UNIT II 

 LIFE DEPENDS ON ADAPTATIONS 



PREVIEW 



Every boy or girl who reads these lines has at one time 

 or another kept a pet. Perhaps it was a dog or cat or a 

 bird. Some of us enjoy watching goldfish or the brightly 

 colored tropical fish that are so much seen in the home 

 aquariums today. Some boys keep turtles and find them 

 very interesting pets. We might take a census of animal 

 pets kept by pupils taking science and add many new 

 animals to the list. 



Some of us prefer gardening or the keeping of plants at 

 home. Hyacinths, jonquils, or other bulbs make a fine 

 showing in the spring, while geraniums are always pretty 

 and easy to grow. We may even have collections of 

 strange spiny-covered cactus plants or a "burl" from a 

 giant redwood. But no matter whether you had plants or 

 animals to care for, you must have noticed that each 

 particular living thing seemed to be fitted to live under 

 certain conditions and only under those conditions. Our 

 desert plants grow best in sand and when it is hot and 

 dry like the deserts from which they originally came. 

 Our goldfish would certainly be very unhappy if they 

 were taken out of the water and it would not be long 

 before they were dead. Our pet canary would be equally 

 unhappy if we tried to keep it in a screened tub of water. 

 Even our pet dog or cat would resent a change of living 

 from the conditions to which it was used. 



Wherever we go, we are constantly seeing examples of 

 the fitness of living things to succeed in the places where 



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