Dear Student
If one organism forms food for different organisms in the ecosystem, there will be a lot of competition among those organisms for food. Competition may lead to extinction of any group of organisms who are dependent for food on one particular organism.
If the organisms itself is the food for the other organisms , then the organism itself may get wiped off from the ecosystem.
This will disturb the ecosystem as all organisms of the ecosystem are important for its proper functioning.
If any one species gets wiped off, one level of ecological pyramid will be disturbed and may disturb the organisms at all levels of the pyramid.
Regards