Realizamos un recorrido por la ontología de Xavier Zubiri propuesta en Sobre la esencia para descubrir cómo aborda el problema de la esencia quidditativa. Tras consideraciones previas, se analiza la tradicional concepción de esencia específica desmigajando paulatinamente la relación esencia-especie-individuo. Con el phylum entendido como esquema constitutivo transmitido genéticamente y la especie como lo que constituye la pertenencia del engendrado a su phylum, la esencia quidditativa es mostrada como momento de la esencia constitutiva individual.

The aim of this article is to analyze Zubiri is concept of phylum. For this purpose, I analyze the meaning of phylum for Zubiri and that of biological phylum, explaining the validity of the former with respect to the latter. The consequences of this concept for evolutionary theory are also presented..

The cellular processes of transport, division and, possibly, early development all involve microtubule‐based motors. Recent work shows that, unexpectedly, many of these cellular functions are carried out by different types of kinesin and kinesin‐related motor proteins. The kinesin proteins are a large and rapidly growing family of microtubule‐motor proteins that share a 340‐amino‐acid motor domain. Phylogenetic analysis of the conserved motor domains groups the kinesin proteins into a number of subfamilies, the members of which exhibit a common molecular organization and (...) related functions. The kinesin proteins that belong to different subfamilies differ in their rates and polarity of movement along microtubules, and probably in the particles/organelles that they transport. The kinesins arose early in eukaryotic evolution and gene duplication has allowed functional specialization to occur, resulting in a surprisingly large number of different classes of these proteins adapted for intracellular transport of vesicles and organelles, and for assembly and force generation in the meiotic and mitotic spindles. (shrink)

The members of the phylum Cnidaria (corals, sea anemones, medusae) are all equipped with stinging cells (cnidocytes, nematocytes), which serve mainly in prey capture and defense. The secretory product of these cells is a most complicated extrusome consisting of a cyst containing a tubule and a liquid matrix. Mechanical stimulation of the cell's cnidocil apparatus by a prey or an offender leads via bioelectrical signal transduction to the explosive discharge of the cnidocyst. In stenoteles of Hydra this process, during (...) which the tubule is everted out of the cyst, takes less than 3 msec. The forces involved are partly due to spring‐like tensions stored in the collagenous structural compartment, and partly to an osmotically generated intracapsular pressure, which can amount to 150 bar (1.5 × 107 Pa). The osmotic machinery depends on the presence in the cyst's matrix of inorganic cations (either K+, Mg2+ or Ca2+) and rare polyanions (poly‐γ‐L‐glutamates), which, so far, have not been reported from recently evolved eukaryotes. The discharging cyst acts like a self‐reloading syringe, injecting poison and other components into the target. Since the cnidocytes are incapable of regenerating their exocytosed cysts, they have to be replaced by new cells derived by differentiation from pluripotent stem cells (interstitial cells). (shrink)

1. Being an Animal Human beings are animals: phylum: chordata, class: mammalia, order: primates, family: hominids, species: homo sapiens, subspecies: homo sapiens sapiens. According to current scientific opinion, we evolved approximately 200,000 years ago in Africa from ancestors whom we share with the other great apes. What does it mean that we are animals? Scientifically speaking, an animal is essentially a complex, multicellular organism that feeds on other life forms. But what we share with the other animals is not (...) just a definition: it is a history – that is, it is a story – and a resulting set of attributes and circumstances, and an ecosystem, and a planet. What is the story? Living things are homeostatic systems – they maintain themselves through a process of nutrition that enables them to work constantly at replacing the fragile materials of which they are composed. Living things also work at reproducing, or contributing to the reproduction, of other living things that maintain themselves in essentially the same way. To engage in those activities is essentially what it means to be alive. And in order to engage in those activities, a living thing must be, in some way, responsive to conditions in its environment. Plants, for instance, respond to dryness, by growing deeper roots, or to sunshine, by turning their leaves in its direction. Even a unicellular organism is drawn to some things and recoils from others. (shrink)

Derek Nurse looks at variations in the form and function of tense and aspect in Bantu, a branch of Niger-Congo, the world's largest language phylum. Bantu languages are spoken in central, eastern, and southern sub-Saharan Africa south of a line between Nigeria and Somalia. By current estimates there are between 250 and 600 of them, as yet neither adequately classified nor fully described. Professor Nurse's account is based on data from more than 200 Bantu languages and varieties, a representative (...) sample of which is freely available on the publisher's website. He devotes substantial chapters to the analysis and comparison of the different tense and aspect systems found in Bantu. He also examines the verbal categories with which they interact, including negation and focus. Synchronic and diachronic perspectives are interwoven throughout the book. Following a brief history of Bantu over the last five thousand years, the final two chapters look systematically at the history of tense and aspect in Bantu. The first deals with the reconstruction of the earlier forms from which contemporary structures, morphemes, and categories are derived, and the second with the processes of change, including grammaticalization, by means of which older analytical structures and independent lexical items moved as they became incorporated as grammatical inflections and categories. (shrink)

