In terms of biology what is the difference between a saturated and unsaturated fat?

 Hi there! I did of a little bit of research about your question and this is what i found:  "Saturated fats are solid at room temperature, while unsaturated fats are liquid at room temperature. This is because saturated and unsaturated fats differ in their chemical structures."

It is evolution, because we all have some of the same traits like eye color or shape or ears.