List several ways in which obelia differs from hydra

Hydra and Obelia are cnidarians (species of aquatic organisms) that belongs to the Class Hydrozoa.  

Several ways in which Obelia differs from Hydra are;

Hydra is a predative species that lives on substrates such as wood, while Obelia is a colonial species that lives as polyps on  branched frameworks.  Hydra is found in freshwater habitats, while Obelia is found in marine habitats. Hydra undergoes the medusa form in its life cycle, while Obelia undergoes the two forms (polyp and medusa) in its life cycle. Hydra has great regenerative powers while Obelia does not have great regenerative powers.