biology vs zoology

biology

noun
  • The structure, function, and behavior of an organism or type of organism. 

  • The study of all life or living matter. 

  • The living organisms of a particular region. 

zoology

noun
  • The part of biology relating to the animal kingdom, including the structure, embryology, evolution, classification, habits, and distribution of all animals, both living and extinct. 

  • A treatise on this science. 

How often have the words biology and zoology occurred in a corpus of books? (source: Google Ngram Viewer )