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.
<h3><u>Answer;</u></h3>
A. <em>18 hydrogen atoms </em>
<h3><u>Explanation;</u></h3>
- <em><u>Alkanes are group of hydrocarbon that are saturated</u></em>. They are saturated in the sense that each carbon atom has maximum number of hydrogen atoms.
- <em><u>The homologous series of alkanes has a general formula of CₓH₂ₓ₊₂.</u></em>
- Therefore,<u><em> an alkane with 8 carbons will have; (2×8) +2 = 18 hydrogen atoms. </em></u>Thus, the formula of the hyrocarbon will be; C₈H₁₈.
Answer:
A. Fingers looking wrinkled
Explanation:
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B..............................
D. All of the above
There would be new plants and animal life in other locations, the layout of the land varies throughout the world, and there are different climates where soils are formed.
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