450 Our Surroundings 



Food may be preserved by destroying the bacteria it contains. 

 Canning, drying, smoking, pickling and cold storage are methods 

 of preserving food. 



Disease bacteria are destroyed by exposure to strong sunlight, 

 by boiling or burning objects containing them, or by the use of 

 germicides liquid solutions or gases which kill by contact. 



FACT AND THOUGHT QUESTIONS 



1. What are bacteria? 



2. Give the characteristics of bacteria. 



3. Describe an experiment to show the growth of bacteria on a sterilized 

 substance. 



4. Mention ways in which bacteria are useful. 



5. Mention ways in which bacteria are harmful. 



6. How may bacteria be destroyed? 



7. Describe the canning of fruit, giving the reason for each step in the 

 process. 



8. Name several dried foods you have eaten. 



9. Why does cold storage preserve foods? 



10. Is it healthy to have very heavy shade close around a dwelling? Why? 



11. What services do nitrogen-fixing plants render the farmer? 



12. Name three ways of preserving and protecting food used in your own 

 home. 



13. How might you protect and preserve food supplies in a woods camp? 



PROJECTS 



1. After sweeping a room place a little of the dust on sterilized agar-agar 

 in a sterilized Petri dish, set aside, observe daily, note and record 

 changes. 



2. Using the compound microscope examine prepared mounted specimens of 

 bacteria. Describe what you see. 



3. Study the public food regulations of your community and prepare a 

 brief abstract of them. 



OUTDOOR OBSERVATION 



On your way to and from school observe and note natural breeding 

 places of bacteria, and unsanitary conditions from the bacteria standpoint, 

 that might easily be remedied. 



REFERENCES 



Story of Bacteria Prudden 



The Story of Germ Life Conn 



Civic Biology Hodge and Dawson 



Applied Biology Bigelow 



