How deep is the root system of a giant sequoia?

Oxygen comes in through pores in the shell. Directly under the shell, there is a small pocket of air. The mi­cro­scop­ic pores on the egg surface allow the CO2 to escape and fresh air to get in, so a de­vel­op­ing bird can breathe.

Prion. All known prion diseases affect the struc­ture of the brain or other neural tissue and all are cur­rent­ly un­treat­able and uni­ver­sal­ly fatal. This includes bovine spongi­form en­cephalopa­thy (BSE, also known as "mad cow dis­ease") in cattle and Creutzfeldt–­Jakob disease (CJD) in humans.

Carbon dioxide is produced by bacteria feeding on the lactic acid. In the Middle Ages, the holes were con­sid­ered a sign of im­per­fec­tion and cheese makers would try to avoid them.

A fizz. When a piece of iceberg ice melts, it makes a fizzing sound called "Bergie Seltzer". This sound is made when the wa­ter-ice in­ter­face reaches com­pressed air bubbles trapped in the ice. As this happens, each bubble bursts, making a 'pop­ping' sound. The bubbles contain air trapped in snow layers very early in the history of the ice, that even­tu­al­ly got buried to a given depth (up to several kilo­me­ter­s) and pres­sur­ized as it trans­formed into firn then to glacial ice.