Newsgroup: it.scienza.biologia
Titolo: Rivita di Biologia

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Rivista di Biologia /
Biology Forum
Abridged Articles
 
http://www.tilgher.it/biologia.html
Diretta da G. Sermonti
Ermanno Giglio-Tos
Dell'eredità e del valore reale e apparente dei caratteri somatici
Riv. Biol. 11 (1929)
Nessuno può negare che, nello stato attuale della scienza, sui caratteri
somatici si impernino tutte le questioni più interessanti della Biologia, e
come questi costituiscono per dir così l'unità di misura nella valutazione
dell'eredità e della variabilità organica. Noi dobbiamo perciò giustamente,
preoccuparci se questa unità di misura abbia un valore reale e costante, o
se pure non sia troppo soggetta ad oscillazioni accidentali nel qual caso
perderebbe assai dell'importanza che generalmente le si suole dare. Occorre
dunque indagare a tale uopo quale sia l'origine di questi caratteri, quale
il modo di manifestarsi, in quali rapporti stiano con l'ambiente e se e come
si trasmettano e si conservino di generazione in generazione.
Un primo principio fondamentale che dovrebbe essere considerato come un
assioma biologico si è che ogni carattere somatico deve avere direttamente o
indirettamente la sua base nel germe. Anche volendo ammettere, come vedremo,
che l'ambiente esterno sia un fattore importante in questo problema non
possiamo tuttavia supporre che esso possa esplicare la sua azione sul nulla.
Questa preammette implicitamente una base sulla quale possa poggiare e
questa base è il soma dell'organismo. Senza il soma e le cellule che lo
formano l'ambiente esterno non potrebbe agire, come nessuna forza può
rendersi palese nelle sue varie manifestazioni senza la materia.
E poiché, come sappiamo, le cellule del soma derivano dal germe è chiaro che
a questo devono risalire in ultima analisi tutte le proprietà che esse
posseggono e che sono causa, sotto l'influsso dell'ambiente, di quei
fenomeni che noi chiamiamo caratteri somatici, siano questi morfologici o
fisiologici.
[...]
Tuttavia nessuno potrà negare che non ostante tutta l'apparenza che possono
presentare questi caratteri per essere ritenuti dai sistematici come buoni e
costanti, la loro fissità sia pure sempre effimera e relativa, e quindi non
sia possibile basarsi sopra di essi per la determinazione delle specie.
Questa verrebbe ad assumere una tale incertezza ed instabilità, oscillante
con la oscillazione dell'ambiente, che perderebbe assolutamente tutto il
concetto vero e scientifico che noi soliamo dare alla specie, la quale viene
generalmente e giustamente considerata come un quid indipendente, sino ad un
certo punto, delle condizioni dell'ambiente.
Noi possiamo quindi anche in questo caso concludere che neanche la fissità o
costanza dei caratteri somatici può essere un criterio assoluto ed esatto
per la determinazione della specie.
Ora se così stanno le cose, se né l'entità o il valore dei caratteri
somatici né la loro costanza o fissità possono essere criteri buoni ed
assoluti per la determinazione delle specie, siamo necessariamente condotti
ad ammettere che il solo buon criterio per raggiungere tale scopo stia nella
costituzione intima del germe.
Dobbiamo dunque anzitutto affermare che la mancanza di un determinato
carattere somatico non è indizio sufficiente per asserire che esso non sia
stato ereditato.
La gravità di questa conclusione, alla quale del resto si è condotti dalla
forza ineluttabile dei risultati sperimentali, non sfugge a nessuno, quando
si pensi che nelle attuali condizioni della scienza il criterio su cui si
imperniano tutte le discussioni dell'eredità è quello unico e solo della
manifestazione dei caratteri somatici.
E come corollario della prima conclusione segue quest'altra: un carattere
somatico qualsiasi può essere contenuto nel germe ed ereditarsi senza
apparire nel soma del discendente nello stesso modo che nel progenitore
(...). Stando alle semplici manifestazioni somatiche si può essere indotti
in gravi errori nell'arguire dell'eredità dei caratteri perché potranno
essere giudicati latenti o nuovi caratteri che non sono tali in realtà, e
creduta mancante l'eredità in casi ove invece essa si è perfettamente
verificata, sebbene si sia manifestata nel soma con caratteri differenti.
Risulta dunque da quanto si è detto finora che data una qualsiasi
costituzione del germe ed ammesso che un determinato carattere sia in essa
rappresentato da un quid qualsiasi il modo di manifestarsi di questo
carattere nel soma dipende dalle condizioni dell'ambiente nelle quali il
carattere somatico deve esplicarsi.
