They do the three vital functions
Interaction: have a developed senses and brain
Reproduction: are oviparous and hermaphrodites.
Nutrition: have a digestive system.
They have bilateral symmetry and have a soft body
There are three types of worms
Platyhelmintes or flat worms
Are divited in rings
Are parasites or aquatics free-livings
Annelids or ringed worms
They have a cilindrical body
They reproduce sexually and have cross-fertilization
There are bristles between metameres
Have cylindrical body
Reproduce sexually and have separated sexes