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Serge Daan - One of the best experts on this subject based on the ideXlab platform.
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Basal Metabolic Rate in relation to body composition and daily energy expenditure in the field vole microtus agrestis
Physiological and Biochemical Zoology, 1997Co-Authors: Peter Meerlo, L Bolle, G H Visser, Dirkjan Masman, Serge DaanAbstract:Basal Metabolic Rate in the field vole (Microtus agrestis) was studied in relation to body composition and daily energy expenditure in the field. Daily energy expenditure was measured by means of doubly labelled water (D2 18O). In the same individuals, Basal Metabolic Rate was subsequently derived from O2 consumption in an open-circuit system in the laboratory. Body composition was obtained by dissecting the animals and determining fresh, dry, and lean dry mass of different organs. Daily energy expenditure for free-living field voles ranged from 1.8 to 4.5 times Basal Metabolic Rate, with an average of 2.9 times Basal Metabolic Rate. Variation in both daily energy expenditure and Basal Metabolic Rate was best explained by body mass. Gender or reproductive activity did not have significant additive effects. Daily energy expenditure and Basal Metabolic Rate showed significant positive relationships to body mass with similar mass exponents of 0.493 and 0.526, respectively. Overall, there was a significant correlation between daily energy expenditure and Basal Metabolic Rate, but the mass-independent residuals (deviations from the allometrically predicted values) did not correlate. Carcass analysis revealed that a number of organs were slightly better predictors for daily energy expenditure and Basal Metabolic Rate than was fresh body mass. Mass-independent residuals of lean dry heart mass and Basal Metabolic Rate were positively correlated, which is in agreement with the idea that Basal Metabolic Rate reflects the size of Metabolically active organs. The study does not provide support for an intraindividual association of Basal Metabolic Rate with daily energy expenditure in the field.
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the relationship between Basal Metabolic Rate and daily energy expenditure in birds and mammals
The American Naturalist, 1996Co-Authors: Robert E Ricklefs, Marek Konarzewski, Serge DaanAbstract:We examined the relationship between daily energy expenditure (DEE) and Basal Metabolic Rate (BMR) in birds and mammals. Two models of the relationship between DEE and BMR were distinguished: a "shared pathways" model in which DEE replaces BMR in the active organism and a "partitioned pathways" model in which DEE includes BMR-that is, BMR is sepaRate from the Metabolic pathways that result in activity metabolism (ACT), and DEE = ACT + BMR. The appropriate null hypotheses for the relationship between Basal and active metabolism are rDEE· BMR = 0 and rACT· BMR = 0, respectively. Correlations of the residuals (d and b) of the logarithms of DEE and BMR from their allometric regressions with the logarithm of body mass were tested against these null models. Using phylogenetically independent contrasts, we found no significant relationship between DEE and BMR in birds, but a strong relationship (rdb = 0.86) among mammals. Thus, the hypothesis that sustained working capacity is related to Basal metabolism is supp...
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seasonality in Basal Metabolic Rate and thermal conductance in a long distance migrant shorebird the knot calidris canutus
Journal of Comparative Physiology B-biochemical Systemic and Environmental Physiology, 1995Co-Authors: Theunis Piersma, N Cadee, Serge DaanAbstract:Knots Calidris canutus live highly seasonal lives, breeding solitarily on high arctic tundra and spending the non-breeding season in large social flocks in tempeRate to tropical estuaries. Their reproductive activities and physiological preparations for long flights are reflected in pronounced plumage and body mass changes, even in long-term captives of the islandica subspecies (breeding in north Greenland and northeast Canada and wintering in western Europe) studied in outdoor aviaries. The three to four fattening episodes in April-July in connection with the flights to and from the high arctic breeding grounds by free-living birds, are represented by a single period of high body mass, peaking between late May and early July in a sample of ten captive islandica knots studied over four years. There are consistent and synchronized annual variations in Basal Metabolic Rate and thermal conductance in three islandica knots. Basal Metabolic Rate was highest during the summer body mass peak. Within the examined individuals, Basal Metabolic Rate scales on body mass with an exponent of about 1.4, probably reflecting a general hypertrophy of Metabolically expensive muscles and organs. Any potential effect of moult on Basal Metabolic Rate was obscured by the large seasonal mass-associated variations. In breeding plumage, insulation (the inverse of thermal conductance) was a factor of 1.35 lower than in winter plumage. This was paralleled by the dry mass of contour feathers being a factor of 1.17 lower. In this subspecies the breeding season is indeed the period during which the costs of thermoregulation are lowest. In captive knots seasonal changes in Basal Metabolic Rate and thermal conductance likely reflect an anticipatory programme adaptive to the variable demands made by the environment at different times of the year.
