history of the earth chapter 14. formation of the earth
TRANSCRIPT
Formation of the Earth
Where does life come from?
Spontaneous generationthe belief that living things arise from nonliving things
Biogenesis all living things come from other living things
Redi’s experiments Spallanzani’s experiments
Pasteur’s experiments
Redi’s Experiment (1626-1697)
Italian physician and poet who demonstrated that the presence of maggots on rotting meat does not result from spontaneous generation but from eggs laid on the meat by flies.
Pg. 279
Spallanzani’s Experiments (1729-1799)
Italian naturalist whose experiments disproved that microorganisms spontaneously generated from meat broth in open flasks.
Pg. 280
Pasteur’s Experiment (1822-1895)
A French chemist who proved that microorganisms are carried by dust and not air.
Improved on Spallanzani’s experimentPg. 281
The First Organic Compounds
Alexander Oparin’s Hypothesis, 1920’s):
Thought that primitive atmosphere contained: NH3, H2, H20, and C-H compounds
At high temperatures, these gases might have formed simple organic compounds like amino acids
Oparin’s Theory Con’t
When the Earth cooled, the water vapor condensed into lakes and seas with the organic compounds within
With the help of lightning and UV radiation, these organic compounds reacted with each other forming macromolecules essential to life.
Can that REALLY happen?
Yes! According to experiments performed by Miller and Urey
Products of experimental synthesis:Amino acidsATPDNA nucleotides
Miller ExperimentMiller Experiment
Water Vapor Forms
Water Vapor Forms
Input Chamber
Input Chamber
CondenserCondenser
Spark Chamber
Spark Chamber
Attempts to Create LifeAttempts to Create Life
“It came from outer space!”
Some scientists hypothesize that organic compounds may have come from meteoroids from space
Microfossil Lab!
Earth’s Age
More than 4 BILLION years old!
How do scientists “know” this?Radiometric dating
Measurement of the decay of commonly occurring radioactive isotopes
Ex) Carbon dating
Fossils
The remains of ancient animals and plants
Found in every continent on earthFormed from sedimentary rockPaleontology- the branch of biology that
studies past forms of life (namely fossils!)
Ancient Bat Saber-Toothed Cat
The Fossil Record
From the 1830s onwards, geologists noted how fossils became more complex through time. The oldest rocks contained no fossils, then came simple sea creatures, then more complex ones like fishes, then came life on land, then reptiles, then mammals, and finally humans. Clearly, there was some kind of 'progress' going on.
The First Prokaryotes
About 3.5 bya the first prokaryotes,
cells without a true nucleus (like bacteria), came into existence.
The first cells were probably anaerobic and heterotrophic.
Resemble modern day Archaebacteria, which live in extreme enviornments
Rise of photosynthesis and aerobic respiration
Cyanobacteria- group of unicellular, autotrophic prokaryotes about 3 bya
Increased the level of atmospheric oxygen
The First Eukaryotes
Endosymbiosis- about 2.0 bya, a small aerobic prokaryote began to live inside a larger anaerobic prokaryote
aerobic prokaryotes evolved to modern mitochondria
Photosynthetic cyanobacteria evolved into chloroplasts
Endosymbiosis:
Extinction 65 mya
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