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Chapter 12 – EUKARYOTES:Protists, Fungi & Helminths

1. Protists

2. Fungi

• Algae

3. Helminths

• Protozoa

1. Protists

A. Algae

B. Protozoa

A. Algae

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Overview of the Algae Characteristics of algae:

• unicellular or multicellular eukaryotes• almost all are photoautotrophs (photosynthetic)

• all are essentially aquatic (live in fresh or saltwater)

Algal phyla we will consider:

• all are capable of asexual reproduction

Phaeophytes (brown algae)

Rhodophytes (red algae)

Chlorophytes (green algae)

DiatomsDinoflagellatesWater Molds

**produce an estimated 80% of O2 in the atmosphere!**

• some are capable of sexual reproduction as well

Brown Algae (Phaeophyta) • macroscopic seaweeds referred to as “kelp”• largest members of the Kingdom Protista

• can grow 20 cm/day• contain distinct

vegetative structures• holdfast anchors

kelp to surface• stemlike stipes

• leaflike blades

• pneumatocystsprovide buoyancy

Red Algae (Rhodophyta) • macroscopic seaweeds that lives in deep water

where only blue light penetrates

• source of“agar” (usedin culture plates)

• source of“carageenan”

(thickeningagent in foods)

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Green Algae (Chlorophyta)

• most are microscopic (uni- & multicellular), someare macroscopic

• believed to have given rise to the plants

Diatoms

• have a unique cell wall structure composed ofa carbohydrate called pectin & silica

• responsible for geometric, glass-like appearance

• widely distributed throughout photic zone

• importantpart of aquatic foodwebs

• unicellular or filamentous (form multicellular filaments)

Dinoflagellates • what are commonly referred to as “plankton”

• unicellular algae with 2perpendicular flagella

• some produce potentneurotoxins

• source of toxic algal blooms (e.g., “red tide”)

• important part of theoceanic food web

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Water Molds (Oomycota) • have a “fungus-like” appearance but are protists

• cell walls made of cellulose (not chitin)

• spores have flagella (fungal cells never have flagella)

• most water moldsare decomposers

• play an importantrole in recyclingnutrients

B. Protozoa

Overview of the ProtozoaCharacteristics of protozoa:

• all are unicellular eukaryotes lacking a cell wall• all are heterotrophs (a few can be photosynthetic)

• capable of asexual reproduction (some sexual repr.)

Protozoan phyla we will consider:Archaeozoa

Microspora

Apicomplexa

CiliophoraEuglenozoaAmoebozoa

• parasitic species have complex life cycles• some form protective cysts (when times are bad)

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Archaezoa • do NOT have mitochondria

• have an analogous organelle called a mitosome

• most have multiple flagella

• several parasitic genera can cause human disease• Trichomonas, Giardia

Apicomplexa

• non-motile obligate intracellular parasites

• have a unique “apical complex” of fibers andvacuoles that release digestive enzymes

• aid in penetration of host animal tissue

• includes species of Plasmodium responsiblefor the disease malaria

• e.g., P. vivax & P. falciparum

Plasmodium vivaxLife Cycle (malaria)

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Ciliophora (“ciliates”)

• some have multiple nuclei

• all have many smallprojections called cilia

• used for locomotion &to direct food into thecytostome (“mouth”)

• have contractile vacuoleto expel excess watertaken in by osmosis(expelled by exocytosis)

Sexual Reproduction in CiliatesMost ciliates are capable of sexual reproductionby a process called conjugation:

conjugating Paramecia

• remaining micronucleusdivides by mitosis (2)

• exchange of 1 micronucleus between cells

• conjugating Paramecia ea produce 4 haploid micronuclei by meiosis, 3 of which disintegrate

• “old” & “new” micronuclei fuse, divide by mitosis,one of which replaces original micronucleus

Euglenozoa

• some are photosynthetic (Euglena)• have a light-sensitive eyespot & a single flagellum

• includes the hemoflagellates (Trypanosoma)• responsible for “sleeping sickness” & Chagas disease

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Amoebozoa

• aka “amoebas”

• have distinct form oflocomotion called“amoeboid movement”

• extend cytoplasmicprojections calledpseudopods

• also used to engulfand ingest food byphagocytosis

Slime Molds • have characteristics of both amoeba & fungi but

but are not true fungi

• slime molds are split into 2 groups:

Cellular Slime Molds• form large aggregates under unfavorable conditions

Plasmodial Slime Molds• only exist in large multinuclear aggregates• are classified in their own phylum

• are considered part of the phylum Amoebozoa

Cellular Slime Mold Life Cycle

in unfavorableconditions

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2. Fungi

Overview of the FungiGeneral characteristics of fungi:

• all are eukaryotic absorptive heterotrophs

• unicellular (yeasts) or multicellular (molds, club fungi)

• capable of asexual & sexual reproduction

• have cell walls that contain chitin• aerobes w/some being facultative anaerobes

• do NOT have flagella (spores are immotile)

• vast majority are terrestrial (i.e., live on land)

• all fungi develop from haploid spores (no embryos)

**study of fungi is known as mycology **

Structure of Multicellular Fungi

The thallus (“body”) of a fungus consists largely of filamentous chains of cells called hyphae:

• vegetative (non-reproductive) or aerial (reproductive)

• some have septa (septate), some don’t (coenocytic)

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Hyphae form a Mycelium

On a rich source of nutrients, many hyphae can beproduced to form a continuous mass called a mycelium.• vegetative hyphae spread across food source & “absorb”

• aerial hyphae grow vertically & produce spores in a number of different ways, depending on the fungus

Reproduction in Filamentous FungiCan reproduce asexually by fragmentation:

