In geophysics the refraction or reflection of seismic waves is used for research into the structure of the Earth's interior, and man-made vibrations are often generated to investigate shallow, subsurface structures.
Flatworms are considered acoelomate, since they have no body cavity, and roundworms are pseudocoelomate because they have a body cavity, but it is not derived from the splittiâ¦ng of the mesoderm tissue. Also, flatworms only have one opening in their digestive system unlike roundworms with two.
Segmented Worms. Roundworms. Flatworms. Phylum Annelida. Phylum Nematoda. Phylum Platyhelminthes. Segmented/sectioned bodies, bilateral symmetry . Bilateral symmetry. Bilateral symmetry, flat and thin bodies. Moist soil, freshwater, or saltwater . Wet soil or water. Parasitic- live inside a host or in water. Complete digestive tract- 2 openings (mouth and anus)