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| 2. |
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| 3. |
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| 4. |
- BERG, OG
(författare)
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PERIODIC SELECTION AND HITCHHIKING IN A BACTERIAL POPULATION
- 1995
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Ingår i: JOURNAL OF THEORETICAL BIOLOGY. - : ACADEMIC PRESS (LONDON) LTD. - 0022-5193. ; 173:3, s. 307-320
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- The accumulation of a neutral marker in a bacterial population under balanced growth in a chemostat follows a jagged curve as adaptive variants continuously appear and sweep the population. Such periodic selection curves are simulated in the present work
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| 5. |
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| 6. |
- BJORKLUND, M
(författare)
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SPECIES SELECTION ON ORGANISMAL INTEGRATION
- 1994
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Ingår i: JOURNAL OF THEORETICAL BIOLOGY. - : ACADEMIC PRESS (LONDON) LTD. - 0022-5193. ; 171:4, s. 427-430
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Selection processes of entities higher than individuals have recently been suggested to play a potential role in macroevolution. In particular, population level traits such as variability seem likely candidates for higher-level selection processes because
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| 8. |
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| 9. |
- Cziáky, Z., et al.
(författare)
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Synthesis of 2H‐pyrano[2,3‐b]quinolines. Part II. Preparation and 1H‐nmr investigations of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines
- 1995
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Ingår i: Journal of Heterocyclic Chemistry. - : Wiley. - 0022-152X .- 1943-5193. ; 32:3, s. 755-760
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Tidskriftsartikel (refereegranskat)abstract
- Diastereoisomers of 4‐hydroxy‐2‐methyl‐3,4‐dihydro‐2H‐pyrano[2,3‐b]quinolines 8 and 9 were synthesized starting from the appropriate 2‐chloroquinoline‐3‐carboxaldehydes 1. The relative configuration of the 1,3‐diol intermediates 4 and 5 was determined on the basis of the 13C‐nmr spectra of their acetonides. The relative stereochemistry of title compounds was confirmed by using homonuclear NOE and selective decoupling experiments, as well as by analysis of the coupling patterns observed in their 1H‐nmr spectra.
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| 10. |
- DUGATKIN, LA, et al.
(författare)
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DELAYED BREEDING AND THE EVOLUTION OF MATE COPYING IN LEKKING SPECIES
- 1995
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Ingår i: JOURNAL OF THEORETICAL BIOLOGY. - : ACADEMIC PRESS (LONDON) LTD. - 0022-5193. ; 174:3, s. 261-267
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Recent experimental evidence indicates that females may copy the mate choice of others. Here, we present a model for the evolution of mate copying Strategies in lekking species. In the model, all females (copiers and non-copiers) assess male quality, but
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| 11. |
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| 12. |
- Klaassen, Marcel, et al.
(författare)
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Departure fuel loads in time-minimizing migrating birds can be explained by the energy costs of being heavy
- 1996
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 183:1, s. 29-34
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Tidskriftsartikel (refereegranskat)abstract
- Lindström & Alerstam (1992Am. Nat.140,477–491) presented a model that predicts optimal departure fuel loads as a function of the rate of fuel deposition in time-minimizing migrants. The basis of the model is that the coverable distance per unit of fuel deposited, diminishes with increasing fuel load. This is an effect of the increasing flight costs associated with increasing body mass. Lindström & Alerstam (1992) found that birds left at lower fuel loads than their model predicted for which they considered various ecological explanations. Alternatively, we hypothesize that the difference between prediction and empirical data might be a result of extra resting metabolic and transport costs associated with an increase in fuel load during stopover. We develop a new version of the Lindström & Alerstam (1992) model taking fuel load associated costs during stopover into account. We fit empirical data from rufous hummingbirdsSelasphorus rufus(Carpenteret al., 1983Proc. Natl. Acad. Sci. U.S.A.80,7259–7263) and bluethroatsLuscinia svecica(Lindström & Alerstam, 1992) to this new model. Estimated fuel-load costs are discussed in relation to knowledge presently available on variations in basal metabolic costs and transport costs with body mass. We show that fuel-load costs within a reasonable range can explain the observed departure fuel loads when migrating birds are time minimizers.
