ch21 lecture

8/11/2019 Ch21 Lecture

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Tobin and Dusheck: Asking About Life, 3E __________ Chapter 21

Copyright 2005Brooks/ColeThomson Learning

The Grab BagProtists and thePurebred Fungi

Chapter 21


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Eukaryotes

DNA contained in nucleussurrounded by membrane

Other membrane organelles mitochondria, chloroplasts


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Protists

Eukaryotes

Diverse group, up to 12

kingdoms?Most are single cells

Do not fit with plants, animals or

fungi Heterotrophic or photosynthetic

Sexual or asexual reproduction


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Examples of Protists


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Protist Reproduction

Some diploid, produce haploidgametes

Some always haploid andasexual

Some haploid with short lived

diploid zygote Some alternate generations with

multicellular haploid phase


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Protist

Reproduction


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6 Groups of Protists

Classification is controversial

Based on DNA sequences

DiscricristalesChromaveolates

Radiolarians and foraminifera

AmebasRed algae

Green algae


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Classification of Protista


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Discricristales

Euglenophytes, eye spot

Heterotrophs in the dark,photosynthesis in the light, usechlorophyll a and b

No cell wall

Trypanosomes cause sleepingsickness


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Discricristales 2

Flagellates

Single celled heterotrophs

Fresh or salt water or parasites

Acrasiomycota, acrasid slime molds

Plentiful nutrients, separate, ameba-like

Scarce nutrients, aggregate to formslug; make fruiting body to producespores asexually


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Chromalveolates

Diverse group with 2 majorlineages:

Dinoflagellates, apicomplexans,ciliates

Water molds, golden algae,diatoms


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Dinoflagellates

Single celledplankton

Rigid cell

wall called atest

2 flagella

Basis ofaquatic foodchains


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Red Tide

Dinoflagellatepopulationexplosion

Some releasetoxins thatget into foodchain, makingshell fishpoisonous andkilling fish


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Apicomplexa

All parasites; complex life cycleMalaria plasmodium


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Ciliates

Free-living,single-cellheterotrophfresh andsalt water

Move with

cilia

Most lackshells


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Oomycota

Behave like molds extendhyphae-like threads into host,absorb nutrients

Parasitic or saprophytic (live ondead organisms)

Reproduce sexually; life cycles

include haploid and diploid phases Some cause disease potato

blight


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Golden Algae

Single-celled and colonial forms;most are plankton

Reproduce asexually

Swarmer cells

Mature colony splits

Can form cysts


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Phaeophytes - Brown Algae

Seaweeds Multicellular, live

in temperate sea

Reproducesexually

Alternation of

haploid anddiploidgenerations


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Diatoms

Most aresingle cells

Silica test

Free-floatingin fresh orsalt water

Reproduce sexually and asexually


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Radiolaria

Glass-likeskeletons

Free-living

plankton

Reproducesexually or

asexually

Some arepredators


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Foraminifera

Marine organisms Sand or mineral tests

Live in sand or

attached toorganisms, somefree-floating

Form chalkysediments

Alternation of

generations


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Amoebazoa

Amebas are Rhizopoda

Live in oceans, fresh water, soiland as parasites

Move with pseudopodia

Reproduce by simple cell division

Plasmodial slime molds arerelatives no cellboundaries(multinuclear); sexualreproduction from fruiting body


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Amoeba proteus


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Chlorophytes-Green Algae

Ancestors ofplants?

Photosynthetic

withchlorophyll aand b

Somemulticellular,most freeliving


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Protists and Chlorphyll


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Fungal Structure Hyphae: thread-like

filaments formmycelium1

Some have no cell boundaries: coenocytic

Dikaryotic have septa between cells, but

are perforated


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Fungi Classification

3 phyla: Zygomycetes

Ascomycetes

Basidiomycetes


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Zygomycetes

Mycelim iscoenocytic

Asexual

reproductionby spores insporangia

Sexual reproductionby formingzygosporangium

with haploid spores


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Ascomycetes Yeast, molds, cupfungi and lichens

Sexual sporesproduced in

asci

Hyphae haveperforatedsepta

PenicilliumandSaccharomycescerevisiae


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Basidomycetes

Called club fungi for basidium reproductivestructure that produces spores

Also

includesrusts andsmuts,plant

parasitesthat do notproduce

basidiocarp


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Thinking About the Possibilities

If you wanted to invent a newfungicide that would kill fungalcells but not human cells, what

differences between the biologyof fungal cells and biology ofhuman cells might you exploit?


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Fungi

EcologicalRoles

Some arepredatory

Most arerecyclers:

Decompose organic matter, make nutrientsavailable

Symbiotic associations


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Lichens

Associations of fungi withphotosynthetic partners (alga or

cyanobacteria) Fungus extracts nutrients from rock,

alga provide energy

Reproduce by fragmentation


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Lichens

b d h k k b f h


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Mycorrhizae

Fungal association with plantroots

Fungi obtain sugar from plant

Fungi supply phosphate andmetal ions to plant

Plants without mycorrhizae donot grow as well

T bi d D h k A ki Ab t Lif 3E Ch t 21


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Mycorrhizaeand Plants

T bi d D h k A ki Ab t Lif 3E Ch t 21


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Evolution of Fungi

Fossil record is poor no hardparts

Zygomycetes were probablyearliest simplest life cycle

Ascomycetes developed fromzygomecetes

Basidomycetes derive fromzygomycetes

Tobin and Dusheck: Asking About Life 3E Chapter 21


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Copyright 2005

Brooks/Cole

Thomson Learning

Thinking About the Possibilities

Identify an edible (for humans)example from each of the groups

we have discussed.

Tobin and Dusheck: Asking About Life 3E Chapter 21


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Key Concepts

Protists and fungi are eukaryotes Protists are polyphyletic and diverse

Protist plankton are important

contributors to aquatic food chains True fungi lack flagella and have cell

walls made of chitin

Fungi play important ecological rolesas decomposers, partners of lichens,and in association with the roots ofhigher plants

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