1. Plants are the main source of atmospheric oxygen.

2. Some 1800 million years ago atmospheric oxygen was fast approaching the present level of about 21 percent of the total.

3. As atmospheric oxygen levels fall, less oxygen will dissolve in seawater, depleting levels slightly.

4. Organisms possessing this enzyme, in the presence of atmospheric oxygen and the substrate contained in the oxidase discs give a red-fuchsia color.

5. Usually, atmospheric oxygen content is about 20%, carbon dioxide containing about 0.03%.

6. As far as we can tell Earth's atmospheric oxygen has remained at about 20 percent for hundreds of millions of years.

7. The cure-inhibition effect of the atmospheric oxygen usually causes the surface stick of the cold-cured unsaturated polyester resin.

8. Once photosynthesis had raised atmospheric oxygen levels high enough, the ozone layer formed, meaning that it was then possible for living things to venture onto the land.

9. The dry conditions and lack of atmospheric oxygen mean that the stuff has not rusted, says Geoffrey Landis of NASA's Glenn Research Center in Cleveland, Ohio.

10. Shelf life of foods, such as bakery products, is principally affected by two major factors:atmospheric oxygen and the growth of aerobic spoiling microorganisms.

11. Atmospheric oxygen levels peaked around 35 percent, compared to 21 percent today.

12. Gas scavenger sachets (21) are also provided within the sealed chamber (12) to remove atmospheric oxygen, thus causing a further reduction in the chamber pressure.

13. During the frying process the fat undergoes several chemical and physical changes caused by heat, water and atmospheric oxygen.

14. At that point, rocks from the era show that atmospheric oxygen started to rise, which would suggest that methane levels dropped.

15. When plants conquered the land they found new places to grow and new ways to be buried, gradually boosting atmospheric oxygen.

16. Plus you will be helping to save our dwindling supply of atmospheric oxygen.

17. University of Washington paleontologist Peter Ward correlated the gap with changes in atmospheric oxygen levels found from studies of the geochemistry of the rock layers...

17. Sentencedict.com is a sentence dictionary, on which you can find nice sentences for a large number of words.

18. Remember the 1980s, when it seemed the Amazon rain forest wasn't long for this world -- and that humanity was threatened as atmospheric oxygen levels correspondingly declined?

19. "It is a car that stores hydrogen on board, and, mixing the hydrogen and atmospheric oxygen in the fuel cell stack, creates electricity," said Mittleman.

20. Mercedes was similarly stingy with details about the fuel cell, saying only that "gaseous hydrogen reacts with atmospheric oxygen at 700 bar."

21. Rust is the product of a slow combination of iron with atmospheric oxygen and water vapor.