Resources are one of two categories - work resources or material resources.
Work resources are things required to do the work and whose availability
effects the schedule. If you're filming a movie and have 3 cameras, those
are work resources, and their number limits you to filming at most 3 scenes
at once- you just don't have enough cameras to film 4 scenes. If buildings,
cages, etc are resources at all, they are probably of that type - you can
only run 10 tests at once because you only have 10 cages for the test
critters and you can only put 1 critter in each cage. Materials are things
that are either physically incorporated into the task's deliverable or are
used up in doing the task. In my movie, film is a material (when exposed it
is the deliverable the task creates) as is fuel for the generator powering
the lights (burned up when the lights are on for a shot). In your scenario,
a material resource might be the food for the test critters. Cages=work
resource, food=material resource.