The earth was formed about 4.5 billion years ago. In the atmosphere there was hydrogen, nitrogen, carbon dioxide, carbon monoxide, ammonia, and methane. No oxygen was present at this time. Thunder, lightning, and water vapor storms were frequent. Shallow and warm muddy sediment had been forming due to long periods off rainfall. Oxygen has been on the earth since about 2.4 billion years ago by way of light trapping and photosynthesis. Since the atmosphere now contained oxygen, aerobic respiration became dominant. Cells were now using oxygen to survive. The origin of life on earth began about 3.5 billion years ago. Fossils were found of the first bacteria as evidence.
Prokaryotic cells do not have a nucleus or membrane bound organelles. The early prokaryotic cells had a replicating membrane, nucleotides, and amino acids. Early cells used carbon dioxide and ATP to form complex cells. Prokaryotic cells have a nucleoid region which contains DNA. The DNA is loose and there are strands in the prokaryotic cell. Eukaryotic cells contain a nucleus and membrane bound organelles. Eukaryotic cells have been using oxygen since 1.7 billion years ago. Eukaryotic cells are larger and are more complex than prokaryotic cells. These cells have more structures inside of the cell. Eukaryotic cells are …show more content…
Organelles join together to form complex cells. Simple cells join together larger cells. The organelles, at one point, were their own bacteria. These organelles had moved into another cell to form eukaryotic cells. These cells have evolved and have lived inside of another cell for so long that they can no longer survive outside of the cell. The mitochondria and chloroplasts have a separate DNA from that of the nucleus. This supports the theory that organelles inside of a cell were once single organisms by themselves. Both the mitochondria and chloroplasts replicate their DNA just like bacteria does, they also have a double