THE DISTRI BUTION OF ANIMALS 471 



believed that the lights which are found on many of these animals not 

 only help in finding food and seeing what is about them in this total 

 darkness, but they also help the animals find one another during the 

 reproductive season. 



REVIEW QUESTIONS 



1. Explain why some species of animals reproduce very rapidly and become 

 established when introduced into a new environment. 



2. Why are birds generally more widely distributed than mammals? 



3. Name several ways in which man aids animal distribution. 



4. What are some of the ecological barriers to dispersal of animals? 



5. How does sporadic migration differ from annual migration? 



6. What are some of the factors which have caused a reduction in the range 

 of certain animals? 



7. Give examples of how man has brought about extinction of some species 



of animals. 



8. How can relic survival explain the discontinuous range of many forms of 



animals? 



9. List the geographic realms and the types of animals found in each. 



10. Name the ecological zones of the oceans, and give the types of animals found 

 in each. 



