Showing papers by "University of Sussex published in 1978"

Mammals, resources and reproductive strategies

Abstract: The breeding systems of mammalian species are strongly influenced by the density and dispersion of their populations. These in turn are affected by variations in the distribution of resources. Through quantitative comparisons, it is possible to trace evolutionary relationships between feeding behaviour, population dispersion, breeding systems and morphology.

Inbreeding and dispersal in the great tit

Abstract: IN populations which normally outbreed, matings between close relatives can result in a decrease in the viability and fertility of their offspring. Such inbreeding depression has been shown in a number of laboratory studies of insects1, birds2 and mammals3. We present here the first detailed evidence of inbreeding depression in a natural population and support for the hypothesis4 that one function of dispersal between birth and breeding sites is to reduce an individual's chance of inbreeding.

Sexual dimorphism in primate teeth

Abstract: A new measure of sexual dimorphism in tooth size (Relative Male Tooth Size) is estimated for a sample of 39 primate species and is used to test predictions concerning the adaptive significance of sexual dimorphism in primate tooth size. It is concluded that both sexual selection and predator defence are important selective forces producing marked sexual dimorphism in the teeth used for fighting.

Adam Smith's Politics: An Essay in Historiographic Revision

Abstract: For most of the two hundred years or so that have passed since the publication of the Wealth of Nations, Adam Smith's writings on political and economic questions have been viewed within a liberal capitalist perspective of nineteenth- and twentieth- century provenance. This essay in interpretation seeks to provide a more historical reading of certain political themes which recur in Smith's writings by bringing eighteenth-century perspectives to bear on the problem. Contrary to the view that sees Smith's work as marking the point at which 'politics' was being eclipsed by 'economics', it claims that Smith has a 'politics' which goes beyond certain political attitudes connected with the role of the state in economic affairs. It argues that he employs a consistent mode of political analysis which cannot be encompassed within the standard liberal capitalist categories, but can be understood by reference to the language and qualities of contemporary political debate, and of the eighteenth-century science of politics cultivated by Montesquieu and, above all, Hume, particularly as revealed by recent scholarship. A concluding chapter draws the various strands of the interpretation together to form a portrait of what Smith might legitimately be said to have been doing when he wrote on these matters.

Statistical Treatment of Experimental Data

Abstract: 1. Introduction. 2. Probability. 3. Random Variables and Sampling Distributions. 4. Some Important Probability Distributions. 5. Estimation. 6. Confidence Intervals. 7. Hypothesis Testing. 8. Tests on Means. 9. Tests on Variances. 10. Goodness of Fit Tests. 11. Correlation. 12. The Straight Line Through the Original or Through Some Other Fixed Point. 13. The Polynomial Through the Origin or Through Some Other Fixed Point. 14. The General Straight Line. 15. The General Polynomial. 16. A Brief Look at Multiple Regression. Appendices: 1. Drawing a Random Sample Using a Table of Random Numbers. 2. Orthogonal Polynomials in x. References. Index.

Population genetics of partial male-sterility and the evolution of monoecy and dioecy

Abstract: Selection on reproductive phenotype in plants is studied, using a theoretical model. Fitnesses of mutant phenotypes with altered male and female fertility are derived, assuming an initially hermaphrodite or monoecious population with no self-incompatibility mechanism, with partial self-fertilisation, and with some inbreeding depression. These fitness expressions are used to derive conditions for the spread of such mutations, in terms of the minimum increase in opposite-sex fertility that will give a phenotype with reduced male or female fertility a selective advantage over the original type, taking into account the effect on the selfing rate of altering the sex phenotype. Conditions for polymorphism are also obtained. The conditions are used to study the evolution of dioecy from monoecy, and the evolution of gynomonoecy and monoecy from the hermaphrodite state.

