338 



ECOLOGICAL FACTORS: 



recent emergence of the vast majority of present-day 

 species, success is associated with change. Almost 

 invariably the best-adapted ecological amplitudes of 

 species persisted; and because environments fluctu- 

 ated and the mechanisms of evolution operated dur- 

 ing this time, ecological amplitudes also changed. 



Success, then, is tenuous because environmental 

 changes occur. When geological processes take place, 

 many individual factors also change and create new 

 problems for organisms in satisfaction of their basic 

 requirements and integration into their environment. 

 Fortunately for life, geological processes are slow 

 enough so that many species can be successful, be- 

 cause evolutionary processes modify their ecological 

 amplitudes while retaining their specific identities. 

 However, success in another sense is not attained 

 through retention of the old species, even with some 

 change in its previous ecological amplitude. Rather, 

 many species might gradually evolve with their en- 

 vironment and become new species. Therefore, the 

 life of an ecosystem evolves through time and so does 

 the nature of the ecosystem. Although evolution of 

 species and ecosystems often occurs, success in the 

 original sense takes place in those species that retain 

 their identify because hereditary changes are not 

 pronounced. 



Ecological success is so complex that man's at- 

 tempts to measure it are truly inadequate. Very little 

 is known about why certain fossil species were suc- 

 cessful for a time and then became extinct. 



SELECTED READINGS 



Daubenmire, R. F., 1959. Plants and Environment. 2d ed. 

 John Wiley & Sons, New York. 



Raid, George K., 1961. Ecology of Inland Waters and Estu- 

 aries. Reinhold Publishing Corp., New York. 



Ricketts, Edward F., and Jack Calvin (edited by Joel 

 Hedgpeth), 1952. Between Pacific Tides. Stanford Uni- 

 versity Press, Stanford, Calif. 



GENERAL ECOLOGV REFERENCES 



Allee, W. C, et al., 1949. Principles of Animal Ecology. W. B. 



Saunders Co., Philadelphia. 

 Benton, Allen H., and William E. Werner, Jr., 1958. Prin- 

 ciples of Field Biology and Ecology. McGraw-Hill Book 



Co., New York. 

 Buchsbaum, Ralph, and Mildred Buchsbaum, 1957. Basic 



Ecology. The Boxwood Press, Pittsburgh, Pa. 

 Clarke, George L., 1954. Elements of Ecology. John Wiley & 



Sons, New York. 

 Elton, Charles, 1947. Animal Ecology. Sidgwick & Jackson 



Ltd., London. 

 Hesse, R., W. C. Allee, and K. P. Schmidt, 1951. Ecological 



Animal Geography, 2nd ed. John Wiley & Sons, New 



York. 

 Kendeigh, S. Charles, 1961. Animal Ecology. Prentice-Hall, 



Inc., Englewood Cliffs, N.J. 

 Moore, Hilary B., 1958. Marine Ecology. John Wiley & 



Sons, New York. 

 Odum, E. P., 1953. Fundamentals of Ecology. W. B. Saunders 



Co., Philadelphia. 

 1963. Ecology. Modern Biology Series. Holt, 



Rinehart & Winston, New York. 

 Reid, George K., 1961 . Ecology of Inland Waters and Estuaries. 



Reinhold Publishing Corp., New York. 

 Russell, Franklin, 1961. Watchers al the Pond. Alfred, A. 



Knopf, New York. 

 Sears, Paul B., 1962. Where There Is Life. Dell Publishing 



Co., New York. 

 Storer, John H., 1953. The Web of Life. New American 



Library, New York. 

 Weaver, J. E., and F. E. Clements, 1938. Plant Ecology. 



McGraw-Hill Book Co., New York. 



