\*Life and Protoplasm 



MORE THAN a million and a quarter dis- 

 tinct species of plants and animals are recog- 

 nized in the world at large, and quite a num- 

 ber of newly discovered species are reported 

 every year. Different organisms have evolved 

 a special fitness to live in almost every part 

 of the environment — in the ocean, on land, 

 and in the air — under a wide variety of con- 

 ditions. Certain species thrive on dry rocks 

 and in stagnant swamps; in hot springs and 

 in polar ices; where oxygen is abundant, and 

 even where oxygen is lacking entirely. 



Some organisms appear to be very simple 

 — like microscopic droplets of clear liquid. 

 But other creatures, like man, possess an ob- 

 viously complicated structure. Gigantic liv- 

 ing things, like whales or redwood trees, 



stand in dramatic contrast to the puniest 

 bacterium, which looks like the smallest 

 speck, even under the best magnification of 

 the microscope. In short, a very rich diversity 

 of living creatures has been evolved upon our 

 earth, and man is challenged to reach an un- 

 derstanding of their nature (Fig. 1-1). 



DISTINCTIVE ACTIVITIES OF LIVING 

 BODIES 



Since biology is the group of sciences that 

 deals with life in all its forms and in all its 

 activities, it is necessary to distinguish as 

 clearly as possible between living and non- 

 living bodies. Such a distinction is not usu- 

 ally difficult, because living bodies are apt to 



Fig. 1-1. The size of organisms varies greatly. This whale (a sulfur bottom 

 whale) weighs over 300,000 pounds, and the elephant weighs 20,000 pounds. 

 But it takes more than a trillon tuberculosis bacilli to make one pound. (Redrawn 

 from Organic Evolution, by Lull. The Macmillan Company.) 



