What organism(s) and processes led to o2 accumulation in our atmosphere?

An easy way to calculate the amount of energy available at each level is to what?

Is this mrna or rna need need the answer in a hurry

Transposon can cause mutations in genes at or near the site of transposon insertion. it is possible for these elements to transpose away from their original site, causing a reversion of the mutant phenotype. in some cases, however, even more severe phenotypes appear when these elements excise from this site, due to events at or near the mutant allele. what might be happening to the transposon or the nearby gene to create more severe mutations?