1. Chapter 16

2. 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. Fossilized mats 2.5 billion years old mark a time when photosynthetic prokaryotes Were producing enough O 2 to make the atmosphere aerobic Layers of a bacterial mat

5. Bacterial mats Figure 16.0Ax2

7. EARLY EARTH AND THE ORIGIN OF LIFE The early atmosphere probably contained H 2 O, CO, CO 2, N 2, PO 4 3- and some CH 4 Volcanic activity, lightning, and UV radiation were intense Figure 16.1A

8. 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 Paleozoic Meso- zoic Ceno- zoic Humans Land plants Animals Multicellular eukaryotes Single-celled eukaryotes Origin of solar system and Earth 1 2 4 3 Proterozoic eon Archaean eon Billions of years ago Atmospheric oxygen Prokaryotes Figure 16.1C

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

10. Miller – Urey Experiment Simulations of such conditions Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA Cooled water containing organic molecules Cold water Condenser Sample for chemical analysis H 2 O “Sea” Water vapor “Atmosphere” Electrode CH 4 NH 3 H2H2 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. Fig. 19.6, p. 297 membrane-bound proto-cells living cells self-replicating system enclosed in a selectively permeable, protective lipid sphere DNARNA enzymes and other proteins formation of protein–RNA systems, evolution of DNA formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions

13. 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 Self-replication of RNA Self-replicating RNA acts as template on which poly- peptide forms. Polypeptide acts as primitive enzyme that aids RNA replication. RNA Polypeptide Figure 16.6A

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

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

16. Fossilized prokaryote and a living bacterium Figure 16.1Dx1

17. Origin of Life

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

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

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