All animals are useful because each species plays a pivotal role in the habitat where it resides. Each animal has a purpose in its ecosystem. The removal of an animal affects the other species that reside in the ecosystem.
All of the species in the world are connected, from the largest animals to the smallest bacteria. Every species has a specific role.
Fungi and bacteria act as decomposers; without them, dead organisms and fecal waste would pile up and overtake an area. They also help replenish the soil's nutrients. Plants would be unable to grow without fungi and bacteria.
Plants compose the first level in an ecosystem's food chain. They are the source of all the energy ultimately found in an area. A process known as photosynthesis allows plants to make their own food. Without plants, herbivores would not have anything to eat and would die out. Herbivores are animals that strictly feed on plants.
Herbivores are eaten by omnivores and carnivores, omnivores eat both plants and animals, and carnivores only eat other animals. Both omnivores and carnivores are known as consumers. Consumers get energy all or in part by eating other animals. Their predation helps keep the population of species in an ecosystem under control. Removing consumers can upset an ecosystem's balance and lead to its collapse.