Download Earth`s Early History

EARTH’S EARLY HISTORY
(CH 19.3)
THE MYSTERIES OF LIFE’S
ORIGINS
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EARLY EARTH
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EVIDENCE PROVES COSMIC DEBRIS COLLIDED WITH ONE ANOTHER TO FORM THE EARTH
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THE EARTH WAS STRUCK BY HUGE OBJECTS (COMETS AND ASTEROIDS)
VOLCANIC ACTIVITY SHOOK THE EARTH
ATMOSPHERE
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LITTLE TO NO OXYGEN
MAJOR GASES: CARBON DIOXIDE, WATER VAPOR, NITROGEN
MINOR GASES: CARBON MONOXIDE, HYDROGEN SULFIDE,
HYDROGEN CYANIDE
4.2 BILLION YEARS AGO – EARTH COOLED AND ALLOWED WATER TO
CONDENSE (STABILITY)
THE FIRST ORGANIC MOLECULES
MILLER AND UREY
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CAN ORGANIC MOLECULES ASSEMBLE IN EARLY EARTH?
THEY TESTED THE THEORY BY COMBINING ELEMENTS FOUND ON EARTH WITH WATER AND STIMULATING LIGHTNING – THEN
THEY LET THE WATER CONDENSE AND COOL
RESULTS: 21 AMINO ACIDS WERE FORMED! (BUILDING BLOCKS OF LIFE)
THEIR RESULTS SUGGESTED HOW ORGANIC COMPOUNDS NECESSARY FOR LIFE AROSE ON A PRIMITIVE EARTH
FORMATION OF MICROSPHERES
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ORGANIC MOLECULES FOR TINY BUBBLES CALLED PROTEINOID MICROSPHERES
MICROSPHERES ARE NOT CELLS BUT HAVE SOME CHARACTERISTICS OF LIVING SYSTEMS
THEY APPEARED ON EARTH 3.8 BILLION YEARS AGO
MILLER AND UREY EXPERIMENT
EVOLUTION OF RNA AND DNA
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SCIENTISTS HAVE NOT FOUND THE ANSWER YET, BUT HAVE SOME HYPOTHESES
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RNA FORMED FROM SIMPLER MOLECULES
RNA EXISTED BEFORE DNA – DNA DIRECTED PROTEIN SYNTHESIS WOULD RESULT FROM THE
PRESCENCE OF RNA
PRODUCTION OF FREE OXYGEN
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BACTERIA HAVE BEEN FOUND THAT LIVED IN THE PRESENCE OF LITTLE TO NO OXYGEN (3.5 BILLION YEARS AGO)
PHOTOSYNTHETIC BACTERIA BECAME COMMON 2.2 BILLION YEARS AGO
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OXYGEN COMBINED WITH IRON – IRON OXIDE (RUST)
NO IRON = BLUE GREEN OCEANS
OXYGEN ACCUMULATED IN THE ATMOSPHERE = FORMATION OF OZONE
SOME ORGANISMS WENT EXTINCT BECAUSE OF THE OXYGEN WHILE OTHERS PROSPERED OR ADAPTED
ORIGIN OF EUKARYOTIC CELLS
ENDOSYMBIOTIC THEORY
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ANCIENT PROKARYOTES BEGAN EVOLVING INTERNAL CELL MEMBRANES (ANCESTOR OF EUKARYOTIC
ORGANISMS)
PROKARYOTES ENTERED THE ANCIENT EUKARYOTES, AND INSTEAD OF DIGESTING THE PROKARYOTES, THE
PROKARYOTES LIVED IN THE EUKARYOTES
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SYMBIOTIC RELATIONSHIPS EVOLVED OVER TIME BETWEEN PRIMITIVE EUKARYOTIC CELLS AND
THE PROKARYOTIC CELLS WITHIN THEM
TWO HYPOTHESES:
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MITOCHONDRIA EVOLVED FROM ENDOSYMBIOTIC PROKARYOTES THAT WERE ABLE TO USE OXYGEN TO
GENERATE ATP (USED IN RESPIRATION)
CHLOROPLASTS EVOLVED FROM ENDOSYMBIOTIC PROKARYOTES THAT HAD THE ABILITY TO
PHOTOSYNTHESIZE (USED IN PHOTOSYNTHESIS)
ENDOSYMBIOTIC THEORY
MODERN EVIDENCE FOR ENDOSYMBIOTIC
THEORY
MODERN EVIDENCE
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MARGUILIS GATHERED EVIDENCE TO SUPPORT ENDOSYMBIOTIC THEORY
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MITOCHONDRIA AND CHLOROPLASTS CONTAIN DNA SIMILAR TO BACTERIAL DNA
THEY HAVE RIBOSOMES THAT RESEMBLE THOSE OF BACTERIA
THEY REPRODUCE BY BINARY FISSION LIKE BACTERIA WHEN CELLS DIVIDE BY MITOSIS
SEXUAL REPRODUCTION AND MULTICELLULARITY
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AFTER EUKARYOTIC CELLS AROSE THEY REPRODUCED SEXUALLY TO SPEED UP EVOLUTIONARY
CHANGE AND PRODUCE GENETIC VARIATION