take on vs take over

take on

verb
  • To assume or take responsibility for. 

  • To (attempt to) dribble round (an opposition player). 

  • To catch on, do well; to become popular. 

  • To obtain the services of (a person) in exchange for remuneration; to give someone a job. 

  • To begin to have or exhibit. 

  • To attempt to fight, compete with, or engage with. 

  • To acquire, bring in, or introduce. 

  • To grieve or be concerned (about something or someone). 

take over

verb
  • To adopt a further responsibility or duty. 

  • To become more successful (than someone or something else). 

  • To assume control of something, especially by force; to usurp. 

  • To appropriate something without permission. 

  • To buy out the ownership of a business. 

  • To relieve someone temporarily. 

  • To annex a territory by conquest or invasion. 

  • Used other than figuratively or idiomatically: see take, over. 

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