PROBLEM QUESTIONS 



169 



food must it of necessity eat ? Using the models, charts, and living 

 specimens, now compare the later stages of the tadpole with those of 

 its earliest life. Are external gills always present? If not, what 

 becomes of them? Examine the internal gills in the older tad- 

 poles. Also try to find out why some tadpoles seem to come to the 

 surface of the water, swallow a bubble of air, and then go under 

 the water again. 



NOTE. — There is a stage in the life of the tadpole when it uses both gills and 

 lungs in breathing. 



At what stage of the metamorphosis does the tadpole breathe 

 by internal gills ? By both lungs and gills ? Which grow first, the 

 front or hind legs? What becomes of the tail? Are there any 

 changes in the appearance of the mouth in an older tadpole ? Are 

 there teeth in the mouth of a tadpole ? A frog ? 



Conclusion. — What changes take place during the life of the 

 tadpole and how do these changes fit it for the life which it has to 

 lead? 



Problem 149 : To work out a comparison of development of 

 the vertebrates. 



Method. — Fill out 

 a table like the accom- 

 panying. 



Conclusion. — In 

 which of the above 

 animal groups do the 

 eggs have the best 

 likelihood of reaching 

 development into 

 adults ? Explain your 

 answer. 



Problem Questions 



1. What do we mean by adaptation to environment? Illus- 

 trate with certain organs in a fish ; in a frog. 



2. Might color be an adaptation ? Give examples. 



3. Might habits of life be adaptations or the results of adapta- 

 tions? Explain. 



