.

Description: The aim of this paper is a free interpretation and reconstruction of a part of Giovanni Virginio Schiaparelli's essay (1898) where the author presents some ideas about a correspondence between living organisms and geometrical curves. From our analysis we derive a new approach to the ago-antagonist conception of the Darwinian evolution theory which is a continuation of [2].