Piper accidentally cuts her finger while chopping vegetables. why does she feel pain?

She feels the pain because the signal in her injured finger pick up the message and pass it to the spinal cord, the synapses of neuron within the spinal cord pass the message to the thalamus region of the brain which then relay the message to various areas of the brain's somatosensory cortex, which then send pain signals back to the hand. 

Interacting group of various species in a common location. for example, a forest of trees and undergrowth plants, inhabited by animals and rooted in soil containing bacteria and fungi, constitutes a biological community.