During which eon did oxygen begin to build up the most in Earth’s atmosphere? Hadean

Phanerozoic

Archean

Proterozoic

i think the answer would d

i think its the first one

small, big, or no change could occur in the phenotype. it could cause something as simple as a cats ears to curl backwards or something as frighting as death. it could also occur in the protien-coding area and have an effect on that but no effect on the amino acids. what has to occur is a changing in the hox gene or the control gene.