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Origins of Life

Origins of Life. AP Biology. What is Life?. First we have to define LIFE … organized as cells respond to stimuli regulate internal processes homeostasis use energy to grow metabolism develop change & mature within lifetime reproduce heredity DNA / RNA adaptation & evolution.

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Origins of Life

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  1. Origins of Life AP Biology

  2. What is Life? • First we have to define LIFE… • organized as cells • respond to stimuli • regulateinternal processes • homeostasis • use energy to grow • metabolism • develop • change & mature within lifetime • reproduce • heredity • DNA / RNA • adaptation & evolution

  3. The Origin of Life is Hypothesis • Special Creation • Was life created by a supernatural or divine force? • Extraterrestrial Origin • Was the original source of organic (carbon) materials comets & meteorites striking early Earth? • Spontaneous Abiotic Origin • Did life evolve spontaneously from inorganic molecules?

  4. Abiotic Origin • 1. abiotic synthesis of small organic molecules • 2. joining of small molecules into macromolecules • 3. packaging of molecules into protocells (coacervates) • 4. origin of self-replicating molecules

  5. Conditions on early Earth • Reducing atmosphere • water vapor (H2O), CO2, N2, NOx, H2,NH3, CH4, H2S • lots of available H & its electron • no free oxygen • Energy source • lightning, UV radiation, volcanic low O2 = organic molecules do not breakdown as quickly

  6. Electrodes discharge sparks (lightning simulation) Water vapor Mixture of gases ("primitive atmosphere") Condenser Water Condensed liquid with complex, organic molecules Heated water ("ocean") Origin of Organic Molecules • Abiotic synthesis • 1920Oparin & Haldane • 1953Miller & Urey • formed organic compounds • amino acids • adenine CH4 H2 NH3

  7. What if Urey got it wrong? • Evidence that the early Earth’s atmosphere differed from Urey’s proposed model. • Geological Evidence • The presences of volcanoes • A lack of hydrogen

  8. https://massasoit.instructure.com/courses/346438/pages/video-the-primordial-soup-with-julia-childhttps://massasoit.instructure.com/courses/346438/pages/video-the-primordial-soup-with-julia-child

  9. Origin of Cells (Coacervates) • Bubbles  separate inside from outside  metabolism & reproduction

  10. Dawn of natural selection Origin of Genetics • RNA is likely first genetic material • multi-functional • codes information • enzyme functions • regulatory molecule

  11. Key Events in Origin of Life • Key events in evolutionary history of life on Earth • life originated 3.5–4.0 bya

  12. Prokaryotes • Prokaryotes dominated life on Earth from 3.5–2.0 bya 3.5 billion year old fossil of bacteria modern bacteria chains of one-celledcyanobacteria

  13. Stromatolites Fossilized mats of prokaryotes resemble modern microbial colonies

  14. Oxygen atmosphere • Oxygen begins to accumulate 2.7 bya • reducing oxidizing atmosphere • evidence in banded iron in rocks = rusting • makes aerobic respiration possible • photosynthetic bacteria (blue-green algae)

  15. Endosymbiosis • Evolution of eukaryotes • origin of mitochondria • engulfed aerobic bacteria, but did not digest them • mutually beneficial relationship • natural selection! internal membrane system aerobic bacterium mitochondrion Endosymbiosis Eukaryotic cell with mitochondrion Ancestral eukaryotic cell

  16. Eukaryotic cell with mitochondrion Endosymbiosis • Evolution of eukaryotes • origin of chloroplasts • engulfed photosynthetic bacteria, but did not digest them • mutually beneficial relationship • natural selection! photosyntheticbacterium chloroplast mitochondrion Endosymbiosis Eukaryotic cell with chloroplast & mitochondrion

  17. http://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.htmlhttp://highered.mcgraw-hill.com/sites/9834092339/student_view0/chapter4/animation_-_endosymbiosis.html

  18. Cambrian explosion • Diversification of Animals • within 10–20 million years most of the major phyla of animals appear in fossil record 543 mya

  19. Diversity of life & periods of mass extinction Cambrian explosion

  20. Cretaceous extinction The Chicxulub impact crater in the Caribbean Sea near the Yucatan Peninsula of Mexico indicates an asteroid or comet struck the earth and changed conditions 65 million years ago

  21. Early mammal evolution • 125 mya mammals began to radiateout & fill niches

  22. Classifying Life • Molecular datachallenges 5 Kingdoms • Monera was too diverse • 2 distinct lineages of prokaryotes • Protists are still too diverse • not yet sorted out

  23. 3 Domain system • Domains = “Super” Kingdoms • Bacteria • Archaea • extremophiles = live in extreme environments • methanogens • halogens • thermophiles • Eukarya • eukaryotes • protists • fungi • plants • animals

  24. KingdomBacteria KingdomArchaebacteria KingdomProtista KingdomFungi KingdomPlantae KingdomAnimalia

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