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Kim Dej

September 20 , 2012 Biology 2F03: Fundamental and Applied Ecology Temperature Temperature - temperature affects organisms in many ways:  directly by affecting metabolism  indirectly by changing the habitat - can you think of ways how temperature affect organisms via habitat  examples: causing currents, stratifying a lake, freezing water (cold drought), drying the soil Question - can plants regulate their temperature: some plants can Temperature as a resource - air temperature = 15C - flower and insect = 25C - dryas flowers keep tracking sun for several hours each day - sunlight reflects parabolic-shaped flowers to heat an insect - warming the flowers to attract insects (dryas) Question - if plants can regulate their own temperature, can they affect their environment too: shading, cooling and warming depending on external temperature Temperature and plants - winter increases temperature and makes the house warmer, evapotranspiration - summer shades and cools - soil surface in full sun heats to high temperature - shading of soil surface by low shrubs lowers maximum temperatures - a layer of leaf litter lowers maximum temperatures even more - greater leaf area wetter area - plants modify their microhabitat T by: shading, accumulating litter, accumulating O horizon Habitat Differences - different habitats have different thermal regimes - why does black sand appear black? Is it warmer or cooler than white sand: black sand is warmer, it appears black because it absorbs all the light - often the arithmetic mean is the same but variation differs - aquatic habitats are less variable - air temperature varies a lot - shadow riffle fairly high variation - aquatic reed bed variation - less variation observed in the deep pool, heat capacity of water is very high Question - how does stream temperature affect Chinook salmon reproduction and survival - can organisms optimize their physiology and growth for the typical range of temperatures: yes Specific adaptations - plants photosynthesize best at preferred T - a moss from a boreal forest photosynthesizes at a maximum rate at 15C - a desert shrub photosynthesizes at a maximum rate at 44C - true of many other metabolic processes in plants and animals - compare enzyme or bacteria Acclimation - migration of insects and birds - organism can adjust and optimize performance for different temperatures - experiment with cuttings of a desert shrub grown in cold and hot chambers - data from shrubs grown in cool water - data from shrubs grown in a hot temperature - photosynthesis rate of shrubs growing in a hotter environment peaks at a higher temperature - plants achieved different optima; of Δ 8C Thermal regulation: main terms - poikilotherms: no or poor regulation - ectotherms: external sources of warmth - endotherm: internal sources of warm
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