PROBLEM QUESTIONS 



109 



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

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

 its earhest 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 (-(jme 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 Kills and 

 lungs in breathing. 



At what stage of the metamorphosis does the ta(li)ole breathe 

 by internal gills? By both lungs and gills? ^^'hi{•h 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 Ik^ adaptations or the results of adajita- 

 tions? Explain. 



