Chapter 22 Objectives

1. Distinguish between anagenesis and cladogenesis.
2. Define morphospecies and explain how this concept can be useful to biologists
3. Define biological species (E Mayr)
4. Describe some limitations of the biological species concept
5. Explain how gene flow between closely related species can be prevented
6. Distinguish between prezygotic and postzygotic isolating mechanisms
7. Describe five prezygotic isolating mechanisms and give an example of each
8. Explain why many hybrids are sterile
9. Explain, in their own words, how hybrid breakdown maintains separate species even if gene flow occurs
10. Explain how introgression affects the gene pool of a species
11. Distinguish between allopatric and sympatric speciation
12. Explain, in their own words, the allopatric speciation model and describe the role of intraspecific variation and geographical isolation
13. Explain why peripheral isolates are susceptible if geographic barriers arise
14. Describe the adaptive radiation model and use it to describe how it might be possible to have many sympatric closely related species even if geographic isolation is necessary for them to evolve
15. Define sympatric speciation and explain how polyploidy can cause reproductive isolation
16. Distinguish between autopolyploidy and allpolyploidy
17. List some points of agreement and disagreement between the two schools of thought about the tempo of speciation (gradualism vs. punctuated equilibrium)