Ch.7
Fungi
Section 4: Fungi
• What are Fungi?
– Fungi are eukaryotes that have cell walls, are
heterotrophs that feed by absorbing their food,
and use spores to reproduce
– Need moist, warm places to grow
– Eat moist food, damp tree barks, lawns coated
with dew, and wet bathrooms
Section 4: Fungi
• What are Fungi?
– Cell Structure
• Size: tiny unicellular (yeast) to large multicellular (fungi)
• All are surrounded by cell walls
• Hyphae: are the branching, threadlike tubes that make
up the bodies of multicellular fungi
• Continuous threads of cytoplasm that contain many
nuclei
• How fungus look
– Loosely tangled
– Tightly packed (mushrooms)
Section 4: Fungi
• What are Fungi?
– Obtaining Food
• Fungi absorb food through hyphae that grow into a
food source
• 1st: fungus grows hyphae into the food source
• 2nd: digestive chemicals ooze from the hyphae into the
food, then break down the food that can be absorbed
• What do the bodies of multicellular fungi consist of?
Section 4: Fungi
• Reproduction in Fungi
– Fungi usually reproduce by making spores. The
lightweight spores are surrounded by a protective
covering and can be carried easily through air or
water to new sites
– Fruiting body: fungi produce spores in
reproductive structures
Section 4: Fungi
• Reproduction in Fungi
– Asexual Reproduction
• When there is adequate moisture and food
• Cells at the tips of their hyphae divide to form spores
• The spores grow into fungi that are genetically identical
to the parents
• Budding: unicellular yeast cells undergo a form of
asexual reproduction, no spores are produced as a
result of this
Section 4: Fungi
• Reproduction in Fungi
– Sexual Reproduction
• When growing conditions become unfavorable sexual
reproduction occurs
• The hyphae of two fungi grow together and genetic
material is exchanged
• New reproductive structure grows from the joined
hyphae and produces spores
• Developing into fungi that is different from their
parents
Section 4: Fungi
• Reproduction in Fungi
– Classification of Fungi
• Club Fungi: produce spores in tiny clublike structures. This
group includes mushrooms, rusts, and puffballs, such as
these.
• Sac Fungi: produce spores in structures that look like long
sacs, such as these. The largest group of fungi, they include
yeasts, morels, and truffles.
• Zygote Fungi: produce very resistant spores. This group
includes many common fruit and bread molds, like Rhizopus.
• What is budding?
Section 4: Fungi
• The Role of Fungi in Nature
– Many fungi provide foods for people. Fungi play
important roles as decomposers and recyclers on
Earth. Some fungi cause disease while others fight
disease. Still other fungi live in symbiosis with other
organisms.
– Food and Fungi
• Yeasts, molds, and mushrooms are examples of fungi that
are a food source
• Yeast cells use the sugar in the dough for food
• Molds are used to make food such as some cheese
Section 4: Fungi
• The Role of Fungi in Nature
– Environmental Recycling
• Many fungi are decomposers, breaking down the
chemicals in dead plant matter, returning important
nutrients to the soil.
• Without fungi and bacteria, Earth would be buried
under dead plants and animals
Section 4: Fungi
• The Role of Fungi in Nature
– Disease-Fighting Fungi
• 1928, a Scottish biologist named Alexander Fleming
hypothesized that mold, a fungus named Penicillium,
produced a substance that killed the bacteria near it
• His work contributed to the first antibiotic, penicillian
• Since the discovery of penicillian many other antibiotics
have been isolated from both fungi and bacteria
Section 4: Fungi
• The Role of Fungi in Nature
– Disease-Causing Fungi
• Many fungi are parasites that cause serious diseases in
plants; example: sac fungus causes Dutch Elm disease
• Corn smut and wheat rust are 2 club fungi that cause
diseases in food crops
• Some fungi cause diseases in humans
– Athlete’s foot
– Ringworm
– Can be treated with antifungal medications
Section 4: Fungi
• The Role of Fungi in Nature
– 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 nutrient’s from the soil for the plant
• Most plants have fungal partners
• Many plants are so dependent on the fungi that they
cannot survive without them
– Example: orchid seeds cannot develop without their fungal
partners
Section 4: Fungi
• The Role of Fungi in Nature
– Lichens
• Consists of a fungus and either algae or autotrophic bacteria
that live together in a mutualistic relationship
• Examples: irregular, flat, crusty patches that grow on tree
barks or rocks
• The fungus benefits from the food produced by the algae or
bacteria
• The algae or bacteria, in turn, obtain shelter, water, and
minerals from the fungus
• Lichens are called “pioneer” organisms because they are the
first organisms to appear on the bare rocks in an area after a
volcanic eruption, fire, or rock slide has occurred
• What two organisms make up a lichen?