Question

what disadvantage would you face if your backbone is made up of just one long bone?

Answer 1

WE would be never be able to sit, bend move properly.
It will be difficult to pick up a thing fallen on the floor and the most bad thing about it would be that we would be as stiff as a scare-crow!
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hope it helps):-

Answer 2

if your backbone is made up of judt ome long bone bending would be difficult and the would be no protection from shocks and jercks