• hyphae fragments grow by mitosis

Produce spores asexually or sexually: Asexual spore production

• occurs at the tip of aerial hyphae

• derived from single parent fungus

• produced by mitosis

Sexual spore production• involves a partner of opposite mating type, meiosis

Asexual Spores

2 types of asexual spores:

1) those not enclosed in a sac are conidiospores(aka conidia)

• produced at the end of an aerial hypha called a conidiophore

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2) sporangiospores are produced within an enclosedsac called a sporangium• forms at the end of hypha called a sporangiophore

Sexual SporesSexual spores in fungi require 3 phases notseen in the production of asexual spores: 1) transfer of a haploid nucleus to a cell of the

opposite mating type: plasmogamy

2) fusion of the haploid nuclei to form a diploid zygote nucleus: karyogamy

• haploid nuclei may reproduce by mitosis before fusing

3) meiosis to produce haploid sexual spores

• this is the ONLY occasion when fungal cells are diploid

The 3 Fungal Phyla

Zygomycota• conjugation fungi (molds)

Ascomycota• sac fungi (yeasts, molds, truffles, lichens)

Basidiomycota• club fungi (mushrooms, smuts, rusts, puffballs)

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Zygomycota • molds with coenocytic hyphae (no septa)

• saprophytic(feed on deadvegetation)

• producespores insporangia

Zygomycote Sexual Reproduction• plasmogamy occurs via conjugation

• results in zygospore which grows a sporangium

**all 3 phyla conjugate, not

just “conjugating fungi”**

Basidiomycota• commonly called the “club fungi” due to the

presence of microscopic, club-shaped basidia:

• reproductive structures that produce basidiospores

• some areparasitic

• many have mutualisticsymbioseswith variousplant species

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Basidiomycote Life Cycle • sexual reproduction via conjugation produces a

basidioma:

• tightly packedaerial hyphaethat make up the“fruiting body”(e.g., mushroom)

• basidia form on the “gills” and produce sporesby meiosis

Ascomycota• produce sexual ascospores in a sac-like ascus

• produceasexual conidia

• includes moldswith septatehyphae, yeastslichens

Ascomycote Sexual Reproduction• conjugation between opposite mating types results in the formation of an ascus followed by karyogamy & meiosis (sometimes followed by mitosis)

• resulting 4 or8 ascosporesreleased whenascus opens

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Budding Yeasts Spherical unicellular fungi.

• reproduce asexuallyby budding

• facultative anaerobes(used for beer, wine…)

• important in biologicalresearch

• studying the cell cycle• production of insulin &

other important thingsSaccharomyces cerevisiae

• also reproduce sexually

Fission Yeasts Oval or rod-shaped unicellular fungi.• reproduce asexuallyby fission

• facultative anaerobes

• biological research

• also very important forstudying the cell cycle

Schizosaccharomyces pombe

• also reproduce sexually

LichensLichens are actually 2 different organisms in a mutualistic symbiosis:

• cyanobacteria or greenalgae living among thehyphae of an ascomycote(or basidiomycote)

• fungus gets free carbs!

• algae or cyanobacteriaprotected from elements

• important pioneers• can grow on inorganic surfaces, begin succession

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LichenStructure

Fungal hyphae form the followingstructures:

• protective cortex

• inner medullawhere algae grow

• rhizines to attachto growth surface

3. Helminths

Overview of the Helminths Helminths are parasitic worms found in 2 animal phyla, the Platyhelminthes (flatworms) and the Nematodes (roundworms).

• multicellular eukaryotic heterotrophs

• have complex life cycles frequently involvingmultiple hosts

• contain distinct organ systems• some may be reduced or absent due to dependence

on host (e.g., no digestive system, no locomotion)

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Platyhelminthes (flatworms):

Nematodes (roundworms):• typically dioecious (2 sexes)

• typically hermaphroditic (monoecious)

• have a proctostome (single opening, no anus)

• have complete digestive system (mouth & anus)

• we will look at 2 classes:

• we will look at 2 types: pinworms & hookworms

Trematodes (flukes) & Cestodes (tapeworms)

Trematodes (flukes)

Members of this class of flatworms are all parasites associated w/particular host tissues (liver, blood, lung)

(liver fluke)

• can have multiple larval stages and intermediate hosts • hermaphroditic (monoecious) • attach to host tissue via oral and ventral suckers• absorb nutrients through outer cuticle

A Fluke Life Cycle (lung fluke)

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Tapeworms(cestodes)

• intestinal parasites

• no digestive system,absorb nutrients

• scolex (head) has hooks& suckers for attachment

• repeating proglottids havemale & female reproductiveorgans (monoecious)

• mature proglottids detach& pass w/feces allowingtransmission to other hosts

A Tapeworm Life Cycle

Pinworms

Enterobius vermicularis

• entire life cyclein human hosts

• live in largeintestine

• females lay eggson anus

• a dioecious parasitic roundworm (nematode)• transmitted to new hosts via eggs

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Hookworms

• live, mate, lay eggs insmall intestine

• dioecious nematodes

• eggs pass with feces,hatch in soil

• larvae enter new hostthrough skin, pass to lungs via blood, lymph

• coughed up, swallowedto reach small intestinerepeat life cycle

cutting plates in mouth used for

attaching toand removing

host tissue

Key Terms for Chapter 12

• mitosome, cytostome, pseudopods

• vegetative, conidia, sporangia

• thallus, hyphae, mycelium, septate, coenocytic

• plasmogamy, karyogamy, saprophytic

• holdfast, stipes, blade, pneumatocyst

• basidia, ascus

• monoecious, dioecious

Relevant Chapter Questions rvw: 1, 2, 5, 11-14 MC: 4, 8-10

• scolex, proglottids