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the energetic cost of feather synthesis is proportional to Basal Metabolic Rate
Physiological and Biochemical Zoology, 1993Co-Authors: Ake Lindstrom, Henk G Visser, Serge DaanAbstract:The cost of feather production, $C_{f}$ (kJ · [g dry feathers]⁻¹), differs substantially between species. We studied the molt cost in one insectivorous songbird (bluethroat, Luscinia s. svecica) and one granivorous songbird (common redpoll, Carduelis f. flammea). We wanted to test whether diferences in diet, body mass (or Basal Metabolic Rate, BMR), or the latitude of molt could explain interspecific differences. In each individual, the resting metabolism, as measured by indirect calorimetry, was positively correlated with feather production Rate. The cost of feather synthesis was estimated at 836 and 683 kJ · (g dry feathers)⁻¹ in the bluethroats and redpolls, respectively. The efciency of feather production was 2.6% and 3.1%. It was concluded that neither diet nor latitudinal constraints alone could explain the differences found between species. The cost of feather production was significantly correlated with both body mass and mass-specific BMR, $BMR_{m}$ (kJ · g⁻¹ · d⁻¹), where $BMR_{m}$ currently sho...
Alessandro Sartorio - One of the best experts on this subject based on the ideXlab platform.
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prediction of Basal Metabolic Rate in obese children and adolescents considering pubertal stages and anthropometric characteristics or body composition
European Journal of Clinical Nutrition, 2014Co-Authors: Stefano Lazzer, Alessandra Patrizi, A De Col, Antonella Saezza, Alessandro SartorioAbstract:Prediction of Basal Metabolic Rate in obese children and adolescents considering pubertal stages and anthropometric characteristics or body composition
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relationship between Basal Metabolic Rate gender age and body composition in 8 780 white obese subjects
Obesity, 2010Co-Authors: Stefano Lazze, Giorgio Edogni, C L Lafortuna, Nicoletta Marazzi, Carlo Usti, Raffaela Galli, Alessandra De Col, F Agosti, Alessandro SartorioAbstract:The objective of the present study was to explore the relationship between Basal Metabolic Rate (BMR), gender, age, anthropometric characteristics, and body composition in severely obese white subjects. In total, 1,412 obese white children and adolescents (BMI > 97° percentile for gender and age) and 7,368 obese adults (BMI > 30 kg/m 2 ) from 7 to 74 years were enrolled in this study. BMR was measured using an indirect calorimeter equipped with a canopy and fat‑free mass (FFM) were obtained using tetrapolar bioelectrical impedance analysis (BIA). Using analysis of covariance, we tested the effect of gender on the relationship between BMR, age, anthropometry, and body composition. In children and adolescents, the predictor × gender interaction was significant in all cases except for FFM × gender. In adults, all predictor × gender interactions were significant. A prediction equation based on body weight (BW), age, and gender had virtually the same accuracy of the one based on FFM, age, and gender to predict BMR in both children and adults (R 2 adj = 0.59 and 0.60, respectively). In conclusion, gender was a significant determinant of BMR in children and adolescents but not in adults. Our results support the hypothesis that the age ‑ related decline in BMR is due to a reduction in FFM. Finally, anthropometric predictors of BMR are as accuRate as body composition estimated by BIA.
