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result(s) for
"Section IV: Evolution"
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The colours of humanity: the evolution of pigmentation in the human lineage
2017
Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory. Functionally naked skin has been the physical interface between the physical environment and the human body for most of the history of the genus Homo, and hence skin coloration has been under intense natural selection. From an original condition of protective, dark, eumelanin-enriched coloration in early tropical-dwelling Homo and Homo sapiens, loss of melanin pigmentation occurred under natural selection as Homo sapiens dispersed into non-tropical latitudes of Africa and Eurasia. Genes responsible for skin, hair and eye coloration appear to have been affected significantly by population bottlenecks in the course of Homo sapiens dispersals. Because specific skin colour phenotypes can be created by different combinations of skin colour–associated genetic markers, loss of genetic variability due to genetic drift appears to have had negligible effects on the highly redundant genetic 'palette' for the skin colour. This does not appear to have been the case for hair and eye coloration, however, and these traits appear to have been more strongly influenced by genetic drift and, possibly, sexual selection. This article is part of the themed issue 'Animal coloration: production, perception, function and application'.
Journal Article
Thermal consequences of colour and near-infrared reflectance
The importance of colour for temperature regulation in animals remains controversial. Colour can affect an animal's temperature because all else being equal, dark surfaces absorb more solar energy than do light surfaces, and that energy is converted into heat. However, in reality, the relationship between colour and thermorégulation is complex and varied because it depends on environmental conditions and the physical properties, behaviour and physiology of the animal. Furthermore, the thermal effects of colour depend as much on absorptance of near-infrared ((MR), 700–2500 nm) as visible (300–700 nm) wavelengths of direct sunlight; yet the NIR is very rarely considered or measured. The few available data on NIR reflectance in animals indicate that the visible reflectance is often a poor predictor of NIR reflectance. Adaptive variation in animal coloration (visible reflectance) reflects a compromise between multiple competing functions such as camouflage, signalling and thermorégulation. By contrast, adaptive variation in NIR reflectance should primarily reflect thermoregulatory requirements because animal visual systems are generally insensitive to NIR wavelengths. Here, we assess evidence and identify key research questions regarding the thermoregulatory function of animal coloration, and specifically consider evidence for adaptive variation in NIR reflectance. This article is part of the themed issue 'Animal coloration: production, perception, function and application'.
Journal Article
Thermal consequences of colour and near-infrared reflectance
by
Newton, Elizabeth
,
Stuart-Fox, Devi
,
Clusella-Trullas, Susana
in
Absorptance
,
Absorptivity
,
Animal Coloration
2017
The importance of colour for temperature regulation in animals remains controversial. Colour can affect an animal's temperature because all else being equal, dark surfaces absorb more solar energy than do light surfaces, and that energy is converted into heat. However, in reality, the relationship between colour and thermoregulation is complex and varied because it depends on environmental conditions and the physical properties, behaviour and physiology of the animal. Furthermore, the thermal effects of colour depend as much on absorptance of near-infrared ((NIR), 700–2500 nm) as visible (300–700 nm) wavelengths of direct sunlight; yet the NIR is very rarely considered or measured. The few available data on NIR reflectance in animals indicate that the visible reflectance is often a poor predictor of NIR reflectance. Adaptive variation in animal coloration (visible reflectance) reflects a compromise between multiple competing functions such as camouflage, signalling and thermoregulation. By contrast, adaptive variation in NIR reflectance should primarily reflect thermoregulatory requirements because animal visual systems are generally insensitive to NIR wavelengths. Here, we assess evidence and identify key research questions regarding the thermoregulatory function of animal coloration, and specifically consider evidence for adaptive variation in NIR reflectance.
This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
Journal Article
The colours of humanity: the evolution of pigmentation in the human lineage
2017
Humans are a colourful species of primate, with human skin, hair and eye coloration having been influenced by a great variety of evolutionary forces throughout prehistory. Functionally naked skin has been the physical interface between the physical environment and the human body for most of the history of the genus Homo, and hence skin coloration has been under intense natural selection. From an original condition of protective, dark, eumelanin-enriched coloration in early tropical-dwelling Homo and Homo sapiens, loss of melanin pigmentation occurred under natural selection as Homo sapiens dispersed into non-tropical latitudes of Africa and Eurasia. Genes responsible for skin, hair and eye coloration appear to have been affected significantly by population bottlenecks in the course of Homo sapiens dispersals. Because specific skin colour phenotypes can be created by different combinations of skin colour–associated genetic markers, loss of genetic variability due to genetic drift appears to have had negligible effects on the highly redundant genetic ‘palette’ for the skin colour. This does not appear to have been the case for hair and eye coloration, however, and these traits appear to have been more strongly influenced by genetic drift and, possibly, sexual selection.
This article is part of the themed issue ‘Animal coloration: production, perception, function and application’.
Journal Article
DIRECT MEASUREMENT OF THE E1 AND E2 CROSS SECTIONS OF THE 12C(α,γ)16O REACTION AT Ec.m. =1.3~1.5MeV
by
MAKII, H.
,
NAGAI, Y.
,
SEGAWA, M.
in
IV. Evolution and Nucleosynthesis in Stars, and Cross Sections — Hydro Static Burning
2004
The E1 and E2 transition cross sections at the center-of-mass energies of 1.3~1.5MeV have been measured by directly detecting the prompt γ ray from the capture state of the 16O nucleus. Using a pulsed α beam, major background due to the 13C(α,n)16O reaction were efficiently reduced, and the cross sections were determined with very good statistical accuracy of 4~10%.
Book Chapter
186RE ISOMER CONTRIBUTION TO 187RE-187OS COSMOCHRONOMETER
by
UTSUNOMIYA, H.
,
HAYAKAWA, T.
