2 BIOLOGY 



animals and plants. The question whether the activities of 

 animals and plants can be explained by the same forces found 

 elsewhere in nature, and the attempt to answer this question 

 in the affirmative, form the basis of the new science of biology. 

 Modern biology is thus something more than the study of 

 animals and plants as dead objects to be collected, named, 

 and classified. It is a study of animals and plants in action; 

 as living beings to be related to their environment. It is this 

 attempt to explain life processes which may be said to have 

 raised biology to the rank of a new science. 



THE FUNDAMENTAL PROPERTIES OF LIVING THINGS 



Distinction between the Living and the non-Living. Since 

 biology (Gr. bios = \iie -\-logos = discourse) is the science of living 

 things, we must first ask how living things may be distinguished 

 from non-living. While it is a comparatively easy matter to 

 recognize the distinction, it is difficult to draw it sharply. 

 Indeed, some biologists are of the opinion that no rigid line 

 can be drawn, and that there are some states of matter which 

 are halfway between the living and the non-living. Whether or 

 not this be so, it certainly is true that between most forms 

 of matter which we call alive and those which we call non- 

 living, there is a marked and recognizable difference, although 

 it may be difficult to define it accurately. Four or five fun- 

 damental properties are characteristic of life: 



1. Activity. The most noticeable difference between the 

 living and the non-living is in the presence or absence of spon- 

 taneous activity. If we wish to find out whether any given 

 body is alive, we watch it carefully to see if it shows any power 

 of independent activity, and if it does so, we call it alive. If 

 the object, a seed for example, seems to be perfectly dormant, 

 we may put it under conditions in which, if alive, it will 

 develop activity. If it then begins to grow into a plant we say 

 that the seed was alive at first but dormant. If, however, it 

 fails to show any power of developing into a plant when placed 



