IV. Kingdom Fungus

Chapter 31 - Fungi

A. Estimated 1.5 million species

Fig. 17.16

D. Fungi are heterotrophs that absorb food after digesting with enzymes they secrete outside their body called exoenzymes

B. Greek, mycos, fungi (mycelium, mycorrhizae, etc…)

hyphae

C. Some are single-celled (in general known as yeast), while most are complex multicellular

IV. Kingdom Fungus

Chapter 31 - Fungi

Fig. 17.16

E. Types -

1. Saprophytes (saprobes, decomposers)

- Break down and absorb nutrients from non-living organic material like a fallen log, dead animals and organismal waste (feces, etc…)

IV. Kingdom Fungus

Chapter 31 - Fungi

“Athletes Foot”

E. Types -

2. Parasitic / Pathogens- Take nutrients from living cells, some pathogenic – 80% of plant diseases caused by fungus.

BlitheOnly 50 out of the known 100,000 fungal species are parasites of animals and these do relatively little damage.

IV. Kingdom Fungus

Chapter 31 - Fungi

Fig. 17.16

3. Mutualistic symbionts

mycorrhizaelhyphae

E. Types -

- mycorrhizae

IV. Kingdom Fungus

Chapter 31 - Fungi

Fig. 17.16

1. Multicellular fungus

F. Body Structure

- Hyphae - Network of tiny filaments making up body of fungus

- Cell walls are made of… Chitin = polysaccharide of modified glucose also found in exoskeletons of insects and crustaceans (arthropods)

- Mycelium (plural, mycelia) – entire interwoven mass of hyphae- High surface area to volume ratio, efficient feeding- 1ml of soil may contain 1km of hyphae

- Like plants, hyphae need to GROW through environment

IV. Kingdom Fungus

Chapter 31 - Fungi

Fig. 17.16

1. Multicellular fungus

F. Body Structure

- Structure of Hyphae

a. Septate hyphae - Most fungi have hyphae divided into cells by septa (crosswalls) with large pores for sharing material

b. Coencytic hyphae – continuous cytoplasm with many, many nuclei due to repeated mitosis without cytokinesis similar to slime molds.

IV. Kingdom Fungus

Chapter 31 - Fungi

1. Produce spores either sexually or asexually

G. Life cycle of fungi

- Carried by wind or water

Puffball mushroon exploding releasing trillions of spores

- We see this when we leave food out or in fridge too long…spores are everywhere in the air….

Spores vs Gametes

Chapter 31 - Fungi

Spore

Cell or cell-like structure involved in asexual reproduction

May be adapted for dispersal and/or survival in unfavorable conditions

Gametes

Cells of sexual reproduction

Part of life cycle of many

- plants

- fungi- algae/protozoan (protists)

Alternation of Generation in Plants

Questions

Chapter 31 - Fungi

2. Mycellium – define.

1. The “root-like” structure of a multicellular fungal organism.

3. Spore vs. Zygote – similarities and differences

4. Kingdoms of life that have evolved to utilize spores to reproduce.

5. Ploidy of mycellium.

6. Any single-celled fungus.

7. When a single cell fungus reproduces by mitotic cell division, but new cell pinches off the parent cell and is smaller to begin with.

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

- Many, but not all reproduce both sexually and asexually. Some do one or the other.

Nuclei of hyphae (mycellium) and spores

are haploid!!

Start here

IV. Kingdom Fungus

Chapter 31 - Fungi

General life cycle of fungus

G. Life cycle of fungi

- Many, but not all reproduce both sexually and asexually. Some do one or the other.

- nuclei of hyphae and spores are haploid.

Specific Example you need to know from the Ascomycota phylum

- The five major fungi phyla – I would not memorize these…

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

Sexual reproduction

Fusion of two cells, a plus (+) and a minus (-), resulting in the combining of the cytoplam (hence plasmogamy). The nuclei do not fuse yet and therefore the cell is dikaryotic (two nuclei).

