Basics of Eco-physiology.pdf

Eco-physiology What is eco-physiology or physiological ecology? How have physiological systems evolved to ensure survival and reproduction in a given environment. How do organisms cope with changing DAILY AND SEASONAL conditions.  Physiological ecology is the science of determining the physiolo...

Eco-physiology What is eco-physiology or physiological ecology? How have physiological systems evolved to ensure survival and reproduction in a given environment. How do organisms cope with changing DAILY AND SEASONAL conditions.  Physiological ecology is the science of determining the physiological controls on ecological phenomena or the study of environmental controls on physiology. Evolutionary physiology deals with understanding how physiological controls evolved Heredity Environmental Factors Physiological Processes Growth and Reproduction Ecological Expression Butler et al. 2021  The study of how animals work Structure and function of various parts Physiology -How these parts work together in a given environment Ecophysiology Physiological processes obey physical and chemical laws Physiological processes are usually regulated Homeostasis – maintenance of internal constancy Phenotype is a product of genotype and its interaction with the environment Genotype – genetic makeup, is the product of evolution Phenotype – expression of genotype in morphology, physiology, and behavior Phenotypic plasticity – single genotype generates more than one phenotypic outcome depending on environmental conditions Physiological processes obey physical and chemical laws Physical properties of a material are linked to function (e.g., bone) Chemical laws govern molecular interactions (e.g., effects of temperature) Electrical laws describe membrane function, including excitation of cells Body size influences biochemical and physical patterns – allometric scaling Physiological processes are usually regulated Homeostasis – maintenance of internal constancy How do animals deal with variations in their environment? Physiological Regulation Conformers Allow internal conditions to change / adjust to reflect external conditions Moyes and Schulte 200 Other examples include… Bask in the sun Conformers can absorb heat energy directly from the sun or from the ground around them. Burrow in the sand Desert lizards can burrow under the sand to cool down or warm up depending on the time of day. Lose or gain water Spider crabs can conform to the salinity in their environment by losing or gaining water. Regulators Maintain relatively constant internal conditions regardless of the conditions in the external environment Keep internal environment within narrow limits  Maintenance of internal conditions in the face of environmental perturbations (homeostasis) Controlled by feedback loops or reflex control pathways Phenotype is a product of genotype and its interaction with the environment Genotype – genetic makeup Phenotype – morphology, physiology, and behavior Phenotypic plasticity – single genotype generates more than one phenotype depending on environmental conditions A, B, C, D 4 Daphnia species Left: absence of predation Right: Under predation threat Weiss 2019  Phenotypic plasticity can be irreversible or reversible Irreversible Polyphenism - developmental plasticity Reversible Acclimation – lab environment (one variable) Acclimatization – natural environment (multiple variables)  Physiology attempts to understand the diversity of animal body form and strategies that animals use to cope with their environments Two types of questions Proximate cause – How? Ultimate cause – Why?  Why are zebras striped: a problem with too many solutions In the sun In shade Several Hypotheses including: Confuse predators Avoid biting flies Social cohesion McCafferty 2007  Why are zebras striped: Thermoregulation is a likely answer 11 populations in Africa Differed in stipe intensity and thickness Differentials air currents between black and white produce greater cooling effects Hotter regions have stronger and more defined stripes Larison et al. 2015 Biotic and abiotic factors influence distribution patterns of species. Species have a typical “Optimal" environmental range. Species survive only short durations under conditions exceeding a threshold in their "critical tolerance limits." The breadth of optimal environments depend on physiological adaptation and energetics. Critical limits can define species distributions, community structure, and response to environmental change. Variation in fitness between environmental factors that define an organism's critical limits is represented in a performance curve. Shape of performance curves can be interpreted at the organismal and cellular level. https://www.istockphoto.com/photos/emperor-penguin  Performance curves Performance curves are influenced by physiological mechanisms that determine the shape of the curves. Performance curves can be constructed for different environmental variables. Concepts of performance curve, optimal https://microbenotes.com/a range, and critical limits apply to all abiotic biotic-factors/ factors, although the mechanisms that define the shape of the curves may differ across abiotic factors.  TNZ - Metabolism is constant and minimized Thermal Endotherms performance curves Ectotherms Pejus temperature more ecologically relevant Pörtner et al. 2006 Species Performance Rocky intertidal curves zone with species distributed in vertical zones Zone of overlap Suggests competition / biotic interactions Thermal neutral zones  Temperature regulation Ectotherms and endotherms Poikilotherms and homeotherms Energy output (Joule) of a poikilotherm (lizard) and a homeotherm (mouse) Behavioural thermoregulation in ectotherms  Temperature regulation in ectotherms Rate at which ectotherms lose or gain heat depend on the medium (land / water/ air) Water better conducts heat faster, so ectotherms in water lose metabolic heat much faster and can also gain heat from water faster. Infrared thermal radiation evolved independently in three different groups of snakes, including pit vipers, boas, and pythons Directed movement Arena with 4 hides Arena with 4 burrows Darbaniyan et al. 2021, Matter Krochmal and Bakken 2003 J Comp Phys  Ectotherms surviving cold / subzero conditions Migration Diapause Hibernation  Insect diapause There is a reduction in metabolic rate (oxygen consumption) Insects monitor environmental cues such as photoperiod length Respond by storing lipids, protein and carbohydrates and using this in diapause.  Hibernation Amphibians and reptiles hibernate or enter a period of lethargy. Unlike mammals hibernating (5% MR), they allow body temperatures to follows the environmental temperatures. Availability of sufficient energy stores for period of starvation and oxygen supply are key. Are physiological differences between species adaptive? Common descent emphasises general biological principles (eg. DNA, membranes etc) Neo-Darwinian synthesis emphasises NS as the major force in evolution leading to thinking that all adaptations are adaptive Not all traits are adaptations to current conditions and may reflect genetic and morphological constraints. Phylogenetic Interia Exaptation  Are traits optimal? Rather than optimal, they should be adequate and sufficient. Some traits are maintained by current selection, but did not originate in response to the same selective pressures. Eg: sutures between bones in the mammalian skull may now be adaptive for allowing the birth of relatively large-brained offspring in some species (humans), but they arose long ago in evolutionary history. Behavioural adaptations  Phylogenetic inertia may be attributable to developmental or genetic constraints in addition to selection. The origin (evolutionary history) and/or current maintenance (phenotype existence) of a trait may adaptive. https://www.istockphoto.com/vector/fetal-skull-dimensions-superior-view-and-lateral-view-of-the- fetal-skull-showing-gm1399888030-453625667