martes, 14 de abril de 2009

Selección del Complexity Digest - Abril

Electric cows, Nature

Excerpt: Having previously shown statistically that cows and deer preferentially align their bodies northâ€"south, Hynek Burda of the University of Duisburg-Essen in Germany and his colleagues now provide more evidence for these animals' magnetic sensing. (...)
Using satellite and aerial photographs, the researchers show that 1,699 cows grazing within 50 metres of overhead power lines at various European locations were randomly oriented. Field observations of 653 deer within 50 metres of power lines in the Czech Republic also revealed random orientation.
See Also: Proc. Natl Acad. Sci. USA doi: 10.1073/pnas.0811194106 (2009)>

  • Source: Electric cows, DOI: 10.1038/458389a, Nature 458, 389, 2009/03/26

Evolution and the second law of thermodynamics, arXiv

Abstract: Skeptics of biological evolution often claim that evolution requires a decrease in entropy, giving rise to a conflict with the second law of thermodynamics. This argument is fallacious because it neglects the large increase in entropy provided by sunlight striking the Earth. A recent article provided a quantitative assessment of the entropies involved and showed explicitly that there is no conflict. That article rests on an unjustified assumption about the amount of entropy reduction involved in evolution. I present a refinement of the argument that does not rely on this assumption.

Geographic Range Limits Of Species, Proc. Biol. Sc.

Excerpt: Understanding the forms that the geographic range limits of species take, their causes and their consequences are key issues in ecology and evolutionary biology. They are also topics on which understanding is advancing rapidly. This themed issue of Proc. R. Soc. B focuses on the wide variety of current research perspectives on the nature and determinants of the limits to geographic ranges. The contributions address important themes, including the roles and influences of dispersal limitation, species interactions and physiological limitation, the broad patterns in the structure of geographic ranges, and the fundamental question of why at some point species no longer evolve (...).

  • Source: Geographic Range Limits Of Species, K.J Gaston -, DOI: 10.1098/rspb.2009.0100, Proceedings B: Biological Sciences, 2009/04/22, Online 2009/02/25

Discovering The Secret Code Behind Photosynthesis, ScienceDaily

Excerpts: (...) discovered that an ancient system of communication found in primitive bacteria, may also explain how plants and algae control the process of photosynthesis. Two-component signal transduction systems (TCSTs) have long been recognised as the main way in which bacteria coordinate their responses to changes in their environment. But recent research has shown that these 'bacterial' two-component systems have also survived in plants and algae, as a way of sending signals within their cells. These systems, which are thought to have evolved from ancient cyanobacteria, are found in chloroplasts - the part of a cell of a plant which conducts photosynthesis, converting light to chemical energy. (...)

On the Origin of Photosynthesis, Science

Excerpt: Where would we be without photosynthesis? In the third essay in Science's series in honor of the Year of Darwin, Mitch Leslie details researchers' efforts to piece together how and when organisms first began to harness light's energy.

The Evolution And Genetics Of Cerebral Asymmetry, Phil. Tran. Biol. Sc.

Excerpt: Handedness and cerebral asymmetry are commonly assumed to be uniquely human, and even defining characteristics of our species. This is increasingly refuted by the evidence of behavioural asymmetries in non-human species. Although complex manual skill and language are indeed unique to our species and are represented asymmetrically in the brain, some non-human asymmetries appear to be precursors, and others are shared between humans and non-humans. In all behavioural and cerebral asymmetries so far investigated, a minority of individuals reverse or negate the dominant asymmetry, suggesting that such asymmetries are best understood in the context of the overriding bilateral symmetry of the brain and body, (...).

Why Are Some People Left-Handed? An Evolutionary Perspective, Phil. Tran. Biol. Sc.

Excerpt: Since prehistoric times, left-handed individuals have been ubiquitous in human populations, exhibiting geographical frequency variations. Evolutionary explanations have been proposed for the persistence of the handedness polymorphism. Left-handedness could be favoured by negative frequency-dependent selection. Data have suggested that left-handedness, as the rare hand preference, could represent an important strategic advantage in fighting interactions. However, the fact that left-handedness occurs at a low frequency indicates that some evolutionary costs could be associated with left-handedness. Overall, the evolutionary dynamics of this polymorphism are not fully understood. Here, we review the abundant literature available regarding the possible mechanisms and consequences of left-handedness. We point out that hand preference is heritable, (...).

Mechanisms And Functions Of Brain And Behavioural Asymmetries, Phil. Tran. Biol. Sc.

Excerpt: For almost a century the field of brain and behavioural asymmetries has been dominated by studies on humans, resting on the evidence that the anatomical structures underlying language functions are asymmetrical, and that human handedness is lateralized at the population level. Today, there is not only evidence of population-level lateralization of brain and behaviour across a variety of vertebrate and invertebrate species, but also a growing consensus that the comparative analysis of the environmental and developmental factors that give origin to neural and behavioural laterality in animal models, together with theoretical analyses of their costs and benefits, will be crucial for understanding the evolutionary pathways (...).

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