Copyright 2009 Pearson Education, Inc. FUNGI

Transcription

1 Copyright 2009 Pearson Education, Inc. FUNGI

2 FUNGI Fungi are absorptive heterotrophic eukaryotes that digest their food externally and absorb the nutrients

3 Most fungi consist of a mass of threadlike hyphae making up a mycelium Hypha FUNGI Hyphal cells are separated by cross walls with pores large enough for ribosomes, mitochondria, and nuclei to cross Some are multinucleate without cross walls Mycelium

4 FUNGI Hyphae have a huge surface area to secrete digestive enzymes and absorb food Fungal hyphae are surrounded by a cell wall with chitin

5 Fungi produce spores in both asexual and sexual life cycles Many fungal species can reproduce both sexually and asexually Fungi produce huge numbers of asexual spores, each of which can germinate to form a new fungus In many fungi, sexual fusion of haploid hyphae leads to a heterokaryotic stage, in which cells contain two genetically distinct haploid nuclei Hours or centuries may pass before parental nuclei fuse to form a short lived diploid phase Zygotes undergo meiosis inside specialized Copyright 2009 Pearson Education, Inc. reproductive structures and disperse haploid

6 Key Haploid (n) Spores (n) Heterokaryotic (n + n) (unfused nuclei) Diploid (2n) Spore producing structures Asexual reproduction Germination Heterokaryotic stage Fusion of cytoplasm Mycelium Germination Spores (n) Sexual reproduction Fusion of nuclei Meiosis Spore producing structures Zygote (2n)

7 Fungi are classified into five groups Sexual reproductive structures are used to classify fungi Fungi with no known sexual stage are known as imperfect fungi Fungi likely evolved from an aquatic, flagellated ancestor shared with animals Chytrids, which have flagellated spores, are the earliest lineage of fungi Animals and fungi diverged into separate lineages 1.5 billion years ago Copyright 2009 Pearson Education, Inc.

8 Chytrids Zygomycetes (zygote fungi) Glomeromycetes (arbuscular mycorrhizal fungi) Ascomycetes (sac fungi) Basidiomycetes (club fungi)

9 Fungi are classified into five groups Zygomycetes Zygote fungi form resistant zygosporangia in which haploid spores form by meiosis This group includes black bread mold Copyright 2009 Pearson Education, Inc.

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11 Fungi are classified into five groups Glomeromycetes These fungi form mycorrhizae, in which invasive hyphae branch into treelike arbuscules within plant roots 90% of plants have symbiotic partnerships with glomeromycetes Copyright 2009 Pearson Education, Inc.

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13 Fungi are classified into five groups Ascomycetes Sac fungi form saclike asci, which produce sexual spores They range in size from yeasts to elaborate morels and cup fungi Some form lichens in association with green algae or cyanobacteria Copyright 2009 Pearson Education, Inc.

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17 Fungi are classified into five groups Basidiomycetes Club fungi are the mushrooms, puffballs, and shelf fungi They have club shaped spore producing structures called basidia These fungi are important forest decomposers Copyright 2009 Pearson Education, Inc.

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22 Fungal groups differ in their life cycles and reproductive structures Hyphae reproduce asexually by producing spores in sporangia at the tips of upright hyphae When food is depleted, the fungus reproduces sexually Mycelia of different mating types join and produce a zygosporangium, which develops into a thick walled structure that can tolerate dry, harsh conditions Under favorable conditions, the parental nuclei fuse and the diploid nucleus undergoes meiosis to form haploid spores Copyright 2009 Pearson Education, Inc.

23 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Zygosporangium (n + n) Mycelia of different mating types Cells fuse Fusion of nuclei Young zygosporangium (heterokaryotic) Sporangium Meiosis 4 Spores (n)

24 Fungal groups differ in their life cycles and reproductive structures Hyphae of different mating types fuse to form a heterokaryotic mycelium, which grows to produce a mushroom Haploid nuclei fuse to form diploid nuclei in the club shaped cells called basidia that line the gills of the mushroom Each diploid nucleus undergoes meiosis to form haploid spores Copyright 2009 Pearson Education, Inc.

