Contents xi 



Control by Need for Minimum Amount of Heat 164 



Control by Need for Chilling 168 



Results of Temperature Limitation 172 



Special Cases of Common Boundaries 172 



Frost Line 173 



Tree Line 173 



Life Zones 175 



Temperature and Moisture Acting Together 181 



Chapter 6 ■ LIGHT 185 



Distribution of Light 186 



Light on Land 186 



Spectral Composition 186 



Intensity of Light 187 



Duration and Amount of Light 188 



Light in Water 191 



Extinction and Modification of Light 191 



Changes in Transparency 197 



Biological Effects of Light 198 



General Effects 198 



Protective Coloration . 199 



Activity and Vision 202 



Photokinesis 202 



Vision 202 



Bioluminescence 204 



Orientation 207 



Periodicity 216 



Diurnal Periodicity 216 



Lunar Periodicity 219 



Seasonal Periodicity 224 



Ultraviolet Light 230 



Ecological Aspects of Photosynthesis 233 



Land Plants 233 



Aquatic Plants 235 



Chapter 7 • OXYGEN AND CARBON DIOXIDE 242 



Oxygen 242 



Availability of Oxygen 243 



Terrestrial Environment 243 



Aquatic Environment 244 



Oxidation-Reduction Potential 251 



Effects of Oxygen Availability 253 



Terrestrial Environment 253 



Aquatic Environment 255 



Carbon Dioxide 259 



Carbon Dioxide in Terrestrial Environment 260 



Carbon Dioxide in Aquatic Environment 262 



Reactions of Carbon Dioxide in Water 262 



Ecological Effects of Carbon Dioxide 265 



