Organic analogy (Parsons)
SYSTEM - Organisms and societies are both self-regulating system of interrelated parts that fit together in fixed ways. In the body, these are cells whereas in society these are institutions (education system, government etc).
SYSTEM NEEDS- Organisms have needs, if these needs are not met, the organism will die. Functionalists see the social system as having basic needs (Eg. adequate socialisation) to maintain social order and survive.
FUNCTIONS - The function for any system is based on the contribution it makes to meeting the system needs, which ensures survival.