12 ENVIRONMENT OF PLANTS AND ANIMALS 



are principally carbon, hydrogen, oxygen, and nitrogen with ten or 

 more others in very minute proportions. It is logical to believe 

 that living things use the chemical elements in their surroundings 

 and in some wonderful manner build up their own bodies from 

 the materials found in their environment. How this is done we 

 shall learn in later chapters. 



Summary. — This chapter has been in the nature of a review of 

 your elementary science ; but it should give you a slightly differ- 

 ent view of the environment because it is considered from the 

 standpoint of living things. We have seen that the chemist's 

 elements and compounds, which give us the factors of the environ- 

 ment, air, water, soil, and food, become a part of living things, 

 which, when they die, are decomposed to form a part of the soil. 

 How this is and why, future chapters will explain. 



Problem Questions 



1 . What are the factors of thb environment ? Why are they so called ? 



2. Are there any factors in the environment which are unnecessary to ani- 

 mals ? To plants ? 



3. How are compounds formed? How broken up? 



4. Compare rapid and slow oxidation in all respects. 



5. Name some compounds found in soil. In water. 



6. What is meant by solution ? 



7. What proof have we that living things use the factors of their environ- 

 ment? 



Problem and Project References 



Hunter, Laboratory Problems in Civic Biology. American Book Company. 

 Hunter and Whitman, Civic Science in Home and Community. American 



Book Company. 

 Broadhurst, Home and Community Hygiene, Chap. XVI. J. B. Lippincott 



Company. 

 Burkett, Stevens, and Hill, Agriculture for Beginners. Ginn and Company. 

 Brigham and McFarlane, Essentials of Geography. • American Book Company. 

 Weed, Chemistry in the Home American Book Company. 



