The Protists

The Protists• Eukaryotes.• Most unicellular.• Most aerobic.• Moist environments• Can be photoheterotrophs, photoautotrophs,

chemoheterotrophs or mixotrophs.• Flagella or cilia.• All protists can reproduce asexually, some

sexually

Endosymbiosis• Eukaryotic cells evolved from symbiotic

combinations of prokaryotic cells.– Mitochondria aerobic heterotrophic

prokaryotic cells– Chloroplasts photosynthetic prokaryotes

Evidence for Endosymbiosis

Similarities between modern bacteria and the chloroplasts/mitochondria of eukaryotes:

*size*enzymes*circular DNA molecules*process of division*ribosomes similar

The Candidate Kingdoms• Archaezoa• Euglenozoa• Alveolata• Stramenopila• Rhodophyta• Green Algae

Candidate Kingdom Archaezoa

• Giardia • have two nuclei,

flagella, and no mitochondria (…parasites)

Candidate Kingdom EuglenozoaAutotrophic and/or

heterotrophic flagellates

• Euglena– 1 or 2 flagella

• Kinetoplastsparasitic, e.g. African Sleeping Sickness (bite of tsetse fly)

Trypanosoma

Candidate Kingdom Alveolata• Dinoflagellates, phytoplankton,

cause red tides, color from xanthophyll.

• Apicomplexans, plasmodium, causes malaria.

• Ciliates, paramecium

Next Group

Dinoflagellates

http://www.microscopy-uk.org.uk/mag/artsep01/dinof.html http://www.microscopy-uk.org.uk/mag/indexmag.html

Apicomplexans

Leishmania

Parasite infected erythrocyte

Life history of Plasmodium

Ciliates

Paramecium

Stentor

Vorticella

Pseudopod “Protists”

Taxonomic lineage unclear, so no clear kingdom found… i.e. “misfits”• Rhizopods, amoebas

• Actinopods, radiolarians and heliozoans (delicate silica shells).

• Foraminiferans, marine with porous calcium shells. Used as index fossils.

• Slime Molds, cytoplasmic streaming

Rhizopod

Amoeba

Actinopods

Radiolarians

Foraminiferans

Slime Molds• Plasmodial Slime Mold – Myxomycota. Heterotrophic,brightly colored,

multinucleated ameboid mass.

Candidate Kingdom Stramenopila• Diatoms (bacillariophyta)– unicellular

plankton with box-like silica walls. Diatomaceous earth.

• Golden Algae (chrysophyta) – yellow and brown carotene and xanthophyll pigments

• Brown Algae (phaeophyta)- largests and most complex. Seaweeds and kelps, may be as long as 60m.

• Water Molds (oomycota) – white rusts and downy mildews

Next Group

Diatoms

Golden Algae - Chrysophyta

Brown Algae - Phaeophyta

Kelp Harvesting

Kelp Structures• Analogous plant-like structures

– Body = thallus– Root-like structure – holdfast– Stem-like structure – stipe– Leaf-like structure - blades

Water molds, white rusts and downy mildews

White rust on spinachWater mold

Candidate Kingdom Rhodophyta

• Red color from pigment

• Marine • Multicellular• Carrageenan

thickener

Candidate Kingdom Green Algae

*Many scientists advocate inclusion of green algae into the plant kingdom.*More than 7000 species, mostly freshwater.

Ulva

*Unicellular – Chlamydomonas*Colonial – Volvox*Multicellular – Ulva

Green Algae - Chlorophyta

Chlamydomonas

Volvox

Spirogyra

Chlamydomonas Life Cycle

Ulva Life Cycle