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| 13. |
- Kóródi, F., et al.
(författare)
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Fused 1,2,4-TriazoIe Heterocycles. IV. Synthesis of Four New Heterocyclic Ring Systems of [1,2,4]Triazolo[1,3]thiazinoquinolines
- 1997
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Ingår i: Journal of Heterocyclic Chemistry. - : Wiley. - 0022-152X .- 1943-5193. ; 34:4, s. 1275-1281
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Tidskriftsartikel (refereegranskat)abstract
- Syntheses of 5H-[1,2,4]triazolo[5′1′:2,3][1,3]thiazino[5,4-c]quinolines 8, 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,4-c]quinolines 9, 5H-[1,2,4]triazolo[5′1′:2,3][1,3]thiazino[5,6-c]quinolines 14 and 5H-[1,2,4]triazolo[3′,4′:2,3][1,3]thiazino[5,6-c]quinolines 15 are described starting from 4-chloro-3-chloromethylquinaldine (4) and 1,2,4-triazole-5-thiols 5 taking advantage of different reactivity of the chlorine atoms of 4 under different reaction conditions. The structures of products 8, 9, 14 and 15 and the intermediates leading to them were confirmed by desulfurization, unequivocal syntheses and nmr spectroscopy as well.
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| 14. |
- Lindahl, B. I. B.
(författare)
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Consciousness and Biological Evolution
- 1997
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Ingår i: Journal of Theoretical Biology. - London : Academic Press. - 0022-5193 .- 1095-8541. ; 187, s. 613-629
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Tidskriftsartikel (refereegranskat)abstract
- It has been suggested that if the preservation and development of consciousness in the biological evolution is a result of natural selection, it is plausible that consciousness not only has been influenced by neural processes, but has had a survival value itself; and it could only have had this, if it had also been efficacious. This argument for mind–brain interaction is examined, both as the argument has been developed by William James and Karl Popper and as it has been discussed by C. D. Broad. The problem of identifying mental phenomena with certain neural phenomena is also addressed. The main conclusion of the analysis is that an explanation of the evolution of consciousness in Darwinian terms of natural selection does not rule out that consciousness may have evolved as a mere causally inert effect of the evolution of the nervous system, or that mental phenomena are identical with certain neural phenomena. However, the interactionistic theory still seems, more plausible and more fruitful for other reasons brought up in the discussion.
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| 15. |
- Lindahl, B. I. B., et al.
(författare)
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Mind as a Force Field : Comments on a New Interactionistic Hypothesis
- 1994
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Ingår i: Journal of Theoretical Biology. - London : Academic Press. - 0022-5193 .- 1095-8541. ; 171, s. 111-122
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Tidskriftsartikel (refereegranskat)abstract
- The survival and development of consciousness in biological evolution call for an explanation. An interactionistic mind-brain theory seems to have the greatest explanatory value in this context.An interpretation of an interactionistic hypothesis, recently proposed by Karl Popper, is discussed both theoretically and based on recent experimental data. In the interpretation, the distinction between the conscious mind and the brain is seen as a division into what is subjective and what is objective, and not as an ontological distinction between something immaterial and something material. The interactionistic hypothesis is based on similarities between minds and physical forces. The conscious mind is understood to interact with randomly spontaneous spatio-temporal patterns of action potentials through an electromagnetic field. Consequences and suggestions for future studies are discussed.
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| 16. |
- Lindahl, B. I. B., et al.
(författare)
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The Mental Force Field Hypothesis : A Reply to Libet
- 1996
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Ingår i: Journal of Theoretical Biology. - London : Academic Press. - 0022-5193 .- 1095-8541. ; 178, s. 225-226
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 17. |
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| 18. |
- Lindahl, BIB, et al.