How hoverflies compute interception courses

Abstract: 1. Males of many species of hoverfly hover in one spot ready to pursue passing objects, presumably in order to catch a mate. We have filmed two of the larger species as they begin their pursuit of an approaching projectile shot at them from a peashooter. Flies do not turn and fly towards the projectile as they would if they were tracking (Land and Collett, 1974). Instead they adopt an interception path, accelerating at a uniform rate (30–35 m · s−2) approximately in the direction in which the target is moving (Fig. 1). 2. If the projectile is made to reverse direction, the male does not respond to the change in the target's course for about 90 ms (Fig. 2). Thus, in contrast to the situation later (Fig. 3), the start of a pursuit is not under continuous sensory control. The fly selects its course when it first sees the target and maintains its interception path as an open-loop response. 3. Males only need to catch conspecifics and can thus assume that their quarry has a typical speed and, since it is of a uniform size, will be detected at a predetermined distance. These assumptions mean that the approach angle of the target at the moment of first sighting can be specified by the image velocity of the target across the retina (\(\dot \theta _e \)). Since the male also “knows” its own acceleration, the direction of flight which will enable it to intercept the target can also be specified in terms of the initial position (θe) and velocity (\(\dot \theta _e \)) of the target image (Figs. 6 and 7). 4. We show that interception should occur if the male obeys the simple rule that the size of the turn it makes (Δφ) is given by $$\Delta \phi \simeq \theta _e - 0.1{\text{ }}\dot \theta _e \pm 180^\circ $$ . Our data indicate that the initial turns of the males do obey this rule (Fig. 8), and that males are “designed” to catch females travelling at about 8 m · s−1. 5. If males are calibrated to catch targets of a particular size and speed, they will be unable to intercept projectiles that are very different in these respects. When large, slowly moving projectiles are launched to pass by the fly, its attempted interception path is predictably inappropriate (Fig. 9).

Short and Long-term Adjustment of Circadian Rhythms in ‘ Permanent ’ Night Nurses

Abstract: Two studies are described in which differences were found in the adjustment of the circadian rhythms of full and part-time night nurses to night work. A distinction was drawn between short-term adjustment that takes place over successive night shifts, and long-term adjustment that may take the form either of a permanent ‘flattening’ of the rhythm, or of a facilitation of short-term adjustment. The results from the first study indicated that even when the potential for greater short-term adjustment was controlled for, the full-time staff showed greater adjustment to night work. The second study examined these differences in long-term adjustment in greater detail. No evidence was found of a permanent ‘flattening’ of the full-timers’ circadian rhythms, although they showed clear evidence of adjustment even on the first of a period of successive night shifts. The full-timers also showed more evidence of adjustment from the first to the second night shift. It is suggested that these differences in long-term ad...

The Perception of Music

Abstract: The author recently described elsewhere a computer program which would transcribe classical melodies played on an organ console into the equivalent of standard musical notation. This program was the fruit of a prolonged effort to understand how Western musicians succeed in making sense of music, in discerning rhythm and the tonal relation hip between notes. The interest of the problem arise from the fact that no two performance of the same piece of music are ever identical so that the listener has to discriminate between those variation of timing and pitch which are structurally significant and those which are merely expressive. In order to under land the ability of some musician to reproduce the cores of music that they hear it is necessary to develop a formally precise theory of rhythm and tonality – a theory which is couched in terms reminiscent of Chomskyan linguistics. But it is also necessary to consider how the listener builds in his mind a representation of the rhythm and tonality of perfo...

Domestic property and social class

Abstract: Cet expose traite de l'importance des consequences des differents modes d'occupation de logement, en ce qui concerne les rapports de classes. L'accent est mis precisement sur la Grande Bretagne ou, environ 40% des ouvriers manuels possedent maintenant leur propre maison, et ou l'extension de l'occupation de l'habitation par le proprietaire a nettement contribue a accroitre les dividions sociales et politiques, au sein de la classe ouvriere. La question qui se pose, est de savoir si de telles divisions ont une base materielle reelle, ou si elles sont principalement ideologiques. On voit que la reponse a cette question aura d'importantes consequences pour l'organisation de luttes politiques autour de la question du logement. L'expose debute par une discussion des perspectives weberiennes et marxistes en matiere d'occupation de logement et de rapports de classes. La perspective weberienne, liee aux travaux de Rex et de Moore sur 'le logement par classes', est rejetee, quoique la possibilite de reformuler le concept du logement par classes, au sein d'une orientation weberienne, soit mise en evidence. Le point de vue marxiste, qui rejette la possession du logement comme etant etrangere a l'identification des interets de classe, est egalement rejete, sous pretexte que l'occupation de l'habitation par le proprietaire est un facteur crucial d'une augmentation reelles des richesses individuelles qui peuvent largement depasser les economics que l'on peut faire sur les salaires de toute une vie. L 'expose montre ensuite, comment la possession de sa maison va dans le sens d'une accumulation des richesses, et comment ceci cree une reelle division d'interet economique entre les proprietaires en jouissance et les locataires, fait qui se manifeste souvent dans les luttes politiques locales. La conclusion qui se degage de ceci est que, les efforts des activistes locaux pour unifier les deux groupes en une alliance politique contre le capital monopole, peut saverer a la fois peu judicieux et nuisible a la productivite.

