The Biology of Human Survival: Life and Death in Extreme Environments

By Claude A. Piantadosi | Go to book overview

12
Air as Good as We Deserve

The evolution of advanced forms of animal life on Earth would not have been possible without molecular oxygen (O2), but too much of it is toxic to virtually all cells and organisms. Oxygen is the third-most abundant element in the universe after hydrogen and helium. It is formed at the heart of stars by the fusion of helium with carbon. More than 90% of the known universe is made up of hydrogen, whereas the other four major molecular building blocks of life, oxygen, carbon, nitrogen, and phosphorus, collectively account for less than a quarter of 1% of its composition. The abundance of hydrogen implies that the cooler spots in the universe are, in chemical terms, reducing environments. This means chemical energy is exchanged primarily by reactions that transfer electrons from hydrogen to suitable acceptors, such as carbon and nitrogen. These reductive processes are responsible for the production of many common, simple compounds in the universe, such as methane (CH4) and ammonia (NH3). This condition was certainly the case on Earth for billions of years, until photosynthesis appeared, which led to the generation of most of the O2 present in the atmosphere today (Gilbert, 1996).


Life in an Oxidizing Atmosphere

The earliest life forms on Earth were unicellular organisms without a nucleus, (prokaryotes), which would have been destroyed by exposure to molecular oxy

-129-

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The Biology of Human Survival: Life and Death in Extreme Environments
Table of contents

Table of contents

  • Title Page iii
  • Preface vii
  • Contents xi
  • 1: The Human Environment 1
  • 2: Survival and Adaptation 10
  • 3: Cross-Acclimation 21
  • 4: Food for Thought 29
  • 5: Water and Salt 41
  • 6: Water That Makes Men Mad 54
  • 7: Tolerance to Heat 63
  • 8: Endless Oceans of Sand 78
  • 9: Hypothermia 89
  • 10: Life and Death on the Crystal Desert 99
  • 11: Survival in Cold Water 119
  • 12: Air as Good as We Deserve 129
  • 13: Bends and Rapture of the Deep 140
  • 14: Sunken Submarines 152
  • 15: Climbing Higher 164
  • 16: Into the Wild Blue Yonder 181
  • 17: G Whiz 193
  • 18: The Gravity of Microgravity 203
  • 19: Weapons of Mass Destruction 212
  • 20: Human Prospects for Colonizing Space 227
  • Bibliography and Supplemental Reading 247
  • Index 255
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