(författare)
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The mental force field hypothesis: Reply
- 1996
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Ingår i: JOURNAL OF THEORETICAL BIOLOGY. - : Elsevier BV. - 0022-5193. ; 178:2, s. 225-226
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)
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| 19. |
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| 20. |
- Lundberg, S., et al.
(författare)
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Parent-offspring conflict over reproductive efforts: Variations upon a theme by Charnov
- 1994
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 170:2, s. 215-218
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Tidskriftsartikel (refereegranskat)abstract
- A novel formulation of the theory of parent-offspring conflict is proposed. The basis of this formulation is an application of traditional life-history theory in combination with simple genetic arguments. The advanatage with this approach is conceptual, and the formulation is not in variance with earlier studies in the area. Parent-offspring conflict is, in our forumlation, not seen as a conflict between individuals, but as a tradeoff-an age-specific selection pressure acting on a trait, which is favourable when an individual is offspring and disadvantageous when it becomes parent. Using an ESS approach we investigate a simple offspring-wins problem: we find that a gene causing assertiveness of offspring will increase when rare, because the advantage thus gained by an assertive individual when young exceeds the cost incurred as adult by that half of its own offspring which belongs to the same assertive genotype.
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| 21. |
- Nicolis, Stamatios C., et al.
(författare)
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Emerging patterns and food recruitment in ants : an analytical study
- 1999
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 0022-5193. ; 198:4, s. 575-592
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Tidskriftsartikel (refereegranskat)abstract
- A model of food recruitment by social insects accounting for the competition between trails in the presence of an arbitrary number of sources is developed and analysed in detail. Both the case of identical environmental characteristics and the case where one source and the corresponding trail are different from the others are considered. Different collective responses depending on the environmental conditions, and without change of individual behaviour, are shown to exist, associated with the possibility that the colony may be led to exploit one source or a group of sources preferentially. The full bifurcation diagram of steady-state solutions is constructed from which the dominant exploitation patterns are identified. The biological relevance of the results is discussed and suggestions are made for their experimental testing in connection with the recruitment behavior of species using trail recruitment. The same phenomenological model can be used for different trail-laying species since the predictions are generic and not restricted to a given species, except for the parameter values used. (C) 1999 Academic Press.
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| 22. |
- Niklas, Karl J., et al.
(författare)
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Non-parametric Statistical Formulas for Factors of Safety of Plant Stems
- 1999
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 0022-5193 .- 1095-8541. ; 197:2, s. 135-147
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Tidskriftsartikel (refereegranskat)abstract
- A previously proposed statistical approach for computing factors of safety (i.e. numerical measures of mechanical reliability) for any load bearing structure, like a vertical plant stem, is here extended to cope with organic structures whose morphological or mechanical properties have Weibull frequency distributions. This approach is illustrated using the actual lengthLand critical buckling lengthLerof flower stalks (peduncles) collected from isogenic garlic (Allium sativum) populations grown under windy field and protected glasshouse conditions. Our analyses of the data indicate thatLandLerof peduncles harvested from both populations have Weibull frequency distributions, that the factor of safety for glasshouse grown peduncles is very near unity (i.e.S=1.03), and that the factor of safety of field grown peduncles is 73% higher than that of glasshouse grown plants (i.e.S=1.73). Comparisons between theS-values computed on the basis of our formulas and on the basis of the quotient of the mean values ofLerandLfor each of the two populations indicate that the statistical method gives biologically realisticS-values and that the difference in theS-values for stems grown under protected and unprotected environmental conditions likely reflects the effects of chronic mechanical perturbation (due to wind-induced drag) on normal stem growth and development.
