Resistance mechanisms refer to the ways in which organisms or cells evolve mechanisms to defend against or counteract the effects of external factors, such as drugs, chemicals, or environmental stressors. In the context of biology and medicine, resistance mechanisms often refer to the ways in which pathogens, such as bacteria or viruses, develop resistance to antibiotics or antiviral drugs. This can occur through various mechanisms, such as mutation of target molecules, upregulation of efflux pumps, or acquisition of resistance genes through horizontal gene transfer. Understanding resistance mechanisms is crucial for developing effective treatments and strategies to combat drug-resistant pathogens.