Biology

Biology

Fungi

The Fungi Kingdom contains molds, mildews, rusts, smuts, yeasts, and mushrooms. Most fungi are saprophytic or parasitic. The saprophytes are helpful because they break down organic material returning nutrients to the soil. Yeasts are useful in the making of bread and fermented drinks. Some parasitic fungi are actually human pathogens, causing athlete's foot and ringworm.

Important Fungi Body Parts:

1. Hypha - the vegetative filament.
2. Septum - perforated cross walls. (in some groups)
The fungi cell wall is made of chitin, a complex polysaccharide found in insects. This distinguishes fungi from plants, which have a cell wall made of cellulose.
3. Mycelium - a mat of interwoven hyphae.

Fungus life cycle:

The life cycle of a fungus begins as a spore (the reproductive body) that grows when conditions are right. Out of the spore wall grows a hypha, that looks like a clear, microscopic fingertip. The body of the fungus is made up of a network of hyphal threads collectively called the mycelium. The mycelium grows in soil or within dead wood or living organisms. When growing conditions are favorable, the mycelium develops fruiting bodies, appearing as what we recognize as mushrooms or as other forms. These fruiting bodies will produce the new spores.

Types of reproduction:

Asexual:

* Fungi reproduce asexually by forming spores. These spores are usually produced by special modified cells at the end of the hyphe.
* Fungi can reproduce asexually by fragmentation. If the hyphe are broken, the pieces will grow into complete new organisms.
* Yeasts reproduce by an asexual process called budding. In this process, the yeast cell pinches itself off to produce a small offspring cell.

Sexual:

* Each of the four divisions of fungi have different forms of sexual reproduction. This topic is covered in Day 2.

Fungi nutrition:

Unlike members of the plant kingdom that use chlorophyll to produce their own food, fungi do not have chlorophyll and must obtain their food from other sources.

	Fungi obtain food in one, or a combination, of these three ways:

	Fungi act as parasites and feed on living things, usually doing some degree of harm. Parasitic fungi use enzymes to break down tissues. Examples: the "Honey Mushroom" (Armillariella mellea) and the "Cauliflower Mushroom" (Sparassis crispa).

	Fungi form a symbiosis (beneficial partnership) with other organisms such as trees and flowering plants: a. Ectomycorrhizal fungi grow thick coats of mycelia around the rootlets of trees and bring water and minerals from the soil into the roots. In return the host tree supplies the fungus with sugars, vitamins and other root substances. This relationship occurs in more than 80% of plants. Examples: the Bolete Family associated with many species of conifer trees, aspen and birch, and the "Dead Man's Foot" (Pisolithus tinctorius) which helps many plants grow. b. Endomycorrhizal fungi are microscopic soil fungi that penetrate the cells of plant roots. This relationship may be beneficial to both parties or may be harmful to the plant.

	Fungi act as decomposers to decay dead plant and animal matter. These saprophytes act as recyclers of dead organic matter, obtaining food from this material. Hyphal tips release enzymes that eventually decompose and release organic materials into the surrounding environment. Saprophytic fungi appear on dead trees, logs, plant litter such as leaves, and even dead insects and animals. Examples: "Gem-studded Puffball" (Lycoperdon perlatum) and "Turkey Tail" (Trametes versicolor).

Review questions: read the READING ASSIGNMENT, then answer the following questions in a word document.

Do not copy the questions, your answer MUST be in complete sentences and reflect the question.

For multiple choice questions, Put the letter of the answer only.

Head your word document:

Unit 11 Day 1 Fungi

Include your name, hour, date and class in your document.

1. Ringworm (pictured on the right) is a fungal infection of the skin. Use the internet to find information to write at least two paragraphs explaining the ringworm infection and how it is contracted.