Chapter 28 The Origins of Eukaryotic Diversity

1. Chapter 28 • The Origins of Eukaryotic Diversity

2. General characteristics • Classification criteria • eukaryotes • not animal, plant or fungi

3. Protist Diversity • The full spectrum of modes of life • from unicellular to multicellular • autotrophic to heterotrophic • asexual to sexual reproduction • pathogenic to beneficial • sessile to mobile

4. Mobility • How Protists move • flagellum • cilia • pseudopod

5. Protists • Ingestive (animal-like); ameoba, paramecium, stentor • Absorptive (fungus-like) • Photosynthetic (plant-like); alga, kelp

6. The Endosymbionic Theory • Mitochondria and chloroplasts were formerly from small prokaryotes living within larger cells (Margulis)

7. Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell

8. Eukaryotic cell with mitochondrion Endosymbiosis • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

9. Lynn Margulis Theory of Endosymbiosis • Evidence • structural • mitochondria & chloroplasts resemble bacterial structure • genetic • mitochondria & chloroplasts have their own circular DNA, like bacteria • functional • mitochondria & chloroplasts move freely within the cell • mitochondria & chloroplasts reproduce independently from the cell

10. Protist Systematics & Phylogeny, I • 1- Groups lacking mitochondria; early eukaryotic link; Giardia (human intestinal parasite; severe diarrhea); Trichomonas (human vaginal infection) • 2- Euglenoids; autotrophic& heterotrophic flagellates; Trypanosoma (African sleeping sickness; tsetse fly)

11. Protist Systematics & Phylogeny, II • Alveolata: membrane-boundcavities (alveoli) under cell surfaces; dinoflagellates (phytoplankton); Plasmodium (malaria); ciliates (Paramecium)

12. Protist Systematics & Phylogeny, III • Stamenophila: water molds/mildews and heterokont (2 types of flagella) algae; numerous hair-like projections on the flagella; most molds are decomposers and mildews are parasites; algae include diatoms, golden, andbrown forms

13. Protist Systematics & Phylogeny, IV • Rhodophyta: red algae; no flagellated stages; phycobilin (red) pigment • Chlorophyta: green algae; chloroplasts; gave rise to land plants; volvox, ulva

14. Protist Systematics & Phylogeny, V • Affinity uncertain: • Rhizopods: unicellular with pseudopodia; amoebas • Actinopods: ‘ray foot’ (slender pseudopodia; heliozoans, radiolarians

15. Protist Systematics & Phylogeny, VI • Mycetozoa: slime molds (not true fungi); use pseudopodia for locomotion and feeding; plasmodial and cellular slime molds

16. Protist Diversity • Beneficial & necessary Protists • phytoplankton • small algae + diatoms • much of the world’s photosynthesis • produces ~90% of atmospheric oxygen • zooplankton • heterotrophic protists + animals • key ecological role at base of marine food web