Reproduction (Continued) 

 rate of and artificial destruction 



of emerging adult blow-flies, 



223 

 rate of and calculation of secondary 



net production of energy, 204 

 rate of and emigration, 228 

 rate of as equalling death rate in 



stablized populations, 217 

 relation between density and 



fecundity of great tit and, 223 

 results of overproduction in, 264 

 survival to next age level of young 



in, 216 

 through broadcasting of eggs, 



spores, and young, 146 

 times of breeding seasons for in 



forests, 299 

 to offset high mortality rates, 9 

 vigor in and vitamin content of 



food consumed, 241 

 volume of culture fluid of Para- 

 mecium and variations in rate 



of, 222 

 wide variation in fecundity of 



different species in, 210 

 Respiration {see also Oxygen): 

 absence of organs for in soil 



animals, 131-132 

 adaptations for, in marine animals, 



356 

 and carbon cycle, 167 

 and photosynthesis approximately 



equal when trophic levels in 



balance, 206-207 

 and reduction of oxygen supply 



of lakes, 64 

 as furnisher of energy for plant's 



activities, 201 

 as user of oxygen in photosynthe- 

 sis, 61 

 measurement of to determine gross 



secondary production of energy, 



204 

 method of by diving beetle, 84-85 

 of air-breathing aquatic insects, 



84-85 

 of burrowing animals in muddy 



and sandy marine habitats, 365 

 of mosquito larvae, 89 

 of stream animals, 51-52 

 role of in measurement of pri- 

 mary production of energy, 



203-204 

 underground, and oxygen- carbon- 

 dioxide content of soil, 165 

 Riffles: 

 as barrier to dispersal of pond or 



lake species, 148 

 change of river to pond and change 



in population of, 82-83 

 defined. 43 

 invertebrate biomass in, 55 



Riffles (Continued) 



two species in as furnishing 



greatest bulk of population, 255 

 River(s) (see ulso Streams): 



base-level of, delined. 42 



character of in maturity, 42 



character of in youth, 42 



debris rafts of as means of dis- 

 persal of eggs and spores, 146 



dispersal of animals of and soil 

 erosion, 146 



land masses as barriers to dis- 

 persal of organisms of, 148 



Mississippi, as isolator of popu- 

 lations during glaciation, 286- 

 288 



peneplain region of, 42 



salt water as barrier to dispersal 

 of organisms of, 148 



slow-flowing as essentially elon- 

 gated ponds, 79 



waterfalls in as barrier to disper- 

 sal of non- flying aquatic organ- 

 isms, 148 



wide, as barriers to dispersal of 

 mammals, insects, birds, 148 

 Rock: 



and chemical composition of soil, 

 163-164 



chemical changes in weathering 

 of, 168-169 



erosion of by water, 168 



on marine shores and succession 

 from sea to land, 368 



plant and animal communities in, 

 102-105 



role of in protecting sea- shore 

 animals from pounding action 

 of waves, 352 



weathering of through plant 

 reactions, 164 



Salinity (see also Salts): 

 of sea: 

 and abundance of populations, 



356 

 as varied by inflow of fresh 



water, 354 

 average figures for, 354 

 factors in maintaining, 356 

 osmotic regulation in adjustment 

 of organisms to, 354 

 terms used to indicate range of 

 tolerance to, 11-12 

 Salts {see also Salinity): 

 absence of and population of lakes, 



65 

 accumulation of during winter in 

 antarctic, 319 



Salts (Continued) 

 accumulation of in marshes 



through sea-wind action, 368 

 and measurement of pH changes 



in lakes, 66 

 and water evaporation in formation 



of saline soils, 172 

 as lacking in podzolic soils, 172 

 calcium, and chernozemic soils, 172 

 content of in bags, 92 

 decrease of in ocean during sum- 

 mer, 358 

 extensive utilization of in sea 



water, 354-356 

 high concentration of in desert 



ponds, 339 

 high concentration of in "salt 



licks," 167 

 in carbon cycle, 167 

 increase of in ocean during winter, 



358 

 in desert soil, as not washed away 



by rainfall, 339 

 kidneys as critical in maintaining 

 proper concentration of, 97-98 

 liberation of in water conditioning, 



173 

 nutrient, in lakes, 65 

 nutritional value of in diet, 190 

 variations in within plants and 

 cycles of herbivores, 241 

 Sand {see also Seres): 

 and soil formation, 163-164 

 animal life in: 

 ants, 107-109 

 birds, 110 

 grasshoppers, 107 

 insects, 109-110 

 reptiles, 110 

 spiders, 109 

 vertebrates, 109-110 

 as habitat, 106-107 

 characteristics of, 105 

 life- history of tiger-beetle found 



in, 112 

 plant communities in, 105-106 

 Saprovores: 

 adaptation of teeth of for food- 

 getting, 188 

 as users of energy lost from 



trophic levels, 202 

 defined, 187 

 in food chains, 195 

 position of in trophic levels, 196 

 role of as transformers, 196 

 role of in providing energy in 



food chain, 205-206 

 size of food of not of major 

 importance, 191 

 Sea {see also Plankton, Marine; 

 Zoogeography): 

 Arctic, condition of during Pleisto- 

 cene era, 284 



Index 439 



