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.