Chapter 3 Section 3: Fungi

Today's Objectives After completing this lesson you will be able to: • Name the characteristics fungi share. • Explain how fungi reproduce. • Describe the roles fungi play in nature.

Examples of fungi

moldy bread

mushrooms

bush cricket attacked by killer fungi

fungi Eukaryotes that have cell walls, are heterotrophs that feeds by absorbing their food, and use spores to reproduce.

Fungi need moist, warm places in which to grow. Fungi thrive on: • moist foods • damp tree barks • lawns coated with dew • damp forest floors • even wet bathroom tiles!

hyphae (HY fee) Hyphae are the branching, thread-like tubes that make up the bodies to multicellular fungi.

Cell Structure • Range in size (tiny unicellular yeasts - large multicellular fungi) • Cells of ALL fungi are surrounded by cell walls • Most fungi are arranged in structures call hyphae (except for simplest fungi like unicellular yeasts) • The hyphae of some fungi are continuous threads of cytoplasm that contain many nuclei • Substances move quickly & freely through the hyphae

The appearance of fungi depends on how its hyphae is arranged, which can be different: • Loosely tangled hyphae (fuzzy-looking molds) • hyphae packed tightly together (stalks and caps of mushrooms) hyphae is tightly packed and appears solid

underground hyphae is thread-like

Fungi are heterotrophs - absorb food through hyphae that grow into a food source 1. 2. 3.

fungus grows hyphae into a food source

digestive chemicals ooze from the hyphae into the food chemicals break down the food into small substances that can be absorbed by the hyphae

Some fungi feed on dead organisms, others are parasites that break down the chemicals in living organisms.

Reproduction in Fungi Fungi usually reproduce by making spores. The light weight spores are surrounded by a protective covering and can be carried easily through air or water to new sites. Fungi produce millions of spores, only a few spores will fall where conditions are right for them to grow.

fruiting body Reproductive structures where fungi produce spores. The appearances of fruiting bodies vary from one type of fungus to another.

Asexual Reproduction • most fungi reproduce both sexually and asexually • fungi make spores asexually when there is adequate moisture and food • cells at the tips of their hyphae divide to form spores • spores grow into fungi that are genetically identical to parent

budding A form of asexual reproduction (unicellular yeast cells) No spores are produced, instead a small yeast cell grows from the body of a parent cell, the new cell breaks away and lives on its own.

Sexual Reproduction • most fungi can also reproduce sexually, especially when growing conditions become unfavorable • hyphae of t wo fungi grow together and genetic material is exchanged • new reproductive structure grows from the joined hyphae and produces spores • spores develop into fungi that differ genetically from parents

Classification of Fungi Three major groups that are named for the appearance of their reproductive structures. 1. Club Fungi 2. Sac Fungi 3. Zygote Fungi

Club Fungi produce spores in microscopic structures that look like clubs Includes: mushrooms, bracket fungi, puffballs and rusts Most poisonous fungi are club fungi

Sac Fungi produce spores in structures that look like long sacs this is the largest group of fungi Includes: yeasts, morels, truffles, and some fungi that cause plant diseases. Also include fungi that make up lichens.

Zygote Fungi produce very resistant spores that can sur vive hard environmental conditions. Includes: many common fruit and bread molds, such as Rhizopus and molds that attack and kill insects.

The Role of Fungi in Nature - Decomposers/recyclers - provide foods for people - cause disease - fight disease - other fungi live in symbiosis with other organisms

Environmental Recycling Many fungi are decomposers Example: many fungi live in soil and break down the chemicals in dead plant matter - essentially cleaning the Earth!

Food and Fungi yeast in bread - feeds on the sugar in bread dough and produces carbon dioxide gas as they feed - the gas forms bubbles, which cause the dough to rise yeast in wine - feeds on sugar in the grapes and produce carbon dioxide and alcohol Other examples: Blue cheese, mushrooms

Disease fighting Fungi - Alexander Fleming - Scottist biologist - discovered fungus named Penicillium while examining a petri dish in which he was growing bacteria (page 93), helped develop the first antibiotic, penicillin. Disease causing Fungi -Many fungi are parasites that cause serious diseases in plants - Dutch elm disease - responsible for killing millions of elm trees in N. America and Europe - Athletes foot, ringworm and other fungus diseases can be treated with antifungal medications.

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 nutrients from the soil for the plant.

Lichens A lichen consists of a fungus and either algae or autotrophic bacteria that live together in a mutualistic relationship. The fungus benefits from the food produced by the algae or bacteria, and the algae or bacteria obtain shelter, water and minerals from the fungus.