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Fungi
The Fungi Kingdom includes spore-forming eukaryotes that lack undulipodia (amastigote) at all stages
of their life cycle, but some taxonomists include chytrids and oomycetes, which are undulipodia, in the
Kingdom.
Almost all fungi are aerobic, and all fungi are heterotrophs, which means that they absorb their food
without ingesting it. Fungi secrete powerful digestive enzymes that break down the food material,
usually decaying plant or animal matter, into compounds that can be absorbed through the fungal
membrane.
Fungi are abundant in most terrestrial habitats. There are about 100,000 known species, a few of
which are marine. Because of their abundance and diversity, there are likely many more species
to be discovered and described.
Reproduction in fungi is generally asexual and occurs through vegetative spores (conidia). These
spores are distributed by wind and water, and are highly resistant to adverse environmental condi-
tions. Under favorable conditions they will germinate and initiate the growth of a new organism. The
germinating spore produces a thin, tubular structure called a hypha. Cross walls called septa divide the
hypha into "cells", though the septa rarely completely enclose an entire portion of the hypha. Some hy-
phae lack septa entirely. Hyphae grow in large masses called mycelia, which constitutes the vegetative
body of the fungus. The cell walls of most fungi are composed of chitin, similar to that found in insects,
which is very impervious to desiccation, thus enabling the fungi to survive under harsh conditions
(Figure 1).
Figure 1
Conidia
Mycellium
Septa
