Neurotransmitters is the word you're looking for.
These reactions are METABOLISM.
Natural selection means that the organisms better adapted to their environment, that is, they have developed the right characteristics/skills/response to the external ambient, have higher chance to survive, making the next generations genetically inherit such acquired surviving characteristics.
These generations will thus have a higher chance of survival, making these species being "naturally selected" as survivors, while those who haven't or are slower in this process, have a higher risk of elimination.
Answer:
A name used by scientists, especially the taxonomic name of an organism that consists of the genus and species.
Explanation:
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