The ecosystem approach to fisheries recognises the interdependence between harvested species and other ecosystem components. It aims to account for the propagation of the effects of harvesting through the food-web. The formulation and evaluation of ecosystem-based management strategies requires reliable models of ecosystem dynamics to predict these effects. The krill-based system in the Southern Ocean was the focus of some of the earliest models exploring such effects. It is also a suitable example for the development of models to support the ecosystem approach to fisheries because it has a relatively simple food-web structure and progress has been made in developing models of the key species and interactions, some of which has been motivated by the need to develop ecosystem-based management. Antarctic krill, Euphausia superba, is the main target species for the fishery and the main prey of many top predators. It is therefore critical to capture the processes affecting the dynamics and distribution of krill in ecosystem dynamics models. These processes include environmental influences on recruitment and the spatially variable influence of advection. Models must also capture the interactions between krill and its consumers, which are mediated by the spatial structure of the environment. Various models have explored predator-prey population dynamics with simplistic representations of these interactions, while others have focused on specific details of the interactions. There is now a pressing need to develop plausible and practical models of ecosystem dynamics that link processes occurring at these different scales. Many studies have highlighted uncertainties in our understanding of the system, which indicates future priorities in terms of both data collection and developing methods to evaluate the effects of these uncertainties on model predictions. We propose a modelling approach that focuses on harvested species and their monitored consumers and that evaluates model uncertainty by using alternative structures and functional forms in a Monte Carlo framework.

Recent data concerning ultradian (circahoralian) intracellular rhythms are used to assess the biochemical mechanisms of direct cell-cell communication. New results and theoretical considerations suggest a fractal nature of ultradian rhythms and their self-organisation. The fundamental and innate nature of these rhythms relates to their self-similarity at different levels of cell and tissue organisation. They can be detected in cell-free systems as well as in cells and organs in vivo. Such rhythms are a means of finding an optimal state of cell function rather than achieving a state of absolute stability. As a consequence, oscillations, being irregular and numerous by the set of periods, are resilient to functional overload and injury. Recent data on the maintenance of their fractal structure and, especially on the selection of optimal periods are discussed. The positive role of chaotic dynamics is stressed.

The ultradian rhythm of protein synthesis in hepatocytes in vitro was used as a marker of direct cell-cell communication. The system demonstrates cell cooperation and synchronisation throughout the cell population, and suggests that the ultradian rhythms are self-organised. These observations also led to the detection of mechanisms of direct cell-cell communication in which extracellular factors have an essential role. Experimental evidence indicated the involvement of gangliosides and/or catecholamines in this large-scale synchronisation of protein synthesis. The response of all, or a major part, of the cell population is important; after the initial trigger effect, a periodic pattern is retained for some time. The influence of Ca2+-dependent protein kinases on protein phosphorylation can be a final step in the phase modulation of rhythms during cell-cell synchronisation.

The intercellular medium plays an important role in self-synchronisation of ultradian rhythms between individual cells. Low cooperative activity of hepatocytes of old rats resulted from altered composition of the intercellular medium rather than direct effects of animal and cellular ageing. Similarly, in the whole body, changes in levels of gangliosides and catecholamines in the blood serum, a natural intercellular medium, can be critical events in age-dependent changes of the serum and accordingly cell-cell synchronisation. Hepatocytes of old rats exhibit some of the properties of young cells following an increase in blood serum ganglioside level, as well as, in in vitro conditions, after the addition of gangliosides to the culture medium.

Together with data on ultradian functional and metabolic rhythms, all the material reviewed here allows us to propose a mechanism of direct cell-cell cooperation via the medium in which the cells exist, that supplements the nervous and hormonal central regulation of organ functions. Ultradian intracellular rhythms may thus provide a finer framework within which the integrated dynamics of respiration, heart rate, brain activity, and even behavioural patterns, are brought to an optimal functional pattern. Innate and direct cell-cell cooperation may have been employed as a means of intercellular regulation during the course of metazoan evolution, that preceded nervous regulation and is presently retained in mammals.

Fitting a line to a bivariate dataset can be a deceptively complex problem, and there has been much debate on this issue in the literature. In this review, we describe for the practitioner the essential features of line-fitting methods for estimating the relationship between two variables: what methods are commonly used, which method should be used when, and how to make inferences from these lines to answer common research questions.

A particularly important point for line-fitting in allometry is that usually, two sources of error are present (which we call measurement and equation error), and these have quite different implications for choice of line-fitting method. As a consequence, the approach in this review and the methods presented have subtle but important differences from previous reviews in the biology literature.

Linear regression, major axis and standardised major axis are alternative methods that can be appropriate when there is no measurement error. When there is measurement error, this often needs to be estimated and used to adjust the variance terms in formulae for line-fitting. We also review line-fitting methods for phylogenetic analyses.

Methods of inference are described for the line-fitting techniques discussed in this paper. The types of inference considered here are testing if the slope or elevation equals a given value, constructing confidence intervals for the slope or elevation, comparing several slopes or elevations, and testing for shift along the axis amongst several groups. In some cases several methods have been proposed in the literature. These are discussed and compared. In other cases there is little or no previous guidance available in the literature.

Simulations were conducted to check whether the methods of inference proposed have the intended coverage probability or Type I error. We identified the methods of inference that perform well and recommend the techniques that should be adopted in future work.

