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LIVES OF PLANTS AND ANIMALS 



U. S. Forest Service 

 In places where the rainfall is sufficient we may find the ideal combination of farms and forests. 



prey upon our deer and he is protecting useful birds which prey 

 upon harmful insects. Man is probably making more changes 

 in life on the earth than any other living factor. But, on the 

 whole, his influence is beneficial, as we will see in the units which 

 follow. 



Practical Exercise 6. What is a parasite ? Give three examples other than 

 those stated in the text. 



Practical Exercise 6. How could a student become a parasite in the school ? 

 Explain. How might you become a parasite at home ? How can you avoid 

 •this? 



Practical Exercise 7. Look up the term saprophyte. How does it differ 

 from a parasite? Give examples of each in your environment, if possible. 



Self-Testing Exercise 



A (1) exists in (2) between organisms living in a 



region. Many (3) prey upon others, using them as (4) 



and thus holding them in check. Man has often (5) this balance 



by (6) new (7) or (8). 



PROBLEM V. HOW DO THE FACTORS OF THE ENVIRONMENT 

 AFFECT ECOLOGICAL RELATIONSHIPS? 



Ecology is the study of plants and animals in relation to their! 

 natural surroundings. Living things can be shown to be affected 