The placozoan Trichoplax adhaerens is a tiny hairy plate and more simply organized than any other living metazoan. After its original description by F.E. Schulze in 1883, it attracted attention as a potential model for the ancestral state of metazoan organization, the “Urmetazoon”. Trichoplax lacks any kind of symmetry, organs, nerve cells, muscle cells, basal lamina, and extracellular matrix. Furthermore, the placozoan genome is the smallest (not secondarily reduced) genome of all metazoan genomes. It harbors a remarkably rich diversity of (...) genes and has been considered the best living surrogate for a metazoan ancestor genome. The phylum Placozoa presently harbors three formally described species, while several dozen “cryptic” species are yet awaiting their description. The phylogenetic position of placozoans has recently become a contested arena for modern phylogenetic analyses and view‐driven claims. Trichoplax offers unique prospects for understanding the minimal requirements of metazoan animal organization and their corresponding malfunctions. (shrink)

This chapter is concerned with the Cambrian explosion. It considers only one particular kind of explanation for the Cambrian radiation: that major innovations in animal body plan were produced from relatively few genetic changes of large phenotypic effect. It investigates the developmental genetic hypothesis of the origin and maintenance of body plans. This chapter suggests that the genetic architecture underlying body plans was not set during the Cambrian and has been immutable since. It shows that the link between body plan (...) and phylum can become blurry when the minor phyla are considered. (shrink)

Chelicerates (scorpions, horseshoe crabs, spiders, mites and ticks) are the second largest group of arthropods and are of immense importance for fundamental and applied science. They occupy a basal phylogenetic position within the phylum Arthropoda, and are of crucial significance for understanding the evolution of various arthropod lineages. Chelicerates are vectors of human diseases, such as ticks, and major agricultural pests, such as spider mites, thus this group is also of importance for both medicine and agriculture. The developmental genetics (...) of chelicerates is poorly understood and a challenge for the future progress for many aspects of chelicerate biology is the development of a model organism for this group. Toward this end, we are developing a chelicerate genetic model: the two‐spotted spider mite Tetranychus urticae. T. urticae has the smallest genome of any arthropod determined so far (75 Mbp, 60% of the size of the Drosophila genome), undergoes rapid development and is easy to maintain in the laboratory. These features make T. urticae a promising reference organism for the economically important, poorly studied and species‐rich chelicerate lineage. BioEssays 29:489–496, 2007. © 2007 Wiley Periodicals, Inc. (shrink)

Ernst Haeckel’s popular book Nat¨urliche Sch¨opfungs- geschichte (Natural history of creation, 1868) represents human species in a hierarchy, from lowest (Papuan and Hottentot) to highest (Caucasian, including the Indo-German and Semitic races). His stem-tree (see Figure 1) of human descent and the racial theories that accompany it have been the focus of several recent books—histories arguing that Haeckel had a unique position in the rise of Nazi biology during the first part of the 20th century. In 1971, Daniel Gasman brought (...) the initial bill of particulars; he portrayed Haeckel as having specific responsibility for Nazi racial programs. He argued that Darwin’s champion had a distinctive authority at the end of the 19th century, throwing into the shadows the myriads of others with similar racial attitudes.1 But it was not simply a general racism that Haeckel expressed; he was, according to Gasman (1971: 157–159), a virulent anti-Semite. Since its original publication, Gasman’s thesis has caught on with a large number of historians, so that in the present period it is usually taken as a truism, an obvious fact of the sordid history of biological thought in the first half of the 20th century.2 Perhaps the most prominent scholar—at least among historians of biology—to adopt and advance Gasman’s contention was Stephen Jay Gould. In his first book, Ontogeny and Phy- logeny (1977), Gould took as his subject Haeckel’s principle of recapitulation, the proposal that during ontogeny the developing embryo went through the same morphological stages as the phylum passed through in its evolutionary descent. So according to this conception, the human embryo begins as a one-celled creature, then takes on the form of an ancient invertebrate (e.g., a gastraea), then of a primitive vertebrate, then of an early mammal, then of a primate, and finally of a distinct.. (shrink)

Three thoughts of culture: (1) the logogram: high-level software, the ROM BIOS of civilisation, the ‘best that has ever been thought and written’ (Matthew Arnold), secular theology, social phylum, explicitly ideal rampart against philistine disaggregation and the entropy of commodification, desperate and universal cognitive erection in the face of the massive loss of integrity brought about by capital; (2) the decay of the logogram: low-level shoring-up routine, localised resistance mediated through patchy and fragmented attempts at reconstitution, quotidian custom and (...) regional habit nostalgically valorised at the point of their historical evaporation, instantly fit only for museums, tourists and markets; (3) the death of the logogram: evacuation of the hard-wired constraint of organic programming, reinterfacing of cognition and culture with the machine, technological reprogramming of consciousness driven by intensive economic shifts. (shrink)

From the early nineteenth century, the successful use of fossils in stratigraphy oriented paleontology towards geology. The consequent marginalising of biological objectives was countered in the twentieth century by the rise of ‘Paläobiologie’, first in the German cultural area and only later, as ‘paleobiology’, in the anglophone world. Several kinds of paleobiological research flourished internationally after the Second World War, among them the novel field of ‘paleoecology’. Within this field there were attempts to apply functional morphology to the problematical cases (...) of fossil organisms, for which functions cannot be observed directly. This article describes the origins of the kind of functional inference for fossils that I proposed in 1961 as the method of ‘paradigms’. Here I summarize some of my ‘worked exemplars’, which were intended to show the paradigm method in action. These case-studies were all taken from the paleontologically important phylum of the Brachiopoda, but the method was claimed to have much wider implications for the interpretation of the fossil record in terms of adaptive evolution. This article takes the history of the paradigm method as far as the late 1960s. I hope to trace, in a sequel, its ambivalent fate during the 1970s and beyond, when for example Gould’s critique of ‘the adaptationist programme’ and the rise of computer-based quantitative methods for the evolutionary interpretation of the fossil record led to the relative eclipse of functional morphology in paleontology. (shrink)

