How does the ozone layer that protects us from harmful UV radiation today connect back to Threshold 5 of Christian's "Big History" - the emergence of living organisms? Choose 1 answer. B These first organisms were the ancestors of plants and animals that produce ozone through photosynthesis. The first bacteria converted glucose into nitrogen which makes up the ozone layer today. Asteroids that hit the earth during this time generated a layer of dust and compounds that make up the ozone layer. Some of the first single-cell bacteria emitted oxygen into the air, helping form the ozone layer.​