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The solar system was comprised from a rotating cloud (solar nebula) of gas and dust, mainly hydrogen and helium atoms. The particles in this rotating cloud began to clump together from the attraction of gravity. While the sun formed in a similar fashion in the centre... The planets formed around it.
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The cooling of earth allowed it to form the "crust". As well, the water that had condensated in the atmosphere formed the oceans.
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The moon is believed to have been created because of a collision between Earth and a "Mars Type" body called "Theia". A piece of mantle of each the Theia and Earth combined off in space to form the Moon. The moon formed 20 to 100 million years after the solar system.
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From 3.8- 4.1 billion years ago astronomers were led to believe that earth collided with astroids and comets. These collisions occurred frequently. This would be considered the "Big Bang Theory". It is unsure whether or not cells could have survived through this time or they formed after?
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The mitochondria and chloroplast were assumed to come from prokaryotic cells that lived as single organisms. First, a eukaryotic cell engulfed an aerobic prokaryote that formed a host relationship with the host eukaryote and developed into a mitochondrion.
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Stromatolites were a by- product of microbial bacteria. Many layers of microbes (cynobacteria) captured sedimentary particles. These accumulated particles created layers of the new material.
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The first evidence of photosynthesis, allowed cynobacteria to convert light to chemical energy. This has only happened once on earth. Oxygen molecules were the byproduct of this process.
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The first multi-cellular life discovered was prokaryotic bacteria life; Up until 2 Billion years ago, when life as we know it started to evolve from those cells. Up until about 1.2 Billion years ago multicellularity has been evolving itself.
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It is estimated that between approximately 2 and 3.5 billion years ago that eukaryotes began to evolve. The indications found when researching the development of the nucleus show the nucleus grew from the outside in. New layers of the nucleolus kept growing, which finally resulted in a independent unit called the nucleus.
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The first sexual reproducing organisms came in the Proterozoic Eon. Single celled protists (eukaryotes) exchanged genetic material approximately 2 Billion years ago.
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Eukaryotes divide themselves into 3 groups at this time. They were: ancestors of modern fungi, plants and animals. These three also began to evolve separately on their own. It was assumed each were still single-celled organisms at the time.
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Three-quarters of the animal and plant population on earth became extinct. It is generally accepted that there was a large asteroid (10 km in width) which contacted earth, created a very lengthy winter in which plants were unable to follow out with the process of photosynthesis. It is not totally known what occurred with the animal population- but, a large crater hole was found in Mexico in the 1990's which helped prove the asteroid theory.
