<u>Answer:</u>
Cyanobacteria start producing pure oxygen around 200 million years ago.
<u>Explanation:</u>
Many scientists believed that Earth did not have any oxygen. Cyanobacteria or the blue green algae are the microbes which produced oxygen for the first time with the help of photosynthesis. This was around 4.5 billion years ago: after Hadean eon.
They were very simple, but they produced oxygen in the early earth’s atmosphere. So, they brought evolution on earth. This “blue-green algae” exists in salt water, rocks and soils and play a major role in maintaining the ecosystem.
Answer:
The first three look like clear quartz then the last two might be obsidian
Explanation:
Tried my best hope this helps!
These are the risk factors associated with the development of ovarian cancer:
1. Over 40 years of age.
2. First pregnancy after 30 years of age.
3. Family history of cancer.
4.High fat diets
5. Endometriosis.
6. History of heavy bleeding.
All these factors increase the probability of having the disease.
To see if the original results are reproducible
