5. Describe three characteristics shared by all members of the phylum Cnidaria.

Members of the phylum Cnidaria share several key characteristics. Here are three of them: 1. **Radial Symmetry**: Cnidarians exhibit radial symmetry, meaning their body parts are arranged around a central axis. This allows them to interact with their environment from all directions, which is particularly advantageous for their lifestyle as many are sessile (attached to a surface) or free-floating. 2. **Cnidocytes**: Cnidarians possess specialized cells called cnidocytes, which contain stinging structures known as nematocysts. These cells are used for capturing prey and for defense. When triggered, nematocysts can inject toxins into other organisms, allowing cnidarians to immobilize or deter predators. 3. **Two Body Forms**: Cnidarians typically have two distinct body forms: the polyp and the medusa. The polyp is a sessile form that is usually cylindrical and attached to a substrate, while the medusa is a free-swimming form that is bell-shaped. Some species can alternate between these two forms during their life cycle. These characteristics are fundamental to the biology and ecology of Cnidarians, influencing their behavior, feeding, and reproduction.