Question

Based on the conditions of early Earth, what conclusion can you draw about the amount of anaerobic respiration that was occurring at Earth’s beginning? Explain your answer.

Answer 1

the atmosphere on the early earth consisted almost of different nitrogen gases, water vapour and carbondioxide. there was no breathable oxygen in the air at those days. so the first life forms had to develope in the absence of oxygen using the anaerobic respiration. so all the first cells used this. they used sunlight, water and carbondioxide to life and the waste product was oxygen. this oxygen then enriched in the atmosphere and the anaerobic life forms had to move in regions deeper in the oceans or in the soil were no oxygen could reach them, since that was toxic for them.
some of them also survived and learned to breath the oxygen and the early animals could develope.
to sum it up: in the beginning there was only anaerobic respiration and then later just mostly aerob respiration once the atmosphere had oxygen

Answer 2

Then it asks me, "If there was a sudden drop in temperature after the evolution of the first living cells, predict how that might have affected the changes in the atmosphere and the evolution of cyanobacteria and other autotrophs. Explain your answer."

Answer 3

well, as it is known. carbon dioxide ia a greenhouse gas. that means it works like a blanket it keeps the heat from the sunlight and reflects it back to earth which leads to an increase in the global temperature.
now in the early atmosphere there was a significant higher amount of carbondioxide. earth in those days was much warmer than now. when the cyanobacteria used the carbondioxide to produce oxygen. those carbon dioxide was replaced by oxygen. so the greenhouse effect decreased which resulted in a drop of the global temperature.
as far as it is known nowadays. ^^

Answer 4

Oh well, that makes much more sense, thank you. It's that in my book didn't explain much about the Anaerobic Respiratory.