25 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) 1 Fusion of two hyphae of different mating types

26 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Mushroom 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

27 Key Haploid (n) Fusion of nuclei 3 Diploid nuclei Heterokaryotic (n + n) Diploid (2n) Basidia Mushroom 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

28 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Fusion of nuclei 3 Basidia Diploid nuclei Meiosis Haploid nuclei 4 Spores released Mushroom Spores (n) 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types

29 Key Haploid (n) Heterokaryotic (n + n) Diploid (2n) Fusion of nuclei 3 Basidia Diploid nuclei Meiosis Haploid nuclei 4 Spores released Mushroom Spores (n) 2 Growth of heterokaryotic mycelium 1 Fusion of two hyphae of different mating types 5 Germination of spores and growth of mycelia

30 CONNECTION: Parasitic fungi harm plants and animals 80% of plant diseases are caused by fungi Between 10 and 50% of the world s fruit harvest is lost each year to fungal attack A variety of fungi, including smuts and rusts, infect grain crops Only 50 species of fungi are parasitic on animals, causing mycoses Human infections include athlete s foot (caused by ringworm) Systemic mycoses are rare but serious fungal infections that spread through the body from Copyright 2009 Pearson Education, Inc.

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34 Lichens consist of fungi living in close association with photosynthetic organisms Lichens consist of algae or cyanobacteria within a fungal network Many lichen associations are mutualistic The fungus receives food from its photosynthetic partner The fungal mycelium helps the alga absorb and retain water and minerals Lichens are important pioneers on new land, where they help to form soil Lichens are sensitive to air pollution, because they obtain minerals from the air Copyright 2009 Pearson Education, Inc.

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36 Fungal hyphae Algal cell

37 Some fungi have mutually beneficial relationships with ants Several species of ants and termites cultivate fungal gardens The insects feed their fungi with leaves, weeding out undesirable fungi The fungi feed on the leaves The ants harvest the swollen hyphal tips Farmer insects and fungal crops have been evolving together for over 50 million years Copyright 2009 Pearson Education, Inc.

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39 Fungi have enormous ecological benefits and practical uses Fungi have many practical uses for humans Some fungi can break down toxic pollutants, including pesticides like DDT and cancer causing chemicals Fungi may be able to clean up oil spills and chemical messes We eat many fungi, from mushrooms to cheeses modified by fungi Yeasts produce alcohol and cause bread to rise Fungi provide antibiotics that are used to treat bacterial disease Fungi are playing important new roles in Copyright 2009 Pearson Education, Inc.

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41 Staphylococcus aureus Penicillium Zone of inhibited growth

42 Leaves carry out photosynthesis Reproductive structures, as in flowers, contain spores and gametes Cuticle covering leaves and stems reduces water loss Stomata in leaves allow gas exchange between plant and atmosphere Lignin hardens cell walls of some plant tissues Stem supports plant; may perform photosynthesis Vascular tissues in shoots and roots transport water, minerals, and sugars; provide support Roots anchor plant; mycorrhizae (rootfungus associations) help absorb water and minerals from the soil

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44 ANCESTRAL GREEN ALGA 1 a. 2 b. c. 3 d.

45 A. Pine tree, a gymnosperm B. Puffball, a club fungus

46 You should now be able to 1. Describe the key plant adaptations for life on land 2. Describe the alternation of generation life cycle; explain why it appears that this cycle has evolved independently in algae and land plants 3. Describe the key events of the moss, fern, and pine life cycles 4. Explain how coal was formed; explain why coal, oil, and natural gas are called fossil fuels Copyright 2009 Pearson Education, Inc.

47 You should now be able to 5. Describe the parts of a flower and explain their functions 6. Describe the stages of the angiosperm life cycle 7. Describe angiosperm adaptations that promote seed dispersal 8. Explain how flowers are adapted to attract pollinators 9. Compare the life cycles and reproductive structures in the fungal groups Copyright 2009 Pearson Education, Inc.

48 You should now be able to 10. Describe the structure and characteristics of lichens 11. Describe the positive ecological and practical roles of fungi Copyright 2009 Pearson Education, Inc.