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BIO120.Lecture (2).docx

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Doug Thomson

BIO120: Species Ranges and the Physical Challenges of the Environment: Heat Balance -relationship between physiological range and geographical range: contrasting examples -examples of one environmental challenge to physiology: heat balance/thermal ecology of animals 1. modes of heat gain and loss; homeostasis 2. size, shape, insulation, evaporative cooling 3. tradeoff principle and adaptive compromises Core Ideas -ranges of tolerance ultimately limit distribution -organisms are complex chemical reactions -reactions occur (enzymes function) best at optimum temperature and osmotic conditions, where fitness is maximized -many mechanisms for homeostasis have evolved to challenge hostile environments -maintenance of homeostasis requires energy and is often limited by constraints and tradeoffs -animals’ geographical ranges often correspond to biomes (limited by climate/vegetation)  limited to special habitats (behavioural habitat selection)  limited by other organisms (enemies, friends)  transcend biomes (ecological versatility)  not at limits because of recent history (limited dispersal) -pronghorm: grazing animal, wide geographical range but narrow ecological habitat range, only found in one particular type of habitat (grassland but not in mountains), fastest running mammal in north America but not very good at jumping, good at flat terrain but not steep, other animals take over the grazing niche in the mountains -sometimes geographical distributions differ between similar species in ways that come down to behavioural choices made by the animal -yellow-rumped warbler: large range, red (summer) blue (winter) purple (permanent) orange (overlap), insect eaters -kirtland’s warbler: close relative to yellow-rumped warbler, has one of tiniest distributions, nests only in jack pine forests of a certain age (narrow habitat preference), extreme habitat specialist -tiger: the same design of this animal can live well in both the tropical rainforest and the boreal forest, broad habitat range -range limited by other animals (not by climate or habitat type)  dense settlement of north America has caused wolves to be hunted which has enabled the coyote to expand their distribution -heat balance is most important -need to control heat loss/gain to maintain balance in narrow limits -either gaining or losing heat from environment which happens through a number of ways that need to be controlled by organism in order for it to maintain heat balance -radiation: heat transfer by electromagnetic radiation, radiant energy that all organisms put out, warmer than environment net flow is from you to environment -conduction: direct contact with substrate (feet lose heat to ground) -convection: heat transfer mediated by moving fluid, water/air
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