How does your body respond to loud noises? is this an internal or external stimulus?

I know this is really late but loud noises are an external stimulus and your body responds by usually covering your ears or if it is sudden you react by jumping or something.

Explanation:

c.) polymerase chain reaction

- "unlike the original dna fingerprinting method, dna profiling does not use restriction enzymes to cut the dna. instead it uses the polymerase chain reaction (pcr)? to produce many copies of specific str sequences. pcr is an automated procedure that generates lots of copies of a specific sequence of dna."

not only is it colder, it also becomes darker, less salty, and more dense.