When the body responds to a relatively harmless substance as if it were a dangerous pathogen and mounts an immune response, this response is called?

This response is known as infection. This is very common in wounds and scratches that occur on the body when not immediately treated. The body's white blood cells attack invading elements that come from the outside environment and immediately assumes that all organisms are viruses that needed to be attacked.

Fossil found in strata reveal that unused body part decrease in size

No that answer is wrong. you have written the function of mitochondria in chloroplast and function of chloroplast in mitochondria.