Biology Chapter 21 Notes Fungi Eukaryotic Heterotroph Have cell walls made of chitin Digest food outside their bodies and then absorb it Saprophytic (eat dead matter), parasitic (harm others while living on them), or Mutualistic (both organisms benefit) Just a few trap and absorb living organisms (carnivores) by waiting for an organism to crawl into their mycelium and then secreting a substance that traps them, then digesting/absorbing it All are multicellular except for yeast Do not move, but can grow very quickly Hyphae – thin filaments, only one cell thick but can be many cells long. Can have cross walls with one or two nuclei in each section, each with a tiny opening

Through with cytoplasm and nuclei can move Can have NO cross walls Mycelium – thick mass of hyphae Fruiting body – reproductive structure growing out of mycelium Reproduction Asexual – cells or hyphae break off and grow on their own. Spores are produced from mitosis, which can undergo mitosis à new fungi Sexual – gametes are not male and female but plus (+) and (-) When + hyphae meets - hyphae they fuse and both nuclei are in the same cell The hyphae grows and produces diploid zygote nucleius which undergoes

meiosis by producing haploid spores, which can undergo mitosis à new fungi sporangia – fungal structure in which spores are produced. Sporangiaphores – specialiazed hyphae that have sporangia at their tips

Fungi Classified according to (1) structure, (2) reproduction 4 main groups Molds (Zygomycota) – create zygospores created during sexual cycle

sac fungi (Ascomycota) – create ascus, reproductive sac that contains spores created during the sexual cycle club fungi (Basidiomycota) – creates a basidium, spore bearing structure that can be found on the underside of mushroom caps imperfect fungi (Deuteromycota) – sexual reproduction part of their life cycle has

never been observed Zygomycota – Common molds Grows on meat, cheese, bread Zygospore – spore formed by sexual reproduction Rhyzoids – rootlike hyphae that anchor fungal hyphae to a surface Stolons – stem-like hyphae that run along a surface

Gametangia – gamete forming structures created when hyphae from two different mating types fuse

Life Cycle

1. Gametangia are formed when a + hyphae and – hyphae fuse 2. Gametangia form diploid (2N) zygotes 3. Zygotes develop into thick-walled zygospores, the may lay dormant 4. When conditions are favorable, zygospores germinate, undergo meiosis

And form a sporangium, which forms haploid (N) spores 5. Haploid spores are spread by wind, animals, etc., land, grow new fungi

Ascomycota (Sac fungi) Ascus – reproductive structure that contains spores Asexual reproduction – Conidia are formed at tip of conidiophores (specialized hyphae) Conidiospores can germinate and form new haploid (N) fungi Sexual reproduction –

1. Ascus forms 2. + hyphae and – hyphae fuse together within the ascus forming a diploid

zygote (2N) 3. Zygote divides by meiosis, forming four haploid (N) cells 4. The four haploid cells divide by mitosis to create 8 haploid cells (N) acospores 5. The ascospores germinate and grow into a haploid mycelium

Yeasts – unicellular fungi, classified as ascomycetes The ascospores are used in baking, caused to germinate by adding nutrients and

Warmth Budding – asexual reproduction in yeasts

Basidiomycota (Club fungi) All decomposers `1 Basidium – spore bearing structure found on the gills that grow on the underside of

mushroom caps. Life Cycle

1. Basidiospore germinates, producing haploid (N) primary mycelium 2. Mycelium grows creating + and – hyphae 3. + and – hyphae fuse to produce diploid (2N) secondary mycelium 4. Secondary mycelia grow and can become enormous 5. Spore producing fruiting bodies push above the ground (mushroom) 6. The cells in the hyphae of the fruiting body swell with water, rapidly

expanding 7. The mushroom cap opens, exposing hundreds of tiny gills on the underside 8. The gills are lined with basidia, each created by the fused + and – hyphae and

each creating a diploid (2N) zygote cell called basidiospore 9. The basidiospores spread

A single mushroom can form billions of spores, a puffball trillions Deuteromycota (Imperfect Fungi) Fungi that cannot be placed in any other category Extremely varied Sexual reproduction has never been observed Penicillium notatum – the source of the antibiotic Penicillan

Plant Disease – fungal disease responsible for 15% crop loss in temperate regions and up to 60% of crop loss in tropical regions Corn Smut Mildews Wheat rust – basidiomycete that grows on barberry plants and produces spores, which

are carried into wheat fields, where they germinate and infect wheat. The rust that has infected the wheat produces a second spore, germinating other wheat plants. Late in the season the rust produces black spores that survive in the winter and germinate in the spring.

Human Disease Athletes foot – deuteromycete that forms mycelium within the outer layer of the skin Of the foot, often between the toes. The red, inflamed sore contains

spores that can be spread easily to other people Ringworm – deuteromycete (same one as althlete’s foot) found in locations other

than the foot. Candida albicans – a yeast that can grow in the moist parts of the human body.

Normally Candida growth is kept in check from bacteria and the host immune system but antibiotics or immune system issues can disrupt the system, allowing the yeast infection to grow

Animal Disease

Cordyceps – fungus that creates spores that become lodged in grasshoppers, germinate, and then produce enzymes that digest the grasshopper’s exoskeleton. Once the exoskeleton is pierced, the spores multiply inside the grasshopper’s body, then digest it from the inside. When all nutrients are gone, the fungi produces fruiting bodies and spores to spread to the next grasshopper.

Symbiotic Relationships Lichens – symbiotic associations between fungi and a photosynthetic organism, usually a

cyanobacterium, green algae, or both. Extremely resistant to drought and cold Grow on dry bare rock, in deserts, on mountains, etc. The photosynthetic organism(s) provides the fungus with energy The fungus provides the photosynthetic organism(s) with water, minerals, and protection from harsh direct sunlight.

Mycorrhizae – associations of plant roots and fungi 80% of all plants have mycorrhizae Fungi aid plants in absorbing water and minerals by covering the roots of

the plants, increasing the surface area. Fungi aid plants by releasing enzymes that free nutrients from the soil. Plants aid fungi by providing the products of photosynthesis Mycorrhizea can be essential, withut it Many trees cannot survive Seeds form some plants cannot germinate (example: orchids) Mycorrhizae can form networks that connect numerous trees, sometimes of different species. Nutrients, water, and information can travel through the mycelium from one tree to another.