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relationship between Basal Metabolic Rate gender age and body composition in 8 780 white obese subjects
Obesity, 2010Co-Authors: Stefano Lazzer, C L Lafortuna, Nicoletta Marazzi, Raffaela Galli, Alessandra De Col, F Agosti, Giorgio Bedogni, Carlo Busti, Alessandro SartorioAbstract:The objective of the present study was to explore the relationship between Basal Metabolic Rate (BMR), gender, age, anthropometric characteristics, and body composition in severely obese white subjects. In total, 1,412 obese white children and adolescents (BMI > 97 degrees percentile for gender and age) and 7,368 obese adults (BMI > 30 kg/m(2)) from 7 to 74 years were enrolled in this study. BMR was measured using an indirect calorimeter equipped with a canopy and fat free mass (FFM) were obtained using tetrapolar bioelectrical impedance analysis (BIA). Using analysis of covariance, we tested the effect of gender on the relationship between BMR, age, anthropometry, and body composition. In children and adolescents, the predictor x gender interaction was significant in all cases except for FFM x gender. In adults, all predictor x gender interactions were significant. A prediction equation based on body weight (BW), age, and gender had virtually the same accuracy of the one based on FFM, age, and gender to predict BMR in both children and adults (R(2)(adj) = 0.59 and 0.60, respectively). In conclusion, gender was a significant determinant of BMR in children and adolescents but not in adults. Our results support the hypothesis that the age-related decline in BMR is due to a reduction in FFM. Finally, anthropometric predictors of BMR are as accuRate as body composition estimated by BIA.
Craig R White - One of the best experts on this subject based on the ideXlab platform.
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Determinants of inter-specific variation in Basal Metabolic Rate
Journal of Comparative Physiology B, 2013Co-Authors: Craig R White, Michael R. KearneyAbstract:Basal Metabolic Rate (BMR) is the Rate of metabolism of a resting, postabsorptive, non-reproductive, adult bird or mammal, measured during the inactive circadian phase at a thermoneutral temperature. BMR is one of the most widely measured physiological traits, and data are available for over 1,200 species. With data available for such a wide range of species, BMR is a benchmark measurement in ecological and evolutionary physiology, and is often used as a reference against which other levels of metabolism are compared. Implicit in such comparisons is the assumption that BMR is invariant for a given species and that it therefore represents a stable point of comparison. However, BMR shows substantial variation between individuals, populations and species. Investigation of the ultimate (evolutionary) explanations for these differences remains an active area of inquiry, and explanation of size-related trends remains a contentious area. Whereas explanations for the scaling of BMR are generally mechanistic and claim ties to the first principles of chemistry and physics, investigations of mass-independent variation typically take an evolutionary perspective and have demonstRated that BMR is ultimately linked with a range of extrinsic variables including diet, habitat temperature, and net primary productivity. Here we review explanations for size-related and mass-independent variation in the BMR of animals, and suggest ways that the various explanations can be evaluated and integRated.
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phylogenetic differences of mammalian Basal Metabolic Rate are not explained by mitochondrial Basal proton leak
Proceedings of The Royal Society B: Biological Sciences, 2012Co-Authors: Elias T Polymeropoulos, Gerhard Heldmaie, Pete Frappell, Onwy M Mcalla, Kerry Withers, Marti Klingenspo, Craig R White, Marti JastrochAbstract:Metabolic Rates of mammals presumably increased during the evolution of endothermy, but molecular and cellular mechanisms underlying Basal Metabolic Rate (BMR) are still not understood. It has been established that mitochondrial Basal proton leak contributes significantly to BMR. Comparative studies among a diversity of eutherian mammals showed that BMR correlates with body mass and proton leak. Here, we studied BMR and mitochondrial Basal proton leak in liver of various marsupial species. Surprisingly, we found that the mitochondrial proton leak was greater in marsupials than in eutherians, although marsupials have lower BMRs. To verify our finding, we kept similar-sized individuals of a marsupial opossum (Monodelphis domestica) and a eutherian rodent (Mesocricetus auratus) species under identical conditions, and directly compared BMR and Basal proton leak. We confirmed an approximately 40 per cent lower mass specific BMR in the opossum although its proton leak was significantly higher (approx. 60%). We demonstRate that the increase in BMR during eutherian evolution is not based on a general increase in the mitochondrial proton leak, although there is a similar allometric relationship of proton leak and BMR within mammalian groups. The difference in proton leak between endothermic groups may assist in elucidating distinct Metabolic and habitat requirements that have evolved during mammalian divergence.
