Question

why loss of one kind of organisms from from a region can harm all the other life forms

Answer 1

Because all organisms are related with each other and that relationship is called food chain and if we take out one organism from it then the whole system is effected.
For ex=If in a food chain there are micro-organisms, grass, deer, tiger and vulture. Now if we take out deer from it then the population of tiger will be affected along with vulture and the grass will in an unstoppable manner. So it is important not to disturb any food chain.