Explain how each species in an ecosystem depends on other species

The food chain. At the bottom are the producers which are eaten by consumers which are eaten by secondary consumers and are consumed by tertiary consumers or apex predators. Let's say the apex predator is removed from an ecosystem. That animal is no longer keeping the population of the species under it in check. Which leads to overpopulation of some organisms/species. This creates a snowball effect in that if too much of one thing is in an ecosystem then that species consumes more which means the species that was being consumed it's population decreases. So on and so forth.