| Introduction
Fungi need to obtain nutrients. Unlike plants, they
cannot photosynthesize, so their energy must be obtained from other
organisms. The strategies fungi use to get their nutrients can be
grouped into three different categories:
a) Saprotrophy
These are the scavengers, which will feed off dead
and decaying organic matter, and do a great deal of good. More on
these in the section on Ecology
b)
Biotrophy
Biotrophs are fungi which feed off living organisms.
The best term to describe these would be “parasites”.
Evolution has favoured biotrophs that are relatively harmless, perhaps
causing a degree of illness in the host but certainly not killing
it. As a result, they tend to have hosts for life, and don’t
need to 'worry' excessively about living outside their hosts or
finding new ones.
c) Necrotrophy
Rather than adapting to their host and coexisting
with it as biotrophs do, necrotrophs tend to kill the host. They
can then act as saprotrophs, feeding extensively on the dead host
before other saprotrophs get in on the act. Due to their savagery,
they need to find new hosts quickly, or risk dying out. As such,
necrotrophs tend to have strategies for spreading quickly, and tend
to attack a greater range of host species. In the long term, however,
necrotrophs are victims of their own success. If they spread so
quickly and with great lethality, they may well wipe out their hosts
and themselves as a result. As such, evolution tends to favour those
which are more moderate in their pathogenicity
(their ability to cause disease). But that doesn’t stop the
necrotrophs from trying…
Only the biotrophs and necrotrophs cause disease, so, we will consider
these pathogens here.
Animal Diseases
Plant Diseases
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