[...]
Di fatto, poiché sappiamo che il germe risulta dall'unione dei due gameti,
parrebbe naturale che, volendolo rappresentare in funzione di questi, ciò si
dovesse fare con una addizione il che equivarrebbe a dire che i caratteri
somatici dei due individui sono dati dall'unione dei caratteri dei gameti e
quindi che in ogni cellula del soma dovrebbero trovarsi rappresentati
contemporaneamente, ma separati, i caratteri dell'uno e dell'altro gamete. E
in realtà se l'ipotesi delle particelle rappresentative dei caratteri
somatici, su cui si basano le teorie più in voga, quella di Weismann
sopratutto, fosse vera dovrebbe essere così.
[...]
Ma a chi esamina attentamente le cose è facile anche persuadersi che il
fondamento stesso di queste teorie non è esatto né conforme alla realtà dei
fatti.
Lo studio dell'istogenesi ci dimostra, come già altrove feci rilevare che il
differenziamento istologico dei vari tessuti si riduce in ultima analisi ad
un vero differenziamento chimico di tutto il bioplasma, differenziamento
chimico che si compie a poco a poco durante lo sviluppo ontogenetico per una
serie graduale di trasformazioni chimiche di cui le varie citodieresi
segnano le tappe.
Quale che sia il differenziamento istologico, ciò che a noi importa
sovrattutto in questo momento di far rilevare si è che neanche un caso solo
noi conosciamo dove un differenziamento simile si possa attribuire all'
azione di una particella sola del bioplasma, come lo vorrebbe la teoria dei
determinanti del Weismann e come si è costretti ad ammettere inevitabilmente
se si accoglie una qualunque delle teorie che a particelle rappresentative
attribuiscono il differenziamento istologico. Tutti i fatti che noi
conosciamo finora relativi all'istogenesi, ci dimostrano invece che le
sostanze caratteristiche dei differenziamenti sono una produzione, una
secrezione in senso lato, non di una sola particella, ma di tutto il
bioplasma e quindi di tutte le particelle sia maschili sia femminili che lo
compongono: che esse insomma sono il risultato di un metabolismo del
bioplasma compitosi col concorso di tutte le biomolecole che lo formano.
[...]
Che cosa dobbiamo dunque concludere sul valore dei caratteri somatici dopo
le considerazioni ora esposte? Che essi sono così subordinati a fattori
variabili, quali sono l'ambiente e la diversa costituzione individuale dei
gameti dovuta alla sessualità, che la loro manifestazione è un criterio
quanto mai fallace per giudicare dell'eredità organica. Ma d'altra parte
siccome questo criterio è l'unico pur troppo che sia accessibile ai nostri
mezzi attuali di indagine biologica, ci è giuocoforza attenersi ad esso,
nonostante la sua fallacia.
E poiché i moderni studi sull'eredità e sulla variabilità, che vanno
lodevolmente rifiorendo ai dì nostri, sono basati esclusivamente sul valore
dei caratteri somatici come termini di misura, lo scopo del presente scritto
si limita solamente a richiamare l'attenzione dei Biologi sull'incertezza
del valore di questi termini e quindi sulla poca attendibilità delle
conclusioni che per avventura non siano state dedotte con quella
circospezione rigorosa che la delicatezza dell'argomento richiede.
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John C. Eccles
The Discipline of Biological Science with Special Reference to the
Neurosciences
Riv. Biol. 73 (1980)
Because of my experience of science in many countries and of a continuing
interest in the philosophy of science, I have developed strong opinions on
many questions of concern to readers of this journal. I will of course be
looking at the subject of research from a very different standpoint from
that of big physics. Fortunately nothing in biology is yet comparable with
the situation in physics, and most biological research is still carried out
under conditions which would have been usual for physics until the 1940's.
Most efforts to build biology up into something equivalent to large scale
physics seem to me to have been disappointing and I think misguided. I
believe that in biology we are still in the enviable position of being able
to work as creative individuals with, of course, small teams blending those
special talents that are required in technical and theoretical attacks on
fundamental problems. I would define science as the systematic attempt to
understand and comprehend the natural world. It is a determination to enter
deeply into the natural world, not just superficially, but to achieve a
rational expression in language and mathematical symbolism of the order and
beauty of operation that lies behind all natural phenomena. This is what the
aim of science is. Its scope is not just the external world. The scope of
science includes ourselves. By that I mean that all aspects of our own
experiences of ourselves - our perceptions, imaginings, emotions and
actions - everything properly comes into the purview of science.
