A keystone (or capstone) is the wedge-shaped stone at the apex of a masonry arch or typically round-shaped one at the apex of a vault. In both cases it is the final piece placed during construction and locks all the stones into position, allowing the arch or vault to bear weight.
Why are they important in maintaining the balance in an ecosystem?
Favorable ecosystem ensures that each organism thrive and multiply as expected. They get enough food to keep them alive. Ecological balance is also important because it leads to the continuous existence of the organisms. ... In addition, ecological balance ensures the stability of the organisms and environment.
