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What do most researches suspect about RNA?
They suspect that it was the first information-storing molecule to form and that RNA "enzymes" catalyze the assembly of the earliest proteins.
T/F Scientist believe that double-stranded DNA evolved later
Researches do not yet understand how DNA, RNA, and hereditary mechanisms first developed so science is currently what?
Unable to resolve disputes concerning the origin of life.
How does RNA change?
What are microscopic fossils?
Microfossils of single-celled prokaryotic organisms that resemble modern bacteriahave been found where?
In rocks for morethan 3.5 billion years old
Why must have the first forms of life evolve in the abscence of oxygen?
Earth's first atmosphere contained very little of that highly reactive gas.
What has been indicated by fossil evidence?
Photosynthetic bacteria became common in the shallow seas of the Precambrian.
By 2.2 billion years photosynthetic bacteria were steadily churning out what... and what is it an endproduct of?
What was the first thing oxygen did?
It combined with iron in the oceans; causing them to "rust"
What is fromed when combining oxygen and iron?
Iron oxide which is now what we mine up
Without iron the oceans turned what?
Colors-brown to blue
T/F Oxygen started accumulating in the atmosphere
As the atmosphere concentration rose, what also decrease?
Methane and hydrogen sulfide began to decrease causing the ozone layer to form. This caused the skies to turn blue.
The oxygen rose to today's level.
What do biologists hypothesize about the gas back then?
They were the gases that started our pollution. To the first cells it was poison.
The rise of oxygen caused what?
The extinction and evolution of animals which used oxygen for respiration.
Those who had evolved in an oxygen-free atmosphere were forced into what?
Airless habitats where their anaerobic descendants remain today.
Why did organism use oxygen for respiration?
To protect themselves
What are prokaryotic cells?
Cells without nuclei
What did prokaryotic cells start to evolve with?
Internal cell membranes.
Smaller prokaryotic cells began to do what?
They began to live inside larger cells
Overtime independence began to form
What is the endosymbiotic theory?
Eukaryotic cells formed from a symbiosis among several different prokaryotic orgainisms. One group of prokaryotes had the ability to use oxygen to generate enrgy-rich moleculesof
The prokaryotes evolved into the mitochondria that are now in the cells of all multicellular organisms.
Other prokaryotes that carried out photosynthesis evolved into the chloroplasts of plants and algae.
The endosymbiotic theory proposes what?
Eukaryotic cells arose from living communities formed by prokaryotic organisms.
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Origin of the Endosymbiotic Theory