Endothermy in Birds and Mammals: How the Relationships between Body Weight and Metabolic Rate, Body Temperature, Sleep and Activity Duration Developed in the History of Formation of Endothermic Vertebrates | Chapter 3 | Innovations in Biological Science Vol. 4

 

Here we present a meta-analysis of literature sources and original data on basal metabolic rates (BMR) in birds and mammals based on 1817 measurements (817 data points from mammals and 1000 from birds). We used these data to estimate scaling coefficients and intercept for all endothermic animals pooled and for birds and mammals separately to study the difference between these classes, and also for the main groups of lower taxonomic status. We considered BMR variation and the duration of activity in three mammalian subclasses: monotremes, marsupials and eutherians, and in three groups of birds: palaeognaths, neognaths non-passerine and passerines, depending on the evolutionary age of these groups. In all groups BMR varies with body size with the different scaling coefficient which is statistically indistinguishable from ¾ in mammals and 2/3 un birds, but with significantly different intercepts. The data for all the considered groups were combined and the common exponent for six allometric equations between the BMR and body weight was established b = 0.7248. Reduced to the common slope, the relative metabolic rate forms the following series: Neognathae - Passeriformes - 1.00, Neognathae - Non-Passeriformes - 0.75, Palaeognathae - 0.53, Eutheria - 0.57, Marsupialia - 0.44, and Monotremata - 0.26. The main finding is that the metabolic rate in the six main groups of mammals and birds consistently increases as the geological time of the group’s divergence approaches the present.

 

Activity duration varies between the main groups of endotherms. Overall sleep duration is a parameter inversely related to the overall activity. A high level of activity is related to high BMR. Placentals and paleognaths have similar BMR, i.e. terrestrial lifestyle without flight is based on nearly equal BMR.

 

We calculated sleep duration in the main groups of endotherms on the basis of literature data. BMR in a taxon correlates with its evolutionary age: the later a clade diverged, the higher is its metabolic rate and the longer is activity period. BMR of eutherians and flightless paleognaths is similar, and these groups evolved at practically the same time. We suggest that each group formed its taxon-specific BMR depending on the ability to maintain thermal homeostasis under the environmental conditions that prevailed during its emergence. Monotremes were the first to branch off from the basal mammals and have the lowest BMR among the endotherms we consider. This level is minimally sufficient for maintaining homeostatic body temperature under a very limited range of environmental conditions. The next level is typical of marsupials and allows them to maintain thermal homeostasis under a broader range of conditions and have a more protracted period of activity. Finally, the metabolic rate typical of placentals and paleognaths formed in the mid-Cretaceous and allowed these groups to occupy a broader range of terrestrial niches. Immediately when the development of blood circulation and respiratory systems made it possible to reach the BMR that allowed maintaining a body temperature of 37 oC, the explosive radiation of mammals and birds started. In the mid and late Cretaceous birds and mammals started to occupy the leading positions in the ecosystems. And at last, some 50 mya passerines that have the highest BMR (nearly 50% higher than eutherians and paleognath birds) adapted to the forest habitats and gained body temperature of ca. 40oC, which is at the upper physiological limit. The duration of activity and body temperature increased in parallel to the BMR. Ecological expansion of birds and mammals resulted in their worldwide geographic distribution. A relatively similar energetic analogue of passerines in mammals are humans, who have BMR ca. 35% higher than predicted by the scaling equation for mammals, have amazing reproductive potential, large brains and longevity much exceeding the live duration which is typical for their body-mass specific mean. Sleep duration in humans is 30% shorter than the mammals-specific mean, and it is one of the evolutionary youngest species. At the moment the global population of humans exceeds 8 billion people.

 

Author(s) Details

Valery M. Gavrilov

Department of Vertebrate Zoology and Zvenigorod Biological Station, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.

 

Please see the book here:- https://doi.org/10.9734/bpi/ibs/v4/3716G

Endothermy in Birds and Mammals: How the Relationships between Body Weight and Metabolic Rate, Body Temperature, Sleep and Activity Duration Developed in the History of Formation of Endothermic Vertebrates | Chapter 3 | Innovations in Biological Science Vol. 4

Here we present a meta-analysis of literature sources and original data on basal metabolic rates (BMR) in birds and mammals based on 1817 measurements (817 data points from mammals and 1000 from birds). We used these data to estimate scaling coefficients and intercept for all endothermic animals pooled and for birds and mammals separately to study the difference between these classes, and also for the main groups of lower taxonomic status. We considered BMR variation and the duration of activity in three mammalian subclasses: monotremes, marsupials and eutherians, and in three groups of birds: palaeognaths, neognaths non-passerine and passerines, depending on the evolutionary age of these groups. In all groups BMR varies with body size with the different scaling coefficient which is statistically indistinguishable from ¾ in mammals and 2/3 un birds, but with significantly different intercepts. The data for all the considered groups were combined and the common exponent for six allometric equations between the BMR and body weight was established b = 0.7248. Reduced to the common slope, the relative metabolic rate forms the following series: Neognathae - Passeriformes - 1.00, Neognathae - Non-Passeriformes - 0.75, Palaeognathae - 0.53, Eutheria - 0.57, Marsupialia - 0.44, and Monotremata - 0.26. The main finding is that the metabolic rate in the six main groups of mammals and birds consistently increases as the geological time of the group’s divergence approaches the present.