There is renewed interest in how the different body plans of extant phyla are related. This question has traditionally been addressed by comparisons between vertebrates and Drosophila. Fortunately, there is now increasing emphasis on animals representing other phyla. Pentamerally symmetric echinoderms are a bilaterian metazoan phylum whose members exhibit secondarily derived radial symmetry. Precisely how their radially symmetric body plan originated from a bilaterally symmetric ancestor is unkown, however, two recent papers address this subject. Peterson et al.(1) propose a (...) hypothesis on evolution of the anteroposterior axis in echinoderms, and Arenas-Mena et al.(2) examine expression of five posterior Hox genes during development of the adult sea urchin. BioEssays 23:211–214, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

Every living entity requires the capacity to defend against viruses in some form. From bacteria to plants to arthropods, cells retain the capacity to capture genetic material, process it in a variety of ways, and subsequently use it to generate pathogen-specific small RNAs. These small RNAs can then be used to provide specificity to an otherwise non-specific nuclease, generating a potent antiviral system. While small RNA-based defenses in chordates are less utilized, the protein-based antiviral invention in this phylum appears (...) to have derived from components of the same ancestral small RNA machinery. Based on recent evidence, it would seem that RNase III nucleases have been reiteratively repurposed over billions of years to provide cells with the capacity to recognize and destroy unwanted genetic material. Here we describe an overview of what is known on this subject and provide a model for how these defenses may have evolved. RNase III nuclease domains are widely used in an array of RNA metabolic functions as well as antiviral defenses. Here, we review their current usage as well as provide insight into how these domains may have shaped all major antiviral pathways over the course of evolution. (shrink)

The standard explanation for the origin of bilateral symmetry is that it conferred an advantage over radial symmetry for directed locomotion. However, recent developmental and phylogenetic studies suggest that bilateral symmetry may have evolved in a sessile benthic animal, predating the origin of directed locomotion. An evolutionarily feasible alternative explanation is that bilateral symmetry evolved to improve the efficiency of internal circulation by affecting the compartmentalization of the gut and the location of major ciliary tracts. This functional design principle is (...) illustrated best by the phylum Cnidaria where symmetry varies from radial to tetraradial, biradial and bilateral. In the Cnidaria, bilateral symmetry is manifest most strongly in the internal anatomy and the disposition of ciliary tracts. Furthermore, the bilaterally symmetrical Cnidaria are typically sessile and, in those bilaterally symmetrical cnidarians that undergo directed locomotion, the secondary body axis does not bear a consistent orientation to the direction of locomotion as it typically does in Bilateria. Within the Cnidaria, the hypothesized advantage of bilateral symmetry for internal circulation can be tested by experimental analysis and computer modeling of fluid mechanics. The developmental evolution of symmetry within the Cnidaria can be further explored through comparative gene expression studies among species whose symmetry varies. BioEssays 27:1174–1180, 2005. © 2005 Wiley Periodicals, Inc. (shrink)

In this paper I investigate the mechanics of killing, brining together neuroscience, military history, and the work of the French philosophers Gilles Deleuze & Félix Guattari. Investigating the Columbine killers and the way they negotiate with the intensity of the act of killing allows me to construct a concept of “political physiology,” defined as “interlocking intensive processes that articulate the patterns, thresholds, and triggers of emergent bodies, forming assemblages linking the social and the somatic, with sometimes the subjective as intermediary.” (...) While most people must be in a blind rage to kill at close range, the Columbine killers raised the threshold at which an evolutionarily inherited non-subjective “rage agent” kicks in, thus allowing themselves to be subjects in the act of killing. Yet they were not “cold-blooded killers,” either, those who lower the intensity of the act of killing below the threshold that prevents most interpersonal violence from reaching lethal proportions, since they committed suicide soon after their killing spree from burning out. The success of the Columbine killing machine warns us of a “machinic phylum” whose singularities are virtually available for incorporation into bodies by subjects willing to undergo extreme experiments in political physiology. (shrink)

. During the lifetime of Pierre Teilhard de Chardin, the Roman Catholic Church passed through deep changes of doctrines as well as ecclesiastical structures, marked by the First and Second Vatican Councils. In that historical period, the perceived threat of the more and more encompassing theory of universal evolution was the main reason that Teilhard was forbidden to publish anything about its theological or philosophical significance. Teilhard survived these lifelong restrictions within his beloved church by embracing the paradigm of the (...) church as “the axis of universal convergence.” His scientific background as a geobiologist gave him the necessary distance from the temporary statements of the magisterium of the Church. Over the whole of human history, however, he believed the Church to be the “phylum” whose development leads to the cosmic Christ as a guidance beam leads to a goal. (shrink)

