how can flatworms and roundworms do function when they dont have organs

Asked by adityajhasaby0107 | 16th Nov, 2015, 03:24: PM

Expert Answer:

For Flatworms:

      1.   Respiration
  • Free-living forms respire through the body surface.
  • Parasitic flatworms are anaerobes.
      2.   Circulation
  • The circulatory system is absent.
      3.   Digestive Tract 
  • The digestive tract is incomplete, i.e. without an anus. However, a muscular suctorial pharynx and highly branched intestine are present.
      4.   Excretion
  • They are ammonotelic.
  • They possess protonephridia which contain flame cells.
      5.   Skeleton
  • They do not have any skeleton.
  • Some flatworms have a cuticle which protects their body from the host’s digestive juices.
      6.   Nervous System
  • It consists of the brains and two longitudinal nerves.
  • Both nerves are connected at intervals by transverse commissures.
  • Hence, the nervous system appears ladder-like.
      7.   Reproduction
  • Asexual reproduction is by transverse binary fission.
  • Possess highly developed reproductive organs.
  • All flatworms are hermaphrodites, except Planaria which is a unisexual animal.
 

For Roundworms:

      1.   Respiration
  • A respiratory system is absent.
      2.   Circulation
  • A circulatory system is absent.
      3.   Digestive Tract
  • The digestive tract is complete.
  • Shows the presence of the muscular pharynx.
      4.   Nutrition
  • Parasitic and found on plants and in animals.
      5.   Excretion
  • Excretion is carried out by a large H-shaped renette cell.
      6.   Skeleton
  • Skeleton is absent.
      7.   Nervous System
  • A circumpharyngeal ring is present from which nerves arise forward and backward.
      8.   Reproduction
  • Sexes are separate.
  • Show sexual dimorphism. The male is smaller than the female, and its posterior end is curved.
  • Asexual reproduction is absent.

Answered by Hemangi Binny | 16th Nov, 2015, 03:55: PM