What resources are essential to survival?

Oxygen: (breathing) The most important neccessity for survival.

Water: The average person can survive for three days without water, since the human body is made up of 75% water, you are always needing a constant supply.

Food: Not the first priority, but it is important for survival, the avergae human can go up to weeks without food. However, it is one of the main sources for energy, in some situations, your body may burn more calories than usual, which constitutes a need for energy.

Warmth: Another neccessity for survival, your body needs to maintain an ideal body temperature (homeostasis).

Sleep: Without sleep, your brain may make you hallucinate, which would affect your conscious decisions.