We talked previously about how some fungi
make spores within a sac, it's called an ascus,
the other type of fungi produce spores from
a structure called the basidium. And on the
left, we see a typical yeast or fungal mycelium.
And the very top, there are spores coming
off the mycelium and that is a basidium. The
spores come off and generate new fungi. And
on the right is a close-up diagram of the
basidium, and at the very tip the fungi produce
spores, those are then released and fall into
the environment to generate new organisms.
Fungi typically live in soil or on dead matter,
you often can't see them. If you just go for
a walk in the woods, the soil is teeming with
fungi, but you don't even see them. I think
even in a city if you walk around there is
plenty of fungi growing in damp places and
they're just so small that you don't notice
them, but they're there and you're inhaling
them quite frequently. I'm sure you have had
some rotting fruit in your refrigerator or
on the table in your kitchen, that green growth
or white fuzzy growth on the surface of the
fruit, that is a mold, it's a filamentous
fungus and these are growing and they're using
nutrients from the fruit and they're producing
spores. So if you can see an orange that looks
like this one, you're breathing in the spores.
Now remember the mycelia that fungi produce,
these are large meshworks or networks of filaments
that spread and spread and spread and these
typically grow in the soil and periodically
they produce mushrooms which pop above the
soil to release their spores. These mycelia
can be small or they can be very big. So the
mycelium on the orange that we just looked
at is relatively small, but some of these
mycelia are miles in diameter. For example
there is a site in Oregon in the US, it's
a 2,400 acre site which is about 9.7 km²,
it has a single contiguous growth of mycelium.
It's one organism that started from a spore
and just kept growing and growing and growing.
You can't see this, it's going in and under
the soil, but periodically the mushrooms come
up from the mycelium and they drop of course
their spores. So we think this might be the
world's largest organism, miles in diameter.
Just to review the two different ways that
fungi produce spores. They produce them from
a basidium and these are called basidiospores
and this is typical of the fungi called basidiomycetes,
or the fungi can produce spores within a sac
called an ascus, the spores are called ascospores
and these fungi are called ascomycetes.