Ce travail pose la question des critères de la „progression biologique“ , d'après les documents fossiles, dans le monde des organismes, c'est-à-dire de ce perfectionnement qui ne s'arrête pas à l'intérieur du cadre d'un phylum donné, comme le „perfectionnement de l'adaptation“, mais qui conduit, au-de-là de phylums de rang différent, à des types supérieurs, par exemple, des Poissons pas les Amphibies et les Reptiles jusqu'aux Mammifères ou aux Oiseaux. Deux groupes de critères y sont recensés en détail, leur contenu (...) est exposé, et on les examine pour voir s'ils caractérisent sans ambiguïté la „progression biologique“. Le premier groupe comprend les critères de „différenciation croissante“ et „d'intégration harmonique”. Ils sont fondés sur la différenciation morphophysiologique ou plus exactement sur la „totalité” des organismes, c'est-à-dire leur multiplicité dans l'unité. Le second groupe de critères, à savoir „indépendance croissante du milieu” et „autonomie individuelle croissante”, part des relations de l'organisme au milieu et aux autres formes vivantes et souligne la „subsistence” des individus, c'est-à-dire leur plus ou moins grande indépendence ou leur stabilité interne. Comme „totalité” et „subsistence” sont les éléments décisifs d'une définition biologique de l'individu, on peut dire que la „progression biologique“ d'un organisme est d'autant plus élevée que sa totalité et subsistence et par là son être individuel sont plus accusés.Tous les critères mentionnés ne sont pas uniformes. Les motifs de leur imprécision sont divers. Tout d'abord, il n'y a pas encore de définition unique et complète de l'individu biologique, de sorte qu'on ne peut circonscrire d'une manière univoque ce qui confère à un organisme une individualité plus forte ou moins forte. Ensuite les lignées au-delà desquelles s'accomplissent des perfectionnements, et dont l'une reste intérieur au phylum , tandis que l'autre le transcende , sont entrelacées si intimement et d'une façon si particulière qu'elles ne se laissent pas séparer franchement et décrire rigoureusement selon leurs signes distinctifs. Tout représentant d'un phylum, peu importe son palier, est en effet nécessairement inséré dans un milieu et en quelque façon spécialisé. Il n'existe pas des types à caractères phylétiques purs, qui ne montrent dans aucune direction un „perfectionnement de l'adaptation”, mais seulement des marques caractéristiques de la „progression biologique”. Enfin nous ne connaissons pas les restes fossiles que le développement ou la formation des grands phylums du règne animal, à savoir du rameau des Vertébrés et des divers groupes des Invertébrés, mais non pas le plus intéressant et le plus important, leur „progression biologique” jusqu'au degré d'organisation qu'ils présentent déjà à l'époque du Silurien ou plutôt du Cambrien. C'est cela seulement qui permettrait une vue plus profonde sur la nature de la „progression biologique”.Die Arbeit stellt die Frage nach den Kriterien des fossil belegten Biologischen Aufstiegs” der Organismenwelt, d.h. derjenigen Vervollkommnung, die sich nicht innerhalb des Rahmens eines gegebenen Bauplans hält, wie die „Anpassungsvervollkommnung”, sondern über verschiedenrangige Baupläne hinweg zu höheren Typen führt, z.B. von den Fischen über die Amphibien und Reptilien zu den Säugern bzw. Vögeln. Ausführlich werden zwei Gruppen von Kriterien besprochen, ihr Inhalt dargelegt und ihre Eindeutigkeit zur Charakterisierung des „Biologischen Aufstiegs” untersucht. Die erste Gruppe umfasst die Kriterien der „zunehmenden Differenzierung” und „harmonischeren Integration”. Diese legen die morphologisch-physiologische Differenzierung oder genauer die „Ganzheit” der Organismen zugrunde, d.h. ihre Vielheit in der Einheit. Die zweite Kriteriengruppe, nämlich „zunehmende Umweltunabhängigkeit” und „zunehmende individuelle Autonomie”, geht von den Beziehungen des Organismus zur Umwelt und zu andern Lebensformen aus und betont die „Subsistenz” der Individuen, d.h. ihr grösseres oder geringeres Losgelöstsein oder ihre Selbständigkeit. Da nun „Ganzheit” und „Subsistenz” die entscheidenden Elemente einer biologischen Definition des Individuums sind, lässt sich sagen, dass der „Biologische Aufstieg” eines Organismus um so höher ist, je stärker seine Ganzheit und Subsistenz und damit sein Individuumsein ist.Eindeutigkeit kommt allen genannten Kriterien nicht zu. Die Gründe für ihre Unschärfe sind verschiedener Art. Zunächst gibt es noch keine eindeutige und vollständige Definition des biologischen Individuums, so dass sich nicht eindeutig umreissen lässt, was einem Organismus eine stärkere oder weniger starke Individualität verleiht. Dann sind die Linien, über die sich Vervollkommnungen vollziehen und von denen die eine innerhalb des Bauplans bleibt , die andere aber über ihn hinausführt so innig und in so eigenartiger Weise miteinander verflochten, dass sie sich nicht sauber scheiden und in ihren charakteristischen Merkmalen genau beschreiben lassen. Jeder Vertreter eines Bauplans, ganz gleich von welcher Ranghöhe, ist nämlich notwendig in eine Umwelt eingepasst und irgendwie spezialisiert. Es gibt keine Typen mit reinen Bauplanmerkmalen, die nach keiner Richtung hin eine „Anpassungsvervollkommnung”, sondern nur Merkmale des „Biologischen Aufstiegs” aufweisen. Schliesslich kennen wir fossil nur die Entfaltung oder Ausgestaltung der Grossbaupläne des Tierreichs, nämlich des Wirbeltierstammes und der verschiedenen Gruppen der Wirbellosen, nicht aber das Interessanteste und Wichtigste, nämlich ihren „Biologischen Aufstieg” zu der organisatorischen Höhe, mit der sie sich im Silur bzw. im Kabrium bereits vorstellen. Das erst würde einen tieferen Einblick in das Wesen des „Biologischen Aufstiegs” vermitteln.This article deals with the question of the criteria for the “biological ascent” of the organic world, resting on fossil evidence. That is, of that improvement which is not only restricted to the framework of a given “general structure” as is the “improvement of adaptation”, but which also leads beyond general structures of differentiated levels to a higher type,e.g. from the fishes through the amphibians and reptiles to the mammals or birds. Two groups of criteria are discussed at length, their content exposed and their univocity for the characterisation of this “biological ascent” is examined. The first group includes the criteria of “increasing differentiation” and “more harmonious integration”. The basis for these is the morphological-physiological differentiation, or more exactly, the “totality” of the organisms,i.e., their variety-in-unity. The second group of criteria, “increasing independence of environment” and “increasing individual autonomy”, is derived from the relationships of the organism to its environment and to other living forms, and stresses the “subsistence” of individuals,i.e., their greater or lesser degree of independence or self-sufficiency. Now since “totality” and “subsistence” are the decisive elements in a biological definition of the individual, it may be said that the “biological ascent” of an organism is higher, the more perfect its totality and subsistence and therefore its individuality is.The criteria mentioned are not univocal. The reasons for this lack of clarity are varied. First of all, there is no univocal and complete definition of the biological individual, so that it cannot be exactly stated just what gives an organism a more or less perfect individuality. Then the lines, along which improvements are made, and according to which the one remains within the general structure and the other goes beyond the general structure , are so intimately and singularly bound together, that they cannot be cleanly distinguished, and their characteristic notes exactly described. For each representative of a general structure, regardless of its level, is necessarily fitted into an environment and somehow or other specialised. There are no types with only notes of the general structure which show in no direction an “improvment of adaption”, but only the signs of “biological ascent”. Finally, we only have fossil evidence for the development or deployment of the “great general structures” of the animal world, namely that of the vertebrates and of the different groups of invertebrates, not for the most interesting and most important, that is, their “biological ascent” to the level of organisation with which they are found in the Silurian or Cambrian periods. Only that would give us a deeper insight into the essence of “biological ascent”. (shrink)

