| 1. |
- Kelber, Almut, et al.
(författare)
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Animal colour vision - behavioural tests and physiological concepts
- 2003
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Ingår i: Biological Reviews. - 1469-185X. ; 78:1, s. 81-118
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Forskningsöversikt (refereegranskat)abstract
- Over a century ago workers such as J. Lubbock and K. von Frisch developed behavioural criteria for establishing that non-human animals see colour. Many animals in most phyla have since then been shown to have colour vision. Colour is used for specific behaviours, such as phototaxis and object recognition, while other behaviours such as motion detection are colour blind. Having established the existence of colour vision, research focussed on the question of how many spectral types of photoreceptors are involved. Recently, data on photoreceptor spectral sensitivities have been combined with behavioural experiments and physiological models to study systematically the next logical question: what neural interactions underlie colour vision? This review gives an overview of the methods used to study animal colour vision, and discusses how quantitative modelling can suggest how photoreceptor signals are combined and compared to allow for the discrimination of biologically relevant stimuli.
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| 2. |
- Lindström, Jan, et al.
(författare)
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From arctic lemmings to adaptive dynamics: Charles Elton's legacy in population ecology
- 2001
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Ingår i: Biological Reviews. - 1469-185X. ; 76:1, s. 129-158
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Forskningsöversikt (refereegranskat)abstract
- We shall examine the impact of Charles S. Eltons 1924 article on periodic fluctuations in animal populations on the development of modern population ecology. We argue that his impact has been substantial and that during the past 75 years of research on multi-annual periodic fluctuations in numbers of voles, lemmings, hares, lynx and game animals he has contributed much to the contemporary understanding of the causes and consequences of population regulation. Elton was convinced that the cause of the regular fluctuations was climatic variation. To support this conclusion, he examined long-term population data then available. Despite his firm belief in a climatic cause of the self-repeating periodic dynamics which many species display, Elton was insightful and far-sighted enough to outline many of the other hypotheses since put forward as an explanation for the enigmatic long-term dynamics of some animal populations. An interesting, but largely neglected aspect in Eltons paper is that it ends with speculation regarding the evolutionary consequences of periodic population fluctuations. The modern understanding of these issues will also be scrutinised here. In population ecology, Eltons 1924 paper has spawned a whole industry of research on populations displaying multi-annual periodicity. Despite the efforts of numerous research teams and individuals focusing on the origins of multi-annual population cycles, and despite the early availability of different explanatory hypotheses, we are still lacking rigorous tests of some of these hypotheses and, consequently, a consensus of the causes of periodic fluctuations in animal populations. Although Elton would have been happy to see so much effort spent on cyclic populations, we also argue that it is unfortunate if this focus on a special case of population dynamics should distract our attention from more general problems in population and community dynamics.
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| 3. |
- Skogsmyr, Io, et al.
(författare)
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Sexual selection: an evolutionary force in plants
- 2002
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Ingår i: Biological Reviews. - 1469-185X. ; 77:4, s. 537-562
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Forskningsöversikt (refereegranskat)abstract
- Sexual selection has traditionally been used to explain exaggerated sexual traits in male animals. Today the concept has been developed and various other sexually related traits have been suggested to evolve in the same manner. In nearly all new areas where the theory of sexual selection has been applied, there has been an intense debate as to whether the application is justified. Is it the case that some scientists are all too ready to employ fashionable ideas? Or are there too many dogmatic researchers refusing to accept that science develops and old ideas are transformed? Maybe the controversies are simply a reflection of the difficulty of defining a theory under constant re-evaluation. Thus, we begin by summarizing the theory of sexual selection in order to assess the influence of sexual selection on the evolution of plant morphology. We discuss empirical findings concerning potentially affected traits. Although we have tried to address criticisms fairly, we still conclude that sexual selection can be a useful tool when studying the evolution of reproductive traits in plants. Furthermore, by including the evidence from an additional kingdom, a fuller understanding of the processes involved in sexual selection can be gained.
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| 4. |
- Warrant, Eric, et al.
(författare)
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Vision in the deep sea
- 2004
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Ingår i: Biological Reviews. - 1469-185X. ; 79:3, s. 671-712
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Forskningsöversikt (refereegranskat)abstract
- The deep sea is the largest habitat on earth. Its three great faunal environments - the twilight mesopelagic zone, the dark bathypelagic zone and the vast flat expanses of the benthic habitat- are home to a rich fauna of vertebrates and invertebrates. In the mesopelagic zone (150-1000 in), the down-welling daylight creates an extended scene that becomes increasingly dimmer and bluer with depth. The available daylight also originates increasingly, from vertically above, and bioluminescent point-source flashes, well contrasted against the dim background daylight become increasingly visible. In the bathypelagic zone below 1000 m no daylight remains, and the scene becomes entirel, dominated by point-like biolumincscence. This changing nature of visual scenes with depth - from extended source to point source - has had a profound effect on the designs of deep-sea eyes, both optically and neurally, a fact that until recently was not fully appreciated. Recent measurements of the sensitivity and spatial resolution of deep-sea eyes - particularly from the camera eyes of fishes and cephalopods and the compound eyes of crustaceans - reveal that ocular designs are well matched to the nature of the visual scene at any criven depth. This match between eye design and visual scene is the subject of this review. The greatest variation eye design is found in the mesopelagic zone, where dim down-welling daylight and bioluminescent point Sources may be visible simultaneously. Some ruesopelagic eyes rely on spatial and temporal Summation to increase sensitivity to a dim extended scene, while others sacrifice this sensitivity to localise pinpoints of bright bioluminescence. Yet other eyes have retinal regions separately specialised for each type of light. In the bathypelagic zone, eyes generally get smaller and therefore less sensitive to point sources with increasing depth. In fishes, this insensitivty, combined with surprisingly high spatial resolution, is very well adapted to the detection and locallsation of point-source bioluminescence at ecologically meaningful distances. At all depths, the eyes of animals active on and over the nutrient-rich sea floor are generally larger than the eyes of pelagic species. In fishes, the retinal ganglion bells are also frequently arranged in a horizontal visual streak, an adaptation for., the wide flat horizon of the sea floor, and all animals living there. These and many other aspects of light viewing and vision in the deep sea are renewed in support of the following conclusion: it is not only the intensity of light at different depths, but also its distribution in space, which has been a major force in the evolution of deep-sea vision.
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