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Chap 5-Bio320 (Fungi)

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CHAPTER 5 Kingdom Fungi
Transcript
Page 1: Chap 5-Bio320 (Fungi)

CHAPTER 5

Kingdom Fungi

Page 2: Chap 5-Bio320 (Fungi)

INTRODUCTION

Like animals, fungi are heterotrophs. They cannot make their own food as plants & algae.

Unlike animals, fungi do not ingest (eat) their food. They digest their food while it is still in the environment by secreting hydrolytic enzymes (exoenzymes) to their surroundings.

Exoenzymes break down complex molecules to smaller organic compounds that the fungi can absorb into their bodies and use.

Can cause many plant diseases, as well as animal and human diseases.

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All fungi are eukaryotes; their cells contain membrane-bound nuclei, mitochondria, and other organelles.

The cells are enclosed by chitinized cell walls.

They grow best in moisture habitat, but are found wherever organic material is available.

When the environment become dry, they survive by going into resting stage or producing spores.

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Fungi can even grow on living human!

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FUNGAL BODY PLAN

Most fungi consists of long, branched, threadlike filaments called hyphae.

As hyphae elongate, the fungus expands into new food source.

Hyphae form a tangled mass known as mycelium.

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Structure of a multicellular fungus. The top photograph shows the sexual structures, called fruiting bodies, of the penny bun fungus (Boletus edulis). The bottom left photograph shows a macroscopic view of a mycelium growing on fallen conifer needles, and the bottom right photograph shows a microscopic view of a mycelium (LM).

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Structure of hyphae. 

Some hyphae are coenocytic (not divided into individual compartment of cells), others are divided by cross walls called septa.

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REPRODUCTION

Most fungi reproduce by means of spores which are:

– nonmotile– dispersed wind, water or animals.

Spores are produced on specialized aerial hyphae that form a reproductive structure called fruiting bodies.

Fungi may produce spore either sexually or asexually.

Fungal cell usually contain haploid nuclei.

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How are the sexual & asexual of fungal

reproduction?

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Generalized life cycle of fungi.  Many—but not all—fungi reproduce both sexually and asexually. Some reproduce only sexually, others only asexually.

Clue:

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CLASSIFICATION OF FUNGI

Based on their sexual spores and fruiting bodies.

*Lichen*

Deuteromycetes

Basidiomycets

Ascomycetes

Zygomycetes

Chytridiomycetes

FUNGI

Page 12: Chap 5-Bio320 (Fungi)

Chytridiomycetes(Phylum Chytridiomycota)

The most primitive group of fungi. Produce flagellated cells at some stage

of their life cycle (all other fungal phyla are nonflagellated).

Parasites or decomposers, found in fresh water, a few in moisture land and marine.

Have cell walls containing chitin, food reserves stored as glycogen.

Reproduce both asexually and sexually.

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Chytrids.  The globular fruiting body of Chytridium sprouts branched hyphae (LM). Inset: Chytrids have a flagellated stage called a zoospore (TEM).

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Allomyces, a common chytridiomycete has alternation of generation

The haploid thallus bear male and female gametangia in which gametes are formed by mitosis. Fusion of gametes produce zygote which developed to diploid thallus.

The diploid thallus bears two kind of spore cases: zoosporangia and resting sporangia.

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Zoosporangia: produce flagellated zoospores that may settle down and develop into new diploid thalli.

Resting sporangia: meiosis occur to form haploid zoospores, each will settle down and develop into haploid thalli.

Page 16: Chap 5-Bio320 (Fungi)

Zygomycetes(Phylum Zygomycota)

All of ±800 species of Zygomycetes produce sexual spores called zygospores.

Have coenocytic hyphae. However, septa do form to separate

the hyphae from fruiting bodies. Most are decomposers, some are

parasites and others are mycorrhyzal fungi associated with plant roots.

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Rhizopus stolonifer is a common zygomycete that break down breads and other food. Bread become moldy when a spore falls on it and then germinates and grows into mycelium.

Sexual reproduction in Rhizopus stolonifer occurs when the hyphae of two different mating types (heterothallic); (+) and (-) grow into contact to one another and form gametangia.

