THE GROWTH AND SCOPE OF BIOLOGY 21 



Similar animals were grouped together because they were believed 

 to be related through common descent. Concepts of evolution and 

 hence of taxonomy were altered in quite recent times by increasing 

 knowledge of genetics which lies at the foundation of both of the sciences 

 just named. 



These five sciences, morphology, physiology, taxonomy, evolution, and 

 genetics, are the main fundamental divisions of pure biology. Because 

 they are all concerned with living things, they necessarily overlap. 

 Evolution and genetics have much in common, as have both with taxon- 

 omy. Physiology and morphology are not wholly separable, since 

 function cannot exist apart from structure. Yet there is considerable 

 independence among them. It is possible to study morphology without 

 being concerned with the function of the structures involved. One may 

 study genetics without knowing or caring what bearing the discovered 

 facts have on evolution. Taxonomy may — and did for a century — 

 proceed without any relation to evolution, even though that kind of 

 taxonomy would be regarded now as without significance. 



Composite Biological Sciences. — There are several divisions of biology, 

 however, which do not possess this degree of independence, but which are 

 only special phases or combinations of the five named above. One of 

 these is paleontology, the science of extinct animals. Paleontology is 

 only a specialized form of zoology, limited in its scope because it is con- 

 cerned only with fossil types, not with living animals. It deals largely 

 with morphology, chiefly of external features, though internal anatomy is 

 sometimes preserved in fossils. Taxonomy is quite feasible in paleon- 

 tology, since external form of fossils, taken in connection with similar 

 kinds of living animals, is sufficient to indicate probable kinship. Evolu- 

 tion is clearly shown by the differences between fossils of successive 

 geological periods. However, the physiological processes of extinct 

 animals can only be inferred from their structure, and knowledge of 

 genetics is impossible in the absence of detailed comparisons of parents 

 and offspring. Paleontology is thus a limited sort of zoology. 



Ecology, which is a study of the relation of living things to the environ- 

 ment, is likewise a composite of the fundamental biological sciences. 

 The ecologist strives to discover in what ways organisms meet the condi- 

 tions imposed by the world around them. He learns in what situations 

 animals live, and why they are there. He studies the interplay of 

 processes within organisms and processes occurring outside. To some 

 extent this relation to the environment is purely structural ; very largely 

 it concerns function. So far as ecology concerns the organisms them- 

 selves, therefore, it is but a combination of morphology and physiology. 

 The other things with which ecology has chiefly to deal concern the 

 organization of the environment. This latter phase of ecologj^ is not 



