Explain briefly 'rivet popper hyposis' of Paul Ehrlich. 

Paul Ehrlich gave the 'rivet' (species) popper hypothesis' which can be explained as follows: 
(a) An aeroplane has thousands of rivets which are important for joining different parts of the plane. 
(b) Some rivets are more Important (key species) than others because they may be present on a part which is structurally crucial (has major ecosystem function) for aeroplane. 
(c) If a person takes out a rivet from a seat to keep It as a memento (causing a species to extinct): nothing is going to happen to the aeroplane. Even if all the rivets from a seat are taken out by subsequent passengers, the only damage will be the collapse of that particular seat. 
(d) If a person takes out a rivet from the wing of the aircraft (key species), there can be some issue of stability during flight. If all the rivets form the wing are taken out, then the flight will end In a disastrous crash. 
This analogy shows that If an organism is highly crucial for an ecosystem, then its extinction can spell doom for the ecosystem.