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?