,
SHINOHARA, N.
in
IV. Evolution and Nucleosynthesis in Stars, and Cross Sections — Hydro Static Burning
2004
A 187Os-187Re pair has been known to be a good cosmochronometer for the r-process nucleosynthesis. The radioactivity 187Re decays to a daughter nucleus 187Os with a half-life of 2.0 × 105 years. The 187Re has been considered to be synthesized predominantly by the r-process, whereas the 187Os has been produced by both the radioactive decay of 187Re and the s-process nucleosynthesis. The s-process contaminations to 187Re and 187Os must be subtracted for an estimation of the passing time from a r-process episode to the present time with an accuracy. An s-process path through a 186Re isomer has been ignored up to now because the neutron capture cross section of the 185Re(n,γ)186mRe reaction at a thermal energy as well as a quasi-stellar energy has not been measured by experimental techniques with an estimation of uncertainty. In order to estimate this s-process contamination through the isomer, a production ratio of the isomer to the ground state in 186Re has been measured through an activation technique with a thermal neutron provided by a nuclear reactor.
Book Chapter
Evolution caused by extreme events
by
Grant, Peter R.
,
Johnson, Marc T. J.
,
Knoll, Andrew H.
in
Adaptation
,
Asteroid collisions
,
Biological Evolution
2017
Extreme events can be a major driver of evolutionary change over geological and contemporary timescales. Outstanding examples are evolutionary diversification following mass extinctions caused by extreme volcanism or asteroid impact. The evolution of organisms in contemporary time is typically viewed as a gradual and incremental process that results from genetic change, environmental perturbation or both. However, contemporary environments occasionally experience strong perturbations such as heat waves, floods, hurricanes, droughts and pest outbreaks. These extreme events set up strong selection pressures on organisms, and are small-scale analogues of the dramatic changes documented in the fossil record. Because extreme events are rare, almost by definition, they are difficult to study. So far most attention has been given to their ecological rather than to their evolutionary consequences. We review several case studies of contemporary evolution in response to two types of extreme environmental perturbations, episodic (pulse) or prolonged (press). Evolution is most likely to occur when extreme events alter community composition. We encourage investigators to be prepared for evolutionary change in response to rare events during long-term field studies.
This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.
Journal Article
NEUTRON CAPTURE CROSS SECTION OF 14C STUDIED BY INTERMEDIATE-ENERGY COULOMB DISSOCIATION
by
FUKUDA, N.
,
NAKAMURA, T.
in
IV. Evolution and Nucleosynthesis in Stars, and Cross Sections — Hydro Static Burning
2004
The neutron capture reaction on 14C leading to the 15C ground state, which is important in the nucleo-synthesis processes in the universe, has been studied by using the Coulomb dissociation of 15C on a Pb target at 68 MeV/nucleon. The dissociation cross sections at large impact parameters over 20 fm has been translated into the energy spectrum of the neutron capture by using the principle of the detailed balance. The energy spectrum shows the typical p-wave capture characteristics, which is understood by the fact that the ground state of 15C is a loosely bound halo state. The present study suggests that such a p-wave neutron capture may often occur at the very neutron rich regions, where important nucleo-synthesis paths are expected.
Book Chapter
The genetic and molecular architecture of phenotypic diversity in sticklebacks
2017
A major goal of evolutionary biology is to identify the genotypes and phenotypes that underlie adaptation to divergent environments. Stickleback fish, including the threespine stickleback (Gasterosteus aculeatus) and the ninespine stickleback (Pungitius pungitius), have been at the forefront of research to uncover the genetic and molecular architecture that underlies phenotypic diversity and adaptation. A wealth of quantitative trait locus (QTL) mapping studies in sticklebacks have provided insight into long-standing questions about the distribution of effect sizes during adaptation as well as the role of genetic linkage in facilitating adaptation. These QTL mapping studies have also provided a basis for the identification of the genes that underlie phenotypic diversity. These data have revealed that mutations in regulatory elements play an important role in the evolution of phenotypic diversity in sticklebacks. Genetic and molecular studies in sticklebacks have also led to new insights on the genetic basis of repeated evolution and suggest that the same loci are involved about half of the time when the same phenotypes evolve independently. When the same locus is involved, selection on standing variation and repeated mutation of the same genes have both contributed to the evolution of similar phenotypes in independent populations.
This article is part of the themed issue ‘Evo-devo in the genomics era, and the origins of morphological diversity’.
Journal Article
Quantifying thermal extremes and biological variation to predict evolutionary responses to changing climate
by
Kingsolver, Joel G.
,
Buckley, Lauren B.
in
Adaptation, Biological
,
Biological Evolution
,
Climate Change
2017
Central ideas from thermal biology, including thermal performance curves and tolerances, have been widely used to evaluate how changes in environmental means and variances generate changes in fitness, selection and microevolution in response to climate change. We summarize the opportunities and challenges for extending this approach to understanding the consequences of extreme climatic events. Using statistical tools from extreme value theory, we show how distributions of thermal extremes vary with latitude, time scale and climate change. Second, we review how performance curves and tolerances have been used to predict the fitness and evolutionary responses to climate change and climate gradients. Performance curves and tolerances change with prior thermal history and with time scale, complicating their use for predicting responses to thermal extremes. Third, we describe several recent case studies showing how infrequent extreme events can have outsized effects on the evolution of performance curves and heat tolerance. A key issue is whether thermal extremes affect reproduction or survival, and how these combine to determine overall fitness. We argue that a greater focus on tails—in the distribution of environmental extremes, and in the upper ends of performance curves—is needed to understand the consequences of extreme events.
This article is part of the themed issue ‘Behavioural, ecological and evolutionary responses to extreme climatic events’.
Journal Article