The biological importance of the ozone layer is

 

Concept: Ozone layer protects earth from UV rays.

Ozone layer depletion results in UV rays, directly reaching to the earth surface. Ozone found in the stratosphere layer of the atmosphere and forms a protective covering and protects earth from UV rays.

Depletion of ozone layer causes increased UV rays. UV rays cause skin cancer. Increase UV rays affect cyanobacteria, as they are sensitive to the ozone layer.

Hence the correct Option is 1.