Learning (Continued) 

 habituation as simplest form of, 



14-15 

 imitation, 15 

 imprinting, 15 

 insight, 15-16 

 Life- forms {see also Life- forms of 



Animals; Life-forms of Plants): 

 as factor in characterizing biotic 



communities, 7 

 defined, 7 

 great variety of among dominants 



on deserts, 332 

 morphological adaptation of 



according to strata within a 



community, 8 

 Life-forms of Animals {see also 



Life-forms): 

 four-footed mammals classified, 8 

 major types, list, 8 

 Life-forms of Plants {see also 



Life-forms): 

 as determiners of physiognomy of 



terrestrial communities, 28 

 characteristics of, 7 

 relation of animal communities 



to, 29-30 

 response to by animals in seeking 



cover, 248 

 system of classification of for 



animal ecologist, 8 

 Life Tables: 

 formulation of, 212 

 mortality curve in, 212 

 obtaining information for construc- 

 tion of, 212-213 

 survivorship curves in, 212, 213- 



214 

 uses of, 212 

 to determine age structure of 



population at any one time, 216 

 with wild populations to find 



mean length of life, 215-216 

 Life- Zone System: 

 confusion of with biome system, 



272 

 designation of faunal areas in, 274 

 development of by C.Hart 



Merriam, 274 

 evolution of species in biotic 



provinces rather than distribu- 

 tion centers of, 272 

 theory of dispersal centers in, 274 

 zones in lacking a uniform and 



characteristic faunal composi- 

 tion, 272 

 Light: 

 and compensation point in sea, 354 

 and sunspot cycles, 243 

 and vitamin content of food, 181 

 as absorbed by atmosphere, 200- 



201, 243 



Light (Continued) 

 as affecting activities of sand dune 



organisms, 106-107 

 as cause of blue color of pure 



water, 61 

 as controlling height of ionosphere 

 and ozone layers above earth, 

 243 

 as not having identical effect on 



all species, 244 

 avoidance of by desert animals, 



338 

 efficiency of use of in photosyn- 

 thesis, 205 

 excessive, as barrier to dispersal, 



148-149 

 exposure of animals to and repro- 

 ductive vigor, 241 

 in arctic tundra, 320-321 

 in developing jungle undergrowth, 



342-343 

 infra-red, effects of on animals, 99 

 intensity: 

 as not equal in all parts of world, 



244 

 as varying on forest floor, 122 

 extreme fluctuations in, 243 

 in Arctic Circle, 216 

 in deserts, 332 

 in forests, vertical gradients in, 



123 

 in grassland, 122 

 measurement of in water, 60 

 measurement of radiation of, 99 

 monopolizing of by plants, 183 

 movements of plankton in response 



to, 67-68, 358-359 

 on south- facing slopes of grass- 

 lands, 124 

 penetration: 

 in ice, 60-61 

 in lakes, 61 

 in ponds, 79 



in sea, variations in, 354 

 in water, factors affecting, 60, 



60-61 

 lateral, under forest canopy, 122 

 to deciduous forest floor, 121 

 reduction of: 

 and change in species composi- 

 tion, 107 

 by water plants, 172 

 sensitivity of lake organisms to, 



60 

 ultra-violet: 

 and sunspot cycle, 244 

 dangers of, 243-244 

 effects of on animals, 99, 244 

 fluctuations in, and ionization of 

 air and ozone formation, 243, 

 243-244 

 in deserts, 332 



Light (Continued) 



variations in as affecting weather, 

 243 



wavelengths of: 

 and growth rates, 99 

 characteristics of, 99 

 Limnology, growth of as a branch 



of ecology, 5-6 

 Lithosphere, as division of environ- 

 ment, 6 

 Littoral Zone of Lakes, 69-71 



few species furnishing bulk of 

 population in, 255 

 Littoral Zone of Sea {see also Sea): 



abundance of benthos in, 359 



algae as protection for animals in, 

 363 



as compared to sublittoral zone, 

 363 



divisions of, 362 



epifauna in as decreasing in vari- 

 ety toward Poles, 359 



extension of, 351-352 



species of animal life in, 363 

 Locomotor Movements: 



aided by mucous glands in nema- 

 todes, 130 



evolution of appendages to facili- 

 tate, 96 



evolution of skeleton to facilitate, 

 96 



hopping as special adjustment of 

 animals to grassland, 329-330 



loss of by parasites in adapting to 

 host, 179 



of animals in response to stream 

 bottom, 50-51 



of organisms in response to 



changes in environment, 12, 12- 

 13 



of reptiles in sand, 110 



of soil animals, 131-132 



of swift-water invertebrates, 47-50 



M 



Mammals {see also Measurement(s) 

 of Populations; Populations): 



abundant varieties of in arctic 

 tundra, 318 



adjustment of to low oxygen pres- 

 sures at high altitudes, 323 



and insects, relative influence of 

 in community, 20 



arctic, choice of microhabitat by, 

 246 



as agents of plant distribution, 177 



as demonstrating nine- ten year 

 cycles, 234 



as demonstrating three-four year 

 cycles, 237 



426 Index 



