6. B. Balancing selection of sickle cell trait 1. heterozygotes -  survival rate against malaria - about 1 in 5 in African populations at risk for malaria - about 1 in 100 are homozygous recessive

7. 2. Black populations not at risk of malaria have  occurrence of the sickle cell allele. a. no more selection pressure for the trait b. directional selection away from the sickle cell allele c. only about 8% of American Black population d. only 1 in 500 individuals are homozygous

8. C. Industrial melanism 1. peppered moth (two alleles) a. light (blends with light tree bark) b. dark (least prevalent in the population) 2. ratios changed with Industrial Revolution (1850’s) 3. concealment hypothesis 4. Kettlewell experiments 5. demonstrated that allele frequencies are influenced by environment 6. reversed by pollution cleanup

10. II. Species Formation - microevolution: adaptation by a species - macroevolution: forming new species - levels of specialization increase to a point where entirely new species formed A. Species 1. group of organisms unlike other groups 2. does not integrate extensively with other groups 3. considered the final stage of evolutionary process

11. B. Ecological races 1. local populations of a species adapt to their environment 2. selections for improvement will occur 3. populations eventually begin to differ - forming ecological races 4. not yet different species

13. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species a. geographic

14. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species a. geographic b. ecological (habitat) c. behavioral

15. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species a. geographic b. ecological c. behavioral d. temporal

16. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species a. geographic b. ecological c. behavioral d. temporal e. mechanical

17. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species f. reproductive - prezygotic mechanisms

18. C. Isolation 1. enhances formation of ecological races and new species 2. there are several isolating mechanisms - they prevent breeding among newly forming races and species f. reproductive - prezygotic mechanisms - postzygotic mechanisms

19. D. Adaptive radiation 1. recent evolution of species from a common ancestor 2. each adapts to a different habitat 3. Darwin’s finches

21. Gradualism Punctuated Equilibrium Timing of Evolution Which is correct?