In May 1804, the first American expedition the western portion of United States called the Lewis and Clark Expedition started in a city of U.S. state of Missouri called St. Louis. The expedition is also known the Corps of Discovery.
Answer:
D. intense volcanic activity.
Explanation:
- The Paleozoic era an era in the geologic time and started about 541 million years. It originated due to the diversity of life forms on the planet. and ended about 252 mn years ago along with the end of Permian era.
- The extinction was related to the changes in climate and exceptionally low sea levels. During which about 95% of the marine species were killed.
I'm pretty sure the answer is true.
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The correct answer is - cyanobacteria.
The atmospheric oxygen came from the cyanobacteria. These were one of the earliest living organisms on Earth. The cyanobacteria was using photosynthesis in order to create its own food. The photosynthesis process requires sunlight, carbon dioxide, water, and oxygen. The oxygen is mostly released as a waste product from the process of photosynthesis, thus the cyanobacteria were literally releasing oxygen that was ending up into the atmosphere. As more and more cyanobacteria there were across the planet, more and more oxygen they were releasing into the atmosphere, slowly changing the composition of the atmosphere, and setting the basis of it as we know it now.
