Adaptation to Physical Stressors, Part 1 PDF

Adaptation to physical stressors, part 1 (Overview and cold/heat) AANT 211: Human Population Biology  Introduction Worldwide distribution – Populations adapt to environmental conditions Usually requires diversity – Humans aren't very diverse Secret to success...

Adaptation to physical stressors, part 1 (Overview and cold/heat) AANT 211: Human Population Biology  Introduction Worldwide distribution – Populations adapt to environmental conditions Usually requires diversity – Humans aren't very diverse Secret to success? – Biology (genetics) – Culture Environmental physiology – Adaptations Physical stressors – Cold/Heat – Hypoxia (high altitude) 2  Environmental Physiology Study of adaptation of individual organism to environmental change and stress Stressors (Limiting factors) Environmental condition that places restraints on population size or range Density dependent E.g. nutrients and disease Density independent E.g. temperature 3  Environmental Physiology If stressor is constant and lasts for many generations adaptations may develop Adaptation – process of attaining beneficial adjustments to the environment (long-term) – evolution through natural selection advantageous trait (physiological, anatomical, behavioral, cultural) increase at population-level Acclimatization – Shorter-term, functional adjustments to complex environmental factors (major environmental changes) – Reversible – Individual-level Habituation – Gradual reduction of responses to repeated stress – Individual-level – Not heritable 4  Adapting to the Environment 1. Behavioral (I) 2. Physiological (I) Acclimatization 3. Developmental (I) 4. Cultural (P) 5. Genetic (P) I=Individual P=Population 5  1. Behavioral Adaptations Actions to increase survival Individual-level Well-suited for rapidly changing conditions Quickly employed Reversible Adaptive and/or maladaptive 6  2. Physiological Adaptations Systemic response to a specific stimulus -Automatically (involuntary) controlled -Phenotypic plasticity - Observed biological changes induced by environment - E.g. pupil dilation, shivering - Quickly employed/reversible -Acclimatization 7 Acclimatization Gradual, long-term responses to complex environmental stresses – Form of phenotypic plasticity – Takes more time to occur – Individual-level – Reversible – Ecological response E.g., hypoxia 8  3. Developmental Adaptations Adaptive traits acquired during development or any time before adulthood - Usually not reversible - Individual-level - Origin of some population differences in biological traits “Developmental conversion” - Process where early exposure in life determines which genetic programs are activated E.g., high altitude Andeans – Enlarged lung volume/chest circumference Inspire more air Compensate for low O2 levels – Differences in individuals? 9  4. Cultural Adaptations Shared understandings and behavior Population-level Food, shelter, clothing Learned techniques & skills to increase survival Passed down (not genetically inherited) Allows humans to adapt to all terrestrial habitats Microenvironment within macroenvironment Adaptive and/or maladaptive 10  5. Genetic Adaptations “Hard wired” in a population or species - Heritable traits - E.g., body shape, skin color, ability to sweat - Ecogeographic rules (Bergmann’s and Allen’s rules) 11 Adaptation to Cold and Heat 12  Adaptation to Cold and Heat Thermoregulation – Ability to adjust to extremes of temperature Biology (physiology, genetics) Behavior Culture – Temp. extremes are deadly Temp. homeostasis – Heat generation – Heat exchange – Heat balance 13  Temperature Homeostasis Heat generation – Metabolism – Food=ATP=heat – Basal vs. active 14  Temperature Homeostasis Heat exchange/transfer: - Radiation - Emission of electromagnetic waves - e.g. rays of sunlight - Conduction - Physical contact - Convection - Movement across skin - Fluid - Air or a liquid - Evaporation - Losing heat - Conversion - Water to gas 15  Temperature Homeostasis Cold environment Hot environment - Increase metabolic activity - Minimize heat gain from - Avoid evaporation (stay dry) metabolic activity - Reduce heat loss due to… - Maximize evaporative heat - Radiation loss - Conduction - Encourage heat loss from… - Convection - Radiation - Discourage gain from… - Conduction - Convection 16  Temperature Homeostasis Balancing heat gain and heat loss Core vs. shell temperature Core (most important) Critical organs – brain, heart, lungs, abdominal (95-106°F) Shell Closer to skin (32-110°F and higher) Flexibility of shell temperature important for physiological adaptations 17  Temperature Adaptation: Cold – Behavioral and Cultural Adaptations Shelter, fire (food and drink), clothing – Biological responses to cold exposure 1. Insulative adjustments 2. Metabolic adjustments 18  Temperature Adaptation: Cold 1. Insulative adjustments Biological/physiological adaptations – Vasoconstriction (hypothalamus) Blood flow (subcutaneous circulation) – Distribution of subcutaneous fat – Body size and shape Surface area to volume ratios ↑ volume (mass) = ↑ heat production ↑ surface area = ↑ heat loss Less surface area to volume (mass) High surface area to volume Short limbs Longer limbs 19 Temperature Adaptation: Cold 2. Metabolic adjustments Metabolic heat generation – increased muscle activity 1. Voluntary activity (exercise) 2. Involuntary shivering Increase metabolism 3x to usual basal metabolic rate (BMR) Increased muscle mass facilitates this process Prolonged shivering promotes heat loss 3. Non-shivering thermogenesis Increasing heat production from brown adipose tissue Brown fat higher in people who live in cold environments Increase during cold acclimatization 20 Neandertal noses: Cold adaptation? Nose shape and size helps regulate temperature and humidity of air we breathe Nose size can affect how much air is inhaled https://www.youtube.com /watch?v=2gHYnkKPqtI&li st=TLGGMi4G6LljNZgxNz A0MjAyNA&t=12s  Temperature Adaptation: Hot & Dry Biological/physiological adaptations – Heat transfer Vasodilation – Heat loss Evaporation Increased sweat gland activity 22  Temperature Adaptation: Hot & Dry Behavioral/cultural – Housing Insulative to keep in cool, night temps – Activity Decrease in high temps of the day – Clothing Increase evaporation Slow solar radiation gain Reduce convective heat gain 23 Temperature Adaptation: Hot & Wet Different set of challenges Behavioral and cultural responses – Ventilation Increase convective cooling Homes raised off the ground Biological response – Identical to dry heat – Sweating: not as effective – Instead encourage rapid exchange of heat from core to shell High surface area to volume ratios Vasodilation in extremities 24 Summary Good at adaptation Plasticity Limitation reflects evolutionary origins Selective pressures from environment have changed