Activity duration varies between the main groups of endotherms. Overall sleep duration is a parameter inversely related to the overall activity. A high level of activity is related to high BMR. Placentals and paleognaths have similar BMR, i.e. terrestrial lifestyle without flight is based on nearly equal BMR.

We calculated sleep duration in the main groups of endotherms on the basis of literature data. BMR in a taxon correlates with its evolutionary age: the later a clade diverged, the higher is its metabolic rate and the longer is activity period. BMR of eutherians and flightless paleognaths is similar, and these groups evolved at practically the same time. We suggest that each group formed its taxon-specific BMR depending on the ability to maintain thermal homeostasis under the environmental conditions that prevailed during its emergence. Monotremes were the first to branch off from the basal mammals and have the lowest BMR among the endotherms we consider. This level is minimally sufficient for maintaining homeostatic body temperature under a very limited range of environmental conditions. The next level is typical of marsupials and allows them to maintain thermal homeostasis under a broader range of conditions and have a more protracted period of activity. Finally, the metabolic rate typical of placentals and paleognaths formed in the mid-Cretaceous and allowed these groups to occupy a broader range of terrestrial niches. Immediately when the development of blood circulation and respiratory systems made it possible to reach the BMR that allowed maintaining a body temperature of 37ºС, the explosive radiation of mammals and birds started. In the mid and late Cretaceous birds and mammals started to occupy the leading positions in the ecosystems. And at last, some 50 mya passerines that have the highest BMR (nearly 50% higher than eutherians and paleognath birds) adapted to the forest habitats and gained body temperature of ca. 40ºС, which is at the upper physiological limit. The duration of activity and body temperature increased in parallel to the BMR. Ecological expansion of birds and mammals resulted in their worldwide geographic distribution. A relatively similar energetic analogue of passerines in mammals are humans, who have BMR ca. 35% higher than predicted by the scaling equation for mammals, have amazing reproductive potential, large brains and longevity much exceeding the live duration which is typical for their body-mass specific mean. Sleep duration in humans is 30% shorter than the mammals-specific mean, and it is one of the evolutionary youngest species. At the moment the global population of humans exceeds 8 billion people.

Author(s) Details:

Valery M. Gavrilov,
Department of Vertebrate Zoology and Zvenigorod Biological Station, M.V. Lomonosov Moscow State University, Moscow 119991, Russia.

Please see the link here: https://stm.bookpi.org/IBS-V4/article/view/14392

Origin and Development of Endothermy: From the Standpoint of Ecological Energetics of Birds | Chapter 12 | Recent Progress in Microbiology and Biotechnology Vol. 3

 The research is based on the findings of an integrated assessment of resting energy expenditure and common behaviour in birds belonging to different systematic classes. Endothermy has evolved separately and in distinct geological ages in birds and mammals. In both classes, however, it emerged as a side effect of selection for enhancement of aerobic metabolism that provided a higher degree of activity. The benefits of having high and steady body temperatures, which are inevitably linked to the intensification of metabolism, have led to thermoregulatory adaptations such as fur and feathers being created. This has made it possible to preserve the heat produced metabolically and reduce the absorption of heat in hot environments. For homoeothermic animals, the advent of endothermy with an aerobic supply of motion activity, possibilities to control metabolism speed, and thermal conductance has opened up a number of possibilities. The achievement of such an energy utilisation level allowed them to preserve Operation over a longer period of time, although the creation of sensory systems led to problems and diversification of the endothermic behavioural repertoire due to stable temperature and high level of oxygen support, enabling the conquest of almost the entire living portion of the biosphere. The creation of nurturing and transmitting knowledge, collected during life, to new generations has favoured this method. Among various groups of reptilian ancestors, the development of high levels of aerobic metabolism in birds and mammals proceeded in parallel. The stage of endothermy, at which aerobic metabolism is capable of sustaining sustained activity, evolved in different ways in birds and mammals: they have different partitions of venous and arterial networks, erythrocytes with or without a cell nucleus, different designs of the lungs, but similarly Minimum metabolic capacity and sufficiently close temperatures of the body that match well to the Earth's environmental conditions. Natural selection made it possible for animals with a high energetic metabolism to increase their diversity and abundance, but only when endothermic animals were able to meet their numerous food resource demands. In the middle of the Cretaceous, this occurred in time with the appearance of angiosperms and the expansion of invertebrate based fauna. The advent of angiosperms and associated invertebrate fauna, which provided the requisite energy channels for the production of homoeothermic endothermic animals, was the catalyst for the explosive radiation of endothermic animals. Apparently, this is how all essential adaptations evolve. Developments in the ecosystem that triggered these processes and caused significant evolutionary breakthroughs were the driving force behind these adaptations.

Author (s) Details

Valery M. Gavrilov
Department of Vertebrates Zoology and Skadovsky Zvenigorod Biological Station, M. V. Lomonosov Moscow State University, Moscow 119992, Russia.

View Book :- https://bp.bookpi.org/index.php/bpi/catalog/book/289