Natural object and Physical structure

Natural object noun - An object occurring naturally; not made by man.

Physical structure and natural object are semantically related. In some cases you can replace phrase "Physical structure" with "Natural object", this phrases are similar.

Physical structure noun - The entire structure of an organism (an animal, plant, or human being).

Natural object and physical structure are semantically related. You can use "Natural object" instead a noun phrase "Physical structure".