A. Plasmogamy.Very much like Fertilization of

gametes

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

Sexual reproduction

- Begins when two distinct mycelia of different mating types (+ and -) secrete pheromones that bind to receptors on each others surfaces.

- Hyphae then grow toward each other using mitotic cell division (they follow the pheromone) and fuse those cells that meet from the + and – will fuse = plasmogamy.

A. Plasmogamy.

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

Sexual reproduction

In the case of ascomycetes, the minus (-) cells move toward the plus (+) cell hyphae, bind, and then fuse (plasmogamy) forming a dikaryotic cell known as an ascus.

A. Plasmogamy.

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

Sexual reproduction

B. Karyogamy

Fusion of the two nuclei of the dikaryotic cell forming a diploid cell…the ZYGOTE (could occur hours, days or years later).

This is similar to a sperm fusing with an ovum. Both haploid followed by plasmogamy, then karyogamy to form the zygote!!

A. Plasmogamy.

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

- Meiosis follows karygomy restoring haploid mycelium that will produce spores.

Sexual reproduction

B. Karyogamy

A. Plasmogamy.

C. Meiosis

Specifically in the ascomycotes, meiosis occurs, but not cytoplasmic division resulting in a four haploid nucleus cell.

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

- Mitosis of the haploid cells will produce spores of the (+) and (-) types.

Sexual reproduction

B. Karyogamy

A. Plasmogamy.

C. Meiosis

In the ascus, mitosis occurs resulting in an eight haploid nucleus cell (ascus).

D. Mitosis

Cell walls form around the nuclei turning them into spores (ascospores)

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

- The (+) and (-) spores grow by mitotic cell division to form new mycelia

Sexual reproduction

B. Karyogamy

A. Plasmogamy.

C. Meiosis

D. Mitosis

E. Germination

IV. Kingdom Fungus

Chapter 31 - Fungi

2. General life cycle of fungus:

G. Life cycle of fungi

- Minus (-) Mycelia (haploid) will use mitotic cell division to make spores and these spores will become new mycelia.

ASexual reproduction

Conidia = Asexual spores of ascomycetes

IV. Kingdom Fungus

Chapter 31 - Fungi

G. Life cycle of fungi

Molds

- Any multicellular fungus that can reproduce rapidly and asexually. It is a general term. Many of these fungi can reproduce sexually, but mold refers only to the asexual stage.

Yeast

- Reproduce predominantly asexually not by using spores, but by budding, a type of simple form of cell division. Sometimes they reproduce sexually.

2. General life cycle of fungus:

IV. Kingdom Fungus

Chapter 31 - Fungi

H. Fungi Evolved from a single-celled flagellated protists

The five major phyla of fungi:

IV. Kingdom Fungus

Chapter 31 - Fungi

H. Fungi Evolved from a single-celled flagellated protists

4. Ascomycetes

- 32,000 species

- Production of sexual spores in saclike asci

- Therefore commonly called sac fungi

- Vary from unicellular yeast including bread/beer/wine making yeast (Saccharomycetes cerevisiae) to cup fungi and morels

- Consist of some of most deadliest plant pathogens making them relevant to agriculture

- More than 40% are lichens – mutualistic relationship between fungi and unicellular chlorophytes (green algae) or with cyanobacteria.

- Others form mycohorrhizae

Lichen growing on a tree:

IV. Kingdom Fungus

Chapter 31 - Fungi

H. Fungi Evolved from a single-celled flagellated protists

4. AscomycetesLichen:

The algae will reproduce asexually.

A mutualistic relationship between:

1. ascomycete fungus and green algae

or

2. Ascomycete fungus and cyanobacteria.

- Algae/cyanobacteria do photosyn and produce organic compounds for fungus, while fungus provides place to live as well as water and minerals obtained mostly from airborne dust or rain – why they can grow on rock ( hence pioneer species in primary succession).