PROBLEM 111 



129 



How does it get to the plant? Does the plant use oxygen as the 

 animal does? 



Conclusion. — 1. How are plants able to store up energy? 

 Where does it come from? What becomes of it? 



2. Explain the carbon cycle. 



3. Explain the oxygen cycle. 



Problem 110 : To find out the course of nitrogen in its rela- 

 tion to plants and animals. 



Method. — Begin at the point of the diagram marked " Free 

 N," following the direction of the arrows. 

 Observations. — What 



k Animal Life 



ising Bacteria 



" free 

 is it 



do we mean by 

 nitrogen''? Where 

 found? How do green 

 plants get the free nitro- 

 gen? In what form does 

 the nitrogen get into the 

 animal body? In what 

 form does the nitrogen 

 leave the bodies of ani- 



&S^ Urea* 

 'Animal Life De 



3tes-*-"Nitric Bacteria 



mals ? What causes this material and the dead bodies of animals 

 to become usable by plants? Does any nitrogen get back into 

 the atmosphere again ? If so, how and when ? Look this up in 

 any good book of reference. 



Conclusion. — 1. Fill out a summarizing table like the accom- 

 panying. 



2. In your notebook 

 explain in a well-writ- 

 ten paragraph what is 

 meant by the nitrogen 

 cycle. 



Problem 111: To prove a hay infusion is an unbalanced 

 aquarium. 



Materials. — Hay, glass jar, microscope, glass slides, cover 

 glasses, and pipette. 



HUNTER LAB. PROB. — 9 



