B I O LO GY I I – LO U LO U S I S

CHAPTER 22FUNGI

22.1 CHARACTERISTICS OF FUNGI

• Fungi grows in one place until its food runs out• Before it dies, it releases millions of spores that

float through the air until they find food• Cycle begins again

WHAT ARE FUNGI?

• »All fungi share three characteristics• 1. Threadlike bodies• 2. Cell walls have chitin• 3. Heterotrophic

1. FUNGI HAVE THREADLIKE BODIES•Made of long slender filaments •Filaments weave together to form fungus body and reproductive structures•Most filaments are loosely woven•Reproductive structures are tightly woven •Like mushrooms

FUNGI COLORS

• Fungi get their color from chemicals that form during metabolic processes• Most of the colorful chemicals are toxic

2. FUNGAL WALLS CONTAIN CHITIN

• A tough carbohydrate found in the cell walls

3. FUNGI ARE HETEROTROPHIC• Fungi are not plants

• Do not contain chlorophyll, not autotrophs• Obtain nutrients by secreting digestive

enzymes that break down organic matter in their environment• Absorb decomposed molecules

• Absorb nutrients • non-living matter• Leaves, branches, dead animals, & waste• Resource recyclers

STRUCTURE AND FUNCTION

• »Fungal body is made of filaments, which increase the surface area allowing fungus to absorb nutrients more efficiently

STRUCTURE OF A MUSHROOM

BODY STRUCTURE• Hypha- a filament of fungus, threadlike • These cells are haploid and identical • Have cell walls called septa that separate

• Mycelium- mass of fungal filaments composes body• Meters long, underground• Sometimes form root-like structures rhizoids that

hold fungi in place and absorb nutrients Hyphae Mycelium Septa

HYPHAE STRUCTURE

OBTAINING NUTRIENTS

• Release enzymes to break down organic and inorganic matter for nutrients• Absorb across cell walls • Saprobes- absorb nutrients from dead organism• Recycle nutrients in ecosystem• Parasite-absorb nutrients from living host• Cause disease like athlete’s foot and ringworm

Ringworm

REPRODUCTION

• »What is the difference between sexual and asexual production of spores in fungi?• Sexual – spores are produced by meiosis

oAllows for genetic diversity

• Asexual - spores are produced by mitosis oAllows for rapid dispersion

• Most fungi do both asexual and sexual reproduction

SEXUAL REPRODUCTION

• Fused hyphae form sexual reproductive structure (like mushroom)• Spores form through fusion of two genetically different nuclei.•Now the nuclei are diploid and undergo meiosis to produce haploid spores

ASEXUAL REPRODUCTION

•Specialized hyphae produce stalks•At tips of stalks haploid spores are produced by mitosis •Genetically identical to parent • Imperfect fungi – fungi without a sexual stage

YEAST

• Unicellular stage of fungi• Reproduce asexually by budding• Occasionally form multicellular hyphae and

reproduce sexually

MOLD

• Rapidly growing, asexually reproducing stage of some types of fungi• “mold” refers to asexual phase

22.2 GROUPS OF FUNGI

• Modern fungi classified into four phyla• Chytridomycota (chytrids)• Zygomycote (zygote fungi)• Ascomycota (sac fungi)• Basidiomycota (club fungi)

• Classified based on type of reproductive structures they form

CHYTRID FUNGI

• Date back 500 million years

• Earliest fungi produced spores and gametes with flagella

• First fungi probably appeared in water

• Only group of modern fungi in water chytrids

CHYTRID FUNGI, CONT.

•Have chitin in their cell walls

•Digest food outside their bodies

• Produce hyphae that form rhizoids•Hold chytrids in place and absorb nutrients .

• Sexual reproductive structures contain spores.

CHYTRID FUNGI, CONT.

• Most are aquatic• Can live on moist land

• Mainly saprobes • Which…feed on dead algae or plants

• Some are parasites• Common parasites of aquarium fish• Reason for decline in amphibians in the

wild

**BATRACHOCHYTRIUM DENDROBATIDIS

• One of biggest threats facing amphibians worldwide• Mechanism by which it kills is

unknown• No known treatment once

infected

ZYGOTE FUNGI

• Common member of phylum Zygomycota

• Named for sexual reproductive structures that produce zygotes inside a zygosporangium

ZYGOTE FUNGI SEXUAL REPRODUCTION

• Begins when hyphae from two mating types join• Different mating types not referred to as

male and female • Why? Because they are physically

identical• Instead “+“ and “–”

ZYGOTE FUNGI SEXUAL REPRODUCTION

• Tough capsule called zygosporangium forms• Resistant to? Hot, cold, and dry

conditions • When conditions are right, nuclei fuse

to form diploid (2n) zygotes• Zygotes undergo meiosis• Zygosporangium germinates, which

produces a sporangium that releases haploid spores.

ZYGOTE FUNGIASEXUAL REPRODUCTION

• More common than sexual reproduction• Haploid spores are produced in sporangia

at the tips of hyphae• Haploid spores produced by mitosis

• Haploid spores are carried by wind to new places

rhizopus

LIFE CYCLE OF ZYGOTE FUNGI

ZYGOTE FUNGI

• Usually live in soil

• Feed on decaying plant and animal matter

• Some species of Rhizopus can cause cancer

CHECK POINT

•Where does meiosis take place in zygote fungi?

