34 rbe Living Things of the Earth unit i 



their eggs in deep waters. Then the streams. Here the eggs are laid. Then 



parents die. The voting fish remain for most of the parents die. The young 



a year near where the eggs hatch. Then develop slowly and eventuallv^ swim out 



they begin the long journey to homes to the sea, where they remain until they 



they have never seen in the rivers of the are ready for spaw ning. Within the last 



two continents. The American eels turn few years much has been learned by 



toward the rivers of our country; their the United States Bureau of Fisheries 



European cousins travel eastward. When about the migrations of fish. Thousands 



they are mature, they swim back to the of fish are tagged and fishermen are 



breeding grounds in the Atlantic Ocean, asked to return the tag with information 



The salmon, \\'hich live in the ocean as to the size of the fish and the place 



when adult, migrate into fresh water at where it was caught. Fish are interestinq^ 



spaivn'mg (egg-laying) time. They swim to read about; see the bibliography at 



far up into the shallow headwaters of the end of the book. 



Questions 



1. Into what five subdivisions or classes can the vertebrates be divided.' 

 What two or three characteristics do all vertebrates have? 



2. Starting with the largest group, the phvlum, list the subdivisions em- 

 ployed by biologists in classifying animals. 



3. In what two respects do mammals difi^er from all the other kinds of 

 vertebrates? Why may they be spoken of as the highest animals? 

 How many species of mammals are known to scientists? 



4. Which mammals are most like man in structure? 



5. List nine kinds of mammals that m.ay be grouped together as plant 

 eaters v ith grinding teeth. What is another characteristic of most of 

 these mammals? Explain. 



6. What are the characteristics of the carnivores? List some carnivores. 



7. Give the name of the gnawing mammals. What can you tell about 

 the gnawing teeth? 



8. Give two reasons why a whale is classified as a mammal. State two 

 interesting facts about whales. What other mammals inhabit the sea? 

 Why are they classified with dogs or cats rather than with whales? 



9. Tell what you know about bats. 



10. What are the characteristics of marsupials? Where do most of them 

 live? Which animals in our countrv are closely related to the Aus- 

 tralian kangaroo? Why is the duckbill called a mammal? List two 

 unusual characteristics of the duckbill. 



11. By which one characteristic can you always recognize a bird? What 

 are other characteristics of a bird? 



12. How are birds classified? 



13. Describe and give examples of birds of prey. In general, are they 

 useful or harmful to man? ]■ Apia in. 



