In a forest ecosystem of Grass → Impala → Hyena, if all the Hyenas are taken away, what will happen ultimately?

The correct answer is D, Impala will die of starvation due to higher population. In this food chain grass is the producer, the impala is the herbivore and the hyena is the predator that keeps the impala population in check. If all hyenas are removed, impalas multiply quickly because nothing hunts them. The larger herd overgrazes the grassland until there is not enough food, and then many impalas starve and their numbers crash. This chain reaction, where removing a top predator upsets every level below it, is called a trophic cascade. It is also why predators such as tigers are protected: they keep an ecosystem in balance. A is wrong because without predators the impala population cannot stay stable; it first rises sharply. B is wrong because the impalas' good time lasts only until the grass runs out. C is wrong because the grassland is the first to suffer, from overgrazing. Exam tip: remove the predator, the prey multiplies, food runs out and the prey starves; only about 10 per cent of energy passes to the next level.