Before we talk about the removal of tertiary consumers from the food chain, we had better review the nature and components of a food chain. At the bottom stand the producers, those organisms like plants, algae, and some bacteria that make their own food through photosynthesis or other such processes. The next step up contains the primary consumers that eat the producers. These are herbivores like rabbits and cows. Then we move up to secondary consumers that eat the primary consumers. These secondary consumers are carnivores or sometimes omnivores (who eat producers like plants as well as other animals).
Now we come to the tertiary consumers. These usually stand at the top of the food chain as the top predators. They eat secondary consumers (and primary consumers and sometimes producers). Examples of tertiary consumers are wolves and big cats like tigers, lions, and jaguars. These animals rarely become prey for other animals.
Tertiary consumers are very important for the life of the food chain, for they control the populations of the secondary and primary consumers below them. Let's imagine what would happen if all the tertiary consumers in one chain somehow died out.
We'll use the example of a hawk as tertiary consumer. With no more hawks to regulate the population of foxes, foxes what soon diminish the population of rabbits. Without rabbits to clear some of the producer plants, those could grow unchecked in some areas and choke each other off. We can see, then, how tertiary consumers help maintain balance in a given food chain and ecosystem.
Let's look at one more example. Wolves are tertiary consumers that help control the population of deer. If the wolves were gone, the deer population could grow exponentially. These deer would seriously diminish the producers in their territory, which could lead to a lack of food as well as increased starvation and disease over time.