| A | B |
|---|
| Aquatic animals that strain floating plants and animals from the water they take in are | filter feeders |
| Many small aquatic organisms move oxygen and carbon dioxide through their skin by the process of | diffusion |
| Sponges benefit some marine animals by | providing a habitat |
| Cnidocytes help a cnidarian survive by | paralyzing prey |
| Whicha are the simplest animals to have body symmetry? | cnidarians |
| Which two functions do nematocysts perform? | defense and capturing prey |
| A characteristic of cnidarians is that they are | carnivorous animals |
| Cnidarians have two basic body types, a medusa and a (an) | polyp |
| The body symmetry of a cnidarian is | radial in both the medusa and polyp stages |
| How do polyps differ from medusas? | Polyps are clyindrical and usually sessile, and medusas are bell-shaped and motile. |
| The nerve cells of cnidarians make up a (an) | nerve net |
| In jellyfishes, the medusa stage reproduces | sexually |
| Many cnidarians can live only in bright light because they depend on | symbionts for energy |
| Fod enters a flatworm's body cavity through a muscular tube called a (an) | pharynx |
| Most free-living flatworms are | hermaphrodites |
| Why don't most parasitic flatworms need a complex digestive system? | They obtain nutrients from food that has already been digested by their host. |
| Roundworms have a | one-way digestive tract |
| Roundworms have a digestive system. | with two openings. |
