Question

explan the general characterstcs of platyhelminthes and nematoda

Answer 1

PLATYHELMINTHES

• members are  mostly parasite & few are free living
• free living⇒planaria
• drsoventraly flattend body, so called flat warm
• LEVEL  OF  ORGANISATION⇒mostly organ level few organ system
• BODY  SYMMETRY⇒bilateral symmetry (1st appear here)
• GERM LAYER⇒triploblastic(1st appear)
• acoelomet
• blind sac body plan
• DIGESTION⇒exclusively extracellular
• respiratory, skeletal, circulatory system is absent
• flame cells present for excretion and osmoregulation
• flame cells also called flame-bulbs or protonephridia or solenocystes
• chief excretory product ammonia
• ladder like nervous system with ventral cords & brain as well as transverse comminsure
• REPRODUCTION⇒ mostly sexual few asexual
• DEVELOPMENT⇒mostly indirect with various larval forms & in few direct dev.
• members have remarkable power of regeneration

Answer 2

The first triploblastic is Platyhelminthes.

Platyhelminthes :

The body is bilateral symmetrical.

The body is flattened and Ribbon shaped.

It is a leaf like in appearance.

Body cavity is absent.

Digestive system is absent.

Circulatory and respiratory systems are absent.