The Origin and Evolution of Microbial Life: Prokaryotes and Protists

1. The Origin and Evolution of Microbial Life: Prokaryotes and Protists Chapter 16

2. 0 How Ancient Bacteria Changed the World • Mounds of rock found near the Bahamas • Contain photosynthetic prokaryotes

3. Stromatolites in northern Canada Figure 16.0Ax1

4. Layers of a bacterial mat • Fossilized mats 2.5 billion years old mark a time when photosynthetic prokaryotes • Were producing enough O2 to make the atmosphere aerobic

5. Bacterial mats Figure 16.0Ax2

7. EARLY EARTH AND THE ORIGIN OF LIFE • The early atmosphere probably contained • H2O, CO, CO2, N2, PO43- and some CH4 • Volcanic activity, lightning, and UV radiation were intense Figure 16.1A

8. Ceno-zoic Meso-zoic Humans Paleozoic Land plants Origin of solarsystem andEarth Animals 4 1 Proterozoiceon Archaeaneon Multicellulareukaryotes years ago Billions of 3 2 Prokaryotes Single-celledeukaryotes Atmospheric oxygen • A clock analogy tracks the origin of the Earth to the present day • And shows some major events in the history of Earth and its life Figure 16.1C

9. 16.2 How did life originate? • Organic molecules • May have been formed abiotically in the conditions on early Earth

10. “Atmosphere” CH4 Water vapor Electrode H2 NH3 Condenser Cold water Cooled watercontaining organic molecules H2O“Sea” Sample forchemical analysis Miller – Urey Experiment • Simulations of such conditions • Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA Figure 16.3B

11. 16.4 The first polymers may have formed on hot rocks or clay • Organic polymers such as proteins and nucleic acids • May have polymerized on hot rocks

12. living cells enzymes and other proteins DNA RNA formation of protein–RNA systems, evolution of DNA formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions membrane-bound proto-cells self-replicating system enclosed in a selectively permeable, protective lipid sphere Fig. 19.6, p. 297

13. Self-replication of RNA RNA Self-replicating RNA acts astemplate on which poly-peptide forms. Polypeptide Polypeptide acts as primitive enzyme that aids RNA replication. • 16.6 Membrane-enclosed molecular co-ops may have preceded the first cells • RNA might have acted as templates for the formation of polypeptides • Which in turn assisted in RNA replication Figure 16.6A

14. DNA infolding of plasma membrane Fig. 19.11, p. 301

15. Membrane RNA Polypeptide LM 650 • Membranes may have separated various aggregates of self-replicating molecules • Which could be acted on by natural selection Figure 16.6B, C

16. Fossilized prokaryote and a living bacterium Figure 16.1Dx1

17. Origin of Life

18. Origin of Life • Hydrothermal Vent Life • http://www.youtube.com/watch?v=4LoiInUoRMQ • How Did Life Originate? • http://www.youtube.com/watch?v=ozbFerzjkz4

19. Hydrogen-Rich, Anaerobic Atmosphere Oxygen in Atmosphere: 10% ARCHAEBACTERIA Extreme halophiles ARCHAEBACTERIAL LINEAGE Methanogens Extreme thermophiles In a second major divergence, the ancestors of archaebacteria and of eukaryotic cells start down their separate evolutionary roads. EUKARYOTES Heterotrophic protistans The amount of genetic information increases; cell size increases; the cytomembrane system and the nuclear envelope evolve through modification of cell membranes. ANCESTORS OF EUKARYOTES chemical and molecular evolution, first into self- replicating systems, then into membranes of proto-cells by 3.8 billion years ago. The first major divergence gives rise to eubacteria and to the common ancestor of archaebacteria and eukaryotic cells. Noncyclic pathway of photosynthesis (oxygen-producing) evolves in some bacterial lineages. Cyclic pathway of photosynthesis evolves in some anaerobic bacteria. EUBACTERIA Oxygen-producing photosynthetic eubacteria (e.g., cyanobacteria) Other photosynthetic eubacteria Heterotrophic and chemoautotropic eubacteria ORIGIN OF PROKARYOTES EUBACTERIAL LINEAGE Aerobic respiration evolves in many bacterial groups. 3.8 billion years ago 3.2 billion years ago 2.5 billion years ago Fig. 19.7a, p. 298-9

20. (The ozone layer gradually develops) 20% ARCHAEBACTERIA Extreme halophiles Methanogens Extreme thermophiles EUKARYOTES ORIGINS OF ANIMALS ORIGINS OF EUKARYOTES Animals the first protistans Heterotrophic protistans origin of mitosis, meiosis ORIGINS OF FUNGI Fungi Photosynthetic protistans Plants ENDOSYMBIOTIC ORIGINS OF MITOCHONDRIA ORIGINS OF PLANTS ENDOSYMBIOTIC ORIGINS OF CHLOROPLASTS Oxygen-producing photosynthetic eubacterium and early eukaryote become symbionts. EUBACTERIA Oxygen-producing photosynthetic eubacteria (e.g., cyanobacteria) Other photosynthetic eubacteria Heterotrophic and chemoautotropic eubacteria Aerobic species becomes endosymbiont of anaerobic forerunner of eukaryotess. 1.2 billion years ago 900 million years ago 435 million years ago present Fig. 19.7b, p. 298-9