Question

what will happen if we kill all the organisms in one tropical level

Answer 1

If we kill all the organisms in one trophic level, then transfer of energy as well as matter tonext higher level will stop. It will lead to over- population at one particularlevel causing amongst the individuals. This wouldseriously disturb the food chain and can cause the collapse of an ecosystem even.
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Answer 2

if all the organisms of a trophic level will killed then the organisms of lower tropic level will increase their population and the organisms above the trophic level will die due to scarcity of food and this leads to the embalanceing of ecosystem.