Now this enterprise of science is dependent on the imaginative and
disciplined activities of unique individuals who ideally form a free and
supranational society. This essential feature of science certainly is not
fully understood and appreciated by the politicians and the bureaucrats who
operate even the most liberal political systems. And in most countries it is
not understood at all. Correspondingly there are not very many countries in
the world where science flourishes in a free-flowering manner. There are
many countries where science does not grow at all or where it is extremely
maimed in its growth.
It is important to draw a sharp distinction between science and technology
or applied science as it is sometimes called. I am not going to say which
has the higher status, but it is necessary to be clear about these two
categories, although the same person can be both a scientist and a
technologist. He can wear, as it were, different hats for different
occasions, but what he does on these two occasions is quite different. There
are technologists in many countries where there are no scientists. In fact
all countries have technologists; even countries in the Stone Age, for
example, have experts in the manufacture of stone axes!
The aim of the technologist is to apply scientific knowledge and empirical
knowledge in some useful way. He may be designing and constructing
scientific equipment. I was a technologist when so engaged. Technologists
are responsible for all the marvellous inventions that have transformed the
conditions of our life. Think of the spectrum of revolutions in the means of
communication, in the materials for all purposes, and in electronics; think
of all the new discoveries and inventions relating to medical practice, to
agriculture and food, to the chemical industry, and to computers. This human
activity is quite different from that of science, although it utilizes or
even exploits the discoveries of science. Of course, a technologist has to
have a wide knowledge, imagination, and high intelligence, just as does a
scientist. I am not underrating the nature of his performance; I am just
saying that it is different from that of the scientist. The difference is a
difference in objectives.
The scientist tries to understand or comprehend the natural world as he
experiences it, using for this purpose hypotheses which are tested under
specially designed experimental conditions in which most elaborate
scientific instruments are often employed. Yet, in the end, no matter how
complex the apparatus is, the information that it delivers has to be looked
at and observed by a scientist, who must examine it critically in relation
to his hypotheses, and then, perhaps, reformulate his hypotheses. The
essence of what a scientist does is to imagine and to explain what lies
behind phenomena, in other words to try to comprehend the natural world. On
the other hand, the technologist is utilizing knowledge about the natural
world for practical purposes.
[...]
The erroneous belief that science eventually leads to the certainty of a
definitive explanation carries with it the implication that it is a grave
scientific misdemeanor to have published some hypothesis that is eventually
falsified. As a consequence, scientists are often loath to admit the
falsification of their hypotheses, and their lives may be wasted in
defending what is no longer defensible. Whereas, according to Popper,
falsification in whole or in part should be the anticipated fate of all
scientific hypotheses, and we should even rejoice in the falsification of an
hypothesis that we have cherished as our brain-child. Such a belief relieves
the scientist from fears and remorse, and science becomes an exhilarating
adventure where imagination and vision can safely lead to conceptual
developments transcending in generality and range the experimental evidence.
The precise formulation of these imaginative insights into hypotheses opens
the way to rigorous testing by experiment, always with the anticipation that
the hypothesis may be falsified and replaced in whole or in part by another
hypothesis of greater explanatory power. In this way conceptual developments
lead to experimental testing which is always designed in relation to
hypotheses. The status of a scientific hypothesis should be measured both by
the effectiveness with which it exposes itself to rigorous experimental
testing, and by its explanatory power, which should go far beyond existing
knowledge. Its status, in other words, would be measured by its predictive
scope.
Descriptions of Popper's views on the methodology of science tend to give an
impression of a rigidity of operation which rarely corresponds to the
experiences of scientists - even of those who, like myself, fully subscribe
to his methodology. As I examine the procedures that I used in the course of
making some scientific discovery, I find that they look much more like the
opportunistic tactics of guerrilla warfare than like the organized
strategies of major battles. Often, at the beginning of a particular
investigation, I had only a very vague horizon-of-expectations (to use
Popper's felicitous phrase), sufficient only to guide me in the design of
initial experiments. In that way I was able to maintain flexibility about
concepts which were developed in the light of the observations, so that my
horizon-of-expectations was advanced and developed. Thus there emerged a
much more rigorous and searching experimental investigation than could have
been designed at the outset.
[...]
The more one surveys the whole world field, the more one is sure that an
early period of association with an élite group is essential for the
development of youthful investigators. I can speak about this personally
because I had the lucky opportunity to go to Sherrington at Oxford in 1925
and be there in what was generally considered to be the foremost
neurophysiological laboratory in the world at that time. Thus for a number
of years at a critical stage of my life (when I was twenty-two to
thirty-four years old) I was associated with youthful research workers from
other countries who had come to work in the Sherrington group.
