2"0 CHAPTER 18 



REFERENCES 



Dobzhansky, I h.. Genetics and the Origin of Species, 3rd Ed.. New York: Columbia 

 University Press, 1951. 



Dobzhansky, Th., Evolution, Genetics, and Man, New York: John Wiley & Sons, 1955. 



Dobzhansky, In.. Ehrman, 1... Pavlovsky, O., and Spassky, B., "The Supcrspecics Dro- 

 sophila paulistorum," Proc. Nat. Acad. Sci., U.S., 51:3-9, 1964. 



Dodson. E. O.. Evolution: Process and Product (Rev. Ed.), New York: Rinehart, 1960. 



Dunn. L. C. and Dobzhansky, Th., Heredity, Race, and Society, 3rd Ed., New York: 

 New Amer. Libr. of World Lit.. 1957. 



Ehrlich. P. R.. and Holm. R. W.. The Process of Evolution, New York: McGraw-Hill 

 Book Co., Inc.. 1963. 



Mayr, E., Animal Species and Evolution, Cambridge: Harvard University Press, 1963. 



Merrill. D. J.. Evolution and Genetics, New York: Holt, Rinehart and Winston, 1962. 



Stebbins, G. L., Variation and Evolution in Plants, New York: Columbia University 

 Press, 1950. 



QUESTIONS FOR DISCUSSION 



18.1. Discuss the validity of the concept of a pure race. 



18.2. To use the frequencies of ABO blood types in tracing the course of past migra- 

 tion, what assumptions must you make? 



18.3. Under what future circumstances would you expect the number of races of 

 human beings to decrease? To increase? 



18.4. Can the definition we have used for a species be applied to forms that reproduce 

 only asexually? Why? 



18.5. Differentiate between genetic sterility and chromosomal sterility. Invent an 

 example of each type. 



18.6. Discuss the hypothesis that a new species can result from the occurrence of a 

 single mutational event. 



18.7. Is geographical isolation a prerequisite for the formation of a new species? 

 Explain. 



18.8. What is the relative importance of mutation and genetic recombination in species 

 formation? 



18.9. Is a species a natural biological entity, or is it — like a race — defined to suit 

 man's convenience? 



18.10. Does the statement, "We are all members of the human race," make biological 

 sense? Why? 



18.11. Suppose intelligent beings, phenotypically indistinguishable from man, arrived 

 on Earth from another planet. Would intermarriage with Earth people be likely 

 to produce fertile offspring? Why? 



18.12. Invent circumstances under which the present single species of man could evolve 

 into two or more species. 



18.13. The cells of triploid and tetraploid autopolyploids are usually larger than those 

 of the diploid. What importance has this fact for fruit growers? 



