Precambrian is the denomination of the largest division in Earth’s geological time. Corresponds to the set of Proterozoic , Archean and Hadean eons . Predates the Neon Fanerozoico .
The lower limit of the Precambrian is not defined, but it ended about 542 million years ago. Precambrian covers 90% of the Earth’s geological record.
Only at the end of the Precambrian did multicellular organisms evolve and sexual division developed. It was also at the end of the Precambrian that the conditions were created for the explosion of life recorded at the beginning of the Eon Fanerozoic.
Features
- Early life on Earth
- Beginning of the movement of tectonic plates
- Appearance of the first cells
- Formation of the atmosphere layer
- Formation of the ozone layer
- Appearance of the first animals and vegetables
Climate
During the Precambrian time period, Earth’s climatic conditions changed considerably and there were significant changes in the atmosphere and oceans.
The atmosphere in that period made the existence of life as we know it today incompatible. Scientists have records of organisms called cyanobacteria – blue algae – unique capable of surviving the air loaded with methane (CH4) and ammonia (NH3) typical of 2.3 billion years ago.
In addition to air, the water in the oceans did not meet the conditions necessary to allow life to exist. The oceans were full of iron. The cleansing of the oceans occurred in a major explosion 2.7 billion years ago. This event allowed an increase in the supply of oxygen in the atmosphere and, only 600 million years ago, the first microorganisms to demand the production of collagen, essential for the formation of skeletons, began to appear.
It was also in Precambrian that the atmosphere started to form the ozone layer (O3) , which acts as protection against the ultraviolet rays emitted by the Sun.
Life
The first signs of life on Earth were identified in the western portion of Greenland. They were fossilized microorganisms in rocks and were 3.8 billion years old. In the microfossils, the carbon bond, essential to life, was evidenced.
These microorganisms were able to survive between 1700 to 1900 million years ago, when the first cells with nuclei began to appear. The latter made use of oxygen in the metabolism and were capable of cell division. The capacity for division was imprinted on the genetic material, the DNA, and was passed on to the following generations. To share Submit Email