Chapter 3 Section 3:
Fungi
Today's Objectives
After completing this lesson you will be able to:
• Name the characteristics fungi share.
• Explain how fungi reproduce.
• Describe the roles fungi play in nature.
Examples of
fungi
moldy bread
mushrooms
bush cricket attacked by killer fungi
fungi
Eukaryotes that have cell walls,
are heterotrophs that feeds by
absorbing their food, and use
spores to reproduce.
Fungi need moist, warm places in which to grow.
Fungi thrive on:
• moist foods
• damp tree barks
• lawns coated with dew
• damp forest floors
• even wet bathroom tiles!
hyphae
(HY fee)
Hyphae are the branching,
thread-like tubes that make up
the bodies to multicellular fungi.
Cell Structure
• Range in size (tiny unicellular yeasts - large multicellular fungi)
• Cells of ALL fungi are surrounded by cell walls
• Most fungi are arranged in structures call hyphae (except for
simplest fungi like unicellular yeasts)
• The hyphae of some fungi are continuous threads of cytoplasm
that contain many nuclei
• Substances move quickly & freely through the hyphae
The appearance of fungi depends on how its hyphae
is arranged, which can be different:
• Loosely tangled hyphae (fuzzy-looking molds)
• hyphae packed tightly together (stalks and caps
of mushrooms)
hyphae is tightly
packed and appears solid
underground hyphae
is thread-like
Fungi are heterotrophs - absorb food through
hyphae that grow into a food source
1.
2.
3.
fungus grows hyphae into a food source
digestive chemicals ooze from the hyphae into the food
chemicals break down the food into small substances that
can be absorbed by the hyphae
Some fungi feed on dead organisms, others are
parasites that break down the chemicals in living
organisms.
Reproduction in Fungi
Fungi usually reproduce by making
spores. The light weight spores are
surrounded by a protective covering
and can be carried easily through air
or water to new sites.
Fungi produce millions of spores, only a few spores will
fall where conditions are right for them to grow.
fruiting body
Reproductive structures where fungi produce
spores.
The appearances of fruiting bodies vary from one
type of fungus to another.
Asexual Reproduction
• most fungi reproduce both sexually and asexually
• fungi make spores asexually when there is adequate
moisture and food
• cells at the tips of their hyphae divide to form spores
• spores grow into fungi that are genetically identical to
parent
budding
A form of asexual reproduction (unicellular yeast
cells)
No spores are produced, instead a small yeast cell
grows from the body of a parent cell, the new
cell breaks away and lives on its own.
Sexual Reproduction
• most fungi can also reproduce sexually,
especially when growing conditions become
unfavorable
• hyphae of t wo fungi grow together and genetic
material is exchanged
• new reproductive structure grows from the
joined hyphae and produces spores
• spores develop into fungi that differ genetically
from parents
Classification of Fungi
Three major groups that are named for the
appearance of their reproductive structures.
1. Club Fungi
2. Sac Fungi
3. Zygote Fungi
Club Fungi
produce spores in microscopic structures that look
like clubs
Includes: mushrooms, bracket fungi, puffballs
and rusts
Most poisonous fungi are club fungi
Sac Fungi
produce spores in structures that look like long sacs
this is the largest group of fungi
Includes: yeasts, morels, truffles, and some fungi
that cause plant diseases. Also include fungi that
make up lichens.
Zygote Fungi
produce very resistant spores that can sur vive hard
environmental conditions.
Includes: many common fruit and bread molds, such
as Rhizopus and molds that attack and kill insects.
The Role of Fungi in Nature
- Decomposers/recyclers
- provide foods for people
- cause disease
- fight disease
- other fungi live in symbiosis with other
organisms
Environmental Recycling
Many fungi are decomposers
Example: many fungi live in soil and
break down the chemicals in dead
plant matter - essentially cleaning
the Earth!
Food and Fungi
yeast in bread - feeds on the sugar in bread
dough and produces carbon dioxide gas as
they feed - the gas forms bubbles, which
cause the dough to rise
yeast in wine - feeds on sugar in the grapes
and produce carbon dioxide and alcohol
Other examples: Blue cheese, mushrooms
Disease fighting Fungi
- Alexander Fleming - Scottist biologist - discovered fungus
named Penicillium while examining a petri dish in which he was
growing bacteria (page 93), helped develop the first antibiotic,
penicillin.
Disease causing Fungi
-Many fungi are parasites that cause serious diseases in plants
- Dutch elm disease - responsible for killing millions of elm trees
in N. America and Europe
- Athletes foot, ringworm and other fungus diseases can be
treated with antifungal medications.
Fungus-Plant Root Associations
Some fungi help plants grow larger and
healthier when their hyphae grow into,or
on, the plant's roots.
The hyphae spread out underground and
absorb water and nutrients from the soil
for the plant.
Lichens
A lichen consists of a fungus and either algae or
autotrophic bacteria that live together in a
mutualistic relationship.
The fungus benefits from the food produced by
the algae or bacteria, and the algae or bacteria
obtain shelter, water and minerals from the
fungus.