I think that scientific élites, if I may call them so, could be more
effectively used than they are at present. With modern techniques of
communication, such as those provided by the various kinds of audiovisual
techniques, it should be possible to distribute their unique scientific
abilities and performances more widely than is done at present. Furthermore,
it should be a moral obligation on the part of the élite to cooperate as
much as possible in such an enterprise. [...]
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Gerry Webster and Brian C. Goodwin
A Structuralist Approach to Morphology
Riv. Biol. 77 (1984)
[...]
The 'Disappearance of the Organism'. One of the major consequences of a
conceptualisation of organisms as structures or self-organising totalities
is, obviously enough, the reinstatement of the organism as the proper object
of biological research; as a real object, existing in its own right and to
be explained in its own terms. This of course was the concept of the
organism held by the rational morphologists but which, during the subsequent
decades, was progressively eroded; firstly, by cell theory with its attempt
to conceptualise the organism in atomistic terms as a population of
virtually autonomous, interacting individuals; and secondly, by Weismann's
concept of a 'central directing agency', in which the organism, conceived as
an 'expressive totality', becomes a kind of epiphenomenon of the genome.
This progressive 'disappearance of the organism' and its replacement by
microscopic entities, to which are attributed some or all of the properties
of the organism, reaches its most absurd and degenerate stage in the concept
of the 'selfish gene' (Dawkins, 1976) in which the entities are freely
invented and endowed with whatever properties are required to 'explain'
biological phenomena.
The 'disappearance of the organism' is clearly illustrated in Maynard Smith'
s (1978) recent discussion of the possibility of the axiomatization of
Darwinian theory, which, he claims: 'will have to be in terms of
hypothetical entities having the properties of multiplication, variation and
heredity. The only entities with these properties are genes. The body is not
replicated - it dies'. It is, no doubt, the case that genes do possess these
properties in the appropriate circumstances, those which are normally
provided by the organism; however, they are not the only entities to do so -
they are also the demonstrated properties of at least some organisms as
wholes (Sonneborn, 1970). Nor does the body necessarily die; asexually
reproducing organisms are potentially immortal and in sexually reproducing
organisms parts of the female body at least (i.e. eggs) survive and produce
the next generation.
The predilection for explaining biological organisation in terms of the
imposition of order by some 'central directing agency' is obviously deeply
rooted in biology, so much so that the existence of such an entity is taken
to be a given fact rather than the theoretical construction it is; one
thinks of a second example, the so-called embryonic organiser (Spemann,
1938). While it is true that biology has produced some facts which are
consistent with such a view, it should be re-emphasised that such facts in
no way necessitate it. There are no a priori grounds whatsoever for
supposing that organisms cannot be self-organising entities, 'decentered
structures', and indeed Kauffman (1969), has clearly demonstrated that
orderly behaviour in time can emerge in a network as a consequence of its
total relational structure; organisation in space can be similarly treated
by the use of field descriptions (Goodwin and Trainor, 1980, 1983;
Meinhardt, 1982; Murray, 1981; Odell et al., 1981).
With a conceptualisation of organisms as self-organising and law-governed
structures, the genome (i.e. effectively the chemical composition) takes its
place as a part of the totality of the constraints on the generative process
along with others such as pre-existing organisation and environmental
factors. A 'random' change in any of these factors will not result in a
'random' change of structure, but in an orderly change to another
possibility, another member of the system of transformations, and typical
form will be conserved. Kauffman's (1969) model of temporal order displays
these properties. It is striking that both genetic and mechanical
perturbations, if they are not lethal, generally result in new forms which
are 'typical', orderly and structurally harmonious even if functionally
disharmonious (i.e. non-adaptive); one thinks, for example, of the homeotic
mutants and the various heteromorphic transformations (see Bateson, 1984;
Ouweneel, 1976). Such phenomena are unintelligible within a
conceptualisation of the organism as an 'expressive totality' generated by a
'central directing agency' which is subject to 'random' changes.
[...]
The Neo-Darwinian Theory of Descent. It will be apparent that we regard the
theory of evolution, and in particular neo-Darwinism, as having extremely
limited explanatory power with respect to the problem of form to which it
was originally addressed. This limitation arises as a consequence of the
absence of any adequate theory of the means of production of 'typical forms'
and is such, we would maintain, as to render debatable the claim that
neo-Darwinism is 'the unifying theory in biology' (Maynard Smith, 1975).
