What did darwin use to describe the ability of an individual to survive ?

Darwin believed in Darwinism which is a theory of biological evolution stating that all species of organisms arise through a process called natural selection to compete, survive, and reproduce

Neurotransmitters are messengers responsible for communication between neurons. they are released from synaptic vesicles and are received by receptors.  the communication is referred to as neurotransmission. the following statement is true about neurotransmitters: a. they're stored in synaptic vesicles in the axon.