Origin and Diversification of Eukaryotes: Protists

1. Origin and Diversification of Eukaryotes: Protists

2. Eukaryotic Cells • Nucleus and membrane bound organelles • Well developed cytoskeleton – structural support that lends to asymmetric forms • May have originated more than 2.7 bya, but 1.8 bya widely accepted

3. 3 stages of diversity documented by fossil records • Initial diversification – 1.8 – 1.3 bya • Origin of multicellularity 1.3 bya – 635 mya • Emergence of large eukaryotes 635-535 mya

4. endosymbiosis • Symbiotic relationship in which one organism lives inside the bosy or cell of another organism. • DNA sequence data suggest that eukaryotes are “combination” organism from Archaea and Bacteria • Endosymbiont theory – mitochondria and plastids were formerly small prokaryotes that began living within larger cells. (See page 485)

5. Multicellularity • Colonies – collection of cells that are connected but show little or no cellular differentiation. • Multicellular organisms with differentiated cells – Algae, plants, fungi and animals

6. Characteristics • Most diverse kingdom • eukaryotic., 1.5 bya • Primarily unicellular/multicellular, • heterotrophic/autotrophic • Usually asexual, some sexual • Found in water, damp soil and sand, leaf litter • Some are parasitic • 14 phyla

7. Characteristics • Characteristics first seen in Protista kingdom • Sexual reproduction (varies, mitosis and meiosis – usually in harsh enviro.) • Multicellularity (coordination among specialized cells) • Complex flagella and cilia (as opposed to simple seen in bacteria)

8. Protist diversity • Heterotrophic protists = protozoans, slime molds, water molds, parasites • Photosynthetic protists = Algae • Some are classified further by how they move: • Amoebas – pseudopodia • Ciliates – cilia, ex. paramecium • Flagellates – flagella, ex. Euglena

9. Algae – Green, Red and Brown • Strict autotrophs, some multicellular • Distinguished by type of pigment they contain • Red • Multicellular, warm ocean waters • Red pigment can absorb light in deep water • Brown • Multicellular, marine • Kelp, grows along coasts, food and shelter • Green • Most freshwater, uni and multicellular • Contains chlorophyll a and b

10. Green Algae • Phylum Chlorophyta • Most unicellular, can be filamentous or colonial • Chlamydomonas – unicellular green algae • Spirogyra – filamentous green algae • Ulva – multicellular green algae (sea lettuce) • Volvox – colonial (loose association of independent cells) green algae

11. Red Algae/Brown Algae • Phylum Rhodophyta • Economically important – • Agar • Wrappings around sushi • Emulsifying agent for production of chocolate • Phylum Phaeophyta • Contain chlorophylls a and c and carotinoid • Kelp, rockweed – grow along shoreline • Harvested for human food and fertilizers • Algin – pectin-like material added to icecream

13. Diatoms • Phylum Chrysophyta – includes golden-brown algae and yellow-green algae • Photosynthetic, significant part of phytoplankton, Important to food chain • Double shell made out of silica, like hat box • Move by excreting chemicals through Diatomaceous earth – • abrasives • holes in shell • Found in oceans and lakes

14. Dinoflagellates • 2 flagella, cellulose plates • Unicellular • Most are marine, make up part of the plankton, important food source, producers • Some produce powerful toxins – “red tide”

15. Euglena • Freshwater, unicellular with 2 flagella • Some photosynthetic with chloroplasts and has ability to ingest food as well • Pellicle – protein fiber inside cell membrane, allows for flexibility and shape change • Eyespot – light sensitive organ, toward light • Contractile vacuole – expels excess water

16. Zooflagellates • Mostly unicellular, hetertrophic protozoans • Symbiotic and parasitic forms • Trypanosomes – transmitted by tsetse fly • Causes African Sleeping Sickness • Giardia lamblia – cysts from contaminated water, intestinal wall, severe diarrhea • Trichomonas vaginalis – STO, infects vagina and urethra of women, prostate of males

17. Amoeba • Pseudopodia – false foot, cytoplasmic extensions • Food vacuole – food enters and moves throughout cell • Contractile vacuole – regulates water • Entamoeba histolytica – amoebic dysentery

18. Forams • marine protist that lives in sand or attaches to other organisms • Tests – porous shells • Thin projections of cytoplasm extend through pores and aid in swimming

19. Paramecium • Freshwater streams and ponds • Unicellular, heterotrophic • Cilia to move • Two nucluei • Macro – cell activities, includes DNA • Micro –cell reproduction, contains chromosomes

20. Sporozoans – parasitic protists • Form spores during their reproductive cycle • Nonmotile, spore forming, unicellular parasites • Malaria – anopheles mosquito, pg 392 • Toxoplasma gondii – toxoplasmosis, during pregnancy, can affect fetus

21. Slime molds - decomposers • Cellular slime mold, small • Behave like amoebas • Ingest bacteria • During stress, form multicellular colonies • Plasmodial slime molds • Mass of cytoplasm that looks like ooze, colorful • Eat bacteria and other organic material, phagocytes

22. Water Molds • Filamentous decomposers • Parasitic to plants and animals in ecosystems • Cell wall contains cellulose, not chitin • Usually have furry growths • Responsible for potato famine in Ireland, 1840’s

23. Beneficial protists • Commensal protists that live in digestive tracts of humans and livestock (hay, cellulose) • Plankton – food, shelter, producers • Largest group of photosynthesizers • Abrasives • Detritivores – recycle chemicals in environment • Symbiotic relationships - coral