The average adult, for instance, breathes 13.5 kilograms of air each day, about four times more in weight than the food and water he or she ingests. If all photosynthesis were to cease tomorrow, the Earth would still have an 8,000-year supply of oxygen. If you turn your back to the wind, low pressure will always be to your left side, high pressure to your right.
Nothing is more natural than meeting a microbe.
It's their scene. It's their scene indeed, and Biddle does a fine job of making it meaningful to his readers.