Question

When did oxygen levels start to decline from 35 percent down to today's levels?

Answer 1

Oxygen levels start to decline from 35 percent down to today's levels D. After the Carboniferous period

Further explanation

Oxygen levels started to decline from 35 percent down to today's levels about 95 million years ago.

The Carboniferous is a geologic period and system that spans 60 million years from the end of the Devonian Period 358.9 million years ago, to the beginning of the Permian Period, 298.9 Mya.  The Carboniferous is occurred 358.9 (+/- 0.4) million years ago - 298.9 (+/- 0.15) million years ago

Whereas the Permian spans 47 million years from the end of the Carboniferous period 298.9 million years ago, to the beginning of the Triassic period 251.902 Mya. It occurred 298.9 (+/- 0.15) million years ago - 251.902 (+/- 0.024) million years ago

The Triassic spans 50.6 million years from the end of the Permian Period 251.9 million years ago, to the beginning of the Jurassic Period 201.3 Mya. Triassic occurred 251.902 (+/- 0.024) million years ago - 201.3 (+/- 0.2) million years ago

The Silurian is a geologic period and system spanning 24.6 million years from the end of the Ordovician Period, at 443.8 million years ago, to the beginning of the Devonian Period, 419.2 Mya. It occured 443.8 (+/- 1.5) million years ago - 419.2 (+/- 3.2) million years ago

Therefore, D. After the Carboniferous period, oxygen levels started to decline from 35 percent down to today's levels

Learn more

1. Learn more about oxygen levels brainly.com/question/11494449
2. Learn more about the Silurian period brainly.com/question/882157
3. Learn more   about the Carboniferous period brainly.com/question/8930188

Answer details

Grade:  9

Subject:  biology

Chapter:  period

Keywords: oxygen levels, the Silurian period, the Carboniferous period, the Permian period, the Triassic period

Answer 2

The oxygen levels on Earth were about 30-35% higher during the Carboniferous. That contributed to the enormous insects that evolved during that geological period. So if the oxygen level was at its peak during the Carboniferous, it only went in one direction after—> down. So the answer could only be D. After the Carboniferous period.