Metazoa are one of the great monophyletic groups of organisms. They comprise several major groups of organisms readily recognizable based on their anatomy. These major groups include the Bilateria (animals with bilateral symmetry), Cnidaria (jellyfish, corals and other closely related animals), Porifera (sponges), Ctenophores (comb jellies) and a phylum currently made up of a single species, the Placozoa. Attempts to systematize the relationships of these major groups as well as to determine relationships within the groups have been made for (...) nearly two centuries. Many of the attempts have led to frustration, because of a lack of resolution between and within groups. Other attempts have led to “a new animal phylogeny”. Now, a study by Dunn et al.,1 using the expresssed sequence tag (EST) approach to obtaining high‐throughput large phylogenetic matrices, presents an “even newer” animal phylogeny. There are two major aspects of this study that should be of interest to the general biological community. First, the methods used by the authors to generate their phylogenetic hypotheses call for close examination. Second, the relationships of animal taxa in their resultant trees also prompt further discussion. BioEssays 30:1043–1047, 2008. © 2008 Wiley Periodicals, Inc. (shrink)

The Crustacea present a variety of body plans not encountered in any other class or phylum of the Metazoa. Here we review our current knowledge on the complement and expression of the Hox genes in Crustacea, addressing questions related to the evolution of body architecture. Specifically, we discuss the molecular mechanisms underlying the homeotic transformation of legs into feeding appendages, which occurred in parallel in several branches of the crustacean evolutionary tree. A second issue that can be approached by (...) the comparative study of Hox genes and their expression in the Crustacea bears on the homology of the abdomen. We discuss whether the so‐called “abdominal” tagma of the crustaceans is homologous to the abdomen of insects. In addition, the homology of the abdomen between malacostracan and non‐malacostracan crustaceans has also been questioned. We also address the question of the molecular developmental basis of the apparent lack of an abdomen in barnacles. We discuss these issues in relation to the problem of constraint versus adaptation in evolution. BioEssays 25:878–887, 2003. © 2003 Wiley Periodicals, Inc. (shrink)

A recent paper by Shu et al.(1) reinterprets the fossil Vetulicola and related forms, all from the Lower Cambrian, as basal deuterostomes, assigning them their own phylum, Vetulicolia. Their conclusion is based on the presence of structures resembling gill slits and a trunk‐like region that shows evidence of segmentation. This report summarizes the fossil evidence for their interpretation and evaluates a possible alternative, that vetulicolians may instead be tunicate‐like chordates. Implications for our understanding of the nature of the primitive (...) deuterostome (and chordate) body plan are discussed. BioEssays 24:208–211, 2002. © 2002 Wiley Periodicals, Inc.; DOI 10.1002/bies.10064. (shrink)

