Microbial Evolution PDF

 1 2 3 Provide a rough Describe the Use a phylogenetic endosymbiotic theory timeline of the tree to determine and provide at least evolution of life three piece...

 1 2 3 Provide a rough Describe the Use a phylogenetic endosymbiotic theory timeline of the tree to determine and provide at least evolution of life three pieces of an organism’s on Earth. evidence to support closest relatives. the theory.  Earth formed approximately 4.6 billion years ago. First organisms (prokaryotes) evolved around 3.8 billion years ago. These early cells were likely microbes They gave rise to all life forms we see today Many life forms went extinct before humans arrived.  About 4 billion years ago, early Earth has extremely hot temperatures and anoxic (lacking oxygen). Water vapor condensed into oceans on the planet’s cooling surface. Volcanic eruptions belched gases like CO2, CH4, NH3  Life arose on Earth via spontaneous natural means due to conditions present at the time. Life came from non-living matter (Aristotle – spontaneous generation). Flies came from rotting meat. Fish from ocean mud.  Stromatolite, layered deposit, mainly of limestone, formed by the growth of blue-green algae (primitive one-celled organisms). These cone-shaped structures discovered in 3.7-billion-year-old rocks in Greenland, about the size of a quarter, may be fossilized colonies of microbes and the earliest fossils of life on Earth, researchers say.  All life today arises from reproduction of pre-existing life, or biogenesis. Louis Pasteur confirmed this through experiments.  Likely suited to harsh early Earth conditions Probably had simple cellular respiration Could develop proton gradients Used ATP synthase to generate energy (ATP)  First cells were likely chemolithoautotrophs Used inorganic chemical energy for metabolism As they proliferated, organic material accumulated This set the stage for new types of organisms  Chemoorganotrophs evolved to use organic compounds. Used organic matter for carbon and energy Oxidized organic compounds Had more negative redox potential Increased number of electrons in metabolism  Longer electron transport chains Resulted in faster growth Accelerated diversity of life forms Opened up new metabolic possibilities.  Appeared around 3.5 billion years ago. Cells evolved phototrophic pigments. Allowed conversion of light energy to chemical energy Initially used anoxygenic phototrophy (do not produce oxygen)  Oxygen production began about 2.7 billion years ago. Byproduct of photosynthesis by early organisms (cyanobacterial ancestors). Early organism split water molecules and released oxygen gas. Oxygen was initially toxic to many early life forms that led to mass extinction of oxygen-intolerant organisms Paved the way for oxygen-dependent life.  Oxygen use in respiration (aerobic respiration) Produces more energy than most other forms of metabolism Gave aerobic organisms a significant advantage Oxygen is extremely toxic to cells without protective mechanisms Posed a danger to anaerobic organisms Led to increased diversity and complexity of life  Occurred around 2 billion years ago Ozone (O3) formed from atmospheric oxygen Created a protective layer around Earth Blocks much of the sun's ultraviolet (UV) radiation UV radiation can cause significant DNA damage  Abiotic synthesis of 1 small organic molecules 2 Joining of these molecules into polymers Formation of 3 protocells (pre-cells) Origin of self-replicating 4 molecules The first stage in the origin of life was the first to be extensively studied in the laboratory. Oparin & Haldane (1920s) hypothesized that conditions on primitive Earth favored chemical reactions that synthesized organic compounds from inorganic compounds.  Conducted by Stanley Miller in 1953. Simulated conditions of early Earth. Produced amino acids spontaneously. Supported the idea of abiotic synthesis of organic compounds. Landmark experiment in origin of life studies.  Life may have begun in submerged volcanoes or deep-sea hydrothermal vents. Meteorites were the source of Earth’s first organic molecules. Small organic molecules form polymers (polymerization) by dripping solutions of organic monomers onto Hot sand Clay - (Fox, 1958) Rock Proteinoids - a polypeptide or mixture of polypeptides obtained by heating a mixture of amino acids.  Heat vaporizes the water in the solution and concentrates the monomers on the underlying materials. ⚬ Some of the monomers spontaneously bond together to form polymers. On early Earth, raindrops, or waves may have washed diluted solutions of organic monomers onto fresh lava or other hot rocks then washed the polymers back into the sea. ⚬ There they could accumulate in great quantities.  Pre-cells have formed spontaneously from abiotically produced organic compounds. Pre-cells: ⚬ have selectively permeable membranes ⚬ can grow by absorbing molecules from their surroundings. ⚬ Swell or shrink when placed in solutions of different salt concentrations.  Early genetic material: RNA (ribozymes) Ribozyme can store genetic information and act as an enzyme Molecular evolution: The RNA varieties that replicate fastest increase their frequency in the population.  Natural selection favored more efficient self-replicators, passing their abilities on to later generations. Gradual evolution of more complex cellular structures (DNA replaced RNA, protocells become true cells.)  Dominated Earth for about 2 billion years Still abundant today, outnumbering eukaryotes Can survive in extreme environments Two main groups: Bacteria and Archaea Play crucial roles in ecosystems and human health Why do you think prokaryotes have been so successful throughout Earth's history?  Evolved from prokaryotes about 1.8 billion years ago Characterized by membrane- bound organelles and a nucleus Likely arose through endosymbiosis First multicellular eukaryotes appeared around 1.2 billion years ago  1 2 3 What are thought to Which of the stages How might faster be the conditions of in life’s origin do you growth and early earth? How think was the most increased would this influence challenging to occur microbial selection? diversity impact naturally? evolution?  4 2 3 How do you think What advantages did How might the life on Earth would the development of ability to use be different without DNA provide over oxygen have the ozone layer? RNA? changed the course of evolution?