Why has the worm adapted / got 5 hearts?

Question: Why has the worm adapted / got 5 hearts?
- Keywords:
  biology,
  heart,
  worm
Asked by anon-202379 to Rebecca on 4 Mar 2019.
- Rebecca Gosling answered on 4 Mar 2019:
  
  Worms hearts aren’t as clever or as strong as ours so they cannot pump the blood as far. Therefore they need more to do the work.

Question: Why has the worm adapted / got 5 hearts?