About 2.5 billion historic period ago, oxygen began slowly to accumulate in the atmosphere, as a result of the photosynthetic activity of the cyanobacteria. Those prokaryotes that were open to use oxygen in ATP production gained a strong advantage, and so they began to prosper and increase. Some of these cells may digest evolved into modern forms of aerobic bacteria. Other cells may have sustain symbionts with larger cells and evolved into mitochondria. As the amount of oxygen and other atmospherical gasses increased, they started blocking out deadly u.v. rays from the sun. The suns rays made life remote of water nearly impossible. These changes made life on drop off possible and evolution occurred as prokaryotes gave rise to land sustainment eukaryotes.
The microfossil record indicates that the first eukaryotes evolved at least 1.5 billion years ago. Eukaryotes are distinguished from prokaryotes by their larger size, the separation of nucleus from cytoplasm by a nuclear envelope, the association of deoxyribonucleic acid with hist star proteins and its organization into a number off distinct chromosomes, and convoluted organelles, among which are chloroplasts and mitochondria. Scientists believe that eucaryotic organisms such as the protists evolved from the prokaryotes. on that point are two main theories which describe how this transition may have occurred. The first is the endosymbiotic theory, or enosymbiosis, and the other is the autogenous theory, or autogenisis. These two theories are not mutually exclusive, meaning one or the other could account for different parts of eukaryotic cells. The endosymbiotic theory states that the formation of eukaryotic cells were symbiotic associations of prokaryotic cells vitality inside larger prokaryotes.
The endosymbiotic hypothesis accounts for the presence in eukaryotic cells of complex organelles not found in the far simpler prokaryotes. galore(postnominal) modern organisms contain intracellular symbiotic bacteria, cyanobacteria, or photosynthetic protists, indicating that such associations are not difficult...
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