Chaosmosis and Subjectivity: The Aesthetics of Félix Guattari (1930-1992) is the first doctoral thesis monographically devoted to the work of this great contemporary thinker. The aim of this study is the analysis of his aesthetics in the context of French post-structuralist thought, by means of a systematic analysis of the influences, stages and foundations of his work. From a state of the field which allows us to understand the historiographical keys in the reception of his thought, we then present the (...) development of the complete Guattarian works, paying special attention to all the historical correlates, in order to thus picture the post-Lacanian Guattari who writes about machinic production, collective enunciation, micropolitics and ecosophy. Next, we address the groundings of Guattarian aesthetic thought in relation to four problem-authors: Joyce, in relation to Guattari’s overwhelming volonté d’écriture; Proust, peak of Guattari’s analytic ambitions, and an opportunity to talk about the phylum machinique in the context of his theory of a nonindividualized enunciation; Kafka, the minor, and collective enunciation; and finally, Schumann, paradigmatic example of the great importance music had in Guattari’s work and life, and suitable viewpoint for a deep theory of the refrain. Ultimately, what this study tries to point out is the centrality of the aesthetic plane in Félix Guattari’s work, just as the profound richness of Guattarian contribution to Contemporary Aesthetics. (shrink)

The placozoan Trichoplax adhaerens has been bridging gaps between research disciplines like no other animal. As outlined in part 1, placozoans have been subject of hot evolutionary debates and placozoans have challenged some fundamental evolutionary concepts. Here in part 2 we discuss the exceptional genetics of the phylum Placozoa and point out some challenging model system applications for the best known species, Trichoplax adhaerens.

Nosso objetivo foi discutir a análise do estatuto das armas e do armamento no quadro de uma reflexão sobre a tecnologia como apresentada por Gilles Deleuze e Félix Guattari na obra Mil Platôs. Os autores oferecem uma interpretação sobre a especificidade desses elementos técnicos a partir de sua ligação com o processo de inovação das sociedades guerreiras nômades. Esse processo é indissociável de certo modo de operação da metalurgia artesanal e itinerante sobre o phylum maquínico, definido como matéria-movimento composta (...) por singularidades e manifesta em traços de expressão determinados. Porém, o phylum maquínico e a linhagem tecnológica do armamento também podem ser capturados por um aparelho de Estado, passando a funcionar de maneira distinta daquela em que operavam quando conexos ao espaço nômade. Essa captura está na gênese de uma indústria armamentista, cerne problemático da relação entre guerra, técnica e capital para o qual se direciona nossa reflexão final. (shrink)

The internal organs of all vertebrates are asymmetrically organised across the left–right axis. The development of this asymmetry is controlled by a molecular pathway that includes the signalling molecule Nodal and the transcription factor Pitx2, proteins encoded by genes that are predominantly expressed on the left side of all vertebrate embryos studied to date. Vertebrates share Phylum Chordata with two other groups of animals, amphioxus and the urochordates (including ascidians). Both these taxa develop left–right asymmetries, and recent studies have (...) begun to address the degree of conservation of nodal and Pitx2 in this process. Pitx2 is a member of the Pitx homeobox gene family, and in both amphioxus and ascidians Pitx gene expression is predominantly left sided. These studies suggest that left–right asymmetry in all chordates is regulated by a conserved developmental pathway, and that this pathway evolved before the separation of the lineages leading to living chordates. BioEssays 24:1004–1011, 2002. © 2002 Wiley‐Periodicals, Inc. (shrink)

In a cluster of books published originally in 1977, the two editions of La Révolution moléculaire, and L’Inconscient machinique, Guattari elaborated a typology of semiotic systems framed in a Peirce-Hjelmslev hybrid conceptual vocabulary. Reading across these three books I want to flesh-out a-signifying semiotics in relation to an infotech strand on the machinic phylum inspired by one of Guattari’s favourite examples of the kind of semiosis put into play by a-signifying signs : credit and/or bank cards. Guattari’s innovation was (...) to develop a-signifying signs in a typology of sign types but with respect to the problem of the relationship between material and semiotic dimensions in the age of planetary computerization and globalization. (shrink)

