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organismal phys

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Western University
Biology 2601A/B
Brent Sinclair

Oct 611 Temperature is variable and changes a lot Winter is long Insects have to deal with the variability of temperatures over the course of winter Endotherms deal with the cold by increasing their metabolic rate to maintain a constant body temperature The temperature of ectotherms however is affect by the environment Their temperature will match the ambient temperature Endothermshomeotherms defend a constant body temperature by producing heat insulation and countercurrent heat exchange devices Ectotherms deal with low temperatures by migration avoid low temperatures altogether and bees expend more energy to heat hive Some cant migrate and expend energy like this so they have to put up with these low temperatures Life below 0C is bad because organisms are mostly water and they can freeze solid When its cold water becomes solid and becomes less dense it expands Water doesnt always freeze at 0C Small quantities of water can supercool to 20C insects tend to be small Freezing will be induced in the presence of a nucleus like ice Ice is an organized lattice and it imposes its structure on the water Silver iodide and certain proteins can also do this How insects survive the cold Insects can be categorized by their ability to tolerate cold and strategy for doing so 1 Chill susceptiblethey die before they freeze die due to something unrelated to freezing 2 Freeze avoidingthey keep from freezing will die if they freeze 3 Freeze tolerantthey survive freezing How do we know that an organism has frozen As the temperature of the environment drops the body temperature drops Eventually the temperature reaches the supercooling point SCP which is the lowest temperature it reaches immediately before freezing There is then an exothermic reaction latent heat of crystallization which is the amount of heat
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