Question

Students were asked to differentiate the following organisms based on the number of germ layers involved in their development.

The organisms are
(i) Spongia (ii) Hydra (iii) Planaria (iv) Starfish

Choose the correct answer with respect to the germ layers of the organisms.

• A. Spongia and Hydra are triploblastic.
• B. Starfish and Spongia are triploblastic.
• C. Starfish is triploblastic and Spongia is diploblastic.
• D. Planaria is diploblastic and Hydra is triploblastic.

Answer 1

The correct option is C Starfish is triploblastic and Spongia is diploblastic.

Germ layer is the layer of cells formed during the embryo development and arranged into the embryonic layer external and internal. If and the organism has three germ layer like ectoderm, mesoderm and endoderm are called as triploblastic and if and the organism has only two layers ectoderm and endoderm is called as diploblastic. Starfish is triploblastic because they are a part of the phyla Echinodermata and its organs are developed from the mesoderm layer. Spongia and hydra are diploblastic as they possess only an ectoderm and an endoderm, around its body cavity (stomach). Planaria is triploblastic.