A study of misbehavior: token reinforcement in the rat.

Abstract: The purpose of this research was to investigate the phenomenon of misbehavior described by Breland and Breland (1961). Rats were trained to obtain ball-bearings and drop them in a hole for food or water reinforcers. In confirmation of the Brelands' observation, many subjects were slow to deliver the balls, and frequently attempted to chew them before they were dropped. A series of four experiments, in which the same rats were used throughout, showed that delivery times tended to be longer with food than with water, and that these times increased when nylon balls were substituted. The effect of motivational level was investigated by varying both deprivation and amount of prefeeding; no effect on delivery time was detected, although other measures of performance were affected by motivational factors. Similar results were obtained in a final experiment that employed a new set of naive subjects. The studies demonstrated that misbehavior can be studied in an experimental situation, and the results supported an analysis in terms of competition between stimulus-reinforcer and response-reinforcer contingencies. The question of why such effects have not been reported in previous token reinforcer studies was unanswered.

Short communication peering - a locust behaviour pattern for obtaining motion parallax information

Abstract: School of Biological Sciences, University of Sussex,Brighton BNi gQG, Sussex, U.K.(Received 12 April 1978)Motion parallax is probably the most important method available to insects forjudging the distance of objects, yet with one exception very little is known about theways in which insects exploit this cue. Almost twenty years ago Wallace (1959)proposed that the side-to-side peering movements of juvenile locusts are performedspecifically to obtain parallax information. Leg movements cause the whole body topivot about the abdomen, shifting the head laterally about 0-5 cm and displacing theretinal image of an object in front of the insect. Provided that the locust knowshow far (or fast) it moves its head and that it can measure image displacement (orvelocity) it can compute the distance of the objec 1t a). (Fig Th.e following suggestslocusts do indeed do something of this kind. When an object on to which a locust isabout to jump is moved horizontally in a frontal plane, in synchrony with peering,locusts are fooled into misjudging the object's distance. For instance, if the objectis moved in the opposite direction to that in which the locust peers, so enhancingimage movement, the locust jumps short (Wallace, 1959).Two features of peering are analysed here which suggest that the behaviourpattern is carefully designed for extracting parallax information.(1) If the head were to rotate during peering there would be added an unwantedcomponent to movement of the retinal image. This would be independent of thedistance of objects in the environment, and would distort the simple relation-betweenimage displacement and distance shown i 1n (a). Fig Film. s of head movement takenduring peering show that the angular orientation of the head remains constantdespite rotation of the body.(2) The precision with which distance can be estimated during peering is limitedby the amplitude of head movement and by the insect's horizontal acuity. Theaccuracy also decreases as the square of the distance between locust and target(e.g. Horridge, 1977). It is shown here that the locust increases its amplitude ofpeering when object distance is raised and so to some extent is able to compensatefor the inherent decline in accuracy with distance.Observations were made on 4th-insta Schistocerca gregariar obtained from alaboratory culture at the University of Sussex. To measure hea (^n^dd orientatio) na 1 cm length of thin needle was stuck to the top of the locust's head and peeringrecorded on 16 mm film at 25 frames.s"

Biological nitrogen fixation by way of an enzyme-bound dinitrogen-hydride intermediate

Abstract: THE molybdenum-containing enzyme nitrogenase1 catalyses the ATP-dependent six-electron reduction of dinitrogen (N2) to NH3. Previous attempts to detect partially reduced nitrogen intermediates, both enzyme-bound and free in solution, have failed2,3. We report here the first detection of an enzyme-bound dinitrogen intermediate, which is only present when the enzyme is reducing N2 and which on both acid and alkali hydrolysis yields hydrazine (N2H4). This dinitrogen intermediate need not be N2H4, because the chemistry of Mo and W dinitrogen complexes (see below) suggests that other enzyme-bound dinitrogen-hydride intermediate species could undergo non-enzymatic hydrolysis on acid and alkali quenching of the enzyme reaction to give N2H4.