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| 23. |
- Pettersson, Gösta
(författare)
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A New Approach for Determination of the Selectively Favoured Kinetic Design of Enzyme Reactions
- 1996
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 183:2, s. 179-183
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Tidskriftsartikel (refereegranskat)abstract
- A new criterion is applied for characterization of the kinetic design of enzymes that should be favoured by a selective pressure in the direction of increased metabolic reaction flux. According to this criterion, the selectively favoured state of a metabolic sequence of enzyme reactions conforming to Michaelis-Menten kinetics is identical with the uniform one which is known to optimize reaction flux for a given average magnitude of enzyme concentrations and of true and apparent first-order rate constants in the reaction system. It is argued that presently observed values of on-velocity constants for metabolite binding to enzymes are unlikely to represent the upper limit for a diffusion-controlled association process and are more likely to represent those corresponding to the selectively favoured kinetic design at the present stage of the evolutionary development of enzyme function.
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| 24. |
- Pettersson, Gösta
(författare)
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Effect of Dynamic Channelling on the Transient-state Kinetics of Coupled Enzyme Reactions
- 1999
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 198:1, s. 135-141
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Tidskriftsartikel (refereegranskat)abstract
- Evidence is presented to show that the presence of a channelled reaction branch in a coupled two-enzyme reaction leads to a slower overall relaxation of the system towards steady state following perturbations of the reaction conditions. A predominant part of the total reaction flux change resulting from perturbations may be governed by transients that are more rapid in the presence than in the absence of a channel, but only under specific conditions that are not likely to be of biological relevance.
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| 25. |
- Pettersson, Gösta
(författare)
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Errors Associated with Experimental Determinations of Enzyme Flux Control Coefficients
- 1996
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Ingår i: Journal of Theoretical Biology. - : Elsevier BV. - 1095-8541 .- 0022-5193. ; 179:3, s. 191-197
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Tidskriftsartikel (refereegranskat)abstract
- An analysis is presented of the likely statistical error and mathematical bias of experimental enzyme flux control coefficient estimates, calculated from observations of the flux changes caused by finite changes of the concentration of an enzyme in a metabolic pathway. The results indicate that such control coefficients are not likely to be determined with satisfactory precision unless the experimental data are evaluated by hyperbolic regression analysis, and the actual flux vs. enzyme concentration profile conforms closely to a hyperbolic relationship. It is concluded that it may not normally be feasible to obtain reliable experimental estimates of enzyme flux control coefficients in realistic systems by the examined direct approach. Arguments are presented to show that the error situation is unlikely to be more favourable as it concerns that indirect calculation of flux control coefficients from transient-state kinetic data or from experimental estimates of infinitesimally defined quantities such as elasticity coefficients and co-response coefficients.
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| 26. |
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| 27. |
- Werdelin, Lars, et al.
(författare)
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The evolution of the scrotum and testicular descent: a phylogenetic view
- 1999
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Ingår i: Journal of Theoretical Biology. - 0022-5193 .- 1095-8541. ; 196, s. 61-72
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Tidskriftsartikel (refereegranskat)abstract
- The adaptive significance of the scrotum and the evolution of the descent of the testicles and epididymis have been a focus of interest among biologists for a long time. In this paper we use three anatomical character states of the scrotum and descensus: (1) testicles descended and scrotal; (2) testicles descended but ascrotal; (3) testicles not descended (testicondy#). These states are then mapped on an up to date phylogeny of the Mammalia. Three main points arise out of this mapping procedure: (1) the presence of a scrotum is either primitive in extant Mammalia or primitive within eutherian mammals except Insectivora; (2) evolution has generally proceeded from a scrotal condition to progressively more ascrotal; (3) loss of testicular descensus is less common in mammalian evolution than is loss of the scrotum. In the light of these findings we discuss some current hypotheses regarding the origin and evolution of the scrotum. We find that these are all incomplete in so far as it is not the presence of the scrotum in various mammal groups that requires explaining. Instead, it is the reverse process, why the scrotum has been lost in so many groups, that should be explained. We suggest that the scrotum may have evolved before the origin of mammals, in concert with the evolution of endothermy in the mammalian lineage, and that the scrotum has been lost in many groups because descensus in many respects is a costly process that will be lost in mammal lineages as soon as an alternative solution to the problem of the temperature sensitivity of spermatogenesis is available.
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| 28. |
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