Biology: Topic 6: Earth's Early History

What is the RNA world?

A hypothesis that proposes that RNA existed by itself before DNA. Several steps could have led to DNA-directed protein synthesis.

What was the effect of oxygen?

At first, the oxygen combined with iron in the oceans, producing rust. Iron, which is not soluble in water, sank to the ocean floor and formed great bands of iron that are the source of most iron ore mined today. Without iron, the oceans changed color from brown to blue-greenoxygen gas began to accumulate in the atmosphere. The ozone layer began to form, and the skies turned their present shade of blue. Over several hundred million years, oxygen concentrations rose until they reached today's levels

How is information in our bodies stored?

Cells are controlled by information stored in DNA, which is transcribed into RNA and then translated into proteins

Who produced oxygen 2.2 million years ago?

During the early Proterozoic Eon, photosynthetic bacteria became common. By 2.2 billion years ago, these organisms were producing oxygen.

What occurred 4.2 million years ago?

Earth cooled enough to allow solid rocks to form and water to condense and fall as rain. Earth's surface became stable enough for permanent oceans to form

Why was early Earth different from what it was today?

Earth's early atmosphere contained little or no oxygen. It was composed of carbon dioxide, water vapor, and nitrogen, with lesser amounts of carbon monoxide, hydrogen sulfide, and hydrogen cyanide. Because of the gases in the atmosphere, the sky was probably pinkish-orange. Because they contained lots of dissolved iron, the oceans were probably brown.

What do scientists hypothesize about early Earth and the origin of life?

Earth's early atmosphere contained little or no oxygen. It was principally composed of carbon dioxide, water vapor, and nitrogen, with lesser amounts of carbon monoxide, hydrogen sulfide, and hydrogen cyanide.

What do eukaryotes cells have that prokaryote cells do not have?

Eukaryotic cells have nuclei, but prokaryotic cells do not. Eukaryotic cells also have complex organelles. Virtually all eukaryotes have mitochondria, and both plants and algae also have chloroplasts.

How did Stanley Miller and Harold Urey create the first molecular diagram?

Filled a sterile flask with water (simulate the oceans) and boiled it.To the water vapor, they added methane, ammonia, and hydrogen, to simulate what they thought had been the composition of Earth's early atmosphere. They passed the gases through electrodes, to simulate lightning. Next, they passed the gases through a condensation chamber, where cold water cooled them, causing drops to form. The liquid continued to circulate through the experimental apparatus for a week. After a week, they had produced 21 amino acids—building blocks of proteins.

What occurred millions of years ago?

For millions of years, violent volcanic activity shook Earth's crust. Comets and asteroids bombarded its surface.

What do scientist think about the atmosphere of early Earth?

Many scientists think that Earth's early atmosphere may have been similar to the gases released by a volcano today

What where the two conclusions that came out of the endosymbiotic theory?

One hypothesis proposes that mitochondria evolved from endosymbiotic prokaryotes that were able to use oxygen to generate energy-rich ATP molecules. Without this ability to metabolize oxygen, cells would have been killed by the free oxygen in the atmosphere.Another hypothesis proposes that chloroplasts evolved from endosymbiotic prokaryotes that had the ability to photosynthesize. Over time, these photosynthetic prokaryotes evolved within eukaryotic cells into the chloroplasts of plants and algae.

What is the evolutionary significance of sexual reproduction?

The development of sexual reproduction sped up evolutionary change because sexual reproduction increases genetic variation.

How can Microscopic fossils of prokaryotes that resemble bacteria have been found in Archean rocks more than 3.5 billion years old?

Those first life forms evolved in the absence of oxygen because at that time, Earth's atmosphere contained very little of that highly reactive gas

What occurred to some organisms who where born without oxygen?

To the first cells, which evolved in the absence of oxygen, this reactive oxygen gas was a deadly poison that drove this type of early life to extinction. Some organisms, however, evolved new metabolic pathways that used oxygen for respiration and also evolved ways to protect themselves from oxygen's powerful reactive abilities.

Endosymbiotic Theory

endosymbiotic theory, prokaryotic cells entered those ancestral eukaryotes. The small prokaryotes began living inside the larger cells.

Miller and Urey's experiment suggested...?

how mixtures of the organic compounds necessary for life could have arisen from simpler compounds on a primitive Earth.

What did Lynn Margulis discover?

mitochondria and chloroplasts contain DNA similar to bacterial DNA. also that mitochondria and chloroplasts have ribosomes whose size and structure closely resemble those of bacteria. she found that mitochondria and chloroplasts, like bacteria, reproduce by binary fission when cells containing them divide by mitosis. These similarities provide strong evidence of a common ancestry between free-living bacteria and the organelles of living eukaryotic cells.

What is the result of S and H experiment?

produced 21 amino acids—building blocks of proteins.We now know that Miller and Urey's ideas were incorrect. But new experiments based on current ideas of the early atmosphere have produced similar results

What 3 ways can RNA sequence evolve?

some RNA sequences help DNA replicate. process messenger RNA after transcription. other RNA sequences catalyze chemical reactions. Some RNA molecules even grow and replicate on their own

What did Stanley Miller and Harold Urrey's experiment suggest?

suggested how mixtures of the organic compounds necessary for life could have arisen from simpler compounds on a primitive Earth.

What did Geological and astronomical evidence suggests?

that Earth formed as pieces of cosmic debris collided with one another. While the planet was young, it was struck by one or more huge objects, and the entire globe melted.

What theory explains the origin of eukaryotic cells?

the endosymbiotic theory proposes that a symbiotic relationship evolved over time, between primitive eukaryotic cells and the prokaryotic cells within them.

What did Stanley Miller and Harold Urey create?

tried recreating conditions on early Earth to see if organic molecules could be assembled under these conditions.