Which group includes invertebrates with soft bodies and bilateral symmetry, some of which are parasites?

The group that includes invertebrates with soft bodies and bilateral symmetry, some of which are parasites, is worms. This classification encompasses a diverse array of organisms, including segmented worms and roundworms, many of which exhibit bilateral symmetry and have soft, elongated bodies. Worms play various roles in ecosystems and can be found in numerous habitats.

In terms of parasitism, certain types of worms, such as nematodes and some flatworms, have adopted parasitic lifestyles, feeding off hosts and affecting their biology. This characteristic of having parasitic species is significant for understanding ecological relationships, human health, and agricultural impacts.

Other groups like crustaceans and mollusks don't fit this description as effectively. Crustaceans have hard exoskeletons and generally display different body plans and symmetry. Mollusks do have soft bodies, but they mostly do not exhibit parasitic behavior. Flatworms are actually a subset of worms, specifically known for their flat bodies and can include parasites, which is why they are a related concept but do not encapsulate all types of worms in general.