7. Plant Life
The plants that can be seen growing all along The Rocinante and other ships are a practically minded solution to the classic science fiction problem of life support.
This hydroponics approach, the concept of which is based on recent and ongoing research into plants in low gravity environments, is another example of how the series takes expected tropes of the genre and re-imagines them with realism in mind.
Where a show like Star Trek would have an artificial system of air recycling, The Expanse utilises the natural effects of photosynthesis to produce oxygen for its vessels. Men like Praxideke Meng fill the role of life support technician; as botanists their work can be the difference between life and death on a ship like The Rocinante.
Replacing and maintaining plants is also a whole lot easier than getting new parts for a complex artificial life support system, and finding the fertiliser for it isn't too hard either.
Just ask Matt Damon when he gets back from Mars.