Introduction A Brief Conceptual Framework for Biology PART ONE: UNDERSTANDING NATURE 1. The Antecedents of Scientific Thought Animism, Totemism, and Shamanism The Paleolithic View Mesopotamia Egypt 2. Aristotle and the Greek View of Nature The Science of Animal Biology The Parts of Animals The Classification of Animals The Aristotelian System Basic Questions 3. Those Rational Greeks? Theophrastus and the Science of Botany The Roman Pliny Hippocrates, the Father of Medicine Erasistratus Galen of Pergamum The Greek Miracle 4. The Judeo-Christian Worldview (...) The Bishop of Hippo Scholastic Thought Islamic Science Books on Beasts Antecedents of a Revolution 5. The Revival of Science Andreas Vesalius and the Study of Structure William Harvey and the Study of Function Sir Francis Bacon’s Great Instauration Induction, Hypothesis, Deduction The Very Small--Animalcules Robert Hooke and the Discovery of Cells 6. Figur’d Stones and Plastick Virtue Marine Life on Mountain Tops? Figured Stones of Unknown Creatures Baron Cuvier Quarries of the Paris Basin Catastrophism and Uniformitarianism William Smith and the Geological Column Understanding Nature in 1850 PART TWO: THE GROWTH OF EVOLUTIONARY THOUGHT 7. The Paradigm of Evolution First Questions The Paradigm of Natural Theology First Answers 8. Testing Darwins Hypotheses Have Life Forms Changed over Time? Do Species Evolve into Different Species over Time? Has There Been Time Enough for Evolution? Is Natural Selection the Mechanism of Change? The Genetic Basis of Natural Selection Accounting for the Diversity of Life 9. In the Light of Evolution Comparative Anatomy Embryonic Development Classification Microstructure Molecular Processes 10. Life over Time The Origin of Life The Rise of Multicelled Organisms What Is a Phylum? Burgess Shale Metazoans Early Evolution of the Vertebrates The Age of Dinosaurs Birds, Mammals, and Flowering Plants The Rancho La Brea Tar Pits Human Evolution The Role of Extinction in Evolution PART THREE: CLASSICAL GENETICS 11. Pangenesis What Is the Question? Hippocrates and Aristotle The Darwinian Answer Assembling the Data Formulating the Hypothesis by Induction Galton’s Rabbits 12. The Cell Theory The Discovery of Cells: Robert Hooke Schwann and Cells in Animals Gametes as Cells Omnis cellula e cellula? The Technology of Cell Research 13. The Hypothesis of Chromosomal Continuity The Ephemeral Nucleus Schneider, Flemming, and Cell Division The Chromosomes and inheritance Gamete Formation Fertilization 14. Mendel and the Birth of Genetics Model for Monohybrid Crosses Model for Dihybrid Crosses Mendel’s Laws Initial Opposition to Mendelism 15. Genetics + Cytology: 1900-1910 Sutton’s Model The Cytological Basis of Mendel’s Laws Boveri and Abnormal Chromosome Sets Variations in Mendelian Ratios The Discovery of Sex Chromosomes 16. The Genetics of the Fruit Fly Morgan’s First Hypothesis Morgan’s Second Hypothesis The Fly Room Linkage and Crossing-Over The Cytological Proof of Crossing-Over Mapping the Chromosomes The Final Proof The Determinants of Sex The Conceptual Foundations of Classical Genetics 17. The Structure and Function of Genes One Gene, One Enzyme The Substance of Inheritance The Watson-Crick Model of DNA Genes and the Synthesis of Proteins The Genetic Code PART FOUR: THE ENIGMA OF DEVELOPMENT 18. First Principles The Peripatetic Stagirite The Death and Rebirth of Scientific Thought Harvey and Malpighi A Two-Millennial Summing Up Preformation versus Epigenesis 19. The Century of Discovery Von Baer’s Discovery of the Mammalian Ovum Darwin’s Contribution to Embryology Haeckel and Recapitulation 20. Descriptive Embryology Germ Layers The External Development of the Amphibian Embryo The Internal Development of the Amphibian Embryo 21. The Dawn of Analytical Embryology His, Roux, and Mosaic Development Driesch and Regulative Development Novelty in Development Cell Lineage Nucleus or Cytoplasm? Fin de Siècle 22. Interactions during Development Amphibian Organizers Secondary Organizers The Reacting Tissue The Chemical Nature of the Organizer Putting It All Together Conclusion Further Reading References Illustration Credits Index. (shrink)

The diploblastic Cnidaria form one of the most ancient metazoan phyla and thus provide a useful outgroup for comparative studies of the molecular control of development in the more complex, and more often studied, triploblasts. Among cnidarians, the reef building coral Acropora is a particularly appropriate choice for study. Acropora belongs to the Anthozoa, which several lines of evidence now indicate is the basal class within the phylum Cnidaria, and has the practical advantages that its reproduction is predictable, external (...) and accessible and that the base content of its genome is not strongly biased. The Acropora system has already provided insights into ancestral linkages of homeobox genes and the evolution of the Pax genes, and has the potential to provide further new perspectives on the age, role in development, and evolution of these and other gene families. BioEssays 22:291–296, 2000. © 2000 John Wiley & Sons, Inc. (shrink)

To answer the question in the title, we take as an example the model for the regulation of agonistic antagonistic couples (MRAAC). It is a model that associates 4 non-linear differential equations and allows to simulate balance, imbalance between two state variables, and control, if necessary, by two control variables of the same nature as the state variables: this control is defined as a bilateral strategy (bipolar therapy in the medical field). The super model for the regulation of agonism antagonistic (...) couples (SMRAAC), that may be also considered as an agonistic antagonistic network (AAN), associates several elementary MRAAC's, but the interconnection structure falls equally under the category of the agonistic antagonism (AA). First we indicate what may be the results of the interconnection, favourable or not. In the last case, a control can be performed, by acting upon a sole couple of the SMRAAC, even if other couples were imbalanced (with two AA control variables only). Simulation examples are given. We bring also a new result with the SMRAAC, i.e. the appearance of strange auractors with this model. The general models belonging to the AA phylum should put on a growing importance in the future, because they could be the sole models enable to control some complex systems by avoiding the perverse effects of the unilateral strategies. (shrink)

Cells in the basal metazoan phylum Cnidaria are characterized by remarkable plasticity in their differentiation capacity. The mechanism controlling asymmetric cell divisions is not understood in cnidarians or in any other animal group. PIWI proteins recently have been shown to be involved in maintaining the self‐renewal capacity of stem cells in organisms as diverse as ciliates, flies, worms and mammals. Seipel et al.1 find that, in the cnidarian Podocoryne carnea, the Piwi homolog Cniwi is transcriptionally upregulated when the polyp (...) generates buds, which will develop into medusae. Since transdifferentiation of striated muscle cells to smooth muscle cells also activated Cniwi expression, Cniwi appears to play a crucial role in differentiation events. The discovery should facilitate elucidation of the poorly understood factors that control asymmetric cell divisions at the beginning of animal evolution. BioEssays 26:929–931, 2004. © 2004 Wiley Periodicals, Inc. (shrink)