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phylogenetically informed analysis of the allometry of mammalian Basal Metabolic Rate supports neither geometric nor quarter power scaling
Evolution, 2009Co-Authors: Craig R White, Tim M Blackburn, Roger S SeymourAbstract:The form of the relationship between the Basal Metabolic Rate (BMR) and body mass (M) of mammals has been at issue for almost seven decades, with debate focusing on the value of the scaling exponent (b, where BMR α Mb) and the relative merits of b = 0.67 (geometric scaling) and b = 0.75 (quarter-power scaling). However, most analyses are not phylogenetically informed (PI) and therefore fail to account for the shared evolutionary history of the species they consider. Here, we reanalyze the most rigorously selected and comprehensive mammalian BMR dataset presently available, and investigate the effects of data selection and phylogenetic method (phylogenetic generalized least squares and independent contrasts) on estimation of the scaling exponent relating mammalian BMR to M. Contrary to the results of a non-PI analysis of these data, which found an exponent of 0.67–0.69, we find that most of the PI scaling exponents are significantly different from both 0.67 and 0.75. Similarly, the scaling exponents differ...
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phylogenetically informed analysis of the allometry of mammalian Basal Metabolic Rate supports neither geometric nor quarter power scaling
Evolution, 2009Co-Authors: Craig R White, Tim M Blackburn, Roger S SeymourAbstract:The form of the relationship between the Basal Metabolic Rate (BMR) and body mass (M) of mammals has been at issue for almost seven decades, with debate focusing on the value of the scaling exponent (b, where BMR is proportional to M(b)) and the relative merits of b= 0.67 (geometric scaling) and b= 0.75 (quarter-power scaling). However, most analyses are not phylogenetically informed (PI) and therefore fail to account for the shared evolutionary history of the species they consider. Here, we reanalyze the most rigorously selected and comprehensive mammalian BMR dataset presently available, and investigate the effects of data selection and phylogenetic method (phylogenetic generalized least squares and independent contrasts) on estimation of the scaling exponent relating mammalian BMR to M. Contrary to the results of a non-PI analysis of these data, which found an exponent of 0.67-0.69, we find that most of the PI scaling exponents are significantly different from both 0.67 and 0.75. Similarly, the scaling exponents differ between lineages, and these exponents are also often different from 0.67 or 0.75. Thus, we conclude that no single value of b adequately characterizes the allometric relationship between body mass and BMR.
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sample size and mass range effects on the allometric exponent of Basal Metabolic Rate
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2005Co-Authors: Craig R White, Roger S SeymourAbstract:The controversial relationship between body mass and Basal Metabolic Rate in animals revolves around two questions: what is the allometric scaling exponent and what is the functional basis for it? For mammals, the first question could be resolved if measurements from all 4600 extant species were available, but this study shows that data for only 150 species, spanning three to four orders of magnitude variation in body mass, are sufficient to accuRately determine the exponent. Because the currently available data set includes about 600 species that vary over five orders of magnitude in body size, further increases in sample size are unlikely to change the estimate of the scaling exponent.
Claus Bech - One of the best experts on this subject based on the ideXlab platform.
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is Basal Metabolic Rate associated with recruit production and survival in free living house sparrows
Functional Ecology, 2016Co-Authors: Bernt Ronning, Claus Bech, Juli Broggi, Borge Moe, Thor Harald Ringsby, Henrik Parn, Ingerid Julie Hagen, Bernterik Saether, H JensenAbstract:Summary 1.Life history theory predicts that available energy is limited and needs to be allocated among different processes such as growth, reproduction and self-maintenance. Basal Metabolic Rate (BMR), a common measure of an animal's maintenance cost, is therefore believed to be a trait of ecological and evolutionary significance. However, although BMR is often assumed to be correlated with fitness, its association with individual variation in fitness in free-living populations is virtually unknown. 2.We examined the relationship between BMR in late winter prior to the breeding season and recruit production (number of offspring recorded the subsequent year), as well as adult survival, in two populations of house sparrow (Passer domesticus) on the islands Leka and Vega in northern Norway. 3.Number of recruits tended to be negatively related to BMR. However, analysing the data for each sex within the two populations revealed that the negative effect of BMR on recruit production was significant only for females on one of the islands. 4.Survival probability was associated with BMR, but the relationship differed both between sexes and populations. In the Leka population, we found evidence for stabilizing selection in the females and disruptive selection in the males. In contrast, there was no effect of BMR on survival in the Vega population. 5.Body mass influenced adult survival, but not recruit production. Furthermore, the relationship between BMR and fitness in females remained significant after controlling for body mass. Thus, the selection on BMR in females was not driven by a BMR-body mass correlation. 6.Basal Metabolic Rate was significantly related to fitness in both populations. However, the results in the present study show spatial variation as well as sex specific differences in the influence of BMR on fitness in house sparrows. This article is protected by copyright. All rights reserved.
