Hydra is a solitary species and lives attached to substrates, whereas Obelia is a colonial species and lives as polyps in an interconnected branching network. Hydra live in freshwater habitats, whereas Obelia is exclusively marine.

What are the structural differences between Obelia Hydra and jelly fish?

Obelia is a form of hydrozoans that have branched stalks. Also, the dominant phase of the life cycle of Obelia is the polyp. However, the polyp form of Obelia is very small. On the other hand, a jellyfish is a form of cnidarians whose dominant phase of the life cycle is a medusa, which is comparatively large.

What is not common among Hydra Aurelia and Obelia?

Complete Answer:

Hydra shows only asexual mode of reproduction via budding. ... As polyp represents the asexual form while the medulla represents the sexual form, it is quite evident that the metagenesis is common in Obelia. Therefore, this is the incorrect option.