The first cells are thought to have been similar to Archaea of today. Archaea is a group of single-celled prokaryotic cells. Being prokaryotic, Archaea lack a nucleus and other membrane-bound organelles that are characteristic of more developed eukaryotic cells. Archaea are able to live in extreme environments. Halophiles are a group of Archaea that are able live in extremely salty environments. Thermophiles are a group Archaea that are able to live in extremely hot temperatures. Because Archaea are primitive in structure and are able to survive in such harsh environments, they are thought to resemble the cells that developed during Earth’s extreme and prehistoric conditions.
The first cell is thought to have developed 3.8 billion years ago. At that time, Earth had little free oxygen in its atmosphere. Instead, the atmosphere was mainly composed of carbon dioxide and nitrogen. Other trace gases were also present such as hydrogen, hydrogen sulfide, and carbon monoxide. The presence of carbon dioxide is thought to have made any water that was present fairly acidic. The temperature is suspected to have been much hotter than it is today. Therefore, cells could have that developed during such a time would have needed to be able to sustain such conditions.
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