Page 18: Chap 5-Bio320 (Fungi)

The life cycle of the zygomycete Rhizopus stolonifer (black bread mold). 

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Pilobolus aiming its sporangia.This zygomycete decomposes animal dung. The mycelium bends its spore–bearing hyphae toward bright light, where grass is likely to be growing. The fungus then shoots its sporangia like cannonballs as far as 2 m. Grazing animals such as cows ingest the fungi with the grass and then scatter the spores in feces.

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Ascomycetes(Phylum Ascomycota)

Ascomycetes sometimes referred to as sac fungi because their sexual spores are produce in microscopic sacs called asci.

Hyphae usually have septa, but the cross walls have pores so that the cytoplasm is continuous.

e.g. yeast, mildews, molds, cup fungi, morels and truffels.

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Ascomycetes (sac fungi). 

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Asexual reproduction involves production of spores called conidia, formed at conidiophores.

Conidia occur in various shapes, sizes, and colors in different species.

Some species is heterothallic; others are homothallic (ability to mate with themselves).

Sexual reproduction occur after 2 gametangia come together and their cytoplasm mingle.

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The life cycle of Neurospora crassa, an ascomycete. 

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Phylum Ascomycota includes species of unicellular yeasts.

Asexual reproduction of yeasts is mainly by budding; a small protuberance (bud) grows and eventually separate from the parent cell. Each bud grow into new yeast cell.

Yeasts also perform sexual reproduction occasionally. How?

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The yeast Saccharomyces cerevisiae in various stages of budding (SEM). 

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TAKE 5…

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Basidiomycetes(Phylum Basidiomycota)

Basidiomycetes or club fungi include the mushrooms, bracket fungi and puffballs.

They develop microscopic club-shaped basidia; an enlarged hyphal cell, on the tip of which develop four basidiospores.

Basidiospores develop outside of a basidium

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Basidiomycetes (club fungi). 

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The life cycle of a mushroom–forming basidiomycete. 

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Glomeromycota?

Describe briefly with an appropriate example.

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Deuteromycetes(Phylum Deuteromycota)

Deuteromycetes, also known as imperfect fungi because in most of them no sexual stage has been observed.

Should further study reveal a sexual stage, these species will be reassigned to different phylum.

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Penicillium, a mold commonly encountered as a saprobe on food. The clusters of bead–like structures in the SEM are conidia, involved in asexual reproduction.

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Lichen

Lichen is actually a symbiotic association between two organism: a phototroph and a fungus.

The fungus is most often an ascomycetes, although in some tropical lichens the fungal is basidiomycetes.

Usually the phototrophs also occur as free-living but the fungal must be a part of lichen.

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Anatomy of an ascomycete lichen (colorized SEM).

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Three types of lichen:1) Crustose?2) Foliose?3) Fruticose?

Phototroph carry out photosynthesis, producing food for both members while fungal supply water and minerals and protect the phototroph against desiccation (dehydration)

} Define in term of how they bond.

Page 38: Chap 5-Bio320 (Fungi)

Lichens grow on tree bark, leaves, exposed rock surfaces.

Vary in size, some are almost invisible, some cover many square kilometers of land.

Reproduce usually by fragmentation – special unit called soredia break off and land on different surface, establish themselves as new lichen.

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Variation in lichen growth forms. 

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ECOLOGICAL IMPORTANCE

Saprotrophs break down organic compounds.

Mychorrizae – mutualistic relationships between fungi and the roots of plants. Fungus supply water and minerals while plants secrete organic compounds needed by fungus.

Lichens play important role in soil formation.

Page 41: Chap 5-Bio320 (Fungi)

ECONOMICAL IMPORTANCE

Edible as foods, production of beer, wine and bread, produces cheese and soy sauce.

Make penicillin and other antibiotics, produce certain drugs, make citric acid and other industrial chemicals.

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TEST 1TEST 1 17TH July 2012 During lecture Chapter 2 – Chapter 4A Bring your own paper for PART B

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Please take care of your handwriting! Seriously.

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Good Luck for your Test 1

End of Chapter 5


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