1 / 32

Life On Earth

Life On Earth. Origins of Life on Earth. “Big Bang” Earth formation Cooling period Early atmosphere H, N, CO, CO 2 Life begins…. Origins of Life on Earth. Spontaneous generation vs. Biogenesis?. Origins of Life on Earth. Conditions of early earth Oxidizing vs. Reducing environments.

nuru
Télécharger la présentation

Life On Earth

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Life On Earth

  2. Origins of Life on Earth • “Big Bang” • Earth formation • Cooling period • Early atmosphere • H, N, CO, CO2 • Life begins…..

  3. Origins of Life on Earth • Spontaneous generation vs. Biogenesis?

  4. Origins of Life on Earth • Conditions of early earth • Oxidizing vs. Reducing environments

  5. Four-Stage Hypothesis • Chemical evolution: formation of simple organics • Monomers to polymers (complex organics) • Origin of enclosed cell membrane • Origin of an self replication What evidence do we have for these hypotheses?

  6. Testing the four-stage hypothesis • Stage 1: Chemical evolution • Miller-Urey experiment

  7. Testing the four-stage hypothesis • Stage 2: Formation of polymers • Evaporation of solutes • Colloidal properties of sand/clay

  8. Testing the four-stage hypothesis • Stage 3: Enclosed membrane • Liposomes • Protobionts and natural selection

  9. Testing the four-stage hypothesis • Stage 4: Self replicating molecules • RNA World

  10. Dawning of the Cell • What were the first cells like? • Where did they live? • How did they get their energy?

  11. Dawning of the Cell • Prokaryotic = “before” “nucleus” • First bacteria split • Archaebacteria • Eubacteria

  12. Dawning of the Cell • Atmospheric changes • Diversity of metabolism Stromatolites

  13. The Unseen Multitudes • Incredibly small • Rapid reproduction • Most are good, some are bad

  14. Sizes and Shapes • Three basic shapes

  15. Reproduction • Prokaryotic Conjugation • Transformation • Transduction

  16. Photoautotrophic • Cyanobacteria • “Blue-green algae” • Heterocysts • 3 – 1.5 bya

  17. Photoheterotrophic • Where did the DO of marine ecosystems go? • Flow cytometry • Most abundant bacteria on earth?

  18. Chemoautotrophic • Deep-sea hydrothermal vents • Produce food using H2S • Cold seeps • CH4

  19. Chemoheterotrophic • Pathogenic Bacteria • Endotoxins • Gram -, glycolipids, membrane breakdown • Exotoxins • Gram +, protein, secretion outside bacterium

  20. Eukaryotic Origin?

  21. Diversity of Protists • Free O2 led to an explosion of diversity • Single and multicelled forms • Early eukaryotes provided the building blocks for the fungi, plants and animals • Protistans represent a diverse group at the crossroads to all the other Kingdoms.

  22. Diversity of Protists • Animal-like Protistans (Protozoans) • Single celled heterotrophs • Plant-like Protistans (algae and seaweeds) • Single and multicellular autotrophs • Some are both heterotrophic and autotrophic

  23. Diversity of Protists • Protozoans • Amoebas • Flagellates • Ciliates

  24. Diversity of Protists • Slime Molds • Analogous to fungi (absorption) • Convergent evolution • Plasmodial slime molds • Cellular slime molds

  25. Diversity of Protists • Plasmodial slime molds • Amoeboid style of feeding • Decomposers • Found on forest floor

  26. Diversity of Protists • Cellular slime molds • Unicellular feeding mode • Under stress conditions aggregate into slug colony • Move to new feeding location and disassemble

  27. Diversity of Protists • Plant-like protists (unicellular algae) • Euglenas • Dinoflagellates • Diatoms • Green algae

  28. Diversity of Protists • Plant-like protists (multicellular algae) • Green seaweed • Red seaweed • Brown seaweed

  29. From Single-celled to multi-celled life

More Related