While an abundance of parasites might seem like a bad thing, their absence actually signals trouble in the environment.

Organisms within an ecosystem are organised into levels. Producer Producers are plants and algae, which photosynthesise. Primary consumer Primary consumers are herbivores, which eat producers.

Food chains and food webs interconnect organisms within an ecosystem. Producers, such as plants and algae, form the base of the food chain by using photosynthesis to convert sunlight into energy.