endosymbiosis & the origin of eukaryotic cells

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The Origin of Eukaryotic Cells Serial Endosymbiotic Theory (SET): Chloroplasts and Mitochondria evolved from symbiotic bacteria that lived inside of a larger prokaryote

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Page 1: Endosymbiosis & The Origin of Eukaryotic Cells

The Origin of Eukaryotic Cells

Serial Endosymbiotic Theory (SET): Chloroplasts and Mitochondria evolved from symbiotic bacteria that lived inside of a larger prokaryote

Page 2: Endosymbiosis & The Origin of Eukaryotic Cells

Clay-mation• https://www.youtube.com/watch?v=EgaGh9-mFnQ

Page 3: Endosymbiosis & The Origin of Eukaryotic Cells

Outline•What is the evidence for endosymbiosis?•What role did endosymbiosis play in the origin of life?•How does endosymbiosis change our view of the branching pattern on the tree of life?

Page 4: Endosymbiosis & The Origin of Eukaryotic Cells

Discuss•“Nothing in molecular biology makes sense expect in light of the evolutionary history of organisms” • -Russian-American geneticist Theodosius Dobzhansky

Page 5: Endosymbiosis & The Origin of Eukaryotic Cells

Domains of Life: Carl Woese (1977)

Page 6: Endosymbiosis & The Origin of Eukaryotic Cells

Moving Beyond Coacervates- The First Cell:Enclosed self-replicating RNA in membrane

Page 7: Endosymbiosis & The Origin of Eukaryotic Cells

Prokaryotic Cells- Archaea & Bacteria

• Ancient, diverse, abundant, ubiquitous, small size, motile• Extremophiles (“extreme-lovers”):

live in high-salt, high-temperature, low-temp, or high-pressure habitats • Inform origin of life research• Used as a model organism in search

for extraterrestrial life-likely that first life forms lived at high temperatures and high in anoxic environments (no oxygen)

Page 8: Endosymbiosis & The Origin of Eukaryotic Cells

Thermal Hot Springs, Yellowstone National Park

Commercial applications (Taq polymerase- enzyme isolated from Thermus aquaticus bacteria in hot springs, Yellowstone National Park

Page 9: Endosymbiosis & The Origin of Eukaryotic Cells

The First Eukaryotic Cells• Evolved 2.7 billion years ago• Larger and more complex than bacteria, Have a nucleus, complex

organelles, cytoskeleton

Page 10: Endosymbiosis & The Origin of Eukaryotic Cells

Origin of Mitochondria and Chloroplasts

• Chloroplasts evolved from cyanobacteria (+ photosynthesis)• Mitochondria evolved from aerobic bacteria (+ cellular respiration to

make ATP)• + = advantage

Page 11: Endosymbiosis & The Origin of Eukaryotic Cells

Evidence• Membranes- Have double cell

membranes• DNA- Have circular DNA, like

bacterial genome• Reproduction- via budding,

just like bacteria• Size- similar size to bacteria

( 1-10 microns)

Page 12: Endosymbiosis & The Origin of Eukaryotic Cells

Advantages of Multicellularity• Cell specialization, larger size, more complexity• Volvox algae with division of labor-with two cell functions: swimming (somatic

cells) & reproduction (gonidium)

Page 13: Endosymbiosis & The Origin of Eukaryotic Cells

What Makes a World Habitable?

• Temperature• Water• Atmosphere• Energy• Nutrients

Page 14: Endosymbiosis & The Origin of Eukaryotic Cells

Case Study: Protists • Unicellular, diverse• Abundant in water, motile

• Medically important• 1845 Irish Potato Famine- protist Phytophthora infestans• Malaria parasite- Plasmodium • Toxin producing algal blooms- Dinoflagellates

• Ecologically important (primary producers)• Critical to understanding evolution of plants, fungi, animals

Page 15: Endosymbiosis & The Origin of Eukaryotic Cells

Case Study: Protists Plant-like: Euglena Animal-like: Ameoba