what is it in the worms that makes them parasitic how have they evolved to become parasites?

Question: what is it in the worms that makes them parasitic how have they evolved to become parasites?
- Keywords:
  evolvution,
  parasite,
  worm
Asked by tash to Anouk, Chris, Judith, Leisha, Seyyed on 20 Jun 2012.
- Anouk Gouvras answered on 20 Jun 2012:
  
  aah tash, you have just asked the million dollar question in my field of research! how and why did parasitism evolve?!?
  
  Scientists are still researching this question, the more we research parasites the more we start to understand them which is good. But also the more theories develop. There is probably no one answer.
- Chris Kettle answered on 20 Jun 2012:
  
  great question – and great response!!!!
- Judith Sleeman answered on 21 Jun 2012:
  
  Yes, huge question, with far-reaching consequences for health and agriculture. Perhaps you’ll be the one to answer it in the future, tash?

Question: what is it in the worms that makes them parasitic how have they evolved to become parasites?