isthmus,”- land bridge-Physically, the Middle and South America regionconsists of Mexico, which geologically is part of theNorth American continent, the isthmus (land bridge)of Central America

isthmus,”- land bridge-Physically, the Middle and South America regionconsists of Mexico, which geologically is part of theNorth American continent, the isthmus (land bridge)of Central America

and the continent of SouthAmerica.”