You need to add the choices in order for someone to answer this question...
The correct answer is option d, that is, neurotransmitters.
A neurotransmitter refers to a chemical component, which is discharged at the terminal of a nerve fiber by the introduction of a nerve impulse, and by diffusing across the junction or synapse. It helps in the transfer of the impulse to another muscle fiber, nerve fiber, or some other composition. Acetylcholine is a kind of neurotransmitter, that is, used by neurons in the CNS and the PNS in the control of activities ranging from heart rate and muscle contraction to digestion and memory.
The correct answer that would best complete the given statement above would be the term ADAPTIVE RADIATION. African cichlids are a group of closely related fish species. There are at least 500 known species living in three small lakes. Over time, specialized teeth and body colorations have evolved for each species in response to mutations and competition for food and mates. This change over time is an example of ADAPTIVE RADIATION. Adaptive radiation by definition, is <span>the diversification of a group of organisms into forms filling different ecological niches.</span>
