Life originated in which era : [CPMT 76]a)Proterozoicb)Mesozoicc)Precambriand)CoenozoicCorrect answer is option 'C'. Can you explain this answer?

Question

Answer

The earliest undisputed evidence of life on Earth dates at least from 3.5billion years ago, during the Eoarchean Era, after a geological crust started to solidify following the earlier molten Hadean Eon.

Answer

The earliest undisputed evidence of life on Earth dates at least from 3.5billion years ago, during the Eoarchean Era, after a geological crust started to solidify following the earlier molten Hadean Eon.

Answer

Life originated in the Precambrian era. The Precambrian era is the longest and oldest geological era, spanning from the formation of the Earth about 4.6 billion years ago to approximately 541 million years ago. It is divided into three major eons: the Hadean, Archean, and Proterozoic.

1. Hadean Eon:
The Hadean eon represents the earliest stage of Earth's history, starting from its formation. During this eon, the Earth was a hostile and inhospitable place with intense volcanic activity, frequent meteorite impacts, and a harsh environment. The extreme conditions made it unlikely for life to exist.

2. Archean Eon:
The Archean eon began around 4 billion years ago and lasted until about 2.5 billion years ago. It was during this eon that the Earth's crust began to solidify, and oceans and continents started to form. The early atmosphere consisted of gases like methane, ammonia, water vapor, and carbon dioxide. The first evidence of life appears in the form of microbial fossils found in ancient rocks dated to be around 3.5 billion years old. These microorganisms were simple, single-celled organisms, such as bacteria and archaea.

3. Proterozoic Eon:
The Proterozoic eon followed the Archean eon and lasted from approximately 2.5 billion years ago to 541 million years ago. During this eon, life continued to evolve and diversify. Oxygen levels in the atmosphere gradually increased due to the activity of photosynthetic organisms, such as cyanobacteria. This rise in oxygen levels led to the development of more complex life forms, including eukaryotic cells and multicellular organisms. Fossil evidence from this eon includes stromatolites, which are layered structures formed by microbial communities.

The Precambrian era encompasses both the Archean and Proterozoic eons, during which life originated and evolved. It is important to note that the term 'Precambrian' refers to the time period before the Cambrian period, which marks the beginning of the Paleozoic era. The Cambrian period is known for the 'Cambrian explosion,' a rapid diversification of complex life forms.

In summary, life originated during the Precambrian era, specifically in the Archean eon around 3.5 billion years ago. The Proterozoic eon, which followed, saw the further evolution and diversification of life forms.

Answer

Precambrian is the largest span of time which starts from the origin of the earth to the start of the Cambrian period. This era is marked by the presence of different layers of sedimentary rocks.

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