Biology 2014-2015

The Kingdom of Fungi

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Section 21-1

mushroom.jpg

What Are Fungi?

    Fungi are eukaryotic heterotrophs that have cell walls.

    Chitin, a complex carbohydrate, makes up their cell walls

    Digest their food outside their bodies and then absorb it

    Feed on decaying matter in the soil

    Live as parasites, absorbing nutrients from their host

 

Structure and Function of Fungi

    All fungi are multicellular except yeasts.

    Composed o f thin fi laments called hyphae

    Cross walls divide some fungi into cells containing one or two nuclei

    Cross walls are tiny openings through which the cytoplasm and nuclei can move

    Mycelium is a tangled mass of hyphae

    Mycelium absorb food due to its large surface area coming into contact with a food source

    Fruitinq body is a reproductive structure growing from the mycelium in the Sofl beneath it.

    Clusters of mushrooms are often part of the same mycelium hence, the same organism.

    A "fairy ring" is composed of the fruiting bodies of mushrooms that developed at the outer edges of a single mycelium.

    As the center nutrients become depleted, new mushrooms sprout only at the edges of the mycelium producing a ring.

 

Reproduction in Fungi

 

    Most fungi reproduce sexually and asexually.

 

Asexual Reproduction

 

    Cells or hyphae break off from a fungus and begin to grow on their own.

    Some produce spores which scatter and produce new organisms (a spore is a reproductive cell)

    Spores are produced in sporangia

    Sporangia are found at the tips of specialized hyphae called sporangiophores

 

Sexual Reproduction

 

    Involves two different mating types

    Not male and female but "+" (plus) and "-" (minus)

    When opposite mating types meet, they fuse, bringing plus and minus together in the same cell.

    Form a diploid zygote nucleus, which enter meiosis producing haploid spores.

 

 

How Fungi Spread

    Fungal spores are found in almost every environment.

    Mold will appear where there is the right combination of moisture and food

    A few liters of fresh air may contain hundreds of spores from many species of fungi

    Spores will grow if they have the right temperature, moisture and food

    Some fungi are specialized to lure animals, which disperse fungal spores over a long distance.

    Stinkhorns smell like rotting meat and attract flies

    The spore-containing fluid in ingested by the flies that distribute it over many miles.