The Peripheral Nervous System consists of nerves and ganglia. Nerves are nothing more than bundles of parallelly arranged nerve fibers surrounded by connective tissue. Each of these fibers is formed by an axon and the sheaths surrounding it. The ganglia, in turn, are accumulations of neurons, which usually form spherical structures, are located outside the central nervous system and are also linked by axons bridges.
A theory of evolution that states that a species evolves in spurts of rapid change and then goes through periods of no change is known as <span>punctuated equilibrium.</span>
