Answer:
All mammals, like dogs, cats, and humans; reptiles, amphibians, fish, birds, and even insects.
Explanation:
All mammals, like dogs, cats, and humans; reptiles, amphibians, fish, birds, and even insects are the animals that have a complete tube-like gut with two openings. A system having a tube with two openings i.e. mouth and an anus is called tubular system. In this tubular system, the animals eat with one opening and the other opening is used for excretion of waste and nitrogenous materials from the body so that's why most of the animals have two openings.
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.
Do you want the definition ?
By assembling the rocks into parts of a bigger rock that might have eroded over time.
Offspring will be heterozygous expressing the dominant trait.
Hope this helps.