Dopamine is a chemical released by neurons to send signals to other nerve cells. the brain includes several distinct dopamine pathways, one of which plays a major role in reward motivated behavior.
smoking is a habit, in a habit there is the cue, routine, and reward. with smoking the cue can be different things, most commonly stress or anxiety. the routine how you react to those cues, the reward is the chemical 'triggers' that are pulled inside you're brain leaving you feeling calm, happy, or relieved, etc.
Answer:
animals would be your awnser you are welcome
Explanation:
The best answer would be "research reasons why species change over long periods of time"
if not i apologize but this is my best guess<span />
A mystery organism is non living