Although the mathematical principles underpinning population-level evolution are now well studied, the origin and evolution of morphological novelties has received far less attention. Here, a broad but general theory for how this sort of change takes place is outlined, relying on functional continuity, least-constrained components of morphology, redundancy and preadaptation. At least four distinct sorts of redundancy are identified: (i) redundancy arising through duplication (amplification); (ii) redundancy arising through regionalisation (parcellation); (iii) redundancy arising through functional convergence; and (iv) redundancy arising from shared function (functional degeneracy). Although organisms are here recognised to be functionally constrained (“burdened”, in Riedl's terminology), these constraints can be overcome through the combination of the four principles given above. Contrary to its common treatment, functional constraint is neither an ever-increasing restriction on the scope of evolution, nor does it require drastic events to overcome or “break” it. Rather, it is an evolutionary quantity, subject to selection at some level. The rules that govern morphological evolution are the primary controls on what is allowed to happen in the evolution of the overall genotype-phenotype system, suggesting strong controls on the sorts of developmental changes that might be associated with macroevolution. This model, then, sees organism functionality as the primary control on evolvability, with exact genetic make-up being of secondary importance. It should prove possible to recast traditional notions of body-plan evolution into the formulations of complex system analysis, which in the future may prove a unifying discipline for fields as disparate as palaeontology and gene regulatory networks. In particular, understanding how morphology can evolve may provide the critical link between the ecological and morphological networks that are currently the intense focus of evolutionary investigations.

This review examines aspects of cetacean brain structure related to behaviour and evolution. Major considerations include cetacean brain-body allometry, structure of the cerebral cortex, the hippocampal formation, specialisations of the cetacean brain related to vocalisations and sleep phenomenology, paleoneurology, and brain-body allometry during cetacean evolution. These data are assimilated to demonstrate that there is no neural basis for the often-asserted high intellectual abilities of cetaceans. Despite this, the cetaceans do have volumetrically large brains. A novel hypothesis regarding the evolution of large brain size in cetaceans is put forward. It is shown that a combination of an unusually high number of glial cells and unihemispheric sleep phenomenology make the cetacean brain an efficient thermogenetic organ, which is needed to counteract heat loss to the water. It is demonstrated that water temperature is the major selection pressure driving an altered scaling of brain and body size and an increased actual brain size in cetaceans. A point in the evolutionary history of cetaceans is identified as the moment in which water temperature became a significant selection pressure in cetacean brain evolution. This occured at the Archaeoceti – modern cetacean faunal transition. The size, structure and scaling of the cetacean brain continues to be shaped by water temperature in extant cetaceans. The alterations in cetacean brain structure, function and scaling, combined with the imperative of producing offspring that can withstand the rate of heat loss experienced in water, within the genetic confines of eutherian mammal reproductive constraints, provides an explanation for the evolution of the large size of the cetacean brain. These observations provide an alternative to the widely held belief of a correlation between brain size and intelligence in cetaceans.

How much effort to expend in any one bout of reproduction is among the most important decisions made by an individual that breeds more than once. According to life-history theory, reproduction is costly, and individuals that invest too much in a given reproductive bout pay with reduced reproductive output in the future. Likewise, investing too little does not maximize reproductive potential. Because reproductive effort relative to output can vary with predictable and unpredictable challenges and opportunities, no single level of reproductive effort maximizes fitness. This leads to the prediction that individuals possessing behavioural mechanisms to buffer challenges and take advantage of opportunities would incur fitness benefits. Here, we review evidence in birds, primarily of altricial species, for the presence of at least two such mechanisms and evidence for and against the seasonal coordination of these mechanisms through seasonal changes in plasma concentrations of the pituitary hormone prolactin. First, the seasonal decline in clutch size of most bird species may partially offset a predictable seasonal decline in the reproductive value of offspring. Second, establishing a developmental sibling-hierarchy among offspring may hedge against unpredictable changes in resource availability and offspring viability or quality, and minimize energy expenditure in raising a brood. The hierarchy may be a product, in part, of the timing of incubation onset relative to clutch completion and the rate of yolk androgen deposition during the laying cycle. Because clutch size should influence the effects of both these traits on the developmental hierarchy, we predicted and describe evidence in some species that females adjust the timing of incubation onset and rate of yolk androgen deposition to match clutch size. Studies on domesticated precocial species reveal an inhibitory effect of the pituitary hormone prolactin on egg laying, suggesting a possible hormonal basis for the regulation of clutch size. Studies on the American kestrel (Falco sparverius) and other species suggest that the seasonal increase in plasma concentrations of prolactin may regulate both a seasonal advance in the timing of incubation onset and a seasonal increase in the rate of yolk androgen deposition. These observations, together with strong conceptual arguments published previously, raise the possibility that a single hormone, prolactin, functions as the basis of a common mechanism for the seasonal adjustment of reproductive effort. However, a role for prolactin in regulating clutch size in any species is not firmly established, and evidence from some species indicates that clutch size may not be coupled to the timing of incubation onset and rate of yolk androgen deposition. A dissociation between the regulation of clutch size and the regulation of incubation onset and yolk androgen deposition may enable an independent response to the predictable and unpredictable challenges and opportunities faced during reproduction.