These remarks are not to be construed as either a rejection of Darwinist
functionalist explanations in biology, or of a historical theory of descent,
the claim that existing species are 'blood relations' which have arisen by
the evolutionary transformations of a smaller number of pre-existing
species. The structuralist position we adopt is perfectly consistent with a
theory of historical descent (though not dependent upon it) and, by
providing a conceptual framework within which a theory of transformations
can be produced, both clarifies some of the issues raised by such a theory
and provides a picture of the evolutionary process which is somewhat
different to that of the neo-Darwinists.
[...]
History and Structure. We have argued above that perturbations of a
structured system will result, if the structure changes at all, in an
orderly change to another member of the potential set comprising the system
of transformations. Small, continuous changes in parameters can result in
either small, continuous changes of form, or in large, discontinuous
alterations as occur at bifurcation points such as the critical values of
initial position and velocity of orbiting bodies, where their motion is
transformed from an elliptical to a parabolic or hyperbolic orbit. More
radical changes can also occur involving the generative 'laws' themselves,
in which case the structure will 'move' into a quite different system of
transformations. Using our Newtonian analogy again, a change from an inverse
square to an inverse cube in the law governing gravitational attraction
would result in the generation of a set of forms of motion that were not
conic sections but families of spirals. Thus both 'micro-evolution' (more or
less continuous change) and 'macro-evolution' (discontinuous change) are
compatible with a structuralist conception of biological organization. With
an adequate generative theory of transformations, the unifying character of
the theory of descent could be put in rational, rather than purely empirical
terms, providing the basis for a realist taxonomy, that is, one based on a
hierarchy of classes of generative processes (see Bhaskar, 1978).
[...]
Conclusion. A structuralist conception of living organisms with its emphasis
on the logical, the universal and the necessary, implies that the organismic
domain as a whole has a 'form' and is, therefore, intelligible (which does
not mean predictable) and that the 'content' - the diversity of living
forms, or at least their essential features - can be accounted for in terms
of a relatively small number of generative rules or laws. This claim will no
doubt strike many as grandiose, and to neo-Darwinists it will seem absurd.
For, from the perspective of neo-Darwinism, with its empiricist concern with
the particular and the contingent and its reliance on the historically
given, there can be no 'plan of Creation' and the domain of the living is,
in the last analysis, fundamentally irrational and, therefore,
unintelligible. Yet, as we have argued, this inadequate conceptualization is
neither inevitable nor necessary; it is itself the result of a historical
'selection' from the domain of possible conceptualizations. Unlike those of
other organisms, our 'selections' can be deliberate choices. Let us now
choose to leave history behind.
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Gianfranco Bruno
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www.geocities.com/gbruno_2000
 
www.university.it/000/notizie/notizierisult.asp?Id=166
 
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Per ora ho letto solo l'articolo in italiano: ma hai visto la data?
Credi che da allora non sia successo niente in Biologia?
Danilo

 Credi che da allora non sia successo niente in Biologia?
Invasato com'è nelle sue teorie, perde di vista ogni decenza.... e Sermonti
stesso non è da meno in questa fioritura di idiozie.
--
Emanuele Passerini
ema.pa...@libero.it
http://go.to/manupippo
ICQ# 34957310

Sono sconcertato, perché ci fai questo? Ho letto con una certa fatica
gli articoli che hai inviato, che utilità hanno? Cosa dovrebbero
dimostrare? Va bene, Eccles si dichiara un popperiano convinto e chi
spiega la differenza tra tecnologia e scienza,  Godwin e Webster
attaccano la sociobioologia con buoni argomenti ed un biologo di
inizio secolo si arrabbatta a ragionare di genotipo e fenopito senza
avere le conoscenze che abbiamo oggi. Tutto ciò dovrebbe mettere in
crisi il darwinismo e l'evoluzionismo? Non mi pare che sia
l'intenzione di nessuno di questi autori, oppure ho capito male? 
Ti ripeto ancora una volta: perché non provi a discutere usando parole
tue? Ti senti talmente insicuro da avere la necessita di appoggiarti
alla lettera dei tuoi autori preferiti? Il tuo è un atteggiamento in
una certa misura intimidatorio. O sembra che voglia esserlo, non ci
riesce molto bene, però.
Nanni

Senti amico, ma come mai hai intrapreso questa guerra santa contro il povero
Darwin?
Le posizioni fondamentaliste come le tue in biologia vanno poco lontano...in
genere esiste sempre l'eccezione alle regole piů generali; ti consiglio di
durare meno fatica a postare ste quattro fregnacce e soprattutto vai a
studiare un libro serio invece di perder tempo con questi libercoli
sensazionalistici.