Book contents
- Frontmatter
- Contents
- Preface
- A guide to the book
- 1 Putting two and two together
- 2 Units, formulae and the use of old envelopes: confronting some obstacles to quantitative thinking
- 3 Aspects of energy metabolism
- 4 Getting things in proportion
- 5 Perilous percentages, dangerous ratios
- 6 Building a trophic pyramid
- 7 Sodium in animals and plants
- 8 Exchanges of water and carbon dioxide
- 9 A geometric series
- 10 Introduction to logarithms
- 11 Bringing logarithms to life
- 12 Exponential relationships
- 13 Aspects of allometry
- 14 More on allometry, and on quantitative patterns in nature
- 15 How the abundance of food affects rates of feeding
- 16 The characterization of trees and other branching systems
- 17 Epilogue
- References
- Notes
- Index
8 - Exchanges of water and carbon dioxide
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- A guide to the book
- 1 Putting two and two together
- 2 Units, formulae and the use of old envelopes: confronting some obstacles to quantitative thinking
- 3 Aspects of energy metabolism
- 4 Getting things in proportion
- 5 Perilous percentages, dangerous ratios
- 6 Building a trophic pyramid
- 7 Sodium in animals and plants
- 8 Exchanges of water and carbon dioxide
- 9 A geometric series
- 10 Introduction to logarithms
- 11 Bringing logarithms to life
- 12 Exponential relationships
- 13 Aspects of allometry
- 14 More on allometry, and on quantitative patterns in nature
- 15 How the abundance of food affects rates of feeding
- 16 The characterization of trees and other branching systems
- 17 Epilogue
- References
- Notes
- Index
Summary
Plants and animals all exchange oxygen and carbon dioxide with the environment. In terrestrial species, any surface for gas exchange is also a route for water loss, and in both animals and plants one finds structural adaptations that minimize evaporative loss without too much restriction on oxygen and carbon dioxide exchange. Higher plants have a generally impermeable cuticle in which special pores regulate gaseous diffusion appropriately. These are the stomata that lead into the air spaces of the spongy tissue of the mesophyll within (Notes). In reptiles, birds and mammals, little water is lost through the skin (except as controlled sweat loss in mammals). Water is lost, however, in the moist breath, and the system of lungs and airways is one that restricts evaporation while allowing adequate oxygen up take and the maintenance of appropriate carbon dioxide tensions in the blood. Here we look at the relationship between water loss in plants (transpiration) and the carbon dioxide uptake necessary for photosynthesis, and also at the relationship between water and carbon dioxide loss in mammals. The two have much in common. In neither case need we pay much attention to the nature of the pathways for diffusion and air flow. This is because the water vapour and the carbon dioxide follow the same routes and any peculiarities of the pathways tend to affect both gases equally. Treating water and carbon dioxide together is thus easier than treating either on its own, this being especially true of the exchanges in plants.
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- Information
- Biology by NumbersAn Encouragement to Quantitative Thinking, pp. 87 - 99Publisher: Cambridge University PressPrint publication year: 1998