**Fungi** are the decomposers in an ecosystem – be it field, rainforest, or your own yard. They eat up dead plant or animal matter and return nutrients back to the ecosystem, which fuels another generation of plants and animals.

**Fungi** species can also act as parasites causing several diseases in plants and animals. Parasitic fungi are responsible for the disease called **corn smut**, and **wheat rust** that affects those important crops in North America. These fungal diseases happened through the contact of spores in the plant species, and there they will germinate and infect them.

In animals, a specific group of fungal species called *deuteromycete* infects the human population causing the infection known as **athletes’ foot**. The fungi form mycelium directly within the outer tissue of the epidermis, and it is accompanied by a red, itchy, inflamed sore, which the spores can easily reproduce and spread from one person to another.

**Fungi form two mutualistic relationships with plants and animals**.

**For plants**, the fungus absorbs nutrients and gives them to the plant. In return, the plant gives the fungus the results of photosynthesis.
**For animals**, fungus decomposes waste and releases nutrients that benefit the animal. It feeds the fungus waste, and that is good for the fungus.

Wheat rust first infects the barberry plant. The rust produces a spore that infects nearby wheat fields. The rust in the wheat produces more spores that infect the whole field. In autumn, the rust creates a special spore that sits through the winter, and in the spring, the spores produce more spores that infect the barberry plant again.

In the garden, many plants depend on fungi to deliver their water and nutrients. In return, the plants give the fungi the products of photosynthesis. If the fungi die, the relationship will break and the plant will die.

Aside from the beneficial effects that most fungi bring into the ecosystem, some of them also cause disruption to the ecosystem. One particular example is the Aspergillus. This fungus is responsible for causing aspergilloma. It is a fungal infection developed in the lungs of the infected person and if it gets serious, it may cause an invasive pulmonary aspergillosis, which is a serious infection accompanied by pneumonia. This fungus does not only affect humans who have a weak immune system, but they have also caused food spoilage, and plant and animal diseases. Huge losses in plant crops and death of animals due to infection can disrupt the ecosystem.