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Download The Origin and Evolution of Microbial Life: Prokaryotes and Protists
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Chapter 16 How Ancient Bacteria Changed the World Mounds of rock found near the Bahamas Contain photosynthetic prokaryotes Stromatolites in northern Canada Figure 16.0Ax1 Fossilized mats 2.5 billion years old mark a time when photosynthetic prokaryotes Were producing enough O2 to make the atmosphere aerobic Layers of a bacterial mat Bacterial mats Figure 16.0Ax2 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 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 Cenozoic Humans Land plants Origin of solar system and Earth Animals 4 1 Proterozoic eon Multicellular eukaryotes Archaean eon 3 2 Prokaryotes Single-celled eukaryotes Figure 16.1C Atmospheric oxygen 16.2 How did life originate? Organic molecules May have been formed abiotically in the conditions on early Earth Miller – Urey Experiment Simulations of such conditions Have produced amino acids, sugars, lipids, and the nitrogenous bases found in DNA and RNA Water vapor CH4 “Atmosphere” Electrode Condenser Cold water H2O “Sea” Figure 16.3B Cooled water containing organic molecules Sample for chemical analysis 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 living cells membrane-bound proto-cells self-replicating system enclosed in a selectively permeable, protective lipid sphere DNA RNA formation of protein–RNA systems, evolution of DNA enzymes and other proteins formation of lipid spheres spontaneous formation of lipids, carbohydrates, amino acids, proteins, nucleotides under abiotic conditions Fig. 19.6, p. 297 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 RNA Self-replicating RNA acts as template on which polypeptide forms. Polypeptide Figure 16.6A Polypeptide acts as primitive enzyme that aids RNA replication. DNA infolding of plasma membrane Fig. 19.11, p. 301 Membranes may have separated various aggregates of self- replicating molecules Which could be acted on by natural selection Membrane LM 650 RNA Figure 16.6B, C Polypeptide Fossilized prokaryote and a living bacterium Figure 16.1Dx1 Origin of Life Origin of Life Hydrothermal Vent Life http://www.youtube.com/watch?v=4LoiInUoRMQ How Did Life Originate? http://www.youtube.com/watch?v=ozbFerzjkz4 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. chemical and molecular evolution, first into selfreplicating systems, then into membranes of proto-cells by 3.8 billion years ago. EUKARYOTES Heterotrophic protistans ANCESTORS OF EUKARYOTES The first major divergence gives rise to eubacteria and to the common ancestor of archaebacteria and eukaryotic cells. ORIGIN OF PROKARYOTES 3.8 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. EUBACTERIA Oxygen-producing photosynthetic eubacteria (e.g., cyanobacteria) Other photosynthetic eubacteria EUBACTERIAL LINEAGE Aerobic respiration evolves in many bacterial groups. 3.2 billion years ago Heterotrophic and chemoautotropic eubacteria 2.5 billion years ago Fig. 19.7a, p. 298-9 (The ozone layer gradually develops) 20% ARCHAEBACTERIA Extreme halophiles Methanogens Extreme thermophiles ORIGINS OF ANIMALS ORIGINS OF EUKARYOTES the first protistans EUKARYOTES Animals 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
