Temperature Relations

1. Temperature Relations Chapter 4

2. Outline • Microclimates • Aquatic Temperatures • Temperature and Animal Performance • Extreme Temperature and Photosynthesis • Temperature and Microbial Activity • Balancing Heat Gain Against Heat Loss • Body Temperature Regulation • Plants • Ectothermic Animals • Endothermic Animals • Surviving Extreme Temperatures

3. Microclimates • 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.

4. Microclimates • Ground Color • Darker colors absorb more visible light. • Boulders / Burrows • Create shaded, cooler environments.

5. Aquatic Temperatures • Riparian vegetation influences stream temperature by providing shade.

6. Temperature and Animal Performance • Biomolecular Level • Most enzymes have rigid, predictable shape at low temperatures

7. Extreme Temperatures and Photosynthesis • Photosynthesis 6CO2 + 12H2O  C6H12O6 + 6CO2 + 6H20 • Extreme temperatures usually reduce rate of photosynthesis.

8. Optimal Photosynthetic Temperatures

9. Temperature and Microbial Activity • Morita studied the effect of temperature on population growth among marine bacteria around Antarctica. • Grew fastest at 4o C. • Some growth recorded in temperatures as cold as - 5.5o C. • Some thermophilic microbes have been found to grow best in temperatures as hot as 110o C.

10. Optimal Growth Temperatures

11. Balancing Heat Gain Against Heat Loss • 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

12. Heat Exchange Pathways

13. Body Temperature Regulation • Poikilotherms • Body temperature varies directly with environmental temperature. • Ectotherms • Rely mainly on external energy sources. • Endotherms • Rely heavily on metabolic energy. • Homeothermsmaintain a relatively constant internal environment.

14. Temperature Regulation by Plants • Desert Plants: Must reduce heat storage. • Hs = Hcd  Hcv  Hr • To avoid heating, plants have (3) options: • Decrease heating via conduction (Hcd). • Increase conductive cooling (Hcv). • Reduce radiative heating (Hr). • 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

15. Temperature Regulation by Plants

16. 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.

17. Temperature Regulation by Ectothermic Animals • Eastern Fence Lizard (Sceloporus undulatus) • Metabolizable energy intake maximized at 33ºC • Grasshoppers • Some species can adjust for radiative heating by varying intensity of pigmentation during development.

18. Temperature Regulation by Endothermic Animals • Thermal neutral zone is the range of environmental temperatures over which the metabolic rate of a homeothermic animal does not change.

19. Thermal Neutral Zones

20. Temperature Regulation by Endothermic Animals • 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.

21. Countercurrent Heat Exchange

22. Temperature Regulation by Endothermic Animals • 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

23. Moth Circulation and Thermoregulation

24. Temperature Regulation by Thermogenic Plants • Almost all plants are poikilothermic ectotherms. • 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.

25. Eastern Skunk Cabbage

26. Surviving Extreme Temperatures • 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

27. Review • Microclimates • Aquatic Temperatures • Temperature and Animal Performance • Extreme Temperature and Photosynthesis • Temperature and Microbial Activity • Balancing Heat Gain Against Heat Loss • Body Temperature Regulation • Plants • Ectothermic Animals • Endothermic Animals • Surviving Extreme Temperatures