408 QUESTIONS, PROBLEMS, AND SUGGESTIONS 



CROCODILIA 



45. How account for the powerful head, the stout linibs, and the strong, 

 compressed tails of alligators and crocodiles? 



46. Why are they aquatic and nocturnal? Their prey? How and when 

 secured? 



47. Why do they hibernate in temperate climates? Why migrate or 

 estivate in dry, tropical regions? 



48. Compare the gavial, alligator, crocodile, and caiman in head. body, 

 tail, and limbs. 



49. Commercial value of any of the Crocodilia? 



50. Why are crocodiles fast becoming extinct? 



AVES 



1. Feathers. — What is a feather? Name kinds, arrangement, colors, 

 and uses to birds and to man. 



2. Are feathers analogous or homologous structures with scales of fishes 

 and reptiles, and with the hair, fur, or wool of mammals? 



3. How account for feathers for birds? Do any have some scales? 

 Give examples. Feathers for flight or warmth? 



4. The Flight of Birds. — Do their feathers, their peculiar respiration 

 (p. 267), and their high temperature (p. 267) correlate for flight? What is 

 flight? In what does it consist? 



5. Why are birds the most successful "flying machines"? Does suc- 

 cess indicate superiority? If so, in what are fishes, amphibians, reptiles, 

 and mammals superior? 



6. Observe Figs. 209, 210, and 212. Do you discover any reptilian 

 affinities? Scientists claim birds have evolved from a reptilian-like an- 

 cestry. Give your reasons for or against their claim. 



7. Colors. — Name birds with alluring colors; with colors for protective 

 resemblance. Do birds ever change colors? If so, when and why? 



8. Defense. — Name all the ways and mean spossessed by birds either 

 directly or indirectly for self-defense or for the defense of their young or 

 their eggs. 



9. Enemies. — Make a list of all enemies, both animate and inanimate, 

 that are detrimental to birds, their young, or their eggs. In spite of this 

 formidable list, why are birds a dominant class of chordates? 



10. Migration. — Give facts and theories of bird migration. Do any birds 

 hibernate? Remain active over winter? 



11. Economics. — Begin with the ostrich and report a list of 50 birds of 

 domestic, scientific, or commercial value to man. 



12. Nests. — Report on all kinds of< materials used for nests, where built, 

 when built, why built, number of eggs in "clutch" for each kind named, 

 time for incubation, care of young, and number of broods for each season. 



