BIOLOGY: THE SCIENCE OF LIFE 3 



life and all living things plants, animals, and man. There 

 are two subdivisions of biology; namely, zoology, treating 

 of animals, and botany, treating of plants. Zoology is often 

 called animal biology, and botany, plant biology. The division 

 of biology into botany and zoology does not mean that plants 

 and animals are entirely unlike; but, on the contrary, we 

 shall find later that these two kinds of living things have 

 many points of remarkable similarity in both structure and 

 activities. This similarity is especially striking in many 

 microscopic living things which so combine both plant and 

 animal characteristics that biologists have not decided 

 whether they are animals or plants. But although there is 

 often a great similarity between animals and plants, it is 

 sometimes convenient to study the two kinds of living things 

 separately, and so biological science is subdivided into 

 botany and zoology. These two subdivisions of biology 

 are most important for advanced students; but the best 

 and most interesting beginning study is that which directs 

 attention to the great facts common to all living things. 

 Hence this book for beginners is called " Biology," to indicate 

 that it uses both animals and plants to illustrate facts and 

 ideas which are true of all living things. 



5. Applied Biology. More important than the similarity 

 of animals and plants is the fact that many animals are in 

 structure and activities very much like the human body; 

 and hence the study of animals and plants helps us to under- 

 stand better the human body and its life-activities. More- 

 over, thousands of animals and plants profoundly affect 

 human life. For example, they provide all the food-supply 

 for mankind ; many harmfully influence human health ; 

 and some, such as pet animals and ornamental plants, 

 contribute much to the pleasures of life. Clearly, some 

 knowledge of the science of living things ought to be of 

 great interest to educated citizens, because it applies in so 

 many ways directly or indirectly to human life. Recogniz- 



