Mutations and rearrangements that occur by misalignment during DNA replication are frequent sources of genetic variation in bacteria. Dislocations between a replicating strand and its template at repetitive DNA sequences underlie the mechanism of these genetic events.
Cnidarians take on two basic forms, a medusa and a polyp. The medusa form is a free-swimming structure which consists of an umbrella-shaped body (called a bell), a fringe of tentacles that hang from the edge of the bell, a mouth opening located on the underside of the bell, and a gastrovascular cavity. The mesoglea layer of the medusa body wall is thick and jelly-like.
The aquatic Phylum Cnidaria includes coral, hydra, jellyfish, and anemones. Cnidarians occur in two very different body forms, the medusa form and the polyp form. The typical jellyfish is often found in its medusae form. They usually occur in bell-shaped bodies lacking a true head and organs, but they are able to swim or float freely. Cnidarians in the polyp form include coral, hydra, and anemones. Polyps are sessile creatures meaning they are permanently attached to substrate and feed only when prey flows through their tubular bodies.