ENVIRONMENT OF PLANTS AND ANIMALS 23 



and other large animals go to sleep during the winter and awake 

 thin and active at the approach of warm weather. Animals or 

 plants used to certain temperatures are killed if removed from 

 those temperatures. Even man, the most adaptable of all ani- 

 mals, cannot stand great changes without discomfort and some- 

 times death. He heats his houses in winter and cools them in 

 summer so as to have the amount of heat most acceptable to him, 

 i.e. about 70° Fahrenheit. 



The Environment determines the Kind of Animals and Plants 

 within It. — In our study of geography we learned that certain 



Vegetation in Northern Russia. The trees in this picture are nearly one hundred 

 years old. They live under conditions of extreme cold most of the year. 



luxuriant growths of trees and climbing plants were characteristic 

 of the tropics with its moist, warm climate. No one would expect 

 to find living there the hardy stunted plants of the arctic region. 

 Nor would we expect to find the same kinds of animal life in warm 

 regions as in cold. The surroundings determine the kind of living 

 things there. Plants or animals fitted to live in a given locality 

 will probably be found there if they have had an opportunity to 



