Consider the following statements: 1) The Earth’s magnetic field has reversed every few hundred thousand years. 2) When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide. [2018]

Consider the following statements:

The Earth’s magnetic field has reversed every few hundred thousand years.
When the Earth was created more than 4000 million years ago, there was 54% oxygen and no carbon dioxide.
When living organisms originated, they modified the early atmosphere of the Earth.

A geomagnetic reversal or a reversal in earth’s magnetic field is a change in a planet’s magnetic field such that the positions of magnetic north and magnetic south are interchanged. Based on palaeomagnetism (magnetism in rocks that was induced by the earth’s magnetic field at the time of their formation), it is observed that over the last 20 million years, magnetic north and south have flipped roughly every 200,000 to 300,000 years. The reversal is not literally ‘periodic’ as it is on the sun, whose magnetic field reverses every 11 years.
The time between magnetic reversals on the Earth is sometimes as short as 10,000 years and sometimes as long as 25 million years. And the time it takes to reverse could be about a few hundred or a few thousand years.

Geologists believe that most of the carbon on the young, hot Earth, >4000 Mya, was in the form of gaseous carbon dioxide, carbon monoxide, and methane. With time, the CO and CH4 reacted with oxide minerals and were transformed into CO2. These reactions did not change the total amount of carbon in the atmosphere. Oxygen did not begin to accumulate in the atmosphere until 2400-2100 Myr ago – a time interval called the “Great Oxidation Event“.

The origin of life, especially photosynthetic organisms, played a crucial role in altering the Earth’s early atmosphere, notably increasing oxygen levels.