19.3 Earth’s Early History (Unit 7)

Flashcard maker : Pedro Huang
Early Earth’s Atmosphere
Earth’s atmosphere contained little oxygen. It was first composed of carbon dioxide, water vapor, and nitrogen, as well as small amounts of carbon monoxide, hydrogen sulfide, and hydrogen cyanide.
history of early earth
earth formed as pieces of cosmic debris collided with one another. It was then truck by huge objects, which caused it to melt. Violent volcanic activity occurred, as well as comets and asteroids. 4.2 billion years ago Earth cooled down to allow solid rock to form
Miller and Urey’s experiment results
The experiment produced 21 amino acids. Their experiment suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds of a primitive Earth.
Miller and Urey’s Experiment
1. Water is heated and water vapor forms (ocean)
2.A mixture of methane, ammonia, and hydrogen is added to the water vapor (atmosphere
3.The circulating gases are bombarded by sparks of electricity (lightning)
4.Cold water cools the chamber, causing droplets to form
5. Liquid is collected and contains amino acids
Miller and Urey’s Experiment Impact
Miller and Urey’s ideas about the composition of the early atmosphere were incorrect. But new experiments, such as Miller in 1995, show that the early atmosphere did produce organic compounds (cytosine and urcail.)
Origination Of Cells
In the Archean Eon, 200-300 million years after the Earth cooled down, cells similar to bacteria were common. The leap from nonlife to life is the greatest gap in scientist’s hypotheses of life’s early history.
Proteinoid Microspheres
bubbles that large organic molecules form. Are not cells, but have some characteristics of living systems like selectively permeable membranes and means of storing and releasing energy.
Hypothesis of Proteinoid Microspheres
Hypotheses suggest that structures like proteinoid microspheres acquired the characteristics of living cells 3.8 billion years ago.
RNA World Hypothesis
inorganic matter
simple organic molecules
RNA nucleotides
RNA able to syntheize proteins, replicate itself, and be able to store information
Helps in protein synthesis, DNA functions in information storage, and proteins help build structures and start chemical reactions
Production of Free Oxygen
The first mirofossils evolved in the absence of oxygen because very little was in the atmosphere. Next, photosynthetic bacteria became common, which churned out oxygen, which formed rust and turned the oceans blue. Oxygen then began to accumulate in the atmosphere, created the first global \”pollution\” crisis, some organisms went extinct.
endosymbiotic theory
theory that proposes that eukaryotic cells formed from a symbiotic relationship among several different prokaryotic cells, Ancestral eukaryotes entered the cells and began to live in them
ancient eukaryotic organisms
ancient prokaryotes that evolved internal cell membranes
Hypothesis of Mitcochondria
mitchondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate ATP. Inside primitive eukaryotic cells, these prokaryotes evolved into mitochondria, which allowed cells to metabolize energy
Hypothesis of Chloroplasts
Chloroplasts evolved from endosymbiotic prokaryotes that had the ability to photosynthesize. These photosynthetic prokaryotes evolved within the eukaryotic cells into chloroplasts.
Modern Evidence of EndoSymbiotic Theory
Similarities of Mitochondria/Chloroplasts and bacteria:
Similar DNA
Similar ribosome size and structure
both reproduce by binary fission
evolutionary significance of sexual reproduction
the development of sexual reproduction sped up evolutionary change because sexual reproduction increases genetic variation
diversity of multicellular organisms
After the evolution of sexual reproduction, early cellular organisms underwent a series of adaptive radiations, which resulted in great diversity

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