The vertebrate endoskeleton is internal while an arthropod's exoskeleton is not
The answer is “The Nervous System”
Endosymbiosis
that is my explanation hopefully its right
answer:
plasma membrane a microscopic membrane of lipids and proteins which forms the external boundary of the cytoplasm of a cell or in closes a vacuole, and regulates the passage of molecules in and out of the cytoplasm
answer number 2
the plasma membrane or cell membrane, is the phospholipid layer that surrounds the cell and protects it from outside environment.
you can use either answer if you have to type or write an answer
A) unproductive wastelands I believe is the answer you are looking for.