Final answer:
Internal organs are not symmetrically arranged as external body features are, with the heart and liver being examples of asymmetric internal organs that are determined by the central left-right axis during development.
Step-by-step explanation:
Internal organs display asymmetrical internal features rather than external symmetry evident in the overall body plan. While the external form of an animal may show bilateral symmetry, where a single plane can divide the body into two equal mirror-image halves, internal organs such as the heart and liver are not symmetrically arranged. The heart typically lies on the left while the liver is on the right side, and the arrangement of these organs is determined by the central left-right axis during embryonic development.