Introduction to Protists

First eukaryotic organism thought to have evolved about 1.5 billion years ago Endosymbiosis – process where one prokaryote lives inside another becoming dependent upon each other Origin of Eukaryotes

Infolding of membrane system forming nucleus and ER Origin of Eukaryotes Endomembrane infolding

Origin of Eukaryotes Evolution of eukaryotic cell- Endosymbiosis – a theory Mitochondria and plastids were prokaryotes that invaded larger cells Relationship began as parasitic or undigested prey

Endosymbiosis Hypothesis A A prokaryote ingested some aerobic bacteria. The aerobes were protected and produced energy for the prokaryote Chloroplasts Aerobic bacteria Mitochondria Cyanobacteria Prokaryote Animal Cell Plant cell B C D A N N N N

Endosymbiosis Hypothesis B Over a long period of time the aerobes became mitochondria, no longer able to live on their own A B C D Chloroplasts Aerobic bacteria Mitochondria Cyanobacteria Prokaryote Animal Cell Plant cell N N N N

Endosymbiosis Hypothesis C Some primitive prokaryotes also ingested cyanobacteria, which contain photosynthetic pigments A B C D Chloroplasts Aerobic bacteria Mitochondria Cyanobacteria Prokaryote Animal Cell Plant cell N N N N

Endosymbiosis Hypothesis D Cyanobacteria became chloroplasts, unable to live on their own A B C D Chloroplasts Aerobic bacteria Mitochondria Cyanobacteria Prokaryote Animal Cell Plant cell N N N N

LUCA model places the archaea as more closely related to eukaryotes than they are to prokaryotes.

Kingdom Protista Plantae Fungi Animalia Protista Eubacteria & Archaea prokaryotic eukaryotic

Kingdom Protista Eukaryotic Mostly unicellular but some multicellular A very heterogeneous group include both heterotrophic and autotrophic forms

binary fission splits into two asexually sexually by conjugation (opposite mating strains join & exchange genetic material) Sexually by producing gametes (meiosis) Reproduction:

3 informal groups Animal-like protists Fungus-like protists Plant-like (algal) protists Kingdom Protista ~ 45,000 species

Amoeba (phylum Cercozoa) Cilliates (phylum Ciliophora) Flagellates (phylum Zoomastigina) Sporozoans (phylum Sporozoa) Animal-like Protists 13,000 species

Classified by the way they move Animal-like Protists cilia flagella pseudopodia

Heterotrophs ingest small food particles & digest it inside food vacuoles containing digestive enzymes

Phylum Cercozoa “Amoeba” Have pseudopods for feeding and movement Animal-like Protists

Foramenifera: Globigerina ooze Covers about 36% of the ocean floor

Phylum Ciliophora (“ciliates”) Largest, most homogeneous Share few characteristics with others Movement coordinated Animal-like Protists 8,000 species

Paramecium

Asexual reproduction Binary fission

Paramecium reproduction 1. Individuals fuse 2. Micronucleus produces 4 haploid nuclei

Phylum Zoomastigina (“zooflagellates”) Move using flagella Move using flagella:1 to thousands of flagella Some parasites African trypanosomiasis – sleeping sickness – tsetse flyAfrican trypanosomiasis – sleeping sickness – tsetse fly Chagas Disease – kissing bugChagas Disease – kissing bug Leishmaniasis – sand flyLeishmaniasis – sand fly giardiasisgiardiasis Animal-like Protists 1,500 species

African sleeping sickness Tsetse fly Trypansoma

The Kissing Bug Chagas disease

Leishmaniasis Sand fly Leishmania

Malaria Mosquito & “victim” Africa = kills 1 million children per year Thousands of sporozoites injected Vaccine? (US support?) Anopheles Mosquito Plasmodium sporozoite gameteocyte

The Sporozoans: Phylum Sporozoa Parasites of animals Alternate between sexual & asexual production

Plasmodium, the parasite that causes malaria, spends part of its life in mosquitoes and part in humans.

Fungus-like Protists Phylum Oomycota (“water molds”; mildew, blights) Some unicellular; others consist of hyphae Decomposers,parasites Cell walls- cellulose Related to algae based on cell wall composition Named after reproductive method 475 species No “septa”

water molds

Downy Mildew

Mildew hyphae

Oomycota Reproduction: the “egg fungi”, a relatively large egg cell is fertilized by a smaller “sperm nucleus,” forming a resistant zygote.

Fungus-like Protists Phylum Myxomycota (“slime molds”) Bizarre Bright colors Moving “slime” mass 550 species

Fungus-like Protists Phylum Acrasiomycota Resemble amoebas Ingest bacteria and yeast Known as cellular slime moulds

Plant-like Protists Dinoflagellates Diatoms Euglena Cocolithophore Green algae Brown Algae Red algae Diatoms Dinoflagellates Radiolarian Cocolithophore

Plant-like Protists Phylum Pyrrophyta (“dinoflagellates”) 1,100 species Cause “red tide” Some live in corals Marine and Freshwater

Zooxanthellae in Coral Polyp

Pyrocystis fusiformis Bioluminescence

HAB (harmful algal blooms) can result in PSP (paraletic shellfish poisoning) Gonyaulax polyhedra, Gymnodium

The numbers are representative values of the concentration in the tissues of dinoflagellate toxin (ppm) Primary producers Primary consumers Secondary consumers Tertiary consumers 0.04 ppm 0.23 ppm 2.07 ppm 13.8 ppm

Plant-like Protists Phylum Chrysophyta - diatoms 13,000 species

epithecate hypothecate Diatom Reproduction- asexual auxospore Discards shell and grows new one

Phylum Euglenophyta (“euglenoids”) Plant-like Protists 800 species

Division Chlorophyta “Green algae” Most freshwater or terrestrial Some marine 7,000 species

Halimeda opuntia Chlorophyta: Green Algae Caulerpa racemosa Caulerpa sertularioides Dictyosphaeria cavernosa Codium edule

Division Phaeophyta “Brown algae” Marine habitats Example: giant kelp forests 1,500 species

Example of complex morphology: Macrocystis a.holdfast - attaches to substrate b.stipe c.blade - main organ of photosynthesis d.bladder - keeps blades near the surface Blade Bladder Stipe Holdfast

Laminaria Life Cycle

Sargassum polyphyllum Sargassum echinocarpum Phaeophyta: Brown Algae Turbinaria ornata Padina japonica Hydroclathrus clathratus

Division Rhodophyta “Red algae” Most in marine habitats 4,000 species

Hypnea chordacea Asparagopsi s taxiformis Galaxaura fastigiata Acanthophora spicifera Ahnfeltia concinna Rhodophyta: Red Algae