What will happen to an ecosystem if:
a. All producers are removed.
b. All organisms of herbivore level are eliminated; and
c. All top carnivore population is removed
(a) If all producers are removed from the ecosystem, primary consumers will die due to lack of food. In turn, the secondary and tertiary consumers will also become extinct as they will also lose their source of nutrients. Essentially, the ecosystem will end.
(b) If all herbivores (primary consumers) are eliminated from an ecosystem, secondary and tertiary consumers will die due to lack of food. Plants (producers) will see an exponential growth for some time, but as other biotic factors are absent, the biogeochemical cycle will stop. All of this will lead to the end of the ecosystem.
(c) If all carnivores (secondary and tertiary consumers) vanish from the ecosystem, the population of herbivores will see an exponential growth. Their nutrient requirement will lead to overgrazing and the plant(producer) population will die. Eventually, the decreasing population of producers will be unable to support the nutrient requirement of herbivores and they will also die due to starvation.