Carbon dioxide and hydrogen monoxide
Feeling pain, hunger, thirst, sleepiness, and being aware of our thoughts and emotions are all examples of Internal stimuli.
Hierarchy - I don’t think I have the full context of the question but the word fits the best of its biology related
Bioaccumulation refers to the accumulation of a toxic chemical in the tissue of a particular organism.
Biomagnification refers to the increased concentration of a toxic chemical the higher an animal is on the food chain.
