Describes a medical or surgical procedure which requires the skin to be cut open and/or objects to be inserted into the body. Describes a species which takes over a new habitat where it was not previously found, often to the detriment of species which were there before. Describes a microbe which is able to enter the body of a host organism and move about inside at will. The microbe may or may not cause any diseases. Describes a cancerous tumor which is able to destroy surrounding healthy tissue and expand into the area where the healthy tissue was.