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Animals Without Backbones

The simplest invertebrates, or animals lacking backbones, are single-cell algaeprotistsspongesbacteriaSelect your answer. The sponge’s hollow placebodysymmetrypartsSelect your answer has neither bones nor symmetrywastebacteriapartsSelect your answer. A sponge’s body has a jellylike substance between its bacteriapartstwo-cellbodySelect your answer layers. Holes allow food and water to flow in and water and wastebacteriasingle-cell algaeprotistsSelect your answer to flow out. It eats many small organisms, including wastebacteriaspongespartsSelect your answer, partssingle-cell algaewastespongesSelect your answer, and two-cellwasteprotistsspongesSelect your answer. Young sponges move around searching for a(n) protistspartsplacesymmetrySelect your answer to settle. Sponges are able to grow back missing partsbacteriabodytwo-cellSelect your answer.