The crystallization kinetics of Fe-Ni based metallic glasses

Abstract: Differential scanning calorimetry is used to study the crystallization kinetics of two commerical Fe-Ni metallic galsses near their glass transition point. For 0.01

Changes in the circadian flight activity of the mosquito Anopheles gambiae in relation to insemination, feeding and oviposition

Abstract: . The effects of different physiological inputs on the circadian pattern of flight activity were examined in Anopheles gambiae. Males and virgin females had a similar activity pattern in which the initial (light-off) peak accounted for a large proportion of the total activity. Starvation caused an increase in activity, but the basic pattern remained unchanged. After insemination, the initial peak in females was greatly reduced, while activity later in the dark phase increased. Blood-feeding was followed by a depression of activity for 2–3 days, but there was an increase in the relative importance of the initial peak until oviposition had taken place. These changes are consistent with the switches in behaviour in the wild, from mating to host-seeking, and then between host-seeking and oviposition. Our results suggest that the changes are brought about by factors which have differential effects on the components of the circadian pacemaker.

Genetics of nitrofurazone resistance in Escherichia coli.

Abstract: Wild-type Escherichia coli cells are sensitive to nitrofurazone (NF) and many other nitrofuran derivatives. A variety of evidence indicated that these compounds are converted to toxic “active” metabolites by reductases present in the bacteria. Sensitive E. coli K-12 acquired threefold-greater resistance to NF in one mutational step. These partially resistant mutants could undergo a second mutation that made them 10 times as resistant as the wild type. Mutation of wild-type strain K-12 to the higher level of resistance in a single step was not observed. The first mutational step was associated with partial loss of reduced nicotinamide adenine dinucleotide phosphate-linked, O2-insensitive NF reductase activity, and the second step was associated with loss of the remaining activity. The two-step mutants did, however, contain other NF reductases that were inhibited by O2 and reduced NF only under anaerobic conditions. We designated the genes that control reductase activity “nitrofuran sensitivity genes” (nfsA and nfsB). Thus, wild-type strains are nfsA+nfsB+, and the resistant double mutants are nfsA nfsB. A variety of crosses established that these genes are both located close to gal, that the most probable sequence is lac nfsB gal nfsA, and that the single-step mutants with an intermediate level of resistance are nfsA nfsB+. The nfsA+nfsB strains contained about 70 to 80% of the wild-type reductase I activity—apparently enough to confer wild-type sensitivity. This reductase activity was resistant to 2 M urea. The nfsA nfsB+ strains had only 20 to 30% of the wild-type activity, and this residual activity was sensitive to 2 M urea.

Lexical development and overextension in child language

Abstract: A common assumption underlying the semantic feature and the functional core hypotheses of lexical development is that attributes abstracted from the referents of a word are sufficient to determine the extension of that word. The present paper begins by challenging this assumption. A contrastive hypothesis is instead advanced to explain the early lexical development of children, and the predictions of this hypothesis are shown to be consistent with available data on overextension. The paper concludes with a critical discussion of the semantic feature and the functional core hypotheses in which it is shown that neither of these hypotheses can account for the data on overextension.

ColE1 plasmid mobility and relaxation complex

Abstract: LIKE other small plasmids, ColE1 cannot promote its own conjugal transfer. Conjugative plasmids such as F′lac allow its efficient mobilisation: ColE1 is nonconjugative but mobile (Mob+) or transmissible. There is now strong evidence that ColE1 transfers actively and autonomously, rather than by integration into the conjugative plasmid or by passive diffusion in the mating aggregate. Passive diffusion is unlikely as many derivatives of ColE1 are transfer-deficient (Mob−) (refs 1–4), as are some other small plasmids. Also the finding that some cells acquire ColE1 but no conjugative plasmid seems to discount cointegrate transfer; so does the observation that some transfer-deficient F′lac mutants can still mobilise ColE1 (ref. 5). Here we show that ColE1 conjugal mobility requires both a specific site on the plasmid DNA and sequences specifying diffusible gene products. We propose that the site is at the transfer origin, which is also where ColE1 mobility protein(s) nick ColE1 in relaxation complex6. Translocation of this site to another normally non-mobile plasmid, allows its mobilisation when ColE1 mobility proteins are supplied in trans.