Kingdom Fungi

For many years fungi were classified as plant For many years fungi were classified as plant. However, there are some characteristics that separate these two groups: 1. Plants have chlorophyll which is used for photosynthesis. Fungi do NOT have chlorophyll and get their food from their environment. 2. Plants have true roots, leaves, and stems, fungi do NOT. 3. Plants have cell walls made from cellulose, while fungi have cell walls made from chitin (a tough sugar that is also used for shells of insects).

Characteristics of Fungi: All are Eukaryotic Heterotrophic Multi-cellular Cannot move on their own Are Saprophytes (or detritivores) since they feed on dead or decaying matter. Some are decomposers.

Physical Structure: Made of up of long strands of HYPHAE. Hyphae consist of chains of cells or one long cell with many nuclei. Cytoplasm flows within the hyphae. The hyphae is surrounded by a plasma membrane and a cell wall.

Hyphae

Mycelium is a chain of hyphae. Mycelia can produce fruiting bodies. This is a reproductive structure of the fungus that grows above ground level. An example is a mushroom.

As fungi grow, their hyphae extend over the food source, releasing enzymes to digest the food. The nutrients can then be absorbed across the cell wall. Fungi can take in large amounts of food due to their mycelium.

A rhizoid is a root like structure. Rhizoids are hyphae that act in absorption of water and aids in support.

The Kingdom of Fungi is very diverse The Kingdom of Fungi is very diverse. Usually it is divided into five main groups: 1. Primitive Fungi (Phylum Chytridiomycota) Smallest and simplest Mostly aquatic Spores have flagella Some are decomposers Others are parasites of protists, plants and animals.

Chytrids

2. Sac Fungi (Phylum Ascomycota) All form a sac called an ascus. The ascus contains spores for reproduction. Some examples are Saccharomyces cerevisiae (yeast), Penicllium chyrysogenum (mold found on oranges), and Aspergillis flavus (mold that makes a toxin, which can contaminate cereals, nuts and milk.

3. Bread Molds (Phylum Zygomycota) Most get food from decomposing dead, decaying matter. Some species form mycorrhizae, which are symbiotic relationships between fungi and roots of plants. The fungi gain carbon while the plant gains inorganic nutrients.

4. Club Fungi (Phylum Basidiomycota) Their fruiting bodies are club-shaped. Includes mushrooms, puffballs, and bracket fungi.

5. Imperfect Fungi (Phylum Deuteromycota) Have no known sexual reproduction Asexual reproduction by spores Resemble sac fungi Example: penicillium Athlete’s foot, and yeast infections This phylum is now used informally. Any of the fungi that do not reproduce sexually in the Phylum Basidiomycota or Phylum Ascomycota are placed into this group.

Athlete’s Foot

Reproduction Depending on the favorability of conditions, fungi will reproduce either sexually or asexually. During favourable conditions, fungi reproduce asexually. During non-favourable conditions, fungi will lean towards sexual reproduction. We will focus on two main groups (phyla) of fungi and their life cycles: Club Fungi and Bread Molds.

Sexual reproduction is the formation of a new individual following the union of two gametes. Asexual reproduction is the lack of fusion of sex cells (sperm and eggs). Offspring are genetically identical to the parent.

Reproduction In Multi-cellular Fungi Club Fungi (Phylum Basidiomycota) Have club-shaped structures known as basidia (are found on the underside of mushrooms). Spores are produced from the basidia during sexual reproduction.

Haploid nuclei (1n) within the basidia fuse to form diploid (2n) zygotes. Zygotes (2n) then undergo meiosis to form haploid spores (1n), which are then released and dispersed by the wind. Upon contact with the ground, the spores grow into hyphae of opposite mating types, fusing to form a diploid (2n) mycelium underground. The mycelium grows a new fruiting body (the mushroom), and the cycle repeats itself.

Bread Molds (Phylum Zygomycota) Reproduce sexually when their food supply is low, but will also reproduce asexually. They produce spores in structures known as sporangia. These structures are at the tips of hyphae.

Sexual reproduction occurs between two hyphae that are of separate types. The hyphae fuse their nuclei together which produces a diploid (2n) zygospore.

During the right conditions, a sporangium will form and produces haploid spores. Spores are released and grow into new haploid hyphae. The hyphae can then reproduce sexually by fusing hyphae nuclei together to produce a zygospore, OR they can reproduce asexually by forming haploid spores in sporangia.

Fungi and Symbiotic Relationships A lichen is a mutualistic relationship between algae and fungi. It consists of fungal hyphae and some algae cells. The algae cells are photosynthetic, making sugars for both the algae and fungi. Lichens grow on rocks, soils, and trees. These structures are able to withstand severe temperatures.

Lichen

Lichens are used as indicators of the amount of pollution, since they are very sensitive to the affects of pollution. Lichens are also both a producer and a decomposer.