What will happen if one organism from the food chain is removed?

A food chain is composed of interrelated organisms. In other words, different organisms that constitute the food chain are dependent on each other. An example is a food chain in a grassland, where the grass is eaten by deer (an herbivore) and the deer are eaten by a carnivore, such as a wolf. If one of these organisms is removed, the food chain is severely impacted. For example, if all the deer die due to some sudden calamity (such as a disease), this will result in a lack of food for the wolf, resulting in their death. The grass will have no predator and hence the grass will grow unchecked. Thus, the removal of one organism from the food chain completely disrupts it.

Luckily, food chains are also inter-connected in what we call a food web, in which various organisms are part of different food chains. In this case, the removal of one organism from the food web destabilizes it for a while and then it reaches a new equilibrium. For example, in the above scenario, some other herbivore would eat the grass and flourish whilst keeping the grass population in check. Similarly, wolves would have other prey to eat besides the deer.

Hope this helps.