RESEARCH IN BIOLOGY 17 



Any attempt at classification of problems or areas of inquiry is cer- 

 tain to lead to oversimplification. A more realistic picture of the questions 

 which still face the biologist can be gained by examining some problems 

 as examples. In most of these, all three of the categories above are in- 

 volved. 



What controls the development of an organism? How is it possible 

 that the fertilized egg of a chicken always develops into a chicken and 

 never into a duck? How are the transformations of groups of cells into 

 tissues and organs controlled? The nucleic acid is the hereditary ma- 

 terial, but how does a nucleic acid molecule bring about such profound 

 changes and differences? If nucleic acids control the synthesis of 

 enzymes, what determines when a given enzyme is formed and when it 

 is not? 



How can the cell membrane exhibit such control over what enters 

 and leaves the cell? How is energy utilized to move molecules or ions in 

 what seems to be the vnrong direction, that is, against diffusion gradients? 

 How does a kidney cell sort molecules and ions? How can plant cells 

 continue to absorb mineral ions even after they are more concentrated 

 inside the cells than in the surrounding soil or water? 



How do some cells or organisms measure temperature and time? How 

 can the hypothalamus control temperature so precisely in mammals and 

 birds? How does it measure temperature and what does it use as a refer- 

 ence point? How do plants and animals measure the length of a day or 

 night in order to respond to the seasons? If all the birds in a flock sud- 

 denly change their direction of flight, is it because they have communi- 

 cated with each other or because all have detected the same minute 

 change in environment? 



How do cells convert light energy into useful chemical energy as they 

 do in photosynthesis and in vision? What chemical and physical proc- 

 esses are involved in color vision? 



What is the nature of the specific structure of the minute parts of 

 cells? How are enzymes and other molecules arranged in space to allow 

 sequences of chemical reactions to proceed in an orderly fashion? 



Such a list of questions makes it seem that the biologist does not 

 know very much. The magnitude of some of the questions should make 

 anyone humble, but at least we now know some of the questions. In 

 their attempts to answer these and other questions, biologists have used 

 a great variety of approaches. Some have led to the great progress we 

 have already made; some have ended in frustration. However, biologists 

 are a persistent lot. They continue their attempts with whatever tech- 



