The Precambrian era envelopes the major bulk of the history of the Earth, beginning from the creation of the planet approx 4.5 billion years ago and terminating with the origination of composite, multicelled forms of life approximately 4 billion years after.
The Precambrian refers to the earliest of the geologic ages that are signified by the distinct layers of sedimentary rock. The Earth was about more than six hundred million years old when life started. The planet had cooled down from its native molten state, creating a solid crust and oceans formed by water vapor in the atmosphere.
At about three billion years ago, the atmosphere of the Earth was virtually devoid of oxygen. At approximately 2.4 billion years ago, oxygen was discharged from the seas as a waste product of photosynthesis by cyanobacteria. The levels of the gas slowly raised, attaining about 1 percent around two billion years ago.
Approximately 800 million years ago, the levels of oxygen attained about 21 percent and started to breathe life into more composite species. The oxygen-rich ozone layer was also created, protecting the surface of the Earth from the harmful solar radiation.
Plant cells have a rectangular shape and a cell wall, while animal cells have a circular shape and no cell wall
Answer: The transcription and translation process allows trna and rrna molecules to be used to synthesize wide variety of polypeptides.
Explanation:
DNA molecule is made up of information for coding proteins. This information is passed on the mRNA during a process known as transcription. Transcription is the first of many steps of DNA based gene expression in which a part of the segment of DNA is copied into RNA (especially mRNA) by the enzyme RNA polymerase.
Both DNA and RNA are nucleic acids, which use base pairs of nucleotides as a complementary language. During the process of transcription, a DNA sequence is read by an RNA polymerase, which gives a complementary, antiparallel RNA strand referred to as a primary transcript.
A large diversity among genes is followed by a large amount of various mRNA molecules. However, the ribosomes consist of rRNA, which is included in the process of translation. Translation is the process whereby ribosomes in the cytoplasm or ER synthesize proteins after the process of transcription of DNA to RNA in the cell's nucleus. The overall process is called gene expression.
The smallest of the three types of RNA is tRNA, which has only 75 to 95 nucleotides and has a role in bringing particular amino acids to the growing polypeptide. It can be concluded that mRNA contribute to the diversity of polypeptide molecules due to the fact that it carries an information about their synthesis.
Answer:
Roughage
Explanation:
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