My English Teacher gave the following rules that will help us learn how to use take on and take up.
(1) take on
-accept a job, responsibility / to employ, hire somebody
-If a vehicle such as a bus or ship takes on passengers, goods, or fuel, it stops in order to allow them to get on or to be loaded on.
- I can’t take on any extra work, I’m too busy.
- They want to take on ten more assistants.
(2) take up
-start a new sport, hobby, school subject / fill space (or time)/ start again, resume
- When I’m fluent in English, I’ll take up Spanish lessons.
- This cupboard takes up too much space, I don’t want it in my living-room.