PART m. GENERAL RELATIONS BETWEEN PLANTS 



AND ANIMALS 



CHAPTER X 



THE SIMPLEST ORGANISMS 



Problems: To study the simplest plants and animals and find in 

 what ways they are alike and different. 



To find out where they live and how each performs some of the 

 functions necessary to life. 



To understand what is meant hy the " cell as a unit.^' 



Laboratory Suggestions 



Laboratory study. Study of pleurococcus, or any unicellular green plant. 

 Laboratory study. Study of amoeba or Paramecium. 

 Laboratory study. To make a hay infusion. 



The Simplest Organisms. — The preceding division of this book 

 has shown us that green plants are food-building organisms ; that, 

 as such, they are of the greatest value to mankind. They are 

 also living organisms, for they breathe, take in food, digest it, pass 

 it through the body so that all parts may have nourishment and 

 throw off waste materials. The fact that they manufacture the 

 organic food substances for themselves makes them different from 

 animals. 



Some plants, however, are not green and so do not make their 

 own food. Such are the many examples of fungi (fun-ji) which 

 live in forests or fields, or which, in the form of common molds, are 

 household pests. Our previous study of science has given us some 

 knowledge of ^' germs " or bacteria, the lowest form of colorless 

 plant. 



As a matter of fact, it is extremely difficult for biologists to make 

 any hard and fast distinction between the simplest plants and the 

 simplest animals. There are many single-celled plants and many 

 single-celled animals. If the cell is green, it is not always safe to 



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