Final answer:
The accumulation of sufficient oxygen in the atmosphere during the Proterozoic led to the formation of ozone, which likely contributed to the eukaryote expansion. Cyanobacteria evolved from phototrophs and began oxygenating the atmosphere, allowing for more efficient catabolic pathways and increased colonization of the land.
Step-by-step explanation:
The accumulation of sufficient oxygen in the atmosphere and sea during the Proterozoic led to the formation of ozone which likely contributed to the eukaryote expansion.
Evidence indicates that during the first two billion years of Earth's existence, the atmosphere was anoxic, meaning that there was no molecular oxygen. Cyanobacteria, also known as blue-green algae, evolved from phototrophs and began the oxygenation of the atmosphere. Increased atmospheric oxygen allowed the development of more efficient O₂-utilizing catabolic pathways and opened up the land to increased colonization.
The increase in atmospheric oxygen also led to the formation of ozone (O₃), which effectively absorbs the ultraviolet light that would otherwise cause lethal mutations in DNA. This created a protective layer, allowing other life forms, including eukaryotes, to thrive and expand.
The accumulation of sufficient oxygen in the atmosphere and sea during the Proterozoic led to the formation of ozone (O3), which likely contributed to the eukaryote expansion. This is because the oxygenation of the atmosphere initiated by cyanobacteria, also known as blue-green algae, created more efficient metabolic pathways that utilize oxygen (O2). It also facilitated the evolution of other life forms by producing ozone, which formed a protective layer that absorbed ultraviolet light, reducing lethal mutations caused by UV radiation.