Herbivores and Carnivores

The grasslands of Africa are covered in grasses and other plants.
Between periodic droughts, there is usually plenty of sunlight, carbon dioxide, and water for these plants to grow and make their own food.
Herds of antelopes feed on the plants.
But a herbivore such as an antelope stores only about 10-20 per cent of the energy from its food.
About 80-90 per cent of the energy is used by the antelope to carry out life functions.
Small groups of lions prey on the antelopes.
When a carnivore such as a lion eats a herbivore such as an antelope, the carnivore gets only the 10-20 per cent of energy stored in the body of the herbivore.
The farther along the food chain you go, the less stored energy there is available.
This means there must be many more antelopes than lions.
Similarly, there must be many, many plants to support the antelope population.