The term “hypnozoite” is derived from the Greek words hypnos and zoon. Hypnozoites are dormant forms in the life cycles of certain parasitic protozoa that belong to the Phylum Apicomplexa and are best known for their probable association with latency and relapse in human malarial infections caused by Plasmodium ovale and P. vivax. Consequently, the hypnozoite is of great biological and medical significance. This, in turn, makes the origin of the name “hypnozoite” a subject of interest. Some “missing” history (...) that is now placed on record shows that Miles B. Markus coined the term “hypnozoite”. While a PhD student at Imperial College London, he carried out research that led to the identification of an apparently dormant form of Cystoisospora. In 1976, he speculated: “If sporozoites of Isospora can behave in this fashion, then those of related Sporozoa, like malaria parasites, may have the ability to survive in the tissues in a similar way.” He adopted the term “hypnozoite” for malaria in 1978 when he wrote in a little-known journal that this name would “… describe any dormant sporozoites or dormant, sporozoite-like stages in the life cycles of Plasmodium or other Haemosporina.” At that time, the existence of a hypnozoite form in the life cycle of Plasmodium was still a hypothetical notion. In 1980, however, Wojciech A. Krotoski published details concerning his actual discovery of malarial hypnozoites, an event of considerable importance. (shrink)

The Cnidaria represent the most ancient eumetazoan phylum. Members of this group possess typical animal cells and tissues such as sensory cells, nerve cells, muscle cells and epithelia. Due to their unique phylogenetic position, cnidarians have traditionally been used as a reference group in various comparative studies. We propose the colonial marine hydroid, Hydractinia, as a convenient, versatile platform for basic and applied research in developmental biology, reproduction, immunology, environmental studies and more. In addition to being a typical cnidarian (...) representative, Hydractinia offers many practical and theoretical advantages: studies that are feasible in Hydra like regeneration, pattern regulation, and cell renewal from stem cells, can be supplemented by genetic analyses and classical embryology in Hydractinia. Metamorphosis of the planula larva of Hydractinia can be used as a model for cell activation and communication and the presence of a genetically controlled allorecognition system makes it a suitable model for comparative immunology. Most importantly, Hydractinia may be manipulated at most aspects of its (short) life cycle. It has already been the subject of many studies in various disciplines, some of which are discussed in this essay. BioEssays 23:963–971, 2001. © 2001 John Wiley & Sons, Inc. (shrink)

We only regard a system or a process as being “scientific” if it displays the three predominant characteristics of the natural sciences: predictability, repeatability and quantifiability. This by definition precludes intuition, subjective judgement, tacit knowledge, heuristics, dreams, etc. in other words, those attributes which are peculiarly human. Furthermore, this is resulting in a shift from judgment to calculation giving rise, in some cases, to an abject dependency on the machine and an inability to disagree with the outcome or even question (...) it. To tolerate such a situation could be seen as an abdication of professional responsibility. In complex technological and scientific environments, it is sometimes said that those who make best use of computers already know what the answer is (in ball park terms) before the calculation. (shrink)

© 2015 Elsevier Inc.Toxoplasma gondii is a protozoan pathogen in the phylum Apicomplexa that resides within an intracellular parasitophorous vacuole that is selectively permeable to small molecules through unidentified mechanisms. We have identified GRA17 as a Toxoplasma-secreted protein that localizes to the parasitophorous vacuole membrane and mediates passive transport of small molecules across the PVM. GRA17 is related to the putative Plasmodium translocon protein EXP2 and conserved across PV-residing Apicomplexa. The PVs of GRA17-deficient parasites have aberrant morphology, reduced permeability (...) to small molecules, and structural instability. GRA17-deficient parasites proliferate slowly and are avirulent in mice. These GRA17-deficient phenotypes are rescued by complementation with Plasmodium EXP2. GRA17 functions synergistically with a related protein, GRA23. Exogenous expression of GRA17 or GRA23 alters the membrane conductance properties of Xenopus oocytes in a manner consistent with a large non-selective pore. Thus, GRA17 and GRA23 provide a molecular basis for PVM permeability and nutrient access. (shrink)

The term "hypnozoite" is derived from the Greek words hypnos (sleep) and zoon (animal). Hypnozoites are dormant forms in the life cycles of certain parasitic protozoa that belong to the Phylum Apicomplexa (Sporozoa) and are best known for their probable association with latency and relapse in human malarial infections caused by Plasmodium ovale and P. vivax. Consequently, the hypnozoite is of great biological and medical significance. This, in turn, makes the origin of the name "hypnozoite" a subject of interest. (...) Some "missing" history that is now placed on record (including a letter written by P. C. C. Garnham, FRS) shows that Miles B. Markus coined the term "hypnozoite". While a PhD student at Imperial College London, he carried out research that led to the identification of an apparently dormant form of Cystoisospora (synonym: Isospora). In 1976, he speculated: "If sporozoites of Isospora can behave in this fashion, then those of related Sporozoa, like malaria parasites, may have the ability to survive in the tissues in a similar way." He adopted the term "hypnozoite" for malaria in 1978 when he wrote in a little-known journal that this name would "... describe any dormant sporozoites or dormant, sporozoite-like stages in the life cycles of Plasmodium or other Haemosporina." At that time, the existence of a hypnozoite form in the life cycle of Plasmodium was still a hypothetical notion. In 1980, however, Wojciech A. Krotoski published (together with several co-workers) details concerning his actual discovery of malarial hypnozoites, an event of considerable importance. (shrink)