Wym???? whats the question?
The primitive atmosphere was changed during the Precambrian era. This modification enabled the emergence of many different forms of life on Earth.
<h3>The Precambrian Era</h3>
The Precambrian Era refers to a period of time consisting of all of the geologic time prior to approximately 600 million years ago.
This Era (Precambrian) was characterized by a primitive atmosphere in which air oxygen was absent in important amounts.
During the Precambrian Era, the concentration of atmospheric oxygen began to rise due to the activity of photosynthetic cyanobacteria.
This increase in atmospheric oxygen facilitated the emergence of aerobic landforms and thus an explosion of biodiversity in the Earth.
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<u>Viruses </u>are microorganisms that are not included in phylogenetic trees because they are acellular.
Viruses can be described as the tiniest microorganisms that have the ability to replicate only using the host machinery. Scientists still have a debate on whether to consider viruses as living or non-living entities as they are unable to function as living organisms without a host.
Viruses also are not included in phylogenetic trees because they lack genes that are common to all species. They do not have proper cellular structures and are acellular due to which their addition to any phylogenetic tree is not possible. Any particular gene is not shared through a viral lineage, due to which creating a virus lineage is not possible.
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