abiotic (无生命的)
Nonliving materials in the environment—such as elements, sunlight, and soil—that influence and are influenced by living (biotic) entities on the planet.
Acetylcholine(乙酰胆素): 运动神经释于一种化学物质,与其接受体结合后，能产生足够的电位变化来引起肌肉运动
A neurotransmitter released from the axons of nerve cells to excite an action potential or trigger a muscle to contract.
active immunity(主动免疫)
Protective immunity to a disease in which the individual produces antibodies as a result of previous exposures to the antigen.
Acids(酸)