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Is Basal Metabolic Rate influenced by age in a long-lived seabird, the snow petrel?
The Journal of Experimental Biology, 2007Co-Authors: Frederic Angelier, Claus Bech, Olivier ChastelAbstract:SUMMARY Ageing is associated with a decline in Basal Metabolic Rate (BMR) in many species, including humans. The evolutionary and physiological causes underlying the relationship between age and BMR are poorly understood. Studies of procellariiform seabirds may provide valuable insight because they have a longer maximum lifespan than expected from their body size and Rates of energy metabolism. Such studies are rare, however, because there are few populations with a high proportion of individuals of known age. We performed a cross-sectional study of energy metabolism in relation to age in a long-lived seabird, the snow petrel Pagodroma nivea. In an Antarctic population that has been subject to a long-term research program, including annual banding of chicks since 1963, we measured BMR of individuals aged between 8 and 39 years. We show that the BMR of the snow petrel does not decrease with increasing age. BMR seems to be sustained at a fixed level throughout the investigated age-span. We review this result in light of the disposable soma theory of ageing, and we discuss whether species-specific relationships between age and Basal Metabolic Rate can be related to differences in maximum lifespan.
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Basal Metabolic Rate heritability and genetic correlations with morphological traits in the zebra finch
Journal of Evolutionary Biology, 2007Co-Authors: Bernt Ronning, Borge Moe, H Jensen, Claus BechAbstract:Studies of genetic variation in Metabolic traits have so far not focused on birds. In our study population of captive zebra finches we found evidence for a significant heritable genetic component in Basal Metabolic Rate (BMR). Heritability of all morphological traits investigated (body mass, head length, tars length and wing length) was significantly larger than zero. All traits were positively phenotypically correlated. Eight of 10 genetic correlations presented in this study differed significantly from zero, all being positive, suggesting the possibility of correlated responses to any selection acting on the traits. When conditioned on the genetic variance in body mass, the heritability of BMR was reduced from 25% to 4%. Hence, our results indicate that genetic changes in BMR through directional selection are possible, but the potential for adaptation independent of body mass may be limited.
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long term repeatability makes Basal Metabolic Rate a likely heritable trait in the zebra finch taeniopygia guttata
The Journal of Experimental Biology, 2005Co-Authors: Bernt Ronning, Claus BechAbstract:SUMMARY Basal Metabolic Rate (BMR) is a physiological trait believed to show adaptational changes. Few studies have tested whether BMR shows stable between-individual variations. Repeatability indicates that the trait might be heritable and therefore a possible target for natural selection. We tested whether BMR was repeatable over a considerable time of the lifespan of a small passerine bird: the zebra finch Taeniopygia guttata . BMR was measured six times over a 2.5 year period in captive zebra finches. BMR residuals showed significant repeatabilities over a short (1.5 months) and a long (2.5 years) period for each sex as well as for both sexes pooled. In contrast to earlier studies on metabolism, our calculated repeatability ( R ) did not change significantly from the short to the long period in either males ( R from 0.501 to 0.465), females ( R from 0.413 to 0.522) or the pooled data ( R from 0.571 to 0.567). Our results show that there are consistent between-individual variations in BMR on which natural selection can work, provided that this trait is heritable.
Roger S Seymour - One of the best experts on this subject based on the ideXlab platform.
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phylogenetically informed analysis of the allometry of mammalian Basal Metabolic Rate supports neither geometric nor quarter power scaling
Evolution, 2009Co-Authors: Craig R White, Tim M Blackburn, Roger S SeymourAbstract:The form of the relationship between the Basal Metabolic Rate (BMR) and body mass (M) of mammals has been at issue for almost seven decades, with debate focusing on the value of the scaling exponent (b, where BMR α Mb) and the relative merits of b = 0.67 (geometric scaling) and b = 0.75 (quarter-power scaling). However, most analyses are not phylogenetically informed (PI) and therefore fail to account for the shared evolutionary history of the species they consider. Here, we reanalyze the most rigorously selected and comprehensive mammalian BMR dataset presently available, and investigate the effects of data selection and phylogenetic method (phylogenetic generalized least squares and independent contrasts) on estimation of the scaling exponent relating mammalian BMR to M. Contrary to the results of a non-PI analysis of these data, which found an exponent of 0.67–0.69, we find that most of the PI scaling exponents are significantly different from both 0.67 and 0.75. Similarly, the scaling exponents differ...
