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Origin of Life.

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Presentation on theme: "Origin of Life."— Presentation transcript:

1 Origin of Life

2 PANSPERMIA A comet or meteorite brought micro-organisms

3 TIDAL POOLS UV light / electrical discharges through volcanic gases onto water

Gases, energy and catalysts (metal sulphides)

5 Theories of Origins of Life
EVIDENCE (can’t do experiments!) Fossils, biochemical links, DNA testing 3 MAIN THEORIES: Panspermia, Thermal vents, Tidal pools, lightning & volcanoes REQUIREMENTS: water, energy (heat / lightning), inorganic mol.s or gases Panspermia theorists don’t believe the correct conditions were available at the time that life arose on Earth All agree that basic nucleotides, were vital in order to reproduce organic molecules

6 Scientists have been able to manufacture organic molecules in the laboratory in the presence of water, heat and gases. The Miller and Urey experiment[1] (or Urey–Miller experiment)[2] was an experiment that simulated hypothetical conditions thought at the time to be present on the early Earth, and tested for the occurrence of chemical origins of life. Specifically, the experiment tested Alexander Oparin's and J. B. S. Haldane's hypothesis that conditions on the primitive Earth favored chemical reactions that synthesized organic compounds from inorganic precursors. Considered to be the classic experiment on the origin of life, it was conducted in 1952[3] and published in 1953 by Stanley Miller and Harold Urey at the University of Chicago.[4][5][6] After Miller's death in 2007, scientists examining sealed vials preserved from the original experiments were able to show that there were actually well over 20 different amino acids produced in Miller's original experiments. That is considerably more than what Miller originally reported, and more than the 20 that naturally occur in life.[7] Moreover, some evidence suggests that Earth's original atmosphere might have had a different composition than the gas used in the Miller–Urey experiment. There is abundant evidence of major volcanic eruptions 4 billion years ago, which would have released carbon dioxide, nitrogen, hydrogen sulfide (H2S), and sulfur dioxide (SO2) into the atmosphere. Experiments using these gases in addition to the ones in the original Miller–Urey experiment have produced more diverse molecules


8 Chloroplasts and mitochondria both have nucleic material.
They may have been separate organisms which were incorporated into cells

9 Genetic variation MEIOTIC MUTATIONS  source of all variation – gamete genes are different SEXUAL REPRODUCTION  increases variation – different combinations of genes in gametes cross-over and recombination independent assortment of chromosomes fertilisation - fusion of random gametes

10 Gene Pools Population - group of individuals of the same species which can interbreed Gene pool is the total group of genes available for reproduction in a population Species may be divided into populations or demes by geographical obstacles

11 Deme – local unit of a population
Gene flow – movement of genes from one population to another via gametes Genetic equilibrium – allele frequencies of a population remain unchanged from generation to generation (Hardy-Weinberg)


13 mountains rivers sea glaciers
Geographical barriers isolate gene pools and prevent normal gene flow between demes mountains POPULATION 2 POPULATION 1 rivers sea glaciers

14 Hardy-Weinberg Theorem
Allele frequencies in a population remain constant - from generation to generation unless disturbed. Hardy–Weinberg equilibrium is impossible in nature Ideal state  baseline to measure genetic change against. non-random mating, mutations, selection, limited population size, "overlapping generations", random genetic drift, gene flow and meiotic drive.

15 Gene pool stability Gene pool change Hardy Weinberg theory true
Large population Small population Random mating Assortative mating No gene flow Gene flow (migration) No mutations Mutations No Natural selection Natural selection Hardy Weinberg theory true Not true - microevolution

16 Videos Prof Wolfe: Fossil formation, dating & indexing
Prof Wolfe: Biochemical similarities

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