When humans farm large plantation of one cash crop, they reduce the biodiversity of the region because they reduce the genetic diversity of the species in the environment. A reduction in genetic diversity means that the genetic variability of the species is reduced hence there are fewer sub-species in the environment. This ultimately reduces the biodiversity of the ecosystem - which is the variability among all the living organisms in the environment.
Hardness is the answer I believe
The nervous system and the integumentary system<span />
