Life Support
  Air, Water, and Nutrition
  Waste Management
  Mental Health
  Suits
  Radiation and Zero-G

Habitat On Mars
  Power
  Structure
  Daily Routine

One Person, One Day, in Space*
Inputs 1.4 pounds of food (dry weight) 7-9 pounds of water 2 pounds of oxygen	Outputs 3.3 pounds of urine 4.0 pounds of metabolic water 2.2 pounds of carbon dioxide .4 pounds of solid waste

 
 
Now, the main questions are: how do we provide the input and how can we recycle the output to create input?

Life Support, both in space and on Mars, can be designed similarly and the same systems will, for the most part, be used in both places. Essentially, we have to send everything the astronauts will need with them, as space is obviously devoid of resources and Mars, as of now, cannot be relied upon to provide anything. Now, to get an idea of the magnitude of that task, look at the figures -- per person per day. Multiply that by the number of people (6) and the number of days (about 200, last I heard), make your calculations, and you have whopping numbers appearing everywhere, from storage volume to amount of fuel to weight. From this stems the governing concepts for designing life support, something you have, no doubt, heard before: Reduce, Reuse, Recycle.  
 
* Shipman, Harry L. (1989). Humans in Space. New York: Plenum Press.