Question

Difference between Diploblastic and Triploblastic organisms.

Answer 1

Hint: The presence of Triploblastic phenomenon resulted in development of organs in the animal phyla which was absent in diploblastic organisms.

Complete Answer:
> Kingdom Animalia includes many phyla. These are
- Phylum Porifera
- Phylum Colenterates
- Phylum Ctenophora
- Phylum Platyhelminthes
- Phylum Aschelminthes
- Phylum Annelida
- Phylum Arthropoda
- Phylum Mollusca
- Phylum Echinodermata
- Phylum Hemichordata
- Phylum Chordata

> Phylum Porifera is the simplest phyla and Phylum Chordata is the most developed group. There are many characteristic features that are seen developing from Porifera to Chordates which explain the evolution of animals. One such feature is formation of germ layers. Based on the number of germ layers, organisms are either Diploblastic or triploblastic organisms.

Difference between Diploblastic and triploblastic organisms is as follows :

Sl. No	Diploblastic Organisms	Triploblastic Organisms
1.	These consist of two germ layers.	These consist of three germ layers.
2.	The two germ layers are Ectoderm and Endoderm.	The germ layers are Ectoderm, Mesoderm and Endoderm.
3.	Diploblastic organisms show radial symmetry.	Triploblastic organisms show bilateral symmetry.
4.	Diploblastic organisms do not develop organs.	Triploblastic organisms develop organs and organ systems.
5.	Mesoderm is absent between Ectoderm and Endoderm but instead Mesoglea is seen in some.(Mesoglea is an undifferentiated layer).	Mesoderm is seen between Ectoderm and Endoderm.
6.	Examples are jellyfish, comb jellies, etc.	Examples are Worms, chordates, etc.

Note:
-Triploblastic feature was first seen in Phylum Platyhelminthes.
-It is seen in all phyla from platyhelminthes to Chordates.
- Only flatworms are Triploblastic and Acoelomate.
- Phylum Nemathelminthes are Triploblastic and Pseudocoelomate.
- Phylum Annelida to Phylum Chordata are Triploblastic and Coelomates.