1. Protists The parasites from sleeping sickness and malaria are protists

2. The world in a drop of water  Even a low-power microscope can reveal a variety of organisms in a drop of pond water  Microscopic eukaryotes as well as bacteria 50  m

3. Kingdom Protista?  These amazing organisms are mostly single-celled eukaryotes informally known as protists  Advances in classification have re-arranged the protists significantly so they are not considered a kingdom any more  BUT don’t fit into the other kingdoms (within the Domain Eukarya) either...

4. Diversity 1.Single cell or multi-cell:  Most are unicellular, some are colonial or multicellular 2.Nutritional diversity:  Photoautotrophs, heterotrophs, and mixotrophs (which combine photosynthesis and heterotrophic nutrition) 3.Habitat variety:  Including freshwater and marine species 4.Life cycles  Both sexual and asexual species

5. Example: Red algae Known as seaweed, but not actually a plant Perform photosynthesis with a red pigment because red light reaches deeper water Very important in the marine food chain

6. Eukaryotes  The first appeared on the earth about 2 billion years ago  Have a nucleus, mitochondria, endoplasmic reticulum, as well as other cell structures not found in prokaryotes  How did these cells evolve?  Endosymbiosis

7. A combination of 2 ideas Endocytosis When a cell wants to bring in a large object, it projects ”arms” from its cell membrane and wraps the cell membrane around the object, engulfing it Symbiosis When 2 organisms cooperate, living together and both benefit from the relationship endocytosis

8. Once upon a time...  There was a big heterotrophic bacteria  It tried to eat another smaller bacteria by engulfing it  It was supposed to dump a lysosome into the vesicle containing the “food” to digest it, but it did not...  The “food” gave the “host” some advantage (because the “food” had unique chemistry) so the “host” was very successful “Food” that was good at breaking down sugar  became a mitochondrion “Food” that was good at photosynthesis  became a chloroplast Endosymbiosis animation

9. The evolution of a eukaryote

10. Evidence? That supports mitochondria and chloroplasts as originally free-living organisms 1.Each organelle has its own DNA 2.Each organelle has its own reproduction schedule 3.Each organelle has 2 membranes Just like PROKARYOTES!

11. Mutually beneficial  Whether the mitochondria/chloroplasts arose because of bad digestion or as parasites is unclear  Key point: The relationship is mutually beneficial  Some protists underwent serial endosymbiosis – in which the host was itself engulfed by another, larger cell at a later time

12. Here are 2 sample species...  Diatoms  Green Algae And then you are going to investigate 3 more...

13. Diatoms  Unicellular algae (includes 100,000 species)  Their walls are made of silica, 2 halves fit together like a shoebox and its lid (its assembly has interesting applications in nanotechnology)  Walls can withstand very high pressures  Reproduce by mitosis (asexual)

14. Green Algae  Photosynthesizers  Precursors of land plants  Live in fresh and salt water, some forms even live on top of snow, turning it pink!  Some species form filaments, colonies, and some are truly multicellular  Some form multinucleate masses

15. Looking at Protists Page 80 in your textbook