Protists Chapter 28

In the beginning… van Leeuwenhoek when observing protozoa: –“no more pleasant site has met my eye than this” (1681) –“My excrement being so thin I was…persuaded to examine it. I have sometimes seen animalcules a- moving very prettily…” (a bad week in 1681)

Understanding the Protista For this class we will focus on: –How they are categorized –General features of protozoa –Exceptions to the general features –Examples of sexual reproduction –Specific species from several, not all, clades of protists (good reason to attend lecture)

Protista

Protists – the first eukaryotes Protozoa Algae (unicellular and colonial) Algae (large – seaweeds, kelp) Diatoms Water molds

A model for the formation of eukaryotic cells: Endosymbiosis

A model for diversity in Protists: Endosymbiosis again

Protists – the first eukaryotes Greater cellular complexity than in prokaryotes The most nutritionally diverse of all eukaryotes –Photoautotrophs –Heterotrophs –Mixotrophs Ecology –Protozoa (ingestive, animal-like) –Fungus-like (absorptive) –Algae (photosynthetic, plant-like) Golden algae

General Features Unicellular and multicellular Colonial and true multicellular Free-living and parasitic Most complex unicellular organism Sexual and asexual reproduction

Euglena: autotrophs but can become heterotrophic (mixotrophs)

A sampling of protists Giardia Euglena Amoeba Trypanosoma

A sampling of protists Diatoms, algae – primary productivity in aquatic and marine systems Colonial Unicellular Multicellular

A sampling of protists Red Algae Kelp Golden Alga Nori (red alga)

Diplomonads and Parabasalids Giardia intestinalis –Water borne parasite –Common in backcountry –Anaerobes –Harm host by mechanical blockage of gut Trichomonas vaginalis –Sexually-transmitted parasite –Outcompetes in disturbed area –Can acquire helpful gene from bacteria –Males asymptomatic

Euglenozoans – just listen Kinetoplastids – Trypanosomes –Cause sleeping sickness (Africa), Chagas disease (Central and S. America) –Antigenic variation in surface proteins –1/3 of genome codes for surface antigens

Alveolates Dinoflagellates –Phytoplankton –Can cause “red tide” –Toxins can sicken or kill humans Pfiesteria shumwayae

Alveolates Apicomplexans –Parasitic –Complex life cycle –Cause of malaria –Know this life cycle!

Malaria Sporozoites infect liver cells Merozoites burst from liver –Infect RBC’s, eat and reproduce in cycle Gametocytes produced Mosquito takes a meal Zygote moves to hemocoel –Produces sporozoites –Injected into next victim

Stramenopiles – just listen Oomycetes – water molds –Look at your dead goldfish Diatoms – unicellular algae with silica wall –Diatomaceous earth Golden algae

Stramenopiles Brown algae –Seaweed –Complex multicellular Seaweed body is a thallus with: –Rootlike holdfast –Stemlike stipe –Leaflike blades

Alternation of generations

Amoebozoans Entamoebas –All in genus Entamoeba are parasitic –E. histolytica (“tissue lysis”) –Causes amoebic dysentery (bloody diarrhea) –100,000 deaths worldwide/yr

Amoebozoans Slime molds, 2 kinds: Plasmodial –Forms a unicellular, multinucleate mass (plasmodium) Cellular –Individual amoebas come together to form a multicellular organism

Red and Green Algae Red algae –Similar to seaweeds (brown algae) Green algae –Uni- and multicellular –Colonial types (Volvox) –Symbionts with fungi (lichens) –Close relatives to land plants

Chlamydomonas nivalis “green” algae