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.
These animals possess three living cell layers (i.e.: ectoderm, mesoderm, and endoderm) which makes them triploblastic. The platyhelminths, or flatworms are an economically important group because they include the parasitic tapeworms and flukes, which affect both humans and the livestock we depend on. These acoelomates are advanced over other radiate animals in several ways: 1. Their bilateral symmetry adapts them for direct movement. 2.