Flatworms are the Most Primitive Animal Phylum to Have

Question

Flatworms are the most primitive animal phylum to have:
A) asymmetry.
B) radial symmetry.
C) organs.
D) a circulatory system.
E) muscle tissue.

Accepted Answer

Flatworms are the most primitive animals that have organs. They have simple organ systems, such as a digestive system, nervous system, and excretory system.

Answer: E
 Flatworms have muscle tissue that allow them to move and prey on other organisms. However, they do not have a well-developed circulatory system, and their level of symmetry varies among different groups.