L;ikes (Coiitiiuicdl 

 amounts of dissolved solids in 



from runoff of falling rain, 65 

 as complete ecosystems, efficiency 



of use of energy in, 206 

 as differing from streams, 59 

 autumn overturn in, 62 

 biomass in: 

 ajid productivity of benthos, 76 

 and productivity of plankton, 76 

 and relation of depth to organisms 



m, 75 

 of benthos, 75 

 of phytoplankton and zooplankton 



compared, 75 

 of plankton and benthos compared, 



75-76 

 of seston, 75 

 chemicals in: 

 amino acids, 65 

 carbohydrates, 65 

 fats, 65 

 color of, 61, 64 

 compensation level in, 61 

 cyclomorphosis in plankton found 



in, 60 

 deep, circulation of water in, 61 

 defined. 59 



derivation of carbon dioxide in, 65 

 dimictic, defined, 63 

 draining of to form mature river, 



42 

 dystrophic, defined, 64 

 effects of low concentration of 



oxygen in on organisms of, 64 

 efficiency of use of solar radiation 



in, 205 

 epilimnion of, 61, 61-62 

 eutrophic: 

 composition of bottom mud of, 



73 

 defined. 64 



seasonal variations in popula- 

 tions of, 73 

 food cycle of: 

 anatomical adaptations of fish in, 



74-75 

 role of bacteria in, 74 

 role of phytoplankton in, 74 

 role of zooplankton in, 74 

 formation of, 59 

 through water accumulation in 

 large basins, 42 

 freezing of in tundra biome, 315 

 gases in: 

 ammonia, 65 

 hydrogen sulphide, 65 

 marsh gas, 65 

 nitrogen, 65 

 hard-water, 65 

 heat in: 

 annual budget of, 63 

 loss of, 63 



Lakes (Conliniud) 

 unpolluted, hydrogen- ion concen- 

 tration of, 66 

 hypolimnion of: 

 amount of oxygen in, 64 

 fertility of, 61-62 

 introduction of exotic species into, 



77 

 land masses as barriers to dis- 

 persal of organisms of, 148 

 life- histories of organisms in, 76- 



77 

 light in: 

 as establishing rhythm in activi- 

 ties of organisms, 60 

 measuring intensity of, 60 

 littoral zone of: 

 differentiation of species distri- 

 bution according to bottom of, 

 70 

 divisions of, 69-70 

 extension of, 69-70 

 vegetation of and populations in, 

 70-71 

 marl formation in, 65 

 measurement of primary produc- 

 tion of energy in 203 

 microscopic animals in, 71 

 monomictic: 

 cold, 63 

 warm, 63 

 occurrence of animals in: 

 amphibians and reptiles, 74 

 bird species, 74 

 mammals, 74 

 oligotrophic, defined, 64 

 orders of: 

 first, 63 

 second, 63 

 third, 63 

 oxygen debt in, 64 

 oxygen in: 

 factors in distribution of at 



various depths, 63 

 reduction of, 64 

 penetration of light into: 

 ajid presence of ice, 60-61 

 factors affecting, 60, 60-61 

 pH of: 

 and toleration of organisms to 



changes in, 66 

 degree of alkalinity of, 65 

 determining acidity or alkalinity 

 of, 66 

 photosynthesis in, 61 

 physical properties of water of: 

 buoyancy, 60 

 density, 59-60 

 pressure, 59 

 salts in: 

 dissolved, accumulation of, 59-6C 

 inorganic, absence of and popula- 

 tions, 65 



Lakes (Continiicil) 

 nutrient, 65 

 saturation of water of with oxygen, 



63-64 

 segregation of fish in, 74 

 similarities of to |)onds, 79 

 soft- water, 65 

 spring overturn in, 63 

 stagnation period in: 

 during summer, 64, 73 

 during winter, 64 

 temperature of: 

 during autumn, 62 

 during spring, 63 

 during summer, 61-62 

 during winter, 62-63 

 terrestrial insects in, 71 

 thermocline in, 61-62 

 turbidity in, 60-61 

 wind action in: 

 currents created by, 61 

 wave action influenced by, 61 

 zones of: 

 limnetic, 70 



profundal, extension of, 70 

 trophogenic, 61 

 tropholytic, 61 

 Land Bridges [see Continents. Dis- 

 persal Pathways) 

 Larvae: 

 and parasitoidism, 182 

 and temperature changes, 7 

 as food for fish, 191-192 

 as parasites on plants, 179 

 black fly, toleration of to currents, 



50 

 caddisfly, adjustment of to cur- 

 rents of stream, 46-47 

 conditioning of to food, 261 

 diel movements of, 68 

 digestion of cloth and feathers by, 



190 

 filter feeding by, 55 

 food preferences of, 188 

 in lakes, 76 

 in soil of forest communities, 130, 



135 

 metamorphic migrations of, 159 

 migration of from lakes during 



summer, 73 

 of flour beetle, and cannibalism, 



223 

 of forest millipede, 144 

 of intertidal organisms, zonation 



of, 362-363 

 of pond organisms, 88-90 

 of stream insects, 53-54 

 of tiger beetles, 112 

 populations of in eutrophic lakes, 

 73 

 Learning: 

 conditioning in, 15 

 defined. 14 



ndex 425 



