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.
Answer:
The mouse and shrew bones were common to all three owls so they were not useful in identifying environments. The gopher bones were unique to the great grey owl of Alaska. Gophers are rodents that are successful in areas with soft soil and lots of grass, so the gopher and this owl would be found in the meadows and evergreen forests of Alaska. The bat was unique to the barking owl of Australia. The bat would be found in woodland habitats where there are many trees the bat can hang from. The gull bones were unique to the short-eared owl of Cuba. Gulls are wetland birds, so the gull and this owl would be found in marshes and coastal areas.
<span>Na+, cl-, hco3-, and k+ are electrolytes. Na+ is sodium. Cl- is chloride. Hco3- is bicarbonate and k+ is potassium. Electrolytes are needed for our organs and cells to function like they should. We obtain some of these electrolytes through the food we eat, such as sodium from salt and potassium from bananas.</span>
The virus becoms infection, and they create an epidemic that will last for a long time. This was the case back in the early days.
Answer:
Repressor protein
Explanation:
Repressor is a protein that binds to deoxyribonucleic acid(DNA) or ribonucleic acid(RNA) it inhibits the expression of one or more genes which is done by binding to the associated silencers.
A DNA binding repressor works by blocking the attachment of RNA polymerase an enzyme that enhance transcription to the promoter, thus preventing genes from been transcribed into messenger RNA.
An RNA binding repressor binds to the messenger RNA and prevents translation of the bases on the messenger RNA into protein. The blocking of expression is called repression.
