Year: 2009
Type: preprint
Abstract: Darwin and Wallace (1858; Darwin 1859) proposed that natural selection acts on random variation in plants and animals to shape new species.Natural selection encompasses the environmental constraints acting on the organism, one of the most important being energy availability.Life exists in a nonequilibrium thermodynamic state requiring the constant flow of energy to sustain its complex structures and to permit the accumulation and transmission of biological information.In the absence of energy flow, complex systems decay.Therefore, life exists through the interplay among structure, energy, and information.The source of most biological energy is the Sun.The high-energy photons collected by photosynthetic cyanobacteria and their chloroplast descendants are used to split water into hydrogen and oxygen.The oxygen is released into the atmosphere and the hydrogen is used to reduce CO 2 to generate glucose.Plant glucose is consumed by herbivores and the energy therein sequentially passed through the animal and fungal food chains.Ultimately, the degraded energy is dissipated as infrared radiation into space.Animal populations grow and multiply until energy becomes limiting.Animals can adapt to available energy resources at three levels: interspecific exploitation of dif ferent energy reservoirs that define the species' niche, intra specific exploitation of differences in regional energy re sources, and individual responses to oscillating envi ron mental energy resources (Fig. 1).Interspecific energy resource adaptation involves exploitation of distinct energy reservoirs through anatomical variation.This helps to delineate species and genera.Energy reservoirs are the distinct source of calories used by a species throughout its existence, perhaps over hundreds of thousands of years.Factors that can define an energy reservoir include being an herbivore versus a carnivore.For herbivores, these could involve eating fruits versus nuts or leaves versus sap.For carnivores, they could encompass being a predator versus a scavenger or consuming blood versus bugs, etc.To exploit alternative energy reservoirs, selection acts on nDNA genetic variation to alter animal anatomical traits, permitting access to novel energy reservoirs.This interaction between the species' anatomy and the energy reservoir helps to define the species' niche (Fig. 1).Intraspecific energy resource adaptation involves the exploitation of regional energy environments through changes in physiology.Within a species' niche, regional energy resources can vary in energy type (carbohydrate, fat, protein), amount, and demand (activity level, stress, etc.).These regional differences can be stable over thousands of years and lead to development of distinct geographically constrained populations within the species.To exploit different regional energy environments, genetic variants in mtDNA and nDNA bioenergetic genes are selected that adjust the bioenergetic metabolism to be in balance with local energy resources (Fig. 2).Individual energy resource adaptation involves adjustments within the individual to short-term oscillations in energy availability and demand.These changes can occur within days to years and include seasonal changes and Mitochondria, Bioenergetics, and the Epigenome in Eukaryotic and Human Evolution
Author: D. C. Wallace
Institution: University of California, Irvine
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: bronze
Awards: G2718742063, G322054087, G3534085635, Adaptive Physiology of mtDNA Longevity Mutations, G4346860958, The Alzheimer's Disease Research Center at the University of California, Irvine, G5484089957, Mitochondrial Diabetes & Manganic Porphyrin Treatment, Mitochondrial Inborn Errors in Metabolism, Mitochondrial Genetics and Aging
OpenAlex ID: W2158122052