Question

Study the graph about oxygen content of Earth’s atmosphere. Oxygen Content of Earth apostrophe s Atmosphere line graph. X axis is Millions of Years Before Present. Y axis is Oxygen in volume percent. The line starts at 1000 millions of years before present at 4 percent oxygen, remains level until 625 Millions of Years Before Present, increases quickly to 13 percent oxygen, then increases slowly to 18 percent oxygen. The line jumps to 35 percent oxygen near 300 millions of years before present, drops quickly to 15 percent oxygen, then increases to 31 percent oxygen near 100 millions of years before present, before dropping down to 20 percent oxygen. Which describes oxygen content as Earth evolved over time? Oxygen levels sharply declined about 400 million years ago. Oxygen levels stay above 15 percent starting 200 million years ago Oxygen levels remain below 5 percent starting 1000 million years ago. Oxygen levels raise significantly between 1000 and 700 million years ago.

Answer 1

Answer: Oxygen levels stay above 15 percent starting 200 million years ago

Explanation:

Answer 2

Explanation:

from the graph study about oxygen content of Earth's atmosphere, we can understand that  

1)

4 billions year ago = None, 3 billions year ago = Cyanobacteria and Archaea , 2 and 1 billions year ago = Bacteria and Green algae , 500 Ma = invertebrate fossils started to existence. Early land plants came in to existence around 398 MA that is Devonian. Dinosaurs are came in to existence during Triassic and Jurassic that is around 251 Ma. Man and animals are recent organism came under Holocene that is 11000 years ago.

2)

The first cells on the earth are anaerobic microorganisms, as the CO2 level is too high they survive by using CO2.

3)

Starting around 2.7 billion years ago, photosynthesis by Cyanobacteria and later plants , pumped “OXYGEN” in to the atmosphere. This caused the decline of anaerobic bacteria and allows the diversification of animals as seen in “CAMBRIAN” around 500 millions year ago.  

Early vascular plants “CAPTURED” CO2 starting before the Carboniferous period that began around 350 millions year.Leading to lower temperatures and allowing and allowing the seed plants to outcompetes seedless plants.

Modern human activities has raised both “CO2 and METHANE” level in the atmosphere to over leading to higher temperature and extinction of other species.