Geographic Distribution of Animals and Plants 603 



dan, species are present in specific habitats because (a) they are pre- 

 vented from migrating elsewhere because of barriers; (b) they have 

 been unable to maintain themselves in other habitats and thus have had 

 to move into this particular region because they were successful in doing 

 so in this type of habitat; (c) they have been so changed in their new 

 habitats that they now constitute a new species. The latter might ex- 

 plain certain origins of species in limited localities at least. 



QUESTIONS AND TOPIC 



1. Select ten animals from each of the seven regions of the world and give 

 reasons why each animal is distributed as it is. 



2. Select ten animals of your immediate community, telling why each is dis- 

 tributed as it is. 



3. What biologic environmental factors have been and are the most influential 

 in the distribution of the animals selected in the second question ? 



4. With somewhat similar conditions in Brazil and Africa, why does the former 

 have the sloth, tapir, and New World monkeys, while the latter does not ? 

 Why does the latter have the elephant, chiinpanzee, and gorilla, while the 

 former does not ? 



5. Why are the marsupials the prevailing mammals of Australia ? 



6. In regions having similar environments, why do we often find an entirely 

 different fauna of animals ? 



7. Why do we frequently find similar forms on the summits of two mountains 

 which are a great distance apart, while the bases of these same mountains 

 are inhabited by entirely different types ? 



8. On mountain tops, why are the types frequently similar to those which live 

 in the polar regions of the world ? 



9. Why is the fauna of the British Isles similar to that of the adjacent con- 

 tinent? 



10. Explain the relationship between long periods of isolation and the develop- 

 ment of endemic species. 



11. List the values derived from a study -of biogeography. What are the rela- 

 tionships between biogeography and geography? 



12. Discuss fully the importance of each of the principles of geographic distri- 

 bution. Which are the most plausible ? Why ? 



13. What does the parallel distribution of organisms in altitude and longitude 

 suggest? Give several examples of each. 



14. Give the general characteristics and boundaries of each of the seven regions 

 into which the animal world is divided. What factors might prevent migra- 

 tion from one region to another ? 



15. How might a certain condition act as a barrier to one type of animal and 

 at the same time act as a method of transportation to another type? Give 

 several examples. 