•Zygosporangium

**ZYGOMYCETE PILOBOLUS

• Grows in animal dung• Produces reproductive structures about 5

to 10 mm high• Can eject spores up to 2 m at a velocity

near 50 km/h

SAC FUNGI

• Phylum Ascomycota

• Characterized by an ascus• Saclike sexual reproductive structure that produces spores• Ascus means “sac”

SAC FUNGISEXUAL REPRODUCTION

• Hyphae of different mating types grow together• Hyphae fuse to form a bridge • The nuclei pair up, one + and one –• Divide to form mass of hyphae that

contain two nuclei per cell

SAC FUNGISEXUAL REPRODUCTION

• In most sac fungi, mass is dikaryotic, having two nuclei• Forms structure called ascocarp

• Cells in ascocarp becomes saclike asci• Nuclei fuse and undergo meiosis• Haploid spores are released

SAC FUNGI ASEXUAL REPRODUCTION

• Usually reproduce asexually• Asexual spores called conidia form by

mitosis on hyphae called conidiophores

• Conidia form in chains and are not covered

• Spores carried by wind to germinate

LIFE CYCLE OF ASCOMYCOTA

CHECK POINT

• In sac fungi, which structure is dikaryotic?

• Answer: ascocarp

**SAC FUNGIASCOMYCOTA

• Cause many plant diseases• Wiped out virtually all chestnut trees in US

around 1980• Resistant cultivars are now being planted

• Also known for important contributions to human health• Penicillum – antibiotic penicillin

CLUB FUNGI

• Phylum Basidiomycota• Include mushrooms, toadstools,

puffballs, jelly fungi, shelf fungi, rusts and smuts• Larges known club fungus in Oregon is

3.5 miles across!

• Characterized by a basidium • Which is a clublike sexual reproductive

structure that produces spores

CLUB FUNGISEXUAL REPRODUCTION

• Specialized hyphae of different mating types grow together• Hypha from one fuses with hypha from

another forming dikaryotic cell• Nuclei remain separate as the cell grows into

new mycelium, in which cell has 2 nuclei• Grows rapidly

• When conditions are right, mycelia form reproductive structure called basidiocarp• Ex – mushroom

SEXUAL REPRODUCTION CONTINUED

•Under basidiocarp there are club-shaped cells called basidia in which the two nuclei fuse• meiosis occurs and spores produced

• Spores carried by wind, then grow

STOP AND THINK

•What might be the reproductive advantage of having gills on the underside of the mushroom?

• Protect spores from rain or make it easier for spores to disperse.

CLUB FUNGIASEXUAL REPRODUCTION

• Rare•Does occur in some rusts and smuts

LIFE CYCLE OF BASIDIOMYCOTA

CLUB FUNGI

CHECK POINT

•Which type of fungi was classified with protists until recently? •A. chytrid fungi•B. club fungi•C. sac fungi•D. zygote fungi •Answer: A chytrid fungi

FUNGAL PARTNERSHIPS• Fungi form Partnerships • In a mutualistic relationship.. Both members benefit

• Lichen • Fungus with photosynthetic partner • Photosynthetic partner provides carbohydrates • Fungus provides protected environment, vitamins,

minerals• Can survive in extreme environments• Can be damaged by chemical changes• Serve as living indicators of air pollution

FUNGAL PARTNERSHIPS

•Mycorrhiza • Fungi and roots of most plants • Photosynthetic partner provides carbohydrates• Fungus provides phosphorus and mineral from soil to roots

LICHEN

• Partnership between fungus and photosynthetic organism such as cyanobacteria or green alga

MYCORRHIZA

• Association between fungus and roots of nearly ALL plants

FUNGI PHYLAMethod of reproduction

Structures Habitat Example(s)

Chytridiomycota

Zygomycota

Ascoymycota

Basidiomycota

22.3 FUNGI AND HUMANS

• Fungi are used for food, medicines, research, alternative fuels and pest control • Most familiar as a food• Provide flavor and color of blue cheese• Yeasts are used in baking, brewing, and

winemaking• Produce citric acid that is used in soft drinks and

candies• Some, liketruffles, are worth $1,000 per pound

• Produce the antibiotic penicillin and cephalosporin• Black bread mold produces cortisone• Used to treat skin rashes and to reduce joint

swelling• Yeast cells modified to make vaccine for

hepatitis B.• Yeast also produces gasohol, a fuel alternative• Fungal insect parasites are used to kill crop-

destroying insects• Helps reduce use of harmful pesticides

FUNGI AND THE ECOSYSTEM

• Fungi play important ecological roles by decomposing organic matter and by breaking down and absorbing minerals from rocks and soil

• Main role in ecosystem decomposition• Can also break down wood

FUNGI AND THE ECOSYSTEM, CONT.

• Through lichens, fungi slowly break down rocks and prepare environment for other organisms

• Through mycorrhizae, fungi absorb minerals from the soil and transfer them to plant roots

• Almost all plants have mycorrhizae• Some, could not survive without them

FUNGI AND DISEASE

• Can causes disease in plants and animals• Cause disease by absorbing nutrients from

host tissues and by producing toxins.

FUNGAL INFECTIONS

• Dermatophytes are fungi that infect skin and nails• Cause athlete’s foot, toenail fungus, and

ringworm

• Yeast is normal resident of body• Antibiotics, hormonal changes, or illness

can cause overgrowth of yeast• Causes yeast infection in reproductive

organs and in mouth

FUNGAL INFECTIONS

• Histoplasmosis is lung infection caused by fungus• Grows in bat and bird feces• Occurs when spores are inhaled• Left untreated, is fatal

FUNGAL TOXINS

• Many produce dangerous toxins • Can cause vomitting, diarrhea, liver damage,

and even death• Aflatoxins – contaminates corn, peanuts, and

cottonseed• Can cause liver cancer

• Indoor molds aggravate allergies• Mold toxins can be linked with pulmonary

bleeding in infants