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phylogenetically informed analysis of the allometry of mammalian Basal Metabolic Rate supports neither geometric nor quarter power scaling
Evolution, 2009Co-Authors: Craig R White, Tim M Blackburn, Roger S SeymourAbstract:The form of the relationship between the Basal Metabolic Rate (BMR) and body mass (M) of mammals has been at issue for almost seven decades, with debate focusing on the value of the scaling exponent (b, where BMR is proportional to M(b)) and the relative merits of b= 0.67 (geometric scaling) and b= 0.75 (quarter-power scaling). However, most analyses are not phylogenetically informed (PI) and therefore fail to account for the shared evolutionary history of the species they consider. Here, we reanalyze the most rigorously selected and comprehensive mammalian BMR dataset presently available, and investigate the effects of data selection and phylogenetic method (phylogenetic generalized least squares and independent contrasts) on estimation of the scaling exponent relating mammalian BMR to M. Contrary to the results of a non-PI analysis of these data, which found an exponent of 0.67-0.69, we find that most of the PI scaling exponents are significantly different from both 0.67 and 0.75. Similarly, the scaling exponents differ between lineages, and these exponents are also often different from 0.67 or 0.75. Thus, we conclude that no single value of b adequately characterizes the allometric relationship between body mass and BMR.
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sample size and mass range effects on the allometric exponent of Basal Metabolic Rate
Comparative Biochemistry and Physiology A-molecular & Integrative Physiology, 2005Co-Authors: Craig R White, Roger S SeymourAbstract:The controversial relationship between body mass and Basal Metabolic Rate in animals revolves around two questions: what is the allometric scaling exponent and what is the functional basis for it? For mammals, the first question could be resolved if measurements from all 4600 extant species were available, but this study shows that data for only 150 species, spanning three to four orders of magnitude variation in body mass, are sufficient to accuRately determine the exponent. Because the currently available data set includes about 600 species that vary over five orders of magnitude in body size, further increases in sample size are unlikely to change the estimate of the scaling exponent.
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does Basal Metabolic Rate contain a useful signal mammalian bmr allometry and correlations with a selection of physiological ecological and life history variables
Physiological and Biochemical Zoology, 2004Co-Authors: Craig R White, Roger S SeymourAbstract:Abstract Basal Metabolic Rate (BMR, mL O2 h−1) is a useful measurement only if standard conditions are realised. We present an analysis of the relationship between mammalian body mass (M, g) and BMR that accounts for variation associated with body temperature, digestive state, and phylogeny. In contrast to the established paradigm that \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $\mathrm{BMR}\,\propto M^{3/ 4}$ \end{document} , data from 619 species, representing 19 mammalian orders and encompassing five orders of magnitude v...
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mammalian Basal Metabolic Rate is proportional to body mass2 3
Proceedings of the National Academy of Sciences of the United States of America, 2003Co-Authors: Craig R White, Roger S SeymourAbstract:The relationship between mammalian Basal Metabolic Rate (BMR, ml of O(2) per h) and body mass (M, g) has been the subject of regular investigation for over a century. Typically, the relationship is expressed as an allometric equation of the form BMR = aM(b). The scaling exponent (b) is a point of contention throughout this body of literature, within which arguments for and against geometric (b = 2/3) and quarter-power (b = 3/4) scaling are made and rebutted. Recently, interest in the topic has been revived by published explanations for quarter-power scaling based on fractal nutrient supply networks and four-dimensional biology. Here, a new analysis of the allometry of mammalian BMR that accounts for variation associated with body temperature, digestive state, and phylogeny finds no support for a Metabolic scaling exponent of 3/4. Data encompassing five orders of magnitude variation in M and featuring 619 species from 19 mammalian orders show that BMR proportional, variant M(2/3).
