TempPhysio PDF

Adaptation and Acclimation Adaptation: a genetically inherited trait that increases fitness. – Result of natural selection Acclimation: a physiological/behavioral response to environmental changes. – Example: Dogs shed excess hair during warm months.  Why is Temperature im...

Adaptation and Acclimation Adaptation: a genetically inherited trait that increases fitness. – Result of natural selection Acclimation: a physiological/behavioral response to environmental changes. – Example: Dogs shed excess hair during warm months.  Why is Temperature important? Biomolecular Level – Most enzymes have a predictable shape at temperatures near their peak activity Low temperatures cause low reaction rates high temperatures destroy the shape.  Adaptation Example Optimal Photosynthetic Temp 6CO2 + 12H2O ! C6H12O6 + 6O2 + 6H20 – Extreme temperatures reduce rate of photosynthesis. – Different plants have different optimal temperatures Optimal Photosynthetic Temperatures  Adaptation Example Temperature effects population growth in bacteria Marine bacteria around Antarctica. – Grew fastest at 4o C. – Some growth recorded in temperatures as cold as - 5.5o C. Thermophilic bacteria have been found to grow best in temperatures as hot as 110o C.  Acclimation Example Trout held at low temps make a “cold” isozyme when held at 2°C, and a “warm” isozyme at 17°C.  HS = Hm + Hcd + Hcv + Hr - He – HS = Total heat stored in an organism – Hm = Gained via metabolism – Hcd = Gained / lost via conduction – Hcv = Gained / lost via convection – Hr = Gained / lost via electromag. radiation – He = Lost via evaporation Heat Exchange Pathways  Climate Effects Macroclimate: Large scale weather variation. Microclimate: Small scale weather variation, usually measured over shorter time period. – Altitude Higher altitude - lower temperature. – Aspect Offers contrasting environments. – Vegetation Ecologically important microclimates.  Ground Color – Darker colors absorb more visible light. Boulders / Burrows – Create shaded, cooler environments. Aquatic Temperatures Riparian vegetation influences stream temperature by providing shade.  Poikilotherms – Body temperature varies directly with environmental temperature. Ectotherms – Rely mainly on external energy sources. Endotherms – Rely heavily on metabolic energy. Homeotherms maintain a relatively constant internal environment.  Desert Plants: Must reduce heat storage. – Hs = Hcd + Hcv + Hr – To avoid heating, plants have (3) options: Decrease heating via conduction (Hcd). Increase convective cooling (Hcv). Reduce radiative heating (Hr). Temperature Regulation by Plants Temperature Regulation by Plants Arctic and Alpine Plants – Two main options to stay warm: Increase radiative heating (Hr). Decrease Convective Cooling (Hcv). Tropic Alpine Plants – Rosette plants generally retain dead leaves, which insulate and protect the stem from freezing. Thick pubescence increases leaf temperature.  Almost all plants are poikilothermic. – However, some plants in family Araceae use metabolic energy to heat flowers. – Skunk Cabbage (Symplocarpus foetidus) stores large quantities of starch in large root, and then translocate it to the inflorescence where it is metabolized thus generating heat. Eastern Skunk Cabbage  Thermoregulation in Ectothermic Animals Liolaemus Lizards – Live in colder environments. Burrows Dark pigmentation Sun Basking Grasshoppers – Some species can adjust for radiative heating by varying intensity of pigmentation during development.  Thermoregulation in Endothermic Animals Thermal neutral zone is the range of environmental temperatures over which the metabolic rate of a homeothermic animal does not change. – Breadth varies among endothermic species. Thermal Neutral Zones  Swimming Muscles of Large Marine Fish – Lateral swimming muscles of many fish (Mackerel, Sharks, Tuna) are well supplied with blood vessels that function as countercurrent heat-exchangers. Keep body temperature above that of surrounding water. Countercurrent Heat Exchange  Warming Insect Flight Muscles – Bumblebees maintain temperature of thorax between 30o and 37o C regardless of air temperature. – Sphinx moths (Manduca sexta) increase thoracic temperature due to flight activity. Thermoregulates by transferring heat from the thorax to the abdomen Moth Circulation and Thermoregulation  Other methods of thermoregulation Inactivity – Seek shelter during extreme periods. Reducing Metabolic Rate – Hummingbirds enter a state of torpor when food is scarce and night temps are extreme. – Hibernation - Winter – Estivation – Summer