These are the frequency domain frequency manipulating concepts. Pole at 50 Hz, Zero at 500 Hz, Pole at 2120 Hz. In this manner, a pole or zero is modeled as a straight line whose slope is 6 dB per octave. 4 octaves away etc. 2 Complex poles.
Impedance increases away from resonance.
2 Complex Poles. Impedance decreases away from resonance. The issue with an accumulated 180 degree phase shift is that 180 degrees phase shift transforms the negative feedback into positive feedback.