Question

Before the ozone layer formed, early life was confined to aquatic habitats primarily because water:

Options

• Shielded organisms from harmful UV radiation

• Provided oxygen directly to cells

• Absorbed all carbon dioxide from the atmosphere

• Prevented anaerobic respiration

Answer 1

Harmful UV radiation could reach shallow waters, so early life survived only within water. Once free oxygen formed the ozone layer and UV radiation was absorbed, life could survive beyond water and eventually migrate towards land.