Organisms that obtain nutrients by breaking down dead organic material are called parasites. Lichens are composed of an archaebacterium and a fungus. In fungus, small pieces of the fungal body can break off to form a new fungus. This asexual process is called gemmules. Many Fungi are composed of interlocking masses of threads which function to absorb nutrients and water.
Fungi are essential decomposers in most ecosystems.
This is because they alone have the ability to decompose cellulose.