why could it be a serious problem if a consumer organism that had no predators...

[miguel]

...was introduced into the system? Based on the food web interactions you just determined, why could it be a serious problem if a consumer organism that had no predators was introduced into the system? (This sometimes occurs when non-native organisms are released from captivity.)

 

[sndMan79]

a consumer (predator) organism with no natural enemies [predators on it] would continue to flourish unchecked until its food source is exhausted, at which point the population will collapse.

The effect of this on other organisms which consume the same food source is to collapse their populations as well due to a lack of the [common to both or all